Do you remember the photo – provided courtesy of Colin McHenry – showing a variety of crocodilian skulls? I published it in an article on the CEE Functional Anatomy meeting, and here it is again. The challenge was to try and identify the largest skull. Suggestions included Saltwater croc Crocodylus porosus, outsized American croc C. acutus or Slender-snouted croc Mecistops cataphractus, but it’s none of those (for the resurrection of the genus Mecistops Gray, 1844 for cataphractus see McAiley et al. 2006). The monster skull is in fact that of a False gharial Tomistoma schlegelii. Yes, a False gharial. Holy shit. Hai-Ren actually got it right: well done you! At 84 cm long this skull might cause you to revise whatever preconceptions you had about a species with the name ‘False gharial’ (having said that, gharials proper ain’t necessarily unimpressive… read on).
Thanks to Markus Bühler of Bestiarium, I’ve just learnt of Rom and Nik Whitaker’s excellent article on gigantic crocs here at Here be dragons, a blog that I’ll definitely be adding to the Tet Zoo sidebar. They provide much discussion of giant Salties, going over the famous 1980 Fly River (New Guinea) croc, the alleged Australian giants seen by Krys and Ron Pawlowski (they claimed to have shot a croc 8.6 m in length), and the various alleged giants from India [for previous discussion of giant size in Saltwater crocs see the comments at Tet Zoo POTD # 14]. They also discuss a gigantic specimen killed in Cambodia in the 1800s: its skull is preserved and, with a dorsal head length of 76 cm (see their article to understand how there is more than one way to measure a croc skull!) and with a mandibular length of 98.3 cm, is the biggest Saltie skull in existence. Then there are giant American crocs (one specimen, in the AMNH [= American Museum of Natural History, New York], is a true monster with a skull 73.5 cm long) and Nile crocs C. niloticus. And then there are the False gharials.
The NHM (= Natural History Museum, London) skull included in Colin’s photo (Colin’s homeboy Pete Edwards provides a scale) is the largest known modern crocodilian skull in existence. Here it is again, this time posing with sea snake guru Colin McCarthy. It isn’t the only gigantic skull from this species: Rom and Nik Whitaker mention one at Munich which is 81.5 cm long, and one at the AMNH which is 76.5 cm long. Unfortunately it isn’t entirely clear what the total lengths of these animals were, and it isn’t yet clear what the skull length : total length ratio of this species is. It’s well known that a fairly consistent 1 : 7 ratio has been proposed for crocodiles, but this seems not to work when applied to particularly large individuals: for full discussion of this you’ll have to read the Here be dragons article.
Based on these giant skulls, we can be fairly confident that Tomistoma exceeds 6 m in total length and is one of the largest extant crocodilians. Most popular books on crocodilians state its maximum length as 4-4.5 m (e.g., Guggisberg 1972, Alderton 1991), so these authors evidently weren’t aware of these giant skulls (Steel (1989) specifically referred to the giant NHM skull however, noting as a result that Tomistoma might attain a length of 5.5 m). In keeping with its sometimes gigantic size, it is probably not limited to a diet of fish ‘and other small vertebrates’ as some of the books say, and it is known to eat macaques at least. Incidentally, there are some fragmentary Siwalik Hills fossils in the NHM collection that look pretty huge, and were provisionally identified by Dino Frey as possibly belonging to Tomistoma. I have no idea whether these remains actually belong to Rhamphosuchus crassidens, a large species from the Miocene of the Siwalik Hills, identified variously as a tomistomine (false gharial) or a gavialoid (true gharial) by different authors. Head (2001) identified Rhamphosuchus as a tomistomine and noted that its length ranged from 8-11 m: not quite the 15-18 m previously mentioned by some (although 8-11 m is still plenty big enough I think).
Finally, let us note that the Gharial itself, Gavialis gangeticus, is not necessarily a small animal [adjacent image, from wikipedia, shows a captive False gharial]. A Gharial skull at Munich is 77.3 cm long (making it the third longest modern crocodilian skull), but again its total length was not recorded. Of course, there are tales of giants that were measured whole: an alleged 7 m specimen was shot on the Kosi River in 1924, a 6.6 m long individual on the Gogra River in 1920, and a 6.4 m animal was killed in the Cheko River in 1934. I have no idea whether these lengths were ever verified. It is well known that gharials have occasionally been found with jewellery in their stomachs, but this has been attributed to their possibly feeding on the remains of funerals, or even on picking up such objects for use as gastroliths. However, big gharials are not limited to a diet of small prey as they are alleged to sometimes take goats and feral dogs. There are a couple of authenticated attacks on humans: 55 year old Sankara Behera was attacked by one in 1979 at the Satkoshia Gorge Sanctuary (Bustard & Singh 1981). It grabbed his arm and he fell into the river; his son rescued him and he later recovered. A few other people have been bitten (Steel 1989), but these attacks mostly seem to have been motivated by territoriality or nest-defence.
Note how I cleverly avoided even mentioning the phylogenetic affinities of Tomistoma and Gavialis, easily the most controversial areas in crocodilian evolutionary biology.
Refs – -
Alderton, D. 1991. Crocodiles & Alligators of the World. Blandford, London.
Bustard, H. R. & Singh, L. A. K. 1981. Gharial attacks on man. Journal of Bombay Natural History Society 78, 610-611.
Guggisberg, C. A. W. 1972. Crocodiles: Their Natural History, Folklore and Conservation. David & Charles, Newton Abbot.
Head, J. J. 2001. Systematics and body size of the gigantic, enigmatic crocodyloid Rhamphosuchus crassidens, and the faunal history of Siwalik group (Miocene) crocodilians. Journal of Vertebrate Paleontology 21 (Supp. to No. 3), 59.
McAliley, L. R., Willis, R. E., Ray, D. A., White, P. S., Brochu, C. A. & Densmore, L. D. 2006. Are crocodiles really monophyletic? – Evidence for subdivisions from sequence and morphological data. Molecular Phylogenetics and Evolution 39, 16-32.
Steel, R. 1989. Crocodiles. Christopher Helm, London.