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What is the current status of the taxon Crocodylus raninus?

What is the current status of the taxon Crocodylus raninus?



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What is the current status of the taxon Crocodylus raninus, the Borneo Crocodile? See Wikipedia Is it now a valid species, a subspecies of Crocodylus porosus (The Saltwater Crocodile) or merely a synonym of the later?

As for Colin Stevenson, "Crocodiles of the World, Reed New Holland 2019", it is not listed as a (valid) species, nor in the IUCN Crocodile Specialist Group.


What is the current status of the taxon Crocodylus raninus? - Biology

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READ THE DEBATE ABOUT CAIMAN CLASSIFICATION

CAIMAN TAXONOMY

OTHER DEBATES IN CROC TAXONOMY
Crocodilian science is full of interesting debates! Here are some more.


SPECIES AND SUBSPECIES

In addition to the 23 recognised crocodilian species, there are a number of subspecies which are often discussed. Most of the commonly discussed subspecies (or species) are listed in the table below. The accepted ones are marked in blue , whereas the doubted or rejected ones are marked in red .

ALLIGATORIDAE
Caiman crocodilus
C. c. crocodilus
C. c. apaporiensis
C. c. fuscus
C. c. yacare
C. c. chiapasius
C. c. paraguayensis
C. c. matagrossiensis
Caiman latirostris
C. l. chacoensis
CROCODYLIDAE
Crocodylus niloticus
C. n. africanus
C. n. chamses
C. n. corviei
C. n. madagascariensis
C. n. niloticus
C. n. pauciscutatus
C. n. suchus
Crocodylus novaeguineae
C. n. novaeguineae
C. n. mindorensis
Crocodylus palustris
C. p. kimbula
Crocodylus porosus
C. p. minikanna
Crocodylus raninus
Osteolaemus tetraspis
O. t. tetraspis
O. t. osborni

As you can see, there have been quite a few different subspecies proposed, and the above isn't even all of them! Subspecies are normally suggested when apparently geographically isolated populations show different morphological characters to the type species, but whether these actually deserve a different classification has been open to considerable debate. Brian Warren has written a very interesting and relevant discussion on caiman taxonomy which discusses some of the issues. In some cases, however, subspecies may turn out to be more than was originally thought: new evidence looking at the DNA of different populations of the African dwarf crocodile, Osteolaemus tetraspis, has revealed that the two different subspecies may be different enough to be classified as totally separate species.

There is another species which is sometimes discussed, Crocodylus raninus. This is thought to occur in Borneo and Kalimantan, and although there is some supportive evidence for it, hard data are still lacking and thus the species is not recognised. Many workers cannot discount the possibility that it might be simply a regional variation on Crocodylus novaeguineae or possibly a hybrid with another sympatric species (e.g. Crocodylus porosus).


SPELLINGS AND MISSPELLINGS

There is another fascinating debate which concerns the actual rules of nomenclature as it applies to the Australian freshwater crocodile. When Gerald Krefft originally described this crocodile, he called it Crocodylus johnsoni after its discoverer, Mr Johnson of Cardwell, Rockingham Bay, Queensland. Six months later he wrote a letter to Dr John E. Gray, who submitted a note to the Australian Museum, pointing out that the species should actually correctly be named Crocodylus johnstoni because its discoverer was actually called Mr Johnston. One wonders whether Krefft often made a habit of misspelling names, as the discoverer's real name was Mr Robert Johnstone! Regardless, Krefft made an error in naming the species through an honest mistake, which he later tried to correct. However, the ICZN (International Code of Zoological Nomenclature) states that in such a case, the original designation is the one which must stand.

Now this is where is gets even more interesting! A similar situation occurred with the American alligator, which was originally named as Alligator mississipiensis without the second "p". However, in this case the ICZN rule was overturned in favour of the current spelling Alligator mississippiensis. Why one, and not the other?

"I may be able to shed some light on this question. A proposal was published in 1956 by the then-secretary of the ICZN, Francis Hemming, to validate Daudin's original 1-'p' spelling. This is published in the Bulletin of Zoological Nomenclature (12[6]:163-175). An objection was raised to this idea by Dr. J.A. Oliver of the New York Zoological Society, who sent a supplementary application to the ICZN in October 1956. Oliver received support for his application from four other practicing herpetologists (including the venerable Hobart Smith).

His reasons were twofold: 1) the name is clearly a misspelling of the geographic locality, and so it should be emended, and 2) it appears as double 'p' in several scientific publications. Regardless of which argument swayed the commission, the application to have the name changed was successful. Volume I, section F of the 1958 Opinions and Declarations Rendered by the International Commission on Zoological Nomenclature contains the full account, including the Opinion ultimately issued emending the spelling to the double 'p' version." Brian Warren

Very interesting! The logic behind changing the name for the American alligator appears to be the same for the Australian freshwater crocodile: the change would correct the misspelling of a proper noun, and the name appears as "johnstoni" in not just several but the majority of scientific publications on the animal. Many Australians ignore the ICZN ruling and use the spelling "johnstoni", although nobody has yet come to the official defence of the freshwater crocodile. Watch this space!


SPELLINGS AND MISSPELLINGS PART II

Another misconception which needs correcting regards the only member of the Gavialidae: the gharial. Or is it the gavial? The name gavial is often used instead of gharial, but which one of the two is right?

The correct common name for Gavialis gangeticus is the gharial. The reason for this is simple: mature male gharials have a bulbous growth on the tip of their snout, which they blow air through to produce a buzzing sound during courtship. This growth is known as a "ghara" in Hindu, which means "pot" or "jar" because that's what it resembles. Gavial is simply a misspelling of this word, which made it into the genus spelling, and which has persisted over time. The use of gavial is not necessarily incorrect, and common names vary so much anyway from one region to another with different crocodilian species. This is why we prefer to use the scientific names to describe species, so there is no ambiguity about what we're talking about. However, there is always room for pedantry!


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Contents

The word crocodile comes from the Ancient Greek krokódilos ( κροκόδιλος ) meaning 'lizard', used in the phrase ho krokódilos tou potamoú, "the lizard of the (Nile) river". There are several variant Greek forms of the word attested, including the later form krokódeilos ( κροκόδειλος ) [4] found cited in many English reference works. [5] In the Koine Greek of Roman times, krokodilos and krokodeilos would have been pronounced identically, and either or both may be the source of the Latinized form crocodīlus used by the ancient Romans. It has been suggested, but it is not certain that the word crocodilos or crocodeilos is a compound of krokè ('pebbles'), and drilos/dreilos ('worm'), although drilos is only attested as a colloquial term for 'penis'. [5] It is ascribed to Herodotus, and supposedly describes the basking habits of the Egyptian crocodile. [6]

The form crocodrillus is attested in Medieval Latin. [5] It is not clear whether this is a medieval corruption or derives from alternative Greco-Latin forms (late Greek corcodrillos and corcodrillion are attested). A (further) corrupted form cocodrille is found in Old French and was borrowed into Middle English as cocodril(le). The Modern English form crocodile was adapted directly from the Classical Latin crocodīlus in the 16th century, replacing the earlier form. The use of -y- in the scientific name Crocodylus (and forms derived from it) is a corruption introduced by Laurenti (1768).

A total of 16 extant species have been recognized. Further genetic study is needed for the confirmation of proposed species under the genus Osteolaemus, which is currently monotypic.

Species name Image Distribution Description/Comments
American crocodile ( Crocodylus acutus ) Throughout the Caribbean Basin, including many of the Caribbean islands and South Florida. A larger sized species, with a greyish colour and a prominent V-shaped snout. Prefers brackish water, but also inhabits lower stretches of rivers and true marine environments. This is one of the rare species that exhibits regular sea-going behaviour, which explains the great distribution throughout the Caribbean. It is also found in hypersaline lakes such as Lago Enriquillo, in the Dominican Republic, which has one of the largest populations of this species. [7] Diet consists mostly of aquatic and terrestrial vertebrates. Classified as Vulnerable, but certain local populations under greater threat.
Hall's New Guinea crocodile (Crocodylus halli) The island of New Guinea, south of the New Guinea Highlands A smaller species that closely resembles and was long classified under the New Guinea crocodile, which it is now considered to be genetically distinct from. It lives south of the mountain barrier that divides the two species' ranges. It can be physically distinguished from the New Guinea crocodile by its shorter maxilla and enlarged postcranial elements. Cranial elements can still widely vary within the species, with populations from Lake Murray having much wider heads than those from the Aramia River. [8]
Orinoco crocodile ( Crocodylus intermedius ) Colombia and Venezuela This is a large species with a relatively elongated snout and a pale tan coloration with scattered dark brown markings. Lives primarily in the Orinoco Basin. Despite having a rather narrow snout, preys on a wide variety of vertebrates, including large mammals. It is a Critically Endangered species.
Freshwater crocodile ( Crocodylus johnstoni ) Northern Australia A smaller species with a narrow and elongated snout. It has light brown coloration with darker bands on body and tail. Lives in rivers with considerable distance from the sea, to avoid confrontations with saltwater crocodiles. Feeds mostly on fish and other small vertebrates.
Philippine crocodile ( Crocodylus mindorensis ) Endemic to the Philippines This is a relatively small species with a rather broader snout. It has heavy dorsal armour and a golden-brown colour that darkens as the animal matures. Prefers freshwater habitats and feeds on a variety of small to medium sized vertebrates. This species is Critically Endangered and the most severely threatened species of crocodile. [9]
Morelet's crocodile ( Crocodylus moreletii ) Atlantic regions of Mexico, Belize and Guatemala A small to medium sized crocodile with a rather broad snout. It has a dark greyish-brown colour and is found in mostly various freshwater habitats. Feeds on mammals, birds and reptiles. It is listed as Least Concern.
Nile crocodile ( Crocodylus niloticus ) Sub-saharan Africa A large and aggressive species with a broad snout, especially in older animals. It has a dark bronze coloration and darkens as the animal matures. Lives in a variety of freshwater habitats but is also found in brackish water. It is an apex predator that is capable of taking a wide array of African vertebrates, including large ungulates and other predators. [10] This species is listed as Least Concern.
New Guinea crocodile ( Crocodylus novaeguineae) The island of New Guinea, north of the New Guinea Highlands A smaller species of crocodile with a grey-brown colour and dark brown to black markings on the tail. The young have a narrower V-shaped snout that becomes wider as the animal matures. Prefers freshwater habitats, even though is tolerant to salt water, in order to avoid competition and predation by the saltwater crocodile. This species feeds on small to mid-sized vertebrates.
Mugger crocodile ( Crocodylus palustris ) The Indian subcontinent and surrounding countries This is a modest sized crocodile with a very broad snout and an alligator-like appearance. It has dark-grey to brown coloration. Enlarged scutes around the neck make it a heavily armoured species. Prefers slow moving rivers, swamps and lakes. It can also be found in coastal swamps but avoids areas populated by saltwater crocodiles. [11] Feeds on a wide array of vertebrates.
Saltwater crocodile ( Crocodylus porosus ) Throughout Southeast Asia , Northern Australia and surrounding waters The largest living reptile and most aggressive of all crocodiles. It is a big-headed species and has a relatively broad snout, especially when older. The coloration is pale yellow with black stripes when young but dark greenish-drab coloured as adults. Lives in brackish and marine environments as well as lower stretches of rivers. This species has the greatest distribution of all crocodiles. Tagged specimens showed long-distance marine travelling behaviour. It is the apex predator throughout its range and preys on virtually any animal within its reach. It is classified as Least Concern with several populations under greater risk. [12]
Borneo crocodile (Crocodylus raninus) Island of Borneo in Southeast Asia A freshwater species of crocodile that has been considered a synonym of the saltwater crocodile.
Cuban crocodile ( Crocodylus rhombifer ) Found only in the Zapata Swamp and Isle of Youth of Cuba It is a small but extremely aggressive species of crocodile that prefers freshwater swamps. [13] The coloration is vibrant even as adults and the scales have a "pebbled" appearance. It is a relatively terrestrial species with agile locomotion on land, and sometimes displays terrestrial hunting. The snout is broad with a thick upper-jaw and large teeth. The unique characteristics and fossil record indicates a rather specialized diet in the past, preying on megafauna such as the giant sloth. This species sometimes displays pack-hunting behaviour, which might have been the key to hunting large species in the past, despite its small size. [14] Today most prey are small to medium sized vertebrates. It is Critically Endangered, and the remaining wild population is under threat of hybridization. [15]
Siamese crocodile ( Crocodylus siamensis ) Indonesia, Brunei, East Malaysia and southern Indochina A fairly small crocodile that prefers freshwater habitats. It has a relatively broad snout and olive-green to dark green coloration. It feeds on a variety of small to mid-sized vertebrates. Listed as Critically Endangered, but might be already extinct in the wild status is unknown. [16]
West African crocodile ( Crocodylus suchus ) Western and Central Africa Recent studies revealed that this is distinct species from the larger Nile crocodile. [17] [18] It has a slightly narrower snout and is much smaller compared to its larger cousin.
Dwarf crocodile ( Osteolaemus tetraspis ) Western Africa It is the smallest of all living crocodiles. It belongs to its own monotypic genus however, new studies indicate there might be two or even three distinct species. [19] It is a heavily armoured species with uniform black coloration in adults, while juveniles have a lighter brown banding. Lives in the tropical forests of Western Africa. Feeds on small vertebrates and large aquatic invertebrates. It is a fairly terrestrial species and exhibits terrestrial hunting, especially at night. This species is classified as Vulnerable.
West African slender-snouted crocodile ( Mecistops cataphractus ) Western Africa A medium sized species with a narrow and elongated snout. Lives in freshwater habitats within tropical forests of the continent. Feeds mostly on fish but also other small to medium sized vertebrates. It is a Critically Endangered species.
Central African slender-snouted crocodile (Mecistops leptorhynchus) Central Africa A medium sized species found in watery areas in dense rainforest. Feeds largely on fish. Insufficient conservation data, but was classified as Critically Endangered when lumped with M. cataphractus, although M. leptorhynchus is doing better in its home range.

A crocodile's physical traits allow it to be a successful predator. Its external morphology is a sign of its aquatic and predatory lifestyle. Its streamlined body enables it to swim swiftly it also tucks its feet to the side while swimming, making it faster by decreasing water resistance. Crocodiles have webbed feet which, though not used to propel them through the water, allow them to make fast turns and sudden moves in the water or initiate swimming. Webbed feet are an advantage in shallow water, where the animals sometimes move around by walking. Crocodiles have a palatal flap, a rigid tissue at the back of the mouth that blocks the entry of water. The palate has a special path from the nostril to the glottis that bypasses the mouth. The nostrils are closed during submergence.

Like other archosaurs, crocodilians are diapsid, although their post-temporal fenestrae are reduced. The walls of the braincase are bony but lack supratemporal and postfrontal bones. [20] Their tongues are not free, but held in place by a membrane that limits movement as a result, crocodiles are unable to stick out their tongues. [21] Crocodiles have smooth skin on their bellies and sides, while their dorsal surfaces are armoured with large osteoderms. The armoured skin has scales and is thick and rugged, providing some protection. They are still able to absorb heat through this armour, as a network of small capillaries allows blood through the scales to absorb heat. The osteoderms are highly vascularised and aid in calcium balance, both to neutralize acids while the animal cannot breathe underwater [22] and to provide calcium for eggshell formation. [23] Crocodilian tegument have pores believed to be sensory in function, analogous to the lateral line in fishes. They are particularly seen on their upper and lower jaws. Another possibility is that they are secretory, as they produce an oily substance which appears to flush mud off. [20]

Size greatly varies among species, from the dwarf crocodile to the saltwater crocodile. Species of the dwarf crocodile Osteolaemus grow to an adult size of just 1.5 to 1.9 m (4.9 to 6.2 ft), [24] whereas the saltwater crocodile can grow to sizes over 7 m (23 ft) and weigh 1,000 kg (2,200 lb). [25] Several other large species can reach over 5.2 m (17 ft) long and weigh over 900 kg (2,000 lb). Crocodilians show pronounced sexual dimorphism, with males growing much larger and more rapidly than females. [20] Despite their large adult sizes, crocodiles start their lives at around 20 cm (7.9 in) long. The largest species of crocodile is the saltwater crocodile, found in eastern India, northern Australia, throughout South-east Asia, and in the surrounding waters.

The brain volume of two adult crocodiles was 5.6 cm 3 for a spectacled caiman and 8.5 cm 3 for a larger Nile crocodile. [26]

The largest crocodile ever held in captivity is a saltwater–Siamese hybrid named Yai (Thai: ใหญ่ , meaning big born 10 June 1972) at the Samutprakarn Crocodile Farm and Zoo, Thailand. This animal measures 6 m (20 ft) in length and weighs 1,114 kg (2,456 lb). [27]

The longest crocodile captured alive was Lolong, a saltwater crocodile which was measured at 6.17 m (20.2 ft) and weighed at 1,075 kg (2,370 lb) by a National Geographic team in Agusan del Sur Province, Philippines. [28] [29] [30]

Teeth

Crocodiles are polyphyodonts they are able to replace each of their 80 teeth up to 50 times in their 35- to 75-year lifespan. [31] [32] Next to each full-grown tooth, there is a small replacement tooth and an odontogenic stem cell in the dental lamina in standby that can be activated if required. [33]

Crocodilians are more closely related to birds and dinosaurs than to most animals classified as reptiles, the three families being included in the group Archosauria ('ruling reptiles'). Despite their prehistoric look, crocodiles are among the more biologically complex reptiles. Unlike other reptiles, a crocodile has a cerebral cortex and a four-chambered heart. Crocodilians also have the functional equivalent of a diaphragm by incorporating muscles used for aquatic locomotion into respiration. [34] Salt glands are present in the tongues of crocodiles and they have a pore opening on the surface of the tongue, a trait that separates them from alligators. Salt glands are dysfunctional in Alligatoridae. [20] Their function appears to be similar to that of salt glands in marine turtles. Crocodiles do not have sweat glands and release heat through their mouths. They often sleep with their mouths open and may pant like a dog. [35] Four species of freshwater crocodile climb trees to bask in areas lacking a shoreline. [36]

Senses

Crocodiles have acute senses, an evolutionary advantage that makes them successful predators. The eyes, ears and nostrils are located on top of the head, allowing the crocodile to lie low in the water, almost totally submerged and hidden from prey.

Vision

Crocodiles have very good night vision, and are mostly nocturnal hunters. They use the disadvantage of most prey animals' poor nocturnal vision to their advantage. The light receptors in crocodilians' eyes include cones and numerous rods, so it is assumed all crocodilians can see colours. [37] Crocodiles have vertical-slit shaped pupils, similar to those of domestic cats. One explanation for the evolution of slit pupils is that they exclude light more effectively than a circular pupil, helping to protect the eyes during daylight. [38] On the rear wall of the eye is a tapetum lucidum, which reflects incoming light back onto the retina, thus utilizing the small amount of light available at night to best advantage. In addition to the protection of the upper and lower eyelids, crocodiles have a nictitating membrane (sometimes called a "third eye-lid") that can be drawn over the eye from the inner corner while the lids are open. The eyeball surface is thus protected under the water while a certain degree of vision is still possible. [39]

Olfaction

Crocodilian sense of smell is also very well developed, aiding them to detect prey or animal carcasses that are either on land or in water, from far away. It is possible that crocodiles use olfaction in the egg prior to hatching. [39]

Chemoreception in crocodiles is especially interesting because they hunt in both terrestrial and aquatic surroundings. Crocodiles have only one olfactory chamber and the vomeronasal organ is absent in the adults [40] indicating all olfactory perception is limited to the olfactory system. Behavioural and olfactometer experiments indicate that crocodiles detect both air-borne and water-soluble chemicals and use their olfactory system for hunting. When above water, crocodiles enhance their ability to detect volatile odorants by gular pumping, a rhythmic movement of the floor of the pharynx. [41] [42] Crocodiles close their nostrils when submerged, so olfaction underwater is unlikely. Underwater food detection is presumably gustatory and tactile. [43]

Hearing

Crocodiles can hear well their tympanic membranes are concealed by flat flaps that may be raised or lowered by muscles. [20]

Touch

Cranial: The upper and lower jaws are covered with sensory pits, visible as small, black speckles on the skin, the crocodilian version of the lateral line organs seen in fish and many amphibians, though arising from a completely different origin. These pigmented nodules encase bundles of nerve fibers innervated beneath by branches of the trigeminal nerve. They respond to the slightest disturbance in surface water, detecting vibrations and small pressure changes as small as a single drop. [44] This makes it possible for crocodiles to detect prey, danger and intruders, even in total darkness. These sense organs are known as domed pressure receptors (DPRs). [45]

Post-Cranial: While alligators and caimans have DPRs only on their jaws, crocodiles have similar organs on almost every scale on their bodies. The function of the DPRs on the jaws is clear to catch prey, but it is still not clear what the function is of the organs on the rest of the body. The receptors flatten when exposed to increased osmotic pressure, such as that experienced when swimming in sea water hyperosmotic to the body fluids. When contact between the integument and the surrounding sea water solution is blocked, crocodiles are found to lose their ability to discriminate salinities. It has been proposed that the flattening of the sensory organ in hyperosmotic sea water is sensed by the animal as "touch", but interpreted as chemical information about its surroundings. [45] This might be why in alligators they are absent on the rest of the body. [46]

Hunting and diet

Crocodiles are ambush predators, waiting for fish or land animals to come close, then rushing out to attack. Crocodiles mostly eat fish, amphibians, crustaceans, molluscs, birds, reptiles, and mammals, and they occasionally cannibalize smaller crocodiles. What a crocodile eats varies greatly with species, size and age. From the mostly fish-eating species, like the slender-snouted and freshwater crocodiles, to the larger species like the Nile crocodile and the saltwater crocodile that prey on large mammals, such as buffalo, deer and wild boar, diet shows great diversity. Diet is also greatly affected by the size and age of the individual within the same species. All young crocodiles hunt mostly invertebrates and small fish, gradually moving on to larger prey. Being ectothermic (cold-blooded) predators, they have a very slow metabolism, so they can survive long periods without food. Despite their appearance of being slow, crocodiles have a very fast strike and are top predators in their environment, and various species have been observed attacking and killing other predators such as sharks and big cats. [47] [48] Crocodiles are also known to be aggressive scavengers who feed upon carrion and steal from other predators. [49] Evidence suggests that crocodiles also feed upon fruits, based on the discovery of seeds in stools and stomachs from many subjects as well as accounts of them feeding. [50] [51]

Crocodiles have the most acidic stomach of any vertebrate. They can easily digest bones, hooves and horns. The BBC TV [52] reported that a Nile crocodile that has lurked a long time underwater to catch prey builds up a large oxygen debt. When it has caught and eaten that prey, it closes its right aortic arch and uses its left aortic arch to flush blood loaded with carbon dioxide from its muscles directly to its stomach the resulting excess acidity in its blood supply makes it much easier for the stomach lining to secrete more stomach acid to quickly dissolve bulks of swallowed prey flesh and bone. Many large crocodilians swallow stones (called gastroliths or stomach stones), which may act as ballast to balance their bodies or assist in crushing food, [20] similar to grit ingested by birds. Herodotus claimed that Nile crocodiles had a symbiotic relationship with certain birds, such as the Egyptian plover, which enter the crocodile's mouth and pick leeches feeding on the crocodile's blood with no evidence of this interaction actually occurring in any crocodile species, it is most likely mythical or allegorical fiction. [53]

Since they feed by grabbing and holding onto their prey, they have evolved sharp teeth for piercing and holding onto flesh, and powerful muscles to close the jaws and hold them shut. The teeth are not well-suited to tearing flesh off of large prey items as are the dentition and claws of many mammalian carnivores, the hooked bills and talons of raptorial birds, or the serrated teeth of sharks. However, this is an advantage rather than a disadvantage to the crocodile since the properties of the teeth allow it to hold onto prey with the least possibility of the prey animal escaping. Cutting teeth, combined with the exceptionally high bite force, would pass through flesh easily enough to leave an escape opportunity for prey. The jaws can bite down with immense force, by far the strongest bite of any animal. The force of a large crocodile's bite is more than 5,000 lbf (22,000 N), which was measured in a 5.5 m (18 ft) Nile crocodile, in the field [54] comparing to 335 lbf (1,490 N) for a Rottweiler, 800 lbf (3,600 N) for a hyena, 2,200 lbf (9,800 N) for an American alligator, [55] [ failed verification ] and 4,095 lbf (18,220 N) for the largest confirmed great white shark. [56] A 5.2 m (17 ft) long saltwater crocodile has been confirmed as having the strongest bite force ever recorded for an animal in a laboratory setting. It was able to apply a bite force value of 3,700 lbf (16,000 N), and thus surpassed the previous record of 2,125 lbf (9,450 N) made by a 3.9 m (13 ft) long American alligator. [57] [58] Taking the measurements of several 5.2 m (17 ft) crocodiles as reference, the bite forces of 6-m individuals were estimated at 7,700 lbf (34,000 N). [59] The study, led by Dr. Gregory M. Erickson, also shed light on the larger, extinct species of crocodilians. Since crocodile anatomy has changed only slightly over the last 80 million years, current data on modern crocodilians can be used to estimate the bite force of extinct species. An 11-to-12-metre (36–39 ft) Deinosuchus would apply a force of 23,100 lbf (103,000 N), nearly twice that of the latest, higher bite force estimations of Tyrannosaurus (12,814 lbf (57,000 N)). [7] [60] [61] [62] The extraordinary bite of crocodilians is a result of their anatomy. The space for the jaw muscle in the skull is very large, which is easily visible from the outside as a bulge at each side. The muscle is so stiff, it is almost as hard as bone to touch, as if it were the continuum of the skull. Another trait is that most of the muscle in a crocodile's jaw is arranged for clamping down. Despite the strong muscles to close the jaw, crocodiles have extremely small and weak muscles to open the jaw. Crocodiles can thus be subdued for study or transport by taping their jaws or holding their jaws shut with large rubber bands cut from automobile inner tubes.

Locomotion

Crocodiles can move quickly over short distances, even out of water. The land speed record for a crocodile is 17 km/h (11 mph) measured in a galloping Australian freshwater crocodile. [63] Maximum speed varies between species. Some species can gallop, including Cuban crocodiles, Johnston's crocodiles, New Guinea crocodiles, African dwarf crocodiles, and even small Nile crocodiles. The fastest means by which most species can move is a "belly run", in which the body moves in a snake-like (sinusoidal) fashion, limbs splayed out to either side paddling away frantically while the tail whips to and fro. Crocodiles can reach speeds of 10–11 km/h (6–7 mph) when they "belly run", and often faster if slipping down muddy riverbanks. When a crocodile walks quickly, it holds its legs in a straighter and more upright position under its body, which is called the "high walk". This walk allows a speed of up to 5 km/h. [64]

Crocodiles may possess a homing instinct. In northern Australia, three rogue saltwater crocodiles were relocated 400 km (249 mi) by helicopter, but returned to their original locations within three weeks, based on data obtained from tracking devices attached to them. [65]

Longevity

Measuring crocodile age is unreliable, although several techniques are used to derive a reasonable guess. The most common method is to measure lamellar growth rings in bones and teeth—each ring corresponds to a change in growth rate which typically occurs once a year between dry and wet seasons. [66] Bearing these inaccuracies in mind, it can be safely said that all crocodile species have an average lifespan of at least 30–40 years, and in the case of larger species an average of 60–70 years. The oldest crocodiles appear to be the largest species. C. porosus is estimated to live around 70 years on average, with limited evidence of some individuals exceeding 100 years. [67]

In captivity, some individuals are claimed to have lived for over a century. A male crocodile lived to an estimated age of 110–115 years in a Russian zoo in Yekaterinburg. [68] Named Kolya, he joined the zoo around 1913 to 1915, fully grown, after touring in an animal show, and lived until 1995. [68] A male freshwater crocodile lived to an estimated age of 120–140 years at the Australia Zoo. [69] Known affectionately as "Mr. Freshie", he was rescued around 1970 by Bob Irwin and Steve Irwin, after being shot twice by hunters and losing an eye as a result, and lived until 2010. [69] Crocworld Conservation Centre, in Scottburgh, South Africa, claims to have a male Nile crocodile that was born in 1900. Named Henry, the crocodile is said to have lived in Botswana along the Okavango River, according to centre director Martin Rodrigues. [70] [71]

Social behaviour and vocalization

Crocodiles are the most social of reptiles. Even though they do not form social groups, many species congregate in certain sections of rivers, tolerating each other at times of feeding and basking. Most species are not highly territorial, with the exception of the saltwater crocodile, which is a highly territorial and aggressive species: a mature, male saltwater crocodile will not tolerate any other males at any time of the year, but most other species are more flexible. There is a certain form of hierarchy in crocodiles: the largest and heaviest males are at the top, having access to the best basking site, while females are priority during a group feeding of a big kill or carcass. A good example of the hierarchy in crocodiles would be the case of the Nile crocodile. This species clearly displays all of these behaviours. Studies in this area are not thorough, however, and many species are yet to be studied in greater detail. [72] Mugger crocodiles are also known to show toleration in group feedings and tend to congregate in certain areas. However, males of all species are aggressive towards each other during mating season, to gain access to females.

Crocodiles are also the most vocal of all reptiles, producing a wide variety of sounds during various situations and conditions, depending on species, age, size and sex. Depending on the context, some species can communicate over 20 different messages through vocalizations alone. [73] Some of these vocalizations are made during social communication, especially during territorial displays towards the same sex and courtship with the opposite sex the common concern being reproduction. Therefore most conspecific vocalization is made during the breeding season, with the exception being year-round territorial behaviour in some species and quarrels during feeding. Crocodiles also produce different distress calls and in aggressive displays to their own kind and other animals notably other predators during interspecific predatory confrontations over carcasses and terrestrial kills.

Specific vocalisations include —

  • Chirp: When about to hatch, the young make a "peeping" noise, which encourages the female to excavate the nest. The female then gathers the hatchlings in her mouth and transports them to the water, where they remain in a group for several months, protected by the female [74]
  • Distress call: A high-pitched call used mostly by younger animals to alert other crocodiles to imminent danger or an animal being attacked.
  • Threat call: A hissing sound that has also been described as a coughing noise.
  • Hatching call: Emitted by a female when breeding to alert other crocodiles that she has laid eggs in her nest.
  • Bellowing: Male crocodiles are especially vociferous. Bellowing choruses occur most often in the spring when breeding groups congregate, but can occur at any time of year. To bellow, males noticeably inflate as they raise the tail and head out of water, slowly waving the tail back and forth. They then puff out the throat and with a closed mouth, begin to vibrate air. Just before bellowing, males project an infrasonic signal at about 10 Hz through the water, which vibrates the ground and nearby objects. These low-frequency vibrations travel great distances through both air and water to advertise the male's presence and are so powerful they result in the water's appearing to "dance". [75]

Reproduction

Crocodiles lay eggs, which are laid in either holes or mound nests, depending on species. A hole nest is usually excavated in sand and a mound nest is usually constructed out of vegetation. Nesting periods range from a few weeks up to six months. Courtship takes place in a series of behavioural interactions that include a variety of snout rubbing and submissive display that can take a long time. Mating always takes place in water, where the pair can be observed mating several times. Females can build or dig several trial nests which appear incomplete and abandoned later. Egg-laying usually takes place at night and about 30–40 minutes. [76] Females are highly protective of their nests and young. The eggs are hard shelled, but translucent at the time of egg-laying. Depending on the species of crocodile, 7 to 95 eggs are laid. Crocodile embryos do not have sex chromosomes, and unlike humans, sex is not determined genetically. Sex is determined by temperature, where at 30 °C (86 °F) or less most hatchlings are females and at 31 °C (88 °F), offspring are of both sexes. A temperature of 32 to 33 °C (90 to 91 °F) gives mostly males whereas above 33 °C (91 °F) in some species continues to give males, but in other species resulting in females, which are sometimes called high-temperature females. [77] Temperature also affects growth and survival rate of the young, which may explain the sexual dimorphism in crocodiles. The average incubation period is around 80 days, and also is dependent on temperature and species that usually ranges from 65 to 95 days. The eggshell structure is very conservative through evolution but there are enough changes to tell different species apart by their eggshell microstructure. [78] Scutes may play a role in calcium storage for eggshell formation. [23]

At the time of hatching, the young start calling within the eggs. They have an egg-tooth at the tip of their snouts, which is developed from the skin, and that helps them pierce out of the shell. Hearing the calls, the female usually excavates the nest and sometimes takes the unhatched eggs in her mouth, slowly rolling the eggs to help the process. The young is usually carried to the water in the mouth. She would then introduce her hatchlings to the water and even feed them. [79] The mother would then take care of her young for over a year before the next mating season. In the absence of the mother crocodile, the father would act in her place to take care of the young. [80] However, even with a sophisticated parental nurturing, young crocodiles have a very high mortality rate due to their vulnerability to predation. [81] A group of hatchlings is called a pod or crèche and may be protected for months. [76]

Cognition

Crocodiles possess some advanced cognitive abilities. [82] [83] [84] They can observe and use patterns of prey behaviour, such as when prey come to the river to drink at the same time each day. Vladimir Dinets of the University of Tennessee, observed that crocodiles use twigs as bait for birds looking for nesting material. [85] They place sticks on their snouts and partly submerge themselves. When the birds swooped in to get the sticks, the crocodiles then catch the birds. Crocodiles only do this in spring nesting seasons of the birds, when there is high demand for sticks to be used for building nests. Vladimir also discovered other similar observations from various scientists, some dating back to the 19th century. [82] [84] Aside from using sticks, crocodiles are also capable of cooperative hunting. [84] [86] Large numbers of crocodiles swim in circles to trap fish and take turns snatching them. In hunting larger prey, crocodiles swarm in, with one holding the prey down as the others rip it apart.

According to a 2015 study, crocodiles engage in all three main types of play behaviour recorded in animals: locomotor play, play with objects and social play. Play with objects is reported most often, but locomotor play such as repeatedly sliding down slopes, and social play such as riding on the backs of other crocodiles is also reported. This behaviour was exhibited with conspecifics and mammals and is apparently not uncommon, though has been difficult to observe and interpret in the past due to obvious dangers of interacting with large carnivores. [87]

Crocodylidae contains two subfamilies: Crocodylinae and Osteolaeminae. [88] Crocodylinae contains 13-14 living species, as well as 6 extinct species. Osteolaeminae was named by Christopher Brochu in 2003 as a subfamily of Crocodylidae separate from Crocodylinae, [89] and contains the two extant genera Osteolaemus and Mecistops, along with several extinct genera. The number of extant species within Osteolaeminae is currently in question. [19]


The Saltwater crocodile, and all that it implies (crocodiles part III)

Crocodiles of the World – part III! Part I is here part II is here.

The Saltwater crocodile Crocodylus porosus, also known as the Estuarine crocodile, Indopacific crocodile or Saltie, is one of the world’s most famous crocodile species, probably being second in line after the Nile croc C. niloticus. Part of the reason this species is so well known to the public is that it often features in films and on TV it’s also famous because it can be large or very large, because it’s a capable macropredator of big mammals, including humans, and because it’s at home in marine habitats as well as terrestrial ones.

As is well known, there are stories of Salties exceeding 8 m, 9 m and even 10 m in total length (a specimen killed in Bangladesh in 1840 was said to be 10.05 m long). It shouldn’t be assumed that these sizes are impossible – maybe individuals did reach them in prehistoric or historic times – but the maximum lengths of authenticated individuals have been about 6.2 m (for the Fly River 1982 specimen and the Mary River animal from the 1980s). Such large animals are – in the modern world – exceptional, and a big adult male Saltie is more typically between 4 m and 5 m long.

Incidentally, the thing often said about crocodilians exhibiting indeterminate growth and growing continually throughout life is probably not true. Determinate growth has now been demonstrated for the American alligator Alligator mississippiensis (Woodward et al. 2011) and is likely present across Crocodylia. Determinate growth is also known for various turtles, snakes, lizards and tuatara.

Saltwater crocs often frequent estuaries, lagoons and mangroves, but animals in some populations spend some or all of their time at sea. Extralimital records from the Cocos Islands southwest of Sumatra, from Fiji, and even from 48 km north of North Cape in New Zealand (Steel 1989) demonstrate an ability to travel far out to sea. Given this ability to live in the ocean and travel so far, why hasn’t the species spread further? Maybe it has, since a skull from the Seychelles show that it has occasionally moved west across the Indian Ocean to within just 1500 km of the African coast (Gerlach & Canning 1993). How far east have they travelled? I'll leave that one to the cryptozoologists. Anyway, recent satellite tagging work has shown that Saltwater crocs exploit sea-surface currents when travelling at sea – a behaviour that became tagged as ‘surfing’ in the popular media – and that this exploitation of marine currents is an important bit of dispersal behaviour in this species (Campbell et al. 2010).

Saltwater crocodiles are one of the easiest crocodile species to identify, mostly because they (normally) entirely lack large scutes between the cervical shield and the back of the head. [Adjacent image by Holger Krisp, Ulm, Germany.] In addition, an obvious gap is also present between the cervical and dorsal shields, and small, triangular scutes are present between the posterior edges of the large, transversely arranged scutes in the dorsal shield (Ross & Mayer 1983). This combination isn’t present in any other species, and it’s a ‘reduced’ compliment compared to what’s present in most other crocodiles. Elsewhere in living crocs, a reduced osteoderm compliment is also present in the American crocodile C. acutus. It’s probably not coincidental that this is also a species with a strong preference for swimming at sea.

The evolving view of crocodile phylogeny once again

We saw in previous articles that crocodiles have often been imagined to consist of distinct Indopacific and New World assemblages, with the Nile crocodile being a close relative of the New World assemblage. Within this (morphology-based) framework, the Saltie is a member of the Indopacific assemblage, and thus close to the Freshwater crocodile C. johnstoni, Philippine crocodile C. mindorensis and New Guinea crocodile C. novaeguineae (Brochu 2000a, b).

However, molecular work has indicated that things may actually be more complicated, with the Indopacific assemblage being non-monophyletic. Rather than being closest to the Freshwater croc and so on, some authors have reported a close affinity between the Saltie and the Mugger (e.g., Densmore & Owen 1989, Gatesy & Amato 2008) others have advocated a sister-group relationship between the Saltie and the Siamese crocodile (McAliley et al. 2006, Meganathan et al. 2010) and yet others find a close relationship between the Saltie and a Siamese crocodile + Mugger clade (Man et al. 2011, Oaks 2011). On balance, it does seem that the Saltwater crocodile is closest to the Mugger and/or the Siamese crocodile. Purely for convenience, I’ll call this the ‘porosus clade’.

With the three members of the ‘porosus clade’ separated from the remainder of the Indopacific assemblage, we’re left with a ‘reduced’ Indopacific assemblage as mentioned last time. Is the ‘porosus clade’ closer to the Nile croc + New World assemblage clade than is the ‘reduced’ Indopacific assemblage? (as per Oaks 2011). Or is the ‘reduced’ Indopacific assemblage closer to the Nile croc + New World assemblage clade than is the ‘porosus clade’? (as in McAliley et al. 2006). We’re not sure – more work is needed.

Anyway, what we do know has some interesting implications. Firstly, it doesn’t seem that Australia's two native crocs - the Saltwater and Freshwater crocodile - are all that close phylogenetically.

Secondly, given that most phylogenetic analyses find the crocodiles of southern Asia and Australasia to be outside the clade that includes the Nile crocodile and the New World assemblage, an Asian-Australasian/Indopacific centre of origin for crocodiles currently looks more likely for Crocodylus (Oaks 2011) than the African origin favoured traditionally. Then again, Osteolaemus and Mecistops are African (as are other, fossil, osteolaemines), and there are fossil members of Crocodylus in Africa too, like the Miocene C. checchiai and the Plio-Pleistocene C. anthropophagus and C. thorbjarnarsoni (Brochu et al. 2010, Brochu & Storrs 2012) (note that other alleged African species of Crocodylus – like ‘C.’ gariepensis from the early Miocene of the Namibia/South Africa border and ‘C.’ pigotti from the early Miocene of Kenya – are not actually within Crocodylus). Is it that all African members of Crocodylus invaded the continent following origination in Asia or Australasia? Or might it still be possible that Crocodylus began its history in Africa and/or Asia? We’ll come back to this issue again in a later article.

If there is a ‘porosus clade’ as discussed above, the fact that Muggers and Siamese crocs are both Asian might mean that the Saltie originated in Asia before colonising Australasia. But, then, people have assumed this anyway given that the Saltie’s Australasian range ‘only’ encompasses New Guinea and the northern, coastal parts of Australia (plus the island groups between and around these regions).

Crocodylus porosus, the… species complex?

The Saltwater crocodile varies a reasonable amount in appearance and body size across its extensive range. For these reasons there have been various suggestions that C. porosus of tradition is actually a species complex that needs splitting up. [Image above of C. porosus skull by Mariomassone.]

In 1844, S. Müller and H. Schlegel suggested that a distinct blunt-snouted population could be recognised among crocodiles then known as C. biporcatus (a name now regarded as a junior synonym of C. porosus) they named this new animal C. raninus. Of the several Javanese and Bornean specimens used in the naming of C. raninus, the two Javanese ones proved to be Siamese crocodiles (Ross 1992). However, the remaining, Bornean individuals could, according to Ross (1992), be reliably distinguished from both the Siamese crocodile as well as from unquestionable C. porosus on the basis of ventral scale counts and on the presence of four postoccipital scutes (the ones arranged just behind the rear margin of the head). Ross’s (1990, 1992) support for the distinction of C. raninus – sometimes known as the Indonesian crocodile or Bornean crocodile – has been followed by some other authors, but the name can’t yet be said to be in universal use. A skull, discovered in Brunei in 1990, has been identified as that of C. raninus (Trutnau & Sommerlad 2006).

Those with a good knowledge of Australasian herpetology will be familiar with Richard W. Wells and C. Ross Wellington’s several publications on the Australasian herpetofauna. This is not the time and place to discuss their articles or the controversy and debate that has surrounded them, but I do need to note very briefly that the numerous taxonomic revisions and proposals made by these authors remain (for the most part) highly controversial. Anyway, Wells and Wellington made two suggestions about Saltwater crocodiles that should be noted here.

Firstly, they suggested that C. porosus included a previously overlooked species of especially large, proportionally short-tailed, large-headed crocodile native to the Finnis and Reynolds Rivers in Northern Territory (Wells & Wellington 1985). They named this supposed species C. pethericki (after Australian biologist Ray Petherick) and designated ‘Sweetheart’ as the holotype. ‘Sweetheart’ was a male Saltwater croc (5.1 m long), captured in July 1979 following a number of incidents where he attacked and damaged boats. Unfortunately, he drowned during capture and is today preserved as a taxidermy mount at the Museum and Art Gallery of the Northern Territory [see photo below by Jpatokal].

According to Wells & Wellington (1985), C. pethericki differs from C. porosus in details of scalation, overall colour (blackish with white venter vs browner with yellowish venter) and eyeshine colour (whitish-blue vs reddish), as well as in proportions. However, their proposal of taxonomic distinction for this form has not been accepted by other workers and it’s generally assumed that the differences they reported are within individual variation, or are related to ontogeny or adaptation to local conditions.

Secondly, Wells & Wellington (1985) questioned the otherwise widely-held opinion that the Saltwater crocs of Australia are conspecific with those of Asia, and hinted at the idea that more than one overlooked species might exist in Australia. This didn’t result in any additional nomenclatural acts, however. The majority of crocodilian experts have not regarded Wells and Wellington's suggestions as worthy of proper investigation. As we'll see in a later article, they made yet other suggestions about the taxonomy and phylogeny of Australian crocodiles.

Here end our all-too-brief look at one of the world’s largest and most charismatic predators. Time to move on. What about the other members of the Indopacific assemblage: the New Guinea and Philippine crocodiles, and the Freshwater crocodile? That’s where we’re going next.

For previous articles on crocodiles, see.

NEWS: TET ZOO VER 2 CONTENT SEEMS TO BE BACK ONLINE AT LEAST SOME ARTICLES HAVE BEEN RESTORED WITH ALL COMMENTS!

Brochu, C. A. 2000a. Congruence between physiology, phylogenetics and the fossil record on crocodylian historical biogeography. In Grigg, G. C., Seebacher, F. & Franklin, C. E. (eds) Crocodilian Biology and Evolution. Surry Beatty & Sons (Chipping Norton, Aus.), pp. 9-28.

- . 2000b. Phylogenetic relationships and divergence timing of Crocodylus based on morphology and the fossil record. Copeia 2000, 657-673.

- . & Storrs, G. W. 2012. A giant crocodile from the Plio-Pleistocene of Kenya, the phylogenetic relationships of Neogene African crocodylines, and the antiquity of Crocodylus in Africa. Journal of Vertebrate Paleontology 32, 587-602.

Campbell, H. A., Watts, M. E., Sullivan, S., Read, M. A., Choukroun, S., Irwin, S. R. & Franklin, C. E. 2010. Estuarine crocodiles ride surface currents to facilitate long-distance travel. Journal of Animal Ecology 79, 955-964.

Densmore, L. D. & Owen, R. D. 1989. Molecular systematics of the order Crocodilia. American Zoologist 29, 831-841.

Gatesy, J. & Amato, G. 2008. The rapid accumulation of consistent molecular support for intergeneric crocodilian relationships. Molecular Phylogenetics and Evolution 48, 1232-1237.

Gerlach, J. & Canning, L. 1993. On the crocodiles of the western Indian Ocean. Phelsuma 2, 54-58.

Man, Z., Yishu, W., Peng, Y. & Wu, X. 2011. Crocodilian phylogeny inferred from twelve mitochondrial protein-coding genes, with new complete mitochondrial genomic sequences for Crocodylus acutus and Crocodylus novaeguineae. Molecular Phylogenetic and Evolution 60, 62-67.

McAliley LR, Willis RE, Ray DA, White PS, Brochu CA, & Densmore LD 3rd (2006). Are crocodiles really monophyletic?--Evidence for subdivisions from sequence and morphological data. Molecular phylogenetics and evolution, 39 (1), 16-32 PMID: 16495085

Meganathan, P. R., Dubey, B., Batzer, M. A., Ray, D. A. & Haque, I. 2010. Molecular phylogenetic analyses of genus Crocodylus (Eusuchia, Crocodylia, Crocodylidae) and the taxonomic position of Crocodylus porosus. Molecular Phylogenetics and Evolution 57, 393-402.

Oaks, J. R. 2011. A time-calibrated species tree of Crocodylia reveals a recent radiation of the true crocodiles. Evolution 65, 3285-3297.

Ross, C. A. 1990. Crocodylus raninus S. Müller and Schlegel, a valid species of crocodile (Reptilia: Crocodylidae) from Borneo. Proceedings of the Biological Society of Washington 103, 955-961.

- . 1992. Designation of a lectotype for Crocodylus raninus S. Müller and Schlegel (Reptilia: Crocodylidae), the Borneo crocodile. Proceedings of the Biological Society of Washington 105, 400-402.

Ross, F. D. & Mayer, G. C. 1983. On the dorsal armor of the Crocodilia. In Rhodin, A. G. J. & Miyata, K. (eds) Advances in Herpetology and Evolutionary Biology. Museum of Comparative Zoology (Cambridge, Mass.), pp. 306-331.

Steel, R. 1989. Crocodiles. Christopher Helm, London.

Trutnau, L. & Sommerlad, R. 2006. Crocodilians: Their Natural History and Captive Husbandry. Edition Chimaira, Frankfurt.

Wells, R. W. & Wellington, C. R. 1985. A classification of the Amphibia and Reptilia of Australia. Australian Journal of Herpetology, Suppl. Ser. 1, 1-61.

Woodward, H. N., Horner, J. R. & Farlow, J. O. 2011. Osteohistological evidence for determinate growth in the American alligator. Journal of Herpetology 45, 339-342.

The views expressed are those of the author(s) and are not necessarily those of Scientific American.


Taxonomy and evolution

Crocodilus porosus was the logical name proposed by Johann Gottlob Theaenus Schneider who depicted a zoological example in 1801. In the nineteenth and twentieth hundreds of years, a few saltwater crocodile examples were portrayed with the accompanying names:

Crocodilus biporcatus proposed by Georges Cuvier in 1807 were 23 saltwater crocodile examples from India, Java, and Timor.

Crocodilus biporcatus raninus proposed by Salomon Müller and Hermann Schlegel in 1844 was a crocodile from Borneo.

Crocodylus porosus australis proposed by Paulus Edward Pieris Deraniyagala in 1953 was an example from Australia.

Crocodylus pethericki proposed by Richard Wells and C. Ross Wellington in 1985 was an enormous bodied, moderately huge headed and short-followed crocodile example gathered in 1979 in the Finnis River, Northern Territory. This implied species was later viewed as an error of the physiological changes that huge male crocodiles experience. Be that as it may, Wells and Wellington’s affirmation that the Australian saltwater crocodiles might be particular enough from northern Asian saltwater crocodiles to warrant subspecies status, as could raninus from other Asian saltwater crocodiles, has been considered to potentially manage validity.

As of now, the saltwater crocodile is viewed as a monotypic species. However, in light of on morphological changeability, it is thought conceivable that the taxon C. porosus includes an animal varieties complex. Borneo crocodile C. raninus examples can dependably be recognized both from saltwater and Siamese crocodiles (C. siamensis) based on the number ventral scales and on the nearness of four postoccipital scutes, which are regularly missing in evident saltwater crocodiles.

Evolution

Fossil survives from a saltwater crocodile uncovered in northern Queensland were dated to the Pliocene. The most seasoned known Crocodylus fossils were dated to the Late Miocene. The saltwater crocodile is a sister taxon of the Nile crocodile and the Siamese crocodile.

Consequences of phylogenetic research demonstrate that Crocodylus developed in the Oligocene Indo-Pacific about 25.5–19.3 million years back. The warm and wet atmosphere in the tropics during this period may have encouraged the dispersal of crocodiles from Australasia to Africa without moving significant distances adrift. The hereditary ancestry including saltwater, Nile, and Siamese crocodiles is evaluated to have wandered 10.60–6.52 million years back. Nile and Siamese crocodiles most likely veered from this gathering 7.94–4.19 million years ago.

The saltwater crocodile has a wide nose contrasted with most crocodiles. Be that as it may, it has a more drawn out nose than the mugger crocodile (C. palustris) its length is twice its width at the base. A couple of edges runs from the eyes along with the focal point of the nose. The scales are oval fit as a fiddle and the scutes are either little contrasted with different species or regularly are completely missing. Likewise, a conspicuous hole is additionally present between the cervical and dorsal shields, and little, triangular scutes are available between the back edges of the huge, transversely organized scutes in the dorsal shield. The overall absence of scutes is viewed as a benefit helpful to recognize saltwater crocodiles in imprisonment or in illegal calfskin exchanging, just as in a couple of territories in the field where sub-grown-up or more youthful saltwater crocodiles may be recognized from different crocodiles. It has fewer protection plates on its neck than other crocodilians.

The grown-up saltwater crocodile’s extensive body appears differently in relation to that of most other slender crocodiles, prompting early unconfirmed presumptions the reptile was an alligator.

Youthful saltwater crocodiles are light yellow in shading with dark stripes and spots on their bodies and tails. This coloration goes on for quite a long while until the crocodiles develop into grown-ups. The shading as a grown-up is a lot darker greenish-dull, with a couple of lighter tan or hazy areas some of the time evident. A few shading varieties are known and a few grown-ups may hold genuinely fair skin, though others might be so dim as to seem blackish. The ventral surface is white or yellow in shading in saltwater crocodiles all things considered. Stripes are available on the lower sides of their bodies, yet don’t expand onto their tummies. Their tails are dim with dim bands.

The heaviness of crocodile increments roughly cubically as length builds (see square-3D shape law).This clarifies why people at 6 m (240 in) gauge more than twice that of people at 5 m (200 in). In crocodiles, straight development in the long run diminishes and they begin getting bulkier at a certain point.

Saltwater crocodiles are the biggest surviving riparian predators on the planet. Be that as it may, they start life genuinely little. Recently brought forth saltwater crocodiles measure around 28 cm (11 in) long and gauge a normal of 71 g (2.5 oz). These sizes and ages are practically indistinguishable from those at normal sexual development in Nile crocodiles, notwithstanding that normal grown-up male saltwater crocodiles are extensively bigger than normal grown-up male Nile crocodiles.

The biggest skull of a saltwater crocodile that could be deductively checked was of an example in the Muséum national d’Histoire Naturelle gathered in Cambodia. Its skull was 76 cm (30 in) long and 48 cm (19 in) wide close to its base, with 98.3 cm (38.7 in) long mandibles. The length of this example isn’t known yet dependent on skull-to-add up to length proportions for exceptionally huge saltwater crocodiles its length was probably someplace in the 7 m (280 in) range. If segregated from the body, the leader of an extremely huge male crocodile can supposedly weigh more than 200 kg (440 lb) alone, including the huge muscles and ligaments at the base of the skull that loan the crocodile its enormous gnawing strength. The biggest tooth estimated at 9 cm (3.5 in) in length. Other crocodilians have a proportionately longer skull, similar to the gharial (Gavialis gangeticus) and the bogus gharial (Tomistoma schlegelii), both their skulls and bodies are less gigantic than in the saltwater crocodile.

Male size: A grown-up male saltwater crocodile, from youthful grown-ups to more established people, ranges 3.5 to 6 m (140 to 240 in) long and gauges 200 to 1,000 kg (440 to 2,200 lb). by and large, grown-up guys extend 4.3 to 4.9 m (170 to 190 in) long and gauge 408 to 522 kg (899 to 1,151 lb). However normal size to a great extent relies upon the area, natural surroundings, and human connections, in this way changes starting with one investigation then onto the next, when figures of each examination are seen independently. In one case, Webb and Manolis (1989) ascribed the normal load of grown-up guys in Australian tidal waterways as just 240 to 350 kg (530 to 770 lb) at lengths of 4 to 4.5 m (160 to 180 in) during the 1980s, perhaps speaking to a decreased weight because of the species being in recuperation following quite a while of overhunting at that stage, as guys this size would regularly weigh around 100 kg (220 lb) heavier. Rarely huge, matured guys can surpass 6 m (240 in) long and weigh more than 1,000 kg (2,200 lb).

The biggest affirmed saltwater crocodile on record suffocated in an angling net in Papua New Guinea in 1979, its dried skin in addition to head estimated 6.2 m (240 in) long and it was evaluated to have been 6.3 m (250 in) when representing shrinkage and a missing tail tip. However, as indicated by proof, as skulls originating from probably the biggest crocodiles at any point shot, the greatest conceivable size achieved by the biggest individuals from this species is viewed as 7 m (280 in). An administrative report from Australia acknowledges that the biggest individuals from the species are probably going to quantify 6 to 7 m (240 to 280 in) long and gauge 900 to 1,500 kg (2,000 to 3,300 lb). Furthermore, an exploration paper on the morphology and physiology of crocodilians by a similar association appraises that saltwater crocodiles arriving at sizes of 7 m (280 in) would weigh around 2,000 kg (4,400 lb). Due to broad poaching during the twentieth century, such people are incredibly uncommon today in many regions, as it sets aside a long effort for the crocodiles to accomplish those sizes. Likewise, a potential prior nearness of specific qualities may have prompted such huge measured saltwater crocodiles, qualities that were at last lost from the general genetic stock because of broad cover-up and trophy chasing in the past.[citation needed] However, with rebuilding of the saltwater crocodile environment and decreased poaching, the quantity of enormous crocodiles is expanding, particularly in Odisha. This species is the main surviving crocodilian to normally reach or surpass 5.2 m (200 in). A huge male from the Philippines, named Lolong, was the biggest saltwater crocodile at any point got and put in imprisonment. He was 6.17 m (20.2 ft) long and weighed 1,075 kg (2,370 lb). Thought to have eaten two residents, Lolong was caught in September 2011 and kicked the bucket in imprisonment in February 2013.[citation needed]


Table of Contents

The poorly known Philippine freshwater crab, Sundathelphusa picta (von Martens, 1868) from Luzon Island is re-described and re-illustrated, using type material as well as other specimens sampled from near its type locality. Two similar congeners from Luzon, S. uva sp. nov. and S. angelito sp. nov., from the provinces of Bataan and Rizal, respectively, are described as new. These three species are united by their relatively small size, rounded and dome-shaped carapaces, proportionately short ambulatory legs, and stout male first gonopods. They are distinguished from each other by a suite of morphological characters, particularly of the carapace, male pleon and gonopods.

KEYWORDS: Decapoda, Sundathelphusa uva, Sundathelphusa angelito, taxonomy, Bataan, Bicol, Rizal

by Camila G. Meneses, Cameron D. Siler, Juan Carlos T. Gonzalez, Perry L. Wood, Jr., and Rafe M. Brown

Philippine Journal of Systematic Biology, Volume 14, Issue 2, 2020, DOI: 10.26757/pjsb2020b14002

Abstract (Primary Research Paper)

Date Posted (Final Published Version) :August 10, 2020

Abstract

We report on the first molecular estimates of phylogenetic relationships of Brachymeles dalawangdaliri (Scincidae) and Pseudogekko isapa (Gekkonidae), and present new data on phenotypic variation in these two poorly known taxa, endemic to the Romblon Island Group of the central Philippines. Because both species were recently described on the basis of few, relatively older, museum specimens collected in the early 1970s (when preservation of genetic material was not yet standard practice in biodiversity field inventories), neither taxon has ever been included in modern molecular phylogenetic analyses. Likewise, because the original type series for each species consisted of only a few specimens, biologists have been unable to assess standard morphological variation in either taxon, or statistically assess the importance of characters contributing to their diagnoses and identification. Here we ameliorate both historical shortfalls. First, our new genetic data allowed us to perform novel molecular phylogenetic analyses aimed at elucidating the evolutionary relationships of these lineages secondly, with population level phenotypic data, from the first statistical sample collected for either species, and including adults of both sexes. We reaffirm the distinctiveness of both named taxa as valid species, amend their diagnoses to facilitate the recognition of both, distinguish them from congeners, and consider the biogeographic affinities of both lineages. Our contribution emphasizes the conservation significance of Sibuyan Island’s Mt. Guiting-Guiting Natural Park, the diverse, idiosyncratic biogeographic histories of its variably-assembled, highly endemic reptile fauna, and the critical importance of multiple, repeated, survey–resurvey studies for understanding forest community species composition and the evolutionary history of Philippine biodiversity.

KEYWORDS: biodiversity, endemism, forest geckos, faunal region, fossoriality, limb reduction

by Emerson Y. Sy, Sabine Schoppe, Mae Lowe L. Diesmos, Theresa Mundita S. Lim, and Arvin C. Diesmos

Philippine Journal of Systematic Biology, Volume 14, Issue 2, 2020, DOI: 10.26757/pjsb2020b14003

Abstract (Primary Research Paper)

Date Posted (Final Published Version) :August 11, 2020

Abstract

The Philippine or Palawan Forest Turtle Siebenrockiella leytensis is the only endemic turtle known to occur in the Philippines. It was assessed as Critically Endangered in 2000 and has been considered as one of the world’s top 25 most endangered turtles since 2003. The species is accorded protection nationally by the Wildlife Protection and Conservation Act of 2001 and its international commercial trade is regulated by the Convention on International Trade in Endangered Species (CITES). However, the publication of its rediscovery in 2004 triggered unrelenting poaching and trafficking for the pet trade nationally and internationally. With the aim of quantifying the extent of poaching and to provide insight on the trade dynamics, we analyzed seizure records from 2004–2018 and conducted physical and online market surveys in 2017–2018. Twenty-three (23) seizure incidents involving 4,723 Philippine Forest Turtles were recorded in the last 15 years. Based on an online survey, we estimated that an additional 1,200 Philippine Forest Turtles were smuggled and illegally sold in China in 2015. The majority of the 74 live individuals exported legally from the Philippines were likely sourced illegally from the wild and declared fraudulently as captive bred by exporters to obtain CITES permits. While habitat loss or degradation is a major threat, the illegal pet trade remains the most important factor threatening the survival of the Philippine Forest Turtles in the wild.

KEYWORDS: chelonian, CITES, pet trade, trafficking, wildlife laundering

by Abner A. Bucol, Rainier I. Manalo, Angel C. Alcala, and Paulina S. Aspilla

Philippine Journal of Systematic Biology, Volume 14, Issue 2, 2020, DOI: 10.26757/pjsb2020b14004

Abstract (Primary Research Paper)

Date Posted (Final Published Version): November 2, 2020

Abstract

Crocodilians have been assumed to influence aquatic primary productivity and fishery yield. However, strong empirical evidence to support such claims is lacking. The long-standing assumption first hypothesized by Fittkau (1970), is that local fisheries (secondary productivity) in areas inhabited by crocodilians would be expected to improve. We tested this hypothesis at two locations in the Philippines, inhabited by the Philippine Crocodile (Crocodylus mindorensis) in Paghungawan Marsh in Siargao Island Protected Landscape & Seascape (SIPLAS), Jaboy, Pilar, Surigao Del Norte, and the Indo-Pacific Crocodile (Crocodylus porosus) in the Rio Tuba River, Bataraza, southern Palawan Island. Water chemistry parameters, with emphasis on nutrient (nitrate and phosphate) levels, were determined using using standard protocols. Catch-per-Unit Effort (CPUE) of gillnets in sites with crocodiles was compared with corresponding control sites without crocodiles. CPUE was higher in areas inhabited by crocodiles, but appeared not to be directly influenced by nutrient levels. Increased fish catches in areas inhabited by crocodiles might be attributed to several factors, such as reduced fishing pressure due to the presence of crocodiles which discouraged the local fishermen to fish intensively. Overall, while fish catch was higher in areas inhabited by crocodiles, it is too early to attribute this to the nutrient output from crocodiles due to several confounding factors.

KEYWORDS: estuarine, fish catch, freshwater, nutrient

by Cameron D. Siler, Elyse S. Freitas, Jennifer A. Sheridan, Stephanie N. Maguire, Drew R. Davis, Jessa L. Watters, Kai Wang, Arvin C. Diesmos, and Rafe M. Brown

Philippine Journal of Systematic Biology, Volume 14, Issue 2, 2020, DOI: 10.26757/pjsb2020b14005

Abstract (Primary Research Paper)

Date Posted (Final Published Version): November 16, 2020

Abstract

The diversity of Philippine amphibians and reptiles has increased over the last few decades, in part due to re-evaluation of species formerly believed to be widespread. Many of these investigations of widespread species have uncovered multiple closely related cryptic lineages comprising species complexes, each restricted to individual Pleistocene Aggregate Island Complexes (PAICs). One group in particular for which widespread cryptic diversity has been common is the clade of Philippine skinks of the genus Brachymeles. Recent phylogenetic studies of the formerly recognized widespread species Brachymeles bonitae have indicated that this species is actually a complex distributed across several major PAICs and smaller island groups in the central and northern Philippines, with numerous species that exhibit an array of digit loss and limb reduction patterns. Despite the recent revisions to the B. bonitae species complex, studies suggest that unique cryptic lineages still exist within this group. In this paper, we resurrect the species Brachymeles burksi Taylor 1917, for a lineage of non-pentadactyl, semi-fossorial skink from Mindoro and Marinduque islands. First described in 1917, B. burksi was synonymized with B. bonitae in 1956, and has rarely been reconsidered since. Evaluation of genetic and morphological data (qualitative traits, meristic counts, and mensural measurements), and comparison of recently-obtained specimens to Taylor’s original description support this species’ recognition, as does its insular distribution on isolated islands in the central portions of the archipelago. Morphologically, B. burksi is differentiated from other members of the genus based on a suite of unique phenotypic characteristics, including a small body size, digitless limbs, a high number of presacral vertebrae, the absence of auricular openings, and discrete (non-overlapping) meristic scale counts. The recognition of this central Philippine species further increases the diversity of non-pentadactyl members of the B. bonitae complex, and reinforces the biogeographic uniqueness of the Mindoro faunal region.

KEYWORDS: biodiversity, endemism, faunal region, fossoriality, limb reduction

by Jeffrey L. Weinell, Alan E. Leviton, and Rafe M. Brown

Philippine Journal of Systematic Biology, Volume 14, Issue 2, 2020, DOI: 10.26757/pjsb2020b14006

Abstract (Primary Research Paper)

Date Posted (Final Published Version): February 8, 2021

Abstract

We describe a new species of reed snake of the genus Calamaria Boie 1827, from Mindoro Island, Philippines. The new species differs from all other species of Calamaria by having the following combination of characters: a high number of subcaudal scale pairs (> 40 in males, > 30 females) and ventrals + subcaudals (> 205 in males, > 210 in females) mental scale not contacting chin shields dorsal surface of head, body, and tail uniformly dark brown and ventral surface of body (extending to include part or all of first longitudinal row of dorsals) uniformly pale (yellow or white in life). The new species is likely most closely related to Calamaria schlegeli Duméril, Bibron, and Duméril 1854, which also has a high number of subcaudal scales compared to other Calamaria species. The new species is the second Calamaria species known from Mindoro Island and the eighth known from the Philippines, and its presumed distant relationship from other Philippine Calamaria suggests an additional colonization of the Philippines by this genus from continental Asia.

KEYWORDS: biodiversity, biogeography, Calamaria alcalai new species, Serpentes, Squamata, systematics

by Kin Onn Chan, Sabine Schoppe, Edmund Leo B. Rico and Rafe M. Brown

Philippine Journal of Systematic Biology, Volume 14, Issue 2, 2020, DOI: 10.26757/pjsb2020b14007

Abstract (Primary Research Paper)

Date Posted (Final Published Version): March 22, 2021

Abstract

Focusing on the phylogenetic relationships of puddle frog populations spanning the biogeographic interface between Sundaland (Borneo) and the Philippines, we demonstrate, for the first time, a widespread geographic pattern involving the existence of multiple divergent and co-distributed (sympatric) evolutionary lineages, most of which are not each other’s closest relatives, and all of which we interpret as probable distinct species. This pattern of co-occurrence in the form of pairs of ecologically distinct puddle frog forms (dyads), prevails throughout northern Borneo, Palawan, Tawi-Tawi, the Sulu Archipelago, and western Mindanao (Zamboanga). Previously obscured by outdated taxonomy and logistical, legal, and security obstacles to field-based natural history studies, this pattern has remained hidden from biogeographers and amphibian biologists by an uncontested proposal that Philippine Occidozyga laevis is a single, “widespread,” and “highly variable” species. In this paper we use an integrative synthesis of new genetic data, organismal phenotypic data, historical literature reports, and ecological observations to elucidate an interesting and potentially widespread pattern of puddle frog species coexistence at the Sundaland–Philippine biogeographic interface. Calling attention to this pattern opens promising possibilities for future research aimed at understanding the scope of this dyads pattern, and whether it extends to the more northern reaches of the Philippines. On either side of Huxley’s and Wallace’s lines, data suggest that the majority of puddle frog dyads at a given locality are not each other’s closest relatives (are more distantly related, or non-monophyletic) and, thus, assembled ecologically, likely coexisting now as a result of their ecological tendencies toward distinct microhabitats (warmer stagnant pools in open areas, versus cool, flowing streams enclosed in forest). If these pairs of species types are determined to be the geographic norm among the more isolated, central, and northern, Philippine faunas, an obvious question will be whether they have evolved into dual ecological forms, possibly in response to ecological opportunity and/or reduced competition.

KEYWORDS: biogeography, taxonomy, microhabitat, cryptic species

by Alan T. White

Philippine Journal of Systematic Biology, Volume 14, Issue 2, 2020, DOI: 10.26757/pjsb2020b14008

Abstract (Primary Research Paper)

Date Posted (Final Published Version): March 22, 2021

Abstract

This review shares lessons learned from the establishment of early marine protected areas (MPAs) in the Philippines about the need to establish baseline information, do systematic monitoring of the status of the marine environment, and to progress towards more integrated forms of management that involve key stakeholders in coastal areas. The tendency for human society to change its perception of what is “normal” through the phenomena of “shifting baselines” is pointed to as a reason why more concerted action is not taken to stop the downward trends of Philippine coastal resources and environment. The small MPAs of Apo, Sumilon and Olango Islands as well as the large Tubbataha Reefs Natural Park, are cited as examples of how the establishment of baselines and the implementation of effective monitoring over time for both biophysical and governance parameters, has been instrumental in maintaining and improving the quality of the marine environment and bringing benefits to people. The development of integrated coastal management and coastal resource management programs within local government units is explained as a way of harnessing local institutions to lead the way towards improved management and stewardship of coastal resources and provide tangible benefits to coastal communities. And, the role of national government is highlighted as a facilitator and a source of technical support to local governments in the implementation of marine conservation and coastal resources management. Finally, the significant influence of Dr. Angel Alcala in marine conservation in the Philippines is noted through his research and related conservation efforts for small-island and fisheries management and his mode of sharing results with local communities and governments so that they could learn from their own mistakes and successes and become better stewards of their resources.

KEYWORDS: Apo, community, coral reefs, Sumilon, tourism, Tubbataha

by Indraneil Das and Genevieve V.A. Gee

Philippine Journal of Systematic Biology, Volume 14, Issue 2, 2020, DOI: 10.26757/pjsb2020b14009

Abstract (Short Communication)

Date Posted (Final Published Version): April 14, 2021

Abstract

In this essay, we commemorate the zoological and herpetological contributions of Angel Chua Alcala, with a review of stamps and pictorial cancellations on herpetological themes from the Philippines. Between 1982 and 2017, a total of 79 such stamps, stamp sheetlets, and undenominated tabs, depicting amphibians and reptiles have been officially issued by the postal administration of the country, all but one within its commemorative stamp releases. Species featured are those of ecotourism importance, in addition to threatened or endemic taxa, although stylized as well as non-local species too have featured on stamps produced by the country.

KEYWORDS: Philippines, philately, stamps, postmarks, amphibians, reptiles

by Harvey B. Lillywhite

Philippine Journal of Systematic Biology, Volume 14, Issue 2, 2020, DOI: 10.26757/pjsb2020b14010

Abstract (Primary Research Paper)

Date Posted (Final Published Version): April 16, 2021

Abstract

Biodiversity and the function of tropical shallow-water marine environments are threatened by numerous anthropogenic factors, especially climate change, overharvesting of resources, and destruction of habitat. Marine snakes are important components of coastal shallow-water systems and should be considered as indicators of the health of coastal ecosystems such as mangroves. Acrochordid snakes (Acrochordidae: Acrochordus) represent a highly distinct evolutionary lineage with unusual adaptations to shallow water habitats and importance to biodiversity of tropical coastal regions. One of three congeneric species, Acrochordus granulatus (file snake), is an interesting and common inhabitant of coastal estuaries and mangroves in the Philippines. This paper reviews unusual attributes of A. granulatus and provides a perspective for its conservation in coastal habitats. Morphological, physiological, and behavioral characters of this snake are specialized for life in shallow-water marine environments such as mangroves. Unusual and specialized features confer abilities for prolonged submergence and include low metabolic rate, large capacity for oxygen storage, cutaneous gas exchange, nearly complete utilization of oxygen stores during aerobic submergence, intracardiac and cutaneous shunts for regulating blood flow, and reclusive behavior. Fresh water is required for water balance, and file snakes are dependent on rainfall in many habitats where they drink from freshwater lenses formed by precipitation on the surfaces of marine water. File snakes feed largely on fishes and are candidates as bio-indicators of the health of shallow-water coastal habitats. Attention should be given to threatening insults on coastal environments including climate change, habitat destruction, harvesting of resources, and other factors in need of research, monitoring, and plans for abatement. Importantly, conservation can be promoted by educating people about the docile behavior, unusual traits, and interesting ecology of A. granulatus.

KEYWORDS: mangrove, shallow water, Acrochordidae, little file snake, conservation physiology, ecophysiology

by Danilo S. Balete†, Lawrence R. Heaney , and Eric A. Rickart

Philippine Journal of Systematic Biology, Volume 14, Issue 2, 2020, DOI: 10.26757/pjsb2020b14011

Abstract (Primary Research Paper)

Date Posted (Final Published Version): February 14, 2021

Abstract

Small mammal communities that occur in habitats on volcanic soil substrates have been extensively studied on Luzon Island, but those that occur in forest over limestone are poorly known and have not been directly compared to those over volcanic soils. We conducted field surveys of small mammals in forest over limestone from ca. 100 m to 590 m elevation in the vicinity of Callao Cave, and in adjacent lowland dipterocarp forest over volcanic soil from 490 m to 900 m, near the location of prior surveys from 1300 m to1550 m on Mt. Cetaceo, an extinct volcanic peak in the northern Sierra Madre range. Despite moderately heavy disturbance to the habitats over karst (limestone) and moderate disturbance to forest over volcanic soils, we found native small mammals overall at levels of species richness and abundance similar to what we have documented elsewhere on Luzon over the same elevational range. Non-native mammals were present at all localities in the karstic habitat but were absent in all types of forest over volcanic soils, even in areas recovering from prior disturbance. Although non-natives were moderately common in karstic areas, they rarely were more common than native species, and non-native species were no more successful at invading the disturbed karstic habitat than the native species were at persisting there. The most abundant small mammal in dipterocarp forest over volcanic soil (Apomys sierra) was absent in karstic localities, despite occurring in adjacent areas at overlapping elevation. Overall, the difference between small mammals in karst and lowland dipterocarp forest was mainly due to species composition rather than total abundance. Comparisons with data from a prior study on the upper slopes of Mt. Cetaceo showed that total native species abundance was highest in montane and mossy forest, typically about three times higher than in lowland dipterocarp forest. We confirmed the current presence of one species, Apomys microdon, reported as a fossil from Callao Cave, but the apparent absence of one other, Batomys sp. both were from deposits dated as ca. 65,000 BP. We also summarize information about large mammals in the study areas. Further study of mammals in the distinctive forest over limestone is clearly needed.

KEYWORDS: biodiversity, biogeography, Cagayan Valley, disturbed forest, elevation, fossils, Muridae, Sierra Madre, Soricidae


Crocodylus mindorensis

Crocodylus mindorensis counts less of 200 specimens and is at serious extinction risk © Giuseppe Mazza

The term &ldquocrocodylus&rdquo has been already defined by us several times, in various texts of other specimens of loricates, word coming from the ancient Greek and meaning worm-shaped pebble, whilst the lemma &ldquomindorensis&rdquo means in Latin &ldquoof Mindoro&rdquo, an island of the Philippines archipelago.

The common names under which this crocodile is locally called in English are Philippine crocodile, Philippine freshwater crocodile and Mindoro crocodile.

The CITES places it into the appendix I, whilst the IUCN for this species estimate a status of &ldquocritically endangered&rdquo, that is CR A1, C2a. Biologists estimate a population of less than 200 specimens.

The reasons which have determined such a low density of population lead to its low geographic distribution, a management incapacity of the populations and to the poor capacity this crocodile has in adapting to the smallest environmental modifications.

It has a very limited distribution and cannot adapt to environment changes © Giuseppe Mazza

Later on, the biologists did consider it as a subspecies or race of the Crocodylus novaeguineae, and as a matter of fact, it was called Crocodylus novaeguineae mindorensis. In 1980, the International Code for Zoological Nomenclature (ICZN), what was successively confirmed by the genetic analysis, has elected this crocodile to the rank of good species, the Crocodylus mindorensis.

In 1975, an expedition of Swedish biologists discovered a crocodile whose geographic distribution was limited to Borneo. They called it Crocodylus raninus, this loricate resembles morphologically to the Crocodylus mindorensis. But the morphological, ecological and genetic proofs are not sufficient for declaring this animal neither as a distinct race, that is Crocodylus raninus, nor as subspecies or race of the Crocodylus mindorensis. Whereas in 1992, American herpetological biologists, by means of genetic analysis, have suggested that the Crodoylus raninus might be a subspecies or race of the Crocodylus porosus, loricate with a vast geographic distribution.

Zoogeography

The species is endemic to the Philippines archipelago: islands of Jolo, Masbate, Mindanao, Busuanga, Negros, and Mindoro.

It does not exceed the 3 m of length, with a strong armour on the back © Giuseppe Mazza

Ecology-Habitat

Its habitat is mainly restricted to the freshwater areas either lentic or lotic, such as small lakes, pools of water, freshwater swamps and tributary fluvial branches. It mainly nourishes of aquatic invertebrates and small vertebrates.

Although in the past the ecological series was present in almost all the 7.107 islands of the Filipino archipelago, nowadays the reality is much deceiving. Furthermore, very little is known about the ecology and the natural history of this species and of its interaction with the Saltwater crocodile (Crocodylus porosus), which, however, is a thing to be studied more deeply. On the other hand, the Filipino government spends very little in economical terms as well as in legislative ones for protecting and conserving this species, and consequently the local biologists often have their hands bound with regard to the poachers.

Protected areas in favour of this splendid crocodile have not yet been created, and it sees day by day losing most of the biotopes where it lives in favour of agriculture the countrymen themselves kill this loricate because, after them, it should damage their crops.

It has 66-68 teeth and eats mainly aquatic invertebrates and small vertebrates © Giuseppe Mazza

In the last years, various groups of Filipino and American biologists are trying with the procreation in captivity as well as with the natural coupling, and also by means of the artificial insemination, to increase the scarce population, an example are the projects activated at the Silliman University, the oldest American university institution, founded in the city of Dumaguete in the province of Negros Oriental.

Morpho-physiology

The Crocodylus mindorensis is a fairly small species. In the wild, the males never exceed the 3,0 m of length, the females are little smaller. It has a fairly broad muzzle for the genus Crocodylus and very strong armour on the back. Its morphology reminds that of the Crocodylus novaeguineae, of which, as said before, it was considered as a subspecies or race till the eighties of the past century. Several species of Asian crocodiles such as the Crocodylus mindorensis, the Crocodylus novaeguineae, the Crocodylus porosus and the Crocodylus siamensis independently from their size, have often a similar morphology which renders them difficult to distinguish, and this has led several zoological biologists to hypothesize their descending from a common progenitor. The young of the saltwater crocodile have a livery coloured in tobacco brown, which turns to dark grey-green when adults. Furthermore, in the young, the neck is more variable for the disposition, for the number and in the dimensions of the post-occipital and nuchal scales, which then continue with the dorsal ones.

Females lay 7-20 eggs and show homo-parental cares also during incubation © Giuseppe Mazza

These variations are present also among various adult individuals. For this reason, the classification or the identification by means of analysis and counting of the scales, leads often to mistakes.

The teeth are 66-68, of which 5 are premaxillary 13-14 are maxillary and 15 are mandibular.

Ethology-Reproductive Biology

The male builds up a nest of fairly modest dimensions, about 1,5 x 0,5 m, and as soon as the female lays the eggs, from 7 to 20, it is covered.

The incubation time is of about 85 days.

This is one of the few species of crocodiles where the female shows phenomena of homo-parental cares also during the incubation of eggs.


What is the current status of the taxon Crocodylus raninus? - Biology

SUBSPECIES:
This species was originally considered to be a subspecies of either C. porosus or, more recently, C. novaeguineae (i.e. C. novaeguineae mindorensis ). There is limited evidence for a separate species called C. raninus , which is very similar to C. mindorensis but restricted to Borneo, to be resurrected. There is considered to be insufficient evidence to justify this, however, and C. raninus is not officially recognised. Recent genetic work suggests that specimens thought to be C. raninus may in fact be C. porosus.

DENTITION:
5 pre-maxillary 13-14 maxillary 15 mandibular
Total no. of teeth = 66-68

IMAGES:
[click on image for enlargement]

Upper body of adult crocodile Front half of juvenile

Although this species was once found over the whole of the Philippines, it is now very critically threatened. In addition to this, very little is known about the natural history or ecology of the species, or its relationship with C. porosus , whose range it overlaps. More surveys are required to determine the present range. Initial population reduction was through commercial exploitation, although the current threat is mainly from removal of suitable habitat for agricultural purposes to satisfy a rapidly expanding human population. There is also very limited governmental support for any conservation measures, and the crocodiles are often killed by the local populace. This situation needs to be changed through awareness programs. Long-term captive breeding and release (through Silliman University and international breeding centres) is judged to be the best course to take at the present time, although it is imperative that a management program is drawn up for the remainder of the wild population (most of which resides in only one protected area). In 1992, there were estimated to be less than 1000 animals in the wild. In 1995, that estimate was revised to be no more than 100 non-hatchlings (note: hatchlings are rarely counted in surveys because their survivorship is so low).

MORE INFORMATION:
For more information on distribution and conservation issues for this species,see the CSG Action Plan resource.


Design and content by Adam Britton © 1995-2012 All rights reserved. [email]


Molecular phylogenetic analyses of genus Crocodylus (Eusuchia, Crocodylia, Crocodylidae) and the taxonomic position of Crocodylus porosus

The genus Crocodylus consists of 11 species including the largest living reptile, Crocodylus porosus. The current understanding of the intrageneric relationships between the members of the genus Crocodylus is sparse. Even though members of this genus have been included in many phylogenetic analyses, different molecular approaches have resulted in incongruent trees leaving the phylogenetic relationships among the members of Crocodylus unresolved inclusive of the placement of C. porosus. In this study, the complete mitochondrial genome sequences along with the partial mitochondrial gene sequences and a nuclear gene, C-mos were utilized to infer the intrageneric relationships among Crocodylus species with a special emphasis on the phylogenetic position of C. porosus. Four different phylogenetic methods, Neighbour Joining, Maximum Parsimony, Maximum Likelihood and Bayesian inference, were utilized to reconstruct the crocodilian phylogeny. The uncorrected pairwise distances computed in the study, show close proximity of C. porosus to C. siamensis and the tree topologies thus obtained, also consistently substantiated this relationship with a high statistical support. In addition, the relationship between C. acutus and C. intermedius was retained in all the analyses. The results of the current phylogenetic study support the well established intergeneric crocodilian phylogenetic relationships. Thus, this study proposes the sister relationship between C. porosus and C. siamensis and also suggests the close relationship of C. acutus to C. intermedius within the genus Crocodylus.


A Few Bad Scientists Are Threatening to Topple Taxonomy

Imagine, if you will, getting bit by an African spitting cobra. These reptiles are bad news for several reasons: First, they spit, shooting a potent cocktail of nerve toxins directly into their victims’ eyes. But they also chomp down, using their fangs to deliver a nasty bite that can lead to respiratory failure, paralysis, and occasionally even death.

Before you go rushing to the hospital in search of antivenin, you’re going to want to look up exactly what kind of snake you’re dealing with. But the results are confusing. According to the official record of species names, governed by the International Commission of Zoological Nomenclature (ICZN), the snake belongs to the genus Spracklandus. What you don’t know is that almost no taxonomists use that name. Instead, most researchers use the unofficial name that pops up in Wikipedia and most scientific journal articles: Afronaja.

This might sound like semantics. But for you, it could mean the difference between life and death. “If you walk in [to the hospital] and say the snake that bit you is called Spracklandus, you might not get the right antivenin,” says Scott Thomson, a herpetologist and taxonomist at Brazil’s Museum of Zoology at the University of São Paulo. After all, “the doctor is not a herpetologist … he’s a medical person trying to save your life.”

In fact, Spracklandus is the center of a heated debate within the world of taxonomy—one that could help determine the future of an entire scientific field. And Raymond Hoser, the Australian researcher who gave Spracklandus its official name, is one of the forefront figures in that debate.

By the numbers, Hoser is a taxonomy maven. Between 2000 and 2012 alone, Hoser named three-quarters of all new genera and subgenera of snakes overall, he’s named over 800 taxa, including dozens of snakes and lizards. But prominent taxonomists and other herpetologists—including several interviewed for this piece—say that those numbers are misleading.

According to them, Hoser isn’t a prolific scientist at all. What he’s really mastered is a very specific kind of scientific "crime": taxonomic vandalism.

To study life on Earth, you need a system. Ours is Linnaean taxonomy, the model started by Swedish biologist Carl Linnaeus in 1735. Linnaeus’s two-part species names, often Latin-based, consist of both a genus name and a species name, i.e. Homo sapiens. Like a library’s Dewey Decimal system for books, this biological classification system has allowed scientists around the world to study organisms without confusion or overlap for nearly 300 years.

But, like any library, taxonomy is only as good as its librarians—and now a few rogue taxonomists are threatening to expose the flaws within the system. Taxonomic vandals, as they’re referred to within the field, are those who name scores of new taxa without presenting sufficient evidence for their finds. Like plagiarists trying to pass off others' work as their own, these glory-seeking scientists use others’ original research in order to justify their so-called “discoveries.”

“It’s unethical name creation based on other people’s work,” says Mark Scherz, a herpetologist who recently named a new species of fish-scaled gecko. “It’s that lack of ethical sensibility that creates that problem.”

The goal of taxonomic vandalism is often self-aggrandizement. Even in such an unglamorous field, there is prestige and reward—and with them, the temptation to misbehave. “If you name a new species, there’s some notoriety to it,” Thomson says. “You get these people that decide that they just want to name everything, so they can go down in history as having named hundreds and hundreds of species.”

Taxonomic vandalism isn’t a new problem. “Decisions about how to partition life are as much a concern of politics and ethics as of biology,” two Australian biologists wrote in a June editorial in the journal Nature on how taxonomy’s lack of oversight threatens conservationThey argued that the field needs a new system, by which the rules that govern species names are legally enforceable: “We contend that the scientific community’s failure to govern taxonomy … damages the credibility of science and is expensive to society."

But the problem may be getting worse, thanks to the advent of online publishing and loopholes in the species naming code. With vandals at large, some researchers are less inclined to publish or present their work publicly for fear of being scooped, taxonomists told me. “Now there’s a hesitation to present our data publically, and that’s how scientists communicate,” Thomson says. “The problem that causes is that you don’t know who is working on what, and then the scientists start stepping on each other’s toes.”

Smithsonian.com spoke with some of these alleged vandals, and the scientists trying to stop them and save this scientific system.

In 2012, Hoser dubbed this species Oopholis adelynhoserae. According to other taxonomists, it is actually the New Guinea crocodile, Crocodylus novaeguineae. (Wikimedia Commons)

If you’re a scientist who wants to name a newly discovered form of life, your first step is to gather two to three lines of evidence—from DNA and morphology, for example—that prove that you’re dealing with something new to science. Then you have to obtain a holotype, or an individual of the species that will serve as an identifier for future researchers. Next you’ll write up your paper, in which you describe your discovery and name it according to taxonomic naming conventions.

Finally, you send your paper off to a scientific journal for publication. If you are the first to publish, the name you’ve chosen is cemented into the taxonomic record. But that last step—publication—isn’t easy. Or at least, it isn’t supposed to be. In theory, the evidence you present must adhere to the high scientific and ethical benchmark of peer-review. Publication can take months, or even years.

However, there’s a loophole. The rules for naming a new animal taxon are governed by the ICZN, while the International Association for Plant Taxonomy (IAPT) governs plants. And while the ICZN requires that names be published, as defined by the commission’s official Code, “publishing” doesn’t actually require peer-review.

That definition leaves room for what few would call science: self-publishing. “You can print something in your basement and publish it and everyone in the world that follows the Code is bound to accept whatever it is you published, regardless of how you did so,” Doug Yanega, a Commissioner at the ICZN, told me. “No other field of science, other than taxonomy, is subject to allowing people to self-publish.”

Thomson agrees. “It’s just become too easy to publish,” he says.

Why not? When the Code was written, the technologies that allow for self-publishing simply didn’t exist. “The Code isn’t written under the assumption that people would deliberately try to deceive others,” Yanega says. But then came the advance of desktop computing and printing, and with it, the potential for deception.

Moreover, the ICZN has no actual legal recourse against those who generate names using illegitimate or unethical science. That’s because the Code, which was last updated in 1999, was written to maintain academic freedom, Yanega says. As the Code reads: “nomenclatural rules are tools that are designed to provide the maximum stability compatible with taxonomic freedom.”

Vandals have zeroed in on the self-publishing loophole with great success. Yanega pointed to Trevor Hawkeswood, an Australia-based entomologist accused by some taxonomists of churning out species names that lack scientific merit.  Hawkeswood publishes work in his own journal, Calodema, which he started in 2006 as editor and main contributor. 

“He has his own journal with himself as the editor, publisher, and chief author,” Yanega says. “This is supposed to be science, but it’s a pile of publications that have no scientific merit.” (In response to questions about the legitimacy of his journal, Hawkeswood delivered a string of expletives directed towards his critics, and contended that Calodema has “heaps of merit.”)

Raymond Hoser also owns his own journal, the Australasian Journal of Herpetology (AJH). AJH has faced similar criticism since it was launched in 2009, despite claims by Hoser that the journal is peer-reviewed. “Although the AJH masquerades as a scientific journal, it is perhaps better described as a printed ‘blog’ because it lacks many of the hallmarks of formal scientific communication, and includes much irrelevant information,” wrote Hinrich Kaiser, a researcher at Victor Valley College in California, and colleagues in the peer-reviewed journal Herpetological Review.

Publications like these let bad science through, taxonomists say. According to them, vandals churn out names of so-called “new species” in their journals, often when the scientific evidence to support a discovery is lacking. And if the names are properly constructed and accompanied by characteristics that are “purported” to distinguish the species, they become valid under the Code. “As long as you create a name, state intention that the name is new, and provide just the vaguest description of a species, the name is valid,” Scherz says.

Hoser, for his part, doesn’t see a problem. “People complain that we name too much stuff,” he told me. “But that’s bullsh*t. There’s a lot out there.”

Like a phylogenetic tree, a cladogram illuminates relationships between groups of animals. (Wikimedia Commons)

Taxonomic vandalism usually isn't subtle. Oftentimes, vandals will explicitly steal others’ science to support their so-called "discovery," taxonomists told me. "They don’t do any of the research, they don’t own any of the research,” as Thomson puts it. One of the most common lines of evidence they steal is what's known as the phylogenetic tree. 

Phylogenetic trees, not unlike family trees, reveal how different animal specimens are related to each other based on their genetics specimens that are genetically similar are grouped together. In some cases, those groupings represent species that have yet to be named, which scientists call “candidate species.” Researchers commonly publish phylogenetic trees on the road to discovering a new species, and then use those published trees as evidence for that species’ uniqueness.

However, gathering enough evidence to make a discovery can take months or even years. Meanwhile, culprits like Hoser swoop in. Once the tree is publically available, vandals use it as evidence to justify a “discovery,” which they quickly publish in their personal journals. “Vandals go through literature and comb through phylogenetic trees, find a group in the phylogenetic tree that could be named, and quickly give it a name,” Scherz said.

It’s difficult to pinpoint the total number of species named by vandals, but Thomson estimates there are tens of thousands. Hoser readily admits that he has used this approach to name tens—if not hundreds—of taxa. “I managed to name about 100 genera [of snakes] by basically looking at phylogenetic trees,” Hoser said. Among them was the African spitting cobra, Spracklandus.

Another approach is based on a theory called “allopatric speciation,” or the evolution of new species through geographic isolation. 

The theory states that when animal populations are physically separated without opportunities to interbreed, they can grow genetically distinct. Over time, the populations can become separate species—meaning, in simplistic terms, that they can’t successfully reproduce with each other. This is a widely-accepted theory, but not proof in itself. Without DNA samples and a detailed examination of several individuals from each population, it’s not so much a discovery as it is a clue.

Taxonomic vandals have been known to take full advantage of this theory to make “discoveries,” says Kaiser. To find and name new species, they will search for geographic barriers that cut through the range of an existing species, such as rivers or mountains. If the species populations look different on either side of the barrier—on one side they’re red and on the other side they’re blue, for example—vandals will automatically declare them two separate species.

“Taxonomic vandals are saying that these are two separate…[species]…but they really have no scientific underpinning of that statement,” Kaiser said of this approach. Hoser, Kaiser writes, uses both existing phylogenetic trees and allopatric speciation to justify generating "new" species names.

For his part, Hoser maintains that the distinctions are often self-explanatory. “Sometimes it's so bloody self-evident that you don't need to resort to molecular-f***ing-genetics and DNA to work out the difference,” Hoser said. “It's like working out the difference between an elephant and a hippopotamus—they’re obviously different animals. You don’t need to be a Rhodes Scholar to figure out the difference.”

His colleagues disagree. “He puts the name on straight away without any evidence,” says Thomson of Hoser. “It’s like throwing darts at a dart board with his eyes closed, and every now and then he hits a bull’s-eye.”

In 2009, Hoser petitioned the ICZN to redefine the lethal Western Diamondback rattlesnake (Crotalus atrox) as the holotype for a new genus he proposed naming "Hoserea" after his wife. He was declined. (Rolf Nussbaumer Photography / Alamy)

While the ICZN doesn’t have the power to regulate these problems, that doesn’t mean individual taxonomists are sitting quietly by.

The scientific community often opts collectively to reject the names that vandals ascribe, even if they’re technically Code-compliant, according to several taxonomists I spoke with. Strictly speaking, this is against the rules of the Code—the names are official, after all. But according to Wolfgang Wüster, a herpetologist at Bangor University, many herpetologists “are scientists first and nomenclaturists second.”

Kaiser, Wüster and other taxonomists have been leading the fight to stamp out vandalism within herpetology. “The scientific community currently appears almost unanimous in their approach not to use Hoser’s nomenclature,” Wolfgang Denzer, a herpetologist, wrote in a critical review of Hoser’s conquests in the open access, peer-reviewed journal Bonn zoological Bulletin.

As stated, many herpetologists refuse to use the name Spracklandus, a name they say is a product of vandalism. Instead they use Afronaja, the name coined by scientists who first published data, which, taxonomists say, Hoser scooped. Unfortunately, this results in what taxonomists call “parallel nomenclature”: when a single taxon is known by more than one name.

Parallel nomenclature is exactly what the Code was intended to prevent.

And for good reason. Confusion created by parallel nomenclature complicates any process that depends on unambiguous species names, such as assigning conservation statuses like “Endangered” or “Threatened.” As the authors write in the Nature editorial, how a species is classified by taxonomists influences how threatened it appears, and thus how much conservation funding it’s likely to receive. As the authors of the editorial write: “Vagueness is not compatible with conservation.”

Parallel nomenclature could also make it more difficult to acquire an export permit for research, taxonomists say. “If you are in one country that uses vandalistic names and try to export an animal, your import and export permits won’t match, which means animals get held up when you cross borders,” Thomson said.

These kind of detrimental consequences—for science and conservation—are why some scientists are calling for a more dramatic solution: revising the Code itself.

A table of "amphibia" from Carl Linnaeus' Systema Naturae. (Carl Linnaeus / Wikimedia Commons)

The boycott against Hoser’s names remains widespread and “undeniably effective,” Yanega says. So effective, in fact, that Hoser submitted a request to the ICZN in 2013, in which he asked the commission to publicly confirm the validity of the name Spracklandus—a name that is already valid by the rule of the Code.

“He was upset by the boycott,” Yanega says, adding that Hoser was seeking validation from the commission.

“The Commission is asked to rule on these seemingly routine matters because widely promulgated recommendations by some herpetologists to use … Afronaja … instead has resulted in instability in nomenclature,” the case reads.

But the case isn’t just about one genus, one name, and one vandal, say the taxonomists I spoke to. “It’s a test of not only which names are going to stand, but also a test—which is how I see it and my colleagues see it—of scientific integrity,” Kaiser says.

It’s still unclear which way the commission will rule, Yanega says. “It depends on how objective we have to be and how well-phrased the question is before us.” If the question, which is still formulating through internal debate, is whether Hoser’s name is destabilizing taxonomy—that is, phrased as a technical, but not ethical, question—the commission will likely rule against him, Yanega adds.

But it’s possible that the scales may tip the other way, Yanega says. And if they do tip in favor of Hoserherpetologists I spoke to said that they would have no choice but to abandon the Code altogether. “The rumors among herpetology are that if the Commission rules in Hoser’s favor, then it’s over,” Sherz said. “Then we drop the Code and make our own, because it just can’t work like this.”

The authors of the Nature editorial offer up a solution: move the code under a different purview. Specifically, they suggest that the International Union of Biological Sciences (IUBS)—the biology branch of the International Council for Sciences—should “take decisive leadership” and start a taxonomic commission. The commission, they propose, would establish hardline rules for delineating new species and take charge in reviewing taxonomic papers for compliance. This process, they say, would result in the first ever standardized global species lists.

"In our view, many taxonomists would welcome such a governance structure,” the authors write. “Reducing the time spent dealing with different species concepts would probably make the task of describing and cataloguing biodiversity more efficient.”

But, barring that, a revision of the Code is unlikely to happen anytime soon, Yanega told me. Because the ICZN strives to act in everyone’s best interest, any change requires consensus across the taxonomic community. “Everything is done with some level of cooperation and consensus,” he said. “We would indeed be willing to change the rules, if we could ever get the community to come to a consensus as to how the rules should be changed.” So far, that hasn’t happened.

Part of the problem is that most branches of taxonomy aren’t impacted as heavily as herpetology, where many prominent vandals operate. That’s because herpetology is home to thousands of undescribed species, so there’s plenty of low hanging fruit for vandals to pick. Moreover, “herpetology maybe does attract more interesting characters than other branches of science,” says Wüster. “Reptiles are kind of pariahs of the animal world”—as are some of the people who study them, it would appear.

“Other disciplines within taxonomy don’t have the same sorts of problems with these same sorts of people,” Yanega says. If scientists who study birds and fish, for instance, are less exposed to the problem of vandalism, they’re not going to support a stricter Code, he adds: “To them, it sounds like you're being dictatorial or practicing censorship.”

But, at least to the herpetologists I spoke to, that’s a price that researchers should be willing to pay for good science. “This is a compromise where we might have to give up some academic freedom for the sake of the community,” Kaiser says. “This crime needs to be weeded out.”


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