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

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


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

The Saltwater croc 'Maximo', photographed at St Augustine Alligator Farm. Image in public domain.

ResearchBlogging.org

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.

Vertically lunging Saltie. Specifically, an individual known as Stumpy (look closely), photographed in the Adelaide River, Northern Territory. Photo by J. Patrick Fischer; in the public domain.

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 croc head; note the absence of large scutes in the region immediately behind the back of the head. Image by H. Krisp, licensed under Creative Commons Attribution 3.0 Unported license.

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.

Saltwater crocs, photographed in captivity by Dave Hone. One of the animals is noticeably overweight.

The evolving view of crocodile phylogeny once again

A more complex version of the crocodile cladogram, now with the 'porosus clade' closer to the Nile croc + New World assemblage clade than is the 'reduced' Indopacific assemblage clade. Based mostly on Oaks (2011). See below for larger version.

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.

Larger version of simplified cladogram shown above. Photos (top to bottom) by Mo Hassan, Davric, Herbert Ponting, Dave Hone, Naish, Wilfried Berns. Image of New Guinea crocodile (icon for 'reduced' Indopacific assemblage) licensed under Creative Commons Attribution-Share Alike 2.0 Germany license.

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?

C. porosus skull - with Gharial (Gavialis gangeticus) in the background - photographed by Mariomassone in Museum of Zoology, St. Petersburg. Licensed under Creative Commons Attribution-ShareAlike 3.0 License.

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.]

C. raninus skull (AMNH 24294) from Ross (1990). It is a relatively robust-snouted skull with more lateral sculpting and pitting than usual in C. porosus. The palatine-pterygoid suture is transverse (in C. porosus it is posterolaterally aligned); other differences are present as well.

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.

Poor Sweetheart, photographed after his demise. I've seen this photo many times and have always wondered what that metal object inside his mouth is. Anyone know?

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.

Sweetheart in his current, taxiderm status at the Museum and Art Gallery of the Northern Territory, Darwin, Australia. Shame no scale is visible. Photo by Jpatokal, licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

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!

Refs – -

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.

- ., Njau, J., Blumenschine, R. J., & Densmore, L. D. 2010. A new horned crocodile from the Plio-Pleistocene hominid sites at Olduvai Gorge, Tanzania. PLoS ONE 5(2): e9333. doi:10.1371/journal.pone.0009333

- . & 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.

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.

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





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  1. 1. vdinets 6:58 pm 06/18/2012

    Darren: isn’t Brunei also on Borneo?
    The argument that salties must be of Asian origin because they occupy only part of Australia is a bit strange. They don’t occupy all of Eurasia, either :-)

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  2. 2. naishd 7:31 pm 06/18/2012

    I’m stupid – you’re right, Brunei is on the island of Borneo.. [main text in article now modified].

    As for the argument about the place of origin for the Saltwater crocodile, the idea is that most of its range is Asian and hence suggestive of an Asian origin – but I see your point.

    Darren

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  3. 3. Finback 9:26 pm 06/18/2012

    It’s worth noting there are claims Sweetheart didn’t die. Some time after the animal shown was killed, another large male was caught upstream several miles from the trap site. This animal, now named Cassius and living in a Queensland animal park, had the front end of his snout sliced off cleanly, as though a blade had run through it, had scars (presumably from propellors) running up and down his back, and whenever a boat would run up the river near his pen, he would go insane, leading them to reinforce his pen’s walls. So it’s been suggested Sweetheart may have escaped into a pleasant retirement, rather than dying; it’s at least nice to think so, given that Sweetheart never actually attacked any humans.

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  4. 4. naishd 4:00 am 06/19/2012

    I’d never heard that. Thanks, Finback. Sweetheart was apparently the inspiration for a 2007 movie, ‘Rogue’.

    Darren

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  5. 5. Jerzy v. 3.0. 5:01 am 06/19/2012

    Population genetics of saltwater croc would be interesting project, no matter new species. Does its ability to travel across seas resulted in panmictic population? How extensive is natural hybridization?

    Crocodylus pethericki can be just a subset of old and large adult, especially male, salties. Large crocodiles show ontogenic change in body proportions, colour and ecology. Tempting to draw parallels with large dinosaurs.

    BTW – anybody knows what determines eyeshine colour of animals? And how variable it can be within species and in one individual?

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  6. 6. Hai~Ren 6:09 am 06/19/2012

    Re: C. porosus extralimital records: Don’t forget that C. porosus was also supposedly present in the Seychelles. I’m sure that if they had managed to become established, they could have eventually colonised Madagascar, Comoros, and the east coast of Africa, maybe even up to the Red Sea.

    One particular area where cryptozoologists in Southeast Asia can contribute is in looking for these supposed C. raninus populations, and finding out if they are actually distinct from verified Bornean populations of C. porosus. They might turn out to represent surviving populations of Bornean C. siamensis.

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  7. 7. naishd 6:12 am 06/19/2012

    Hai-Ren – Re: Seychelles, look at the article again!

    Darren

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  8. 8. Dartian 6:47 am 06/19/2012

    Darren:
    the Freshwater crocodile

    Pet peeve: Could we please start calling this species by the vernacular name ‘Australian crocodile’ instead (or ‘Australian freshwater crocodile’, if you insist) – at least in international contexts?

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  9. 9. StupendousMan 8:49 am 06/19/2012

    I have grabbed a copy of the entire Tet Zoo v2 material, including comments, in case it disappears again. I’d be happy to give a copy of the archive to anyone who asks, but be aware that it’s 130 MB.

    I suppose that someone might choose to make the material available in some coherent and somewhat permanent fashion; let me know if I can help. I have no idea what IP issues might be involved.

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  10. 10. Hai~Ren 8:56 am 06/19/2012

    Darren: Oops, must have missed that on my first skimming. But if you’re hinting that cryptozoologists may find C. porosus along the east coast of Africa, wouldn’t it be a case of asking how far west they have travelled?

    By the way, as Darren tweeted, Tet Zoo version 2 is back on Scienceblogs, with comments fully restored. Hurray! Either it was something that the people at Scienceblogs had been working on all along, or maybe our complaints were heard. Whatever the case, I guess now would be a good time to re-archive the posts (with comments) and store them somewhere, just in case a similar disaster happens. Might want to do this for version 1 too, just in case.

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  11. 11. naishd 10:21 am 06/19/2012

    Thanks for comments. Name of the Freshwater crocodile (comment 8): I’m all for being specific, and would use ‘Australian freshwater crocodile’ (or whatever) were there the risk of confusion. However, when referring to the crocodiles of Australia, is there a risk of confusion? I don’t think so… everyone seems to know what you’re talking about (smiley). “Australian crocodile” is not, to my knowledge, a well known moniker for this species (at least, not in English).

    With regard to comment 10, when asking “how far east have they travelled?”, I was referring to eastward movement of C. porosus across the Pacific, in the direction of the Americas. Stories of big, crocodile-like animals seen in the Atlantic and western Indian Ocean have been suggested to be sightings of sea-going Nile crocs – I was hinting at the idea that sightings of big, crocodile-like animals seen out at sea in the open Pacific might, similarly, be Saltwater crocs.

    And thanks to all for thoughts on backing up the different versions of Tet Zoo.

    Darren

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  12. 12. Hai~Ren 11:52 am 06/19/2012

    Darren: Oh yes, I’d wanted to add in a caveat in my original comment, “unless you’re talking about crocodiles swimming east from Philippines/Indonesia/Polynesia to Hawaii or the Galapagos…”

    As an aside, the latest issue of Biawak has an account of estuarine crocodile predation on Malayan water monitor in Singapore, witnessed by some of my friends. Plus observations on parthenogenesis in argus monitor.

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  13. 13. Wilbert Friesen 3:18 pm 06/19/2012

    Yeah !!!! The briljant epic Tet Zoo 2 is back on line Yes !!! Hoeraaaaa !!! Borhyaenids and Prothylacinids here I come !

    Concerning the crocs.
    I always wondered why phylogenetic changes are so incredible rapid with some species and so syrupy slow with other creatures. For example Quinkana survived from the late Oligocene to the Pleistocene but other (crocodile) genera just show up and die out in a ‘few seconds’ time. A flick of the switch.

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  14. 14. Heteromeles 8:39 pm 06/19/2012

    @13: As for the endurance of species, my uninformed guess is that it’s a result of two factors:

    A. Many phenomena in nature seemed to follow a j-shaped/long-tail distribution, with a few common and many rare representatives. There’s no particular reason to think this doesn’t apply to species longevity, especially given that in almost any speciose group, there are a few common and many rare species. Therefore, I’d expect any clade to have a few Lazarus Longs, no matter what the clade is. By analogy, there has to be a world’s richest man, one species in every clade has to outlive all the others, if only by pure chance. (see Black Swan Theory for a more verbose explanation).

    2. The fossil record is notoriously incomplete, and the species that live near good depositional zones are going to be over-represented. Yes, crocodilians tend to live in depositional environments, but still, estuarine species might do better as fossils than those in upland ponds or terrestrial environments.

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  15. 15. Jurassosaurus 9:15 pm 06/19/2012

    Another possible reason could just be lazy taxonomists (see Leidyosuchus for example).

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  16. 16. Dartian 12:16 am 06/20/2012

    Darren:
    However, when referring to the crocodiles of Australia, is there a risk of confusion?

    But you weren’t talking specifically about Australia there; you were listing a bunch of “Indopacific” species – all of which, as it happens, mainly live in freshwater (and, furthermore, in countries/regions where the saltwater crocodile Crocodylus porosus also occurs).

    everyone seems to know what you’re talking about

    Maybe, but if you are going to use the it-makes-sense-in-context argument, I can’t resist pointing out that pretty much the same thing could be said about the word ‘raptor’. In few if any situations is there any real risk of anyone confusing extant birds of prey with certain smallish, flesh-eating Mesozoic dinosaurs. Yet you are on record as opposing the use of ‘raptor’ for both these groups of archosaurs. Isn’t that a bit inconsistent?

    “Australian crocodile” is not, to my knowledge, a well known moniker for this species (at least, not in English).

    Ah, but you could start making it a well known moniker! I mean seriously; your blog even has its own TV Tropes page – that’s proof positive that you are now definitely a Somebody! ;)

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  17. 17. John Scanlon FCD 1:30 am 06/20/2012

    re Jerzy’s comment on panmixis (-ia?) and hybridization, that would allow several of the proposed phylogenies to be correct at the same time (win-win!).

    Otherwise we’ll have to take the names off all the Plio-Pleistocene C. porosus fossils from northern Australia :(

    But if Salties are the Homo erectus of crocs, they can be immediate ancestors of various ‘freshwater’ species (which might then hybridise occasionally with each other) and produce almost any pattern of synapomorphies you can imagine (hey, it worked for hominids). More nuclear genes and more morphological characters needed!

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  18. 18. naishd 5:00 am 06/20/2012

    Thanks for all the great comments. With relevance to many of the comments above – does anybody know if any large-scale, cross-country phylogeographic study has been done on Saltwater crocs, or if any such project is underway, or planned? If such work hasn’t been done, or isn’t being planned, it seems to me to be high time that such a project was funded. Any results would be important for our understanding of the spread and evolution of this species, and also for its conservation biology and dispersal behaviour.

    Darren

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  19. 19. Jerzy v. 3.0. 5:06 am 06/20/2012

    Re: species longevity. I heard on some study on, I think Paleozoic invertebrates, that no factor predicts future extinction of species in geological scale.

    Simply: if an ecological niche of a species persists, the species will persist, otherwise it will disappear: go extinct or evolve.

    It is sometimes said that specialized species go extinct quickly and unspecialized species survive long. However, anteaters and turtles, for example, are specialized forms changing very little.

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  20. 20. Jerzy v. 3.0. 5:11 am 06/20/2012

    Re: C porosus – what was about its supposed ocurence in East Africa?

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  21. 21. naishd 5:14 am 06/20/2012

    Presence of C. porosus in east Africa: as discussed in the article above, while I’ve been able to find records from the Seychelles (1500 km off African coast)….

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

    … I have yet to see anything in the literature on definitive African occurrences. Have you? If anyone knows anything, please say so.

    Darren

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  22. 22. Rappy 8:52 am 06/20/2012

    Long time reader, first time commenter.

    While I could simply say that this is a great article as usual, I figured I’d add something helpful concerning the photograph of Sweetheart and the mystery object you wanted identified.

    According to Steve Grenard’s Handbook of Alligators and Crocodiles, the metal tube inside of Sweetheart’s jaws is a motor cowl, the covering of a boat engine that Grenard’s caption states Sweetheart “liked to play with while alive”. While I can’t be 100% certain this is accurate, the object in question could feasibly be a decidedly crushed motor cowl, so I’m going with Grenard’s claim.

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  23. 23. naishd 12:18 pm 06/20/2012

    Rappy – thanks. I always thought it was a part of a boat engine.

    Darren

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  24. 24. John Scanlon FCD 12:58 am 06/21/2012

    I always thought it was a plastic bucket. I cut the B&W photo out of a magazine in about August 1979 (slightly higher resolution than shown above) and it never occurred to me that it would be a piece of metal. I really don’t think it is: the way it bends around the teeth looks like it’s temporarily bent by sustained pressure, not like it’s been crushed. And if it was a beloved toy piece of motorboat, how many times could Sweetheart have bitten it while ‘playing’, without flattening and tearing it?

    The photos of Sweetheart being pulled out of the river (on the Northern Territory Library site) show his mouth open with top-jaw rope, and closed with the rope wrapped around both jaws, and there’s no cylindrical piece of metal in sight. But plastic buckets are ubiquitous and, if sturdily made (1970s!), might be just the sort of handy object used to prop the jaws open for a photo.

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  25. 25. Dartian 1:54 am 06/21/2012

    John:
    looks like it’s temporarily bent by sustained pressure

    But how can there be sustained pressure if the crocodile is dead?

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  26. 26. John Scanlon FCD 3:05 am 06/21/2012

    It’s supporting the upper jaw.

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  27. 27. Dartian 3:39 am 06/21/2012

    John:
    It’s supporting the upper jaw.

    I realise that, but is the (literal) dead weight of a crocodile’s upper jaw sufficient to bend a sturdy plastic bucket like that?

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  28. 28. naishd 4:04 am 06/21/2012

    A higher-res version of the image here seems to show that it is indeed a bucket, since the wire handle can clearly be seen to be connected at two points on either side of the rim.

    Darren

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  29. 29. John Scanlon FCD 4:57 am 06/21/2012

    Was it Herodotus or Aristotle who is supposed to have claimed that in crocs the upper jaw rotates against the skull instead of the lower? (Or was this only a misreading of the obvious fact that you can’t lower the mandible when it’s resting on the ground?)

    Anyway, we had a porosus skull for comparison in the lab in Mount Isa, from a Normanton individual that would have been about 4.1 m by Greer’s equation. It was formerly glued and plastered together and partly painted, but I did some cleaning and separated the skull and mandible. Since the quadrate-articular joint is right at the back, and the snout is quite broad and moderately deep, it takes quite a bit of force to keep the mouth open (somebody possibly sometimes demonstrated this on arms and bodies of schoolkids visiting the lab). A flimsy modern bucket under the large maxillary teeth could have been squashed by the weight of the dry bones alone.

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  30. 30. Dartian 5:01 am 06/21/2012

    Darren:
    A higher-res version of the image here seems to show that it is indeed a bucket, since the wire handle can clearly be seen to be connected at two points on either side of the rim.

    Hm. Alrighty then.

    There’s a hole in the bucket, dear Liza, dear Liza…

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  31. 31. Dartian 5:16 am 06/21/2012

    John:
    Was it Herodotus or Aristotle who is supposed to have claimed that in crocs the upper jaw rotates against the skull instead of the lower?

    Aristotle, Herodotus, and Pliny the Elder all made that claim. (Although the two latter could of course have copied this ‘information’ from Aristotle.)

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  32. 32. Dartian 5:21 am 06/21/2012

    the two latter could of course have copied this ‘information’ from Aristotle

    Agh, scratch that; Herodotus, of course, lived before Aristotle.

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  33. 33. John Scanlon FCD 8:48 am 06/21/2012

    And there doesn’t seem to be much evidence that Aristotle was read by anyone for some hundreds of years after he lived, afair without googling.

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  34. 34. Lars Dietz 9:13 am 06/21/2012

    “And there doesn’t seem to be much evidence that Aristotle was read by anyone for some hundreds of years after he lived, afair without googling.”

    Well, he was quite influential in his own time, and into Roman times. Much of Pliny’s Naturalis Historia was based on Aristotle, with or without attribution. Of course Pliny also used other sources (many of which are now lost), and could have gotten the story directly from Herodotus. Aristotle’s works weren’t as widely known in Early Medieval Europe, but they survived in the Muslim world in Arabic translations, and Latin translations of these later made it to Europe in (I think) the 13th century.
    By the way, Herodotus also claimed that the crocodile has no tongue, and therefore its teeth are cleaned by a bird called “trochilos”, generally thought to be the Egyptian Plover. The second part of this story is still widely believed, although there is no real evidence for it.

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  35. 35. vdinets 10:25 am 06/21/2012

    Lars: crocodile tongue is attached to the jaw along almost all of its length, and is not particularly movable, so Herodotus probably didn’t recognize it as tongue. As for the bird, it could well be some species present in the Nile Delta, but absent (or lacking the teeth-cleaning habit) in the rest of Africa. Crocs later went extinct in the Lower Egypt, so we’ll never know if Herodotus was correct or not. As a consolation, I do have a few photos of small fish cleaning the teeth of an American crocodile in the wild :-)

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  36. 36. Lars Dietz 12:32 pm 06/21/2012

    vdinets: Of course that would be a possibility, but then Herodotus often reported myths as fact, and even in antiquity some called him a liar. By the way, from Wikipedia: “In particular, it is possible that he copied descriptions of the crocodile, hippopotamus and phoenix from Hecataeus’s ‘Circumnavigation of the Known World’ (Periegesis/Periodos ges), even mis-representing the source as ‘Heliopolitans’ (Histories 2.73).” So even he probably got at least a second-hand account.

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  37. 37. Mythusmage 6:21 pm 06/21/2012

    Australian crocodiles: Funny, but I thought the colloquail names were “saltie” and “freshie”.

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  38. 38. vdinets 12:12 am 06/22/2012

    Lars: it could be just a legend, of course, but note that some later naturalists have also reported seeing this. Among them was Alfred Brehm, who was very influential in his time, although I don’t remember where exactly did his claimed sighting happen. I am also not aware of him ever being caught lying… but I didn’t do any research on this.

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  39. 39. Dartian 1:47 am 06/22/2012

    I thought the colloquail names were “saltie” and “freshie”

    And the colloquial name of Australia is ‘Oz’, but you won’t find that name used in any official context (e.g., in an atlas). Names matter, even vernacular ones. Anyone who thinks that ‘freshwater crocodile’ is an unambiguous, confusion-safe name should go to, say, India (where English is an official language) and ask random people there if they have ever heard of the ‘freshwater crocodile’. How many do you think will immediately know that you’re referring to Crocodylus johnstoni?

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  40. 40. John Scanlon FCD 9:48 am 06/22/2012

    vdinets: Brehm’s name doesn’t come up very often these days. I found a complete set of volumes of an early C20 edition of Tierleben in a secondhand bookshop in Sydney some years ago, a bit battered and going cheap, but have hardly read any of it (I find German hard to skim, can only access it serially rather than randomly, and the Fraktur doesn’t help). Somewhere in a box since last move (I haven’t been fully unpacked for about 24 years), probably with my Grandma’s set of Goldsmith’s Earth and Animated Nature.

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  41. 41. vdinets 8:49 pm 06/22/2012

    Dartian: I think virtually any non-zoologist anywhere in the world, if asked what an “Australian crocodile” is, would immediately think of Steve Irvin and salties.

    In fact, “freshwater crocodile” is not that bad a name, considering that very few (if any) other crocs have never been recorded in salt or at least brackish water.

    John: I have a Russian translation (in two volumes)… but it’s in my mom’s apartment in Moscow.

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  42. 42. Rappy 11:59 pm 06/22/2012

    Looking at it in more detail, yeah, it is indeed a bucket.

    That does make me wonder where Grenard got the whole motor cowl claim from, though. Maybe an attempt to shoehorn in Sweetheart’s life story?

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  43. 43. Surroundx 4:17 am 06/23/2012

    You can tell the object in “Sweetheart’s” mouth is a plastic bucket even in the lowish resolution photograph above. The metal semi-circle handle is clearly visible.

    Regarding the true identity of Sweetheart, Robert Reid quotes G. J. (George Craig), owner of the Cassius mentioned by Finback (post #3). Craig believes that Cassius is the real Sweetheart. He had this to say:

    “The stuffed croc in Darwin is only 16 feet 10 inches and has no scars at all. It just doesn’t add up. With his tail complete, Cassius would be a true 18-footer and there aren’t many of those around. His injuries are consistent with Sweetheart’s recorded attacks on boats and his aggressive behaviour makes him the meanest crocodile I have ever encountered. He gets agitated when he hears a marine engine. He’s Sweetheart all right.”

    (Robert Reid, Croc!, pp. 39)

    While perusing my library and Google Scholar for records of Crocodylus porosus in Africa, I came across the following interesting claim:

    “[T]here is a strong case that crocodiles have attained 20-metre and over sizes in the Indo-Pacific region up until fairly recent times.”

    (Robert Reid, Croc!, pp. 239)

    The context is the fossil record. Reid isn’t claiming there crocodiles that big alive still. But it still seems extraordinary. So far as I know, no fossil member of the genus Crocodylus has been reported as growing to more than 10 metres. Is this just pure misinformation, or is there actually some substance to this claim?

    Reference:

    Reid, Robert. (2008). Croc! Savage Tales from Australia’s Wild Frontier. Crows Nest, N.S.W.: Allen & Unwin.

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  44. 44. Lars Dietz 1:21 pm 06/23/2012

    I’ve looked up the description of the Egyptian Plover in Brehms Tierleben, and he only says that he observed it entering crocodiles’ mouths repeatedly, but not where. I don’t remember anything about him lying either, though, although his descriptions are often very anthropomorphised. Meinertzhagen also claimed to have observed it in Sudan (also with Spur-winged Plovers in southern Africa), but of course he’s not a reliable source. Geoffroy Saint-Hilaire also claimed to have seen a bird fly into the crocodile’s mouth, but he makes it clear that the bird he saw was actually the Little Ringed Plover. So maybe shorebirds sometimes do try to pick parasites or food from crocs’ mouths, but it’s clearly not a regular symbiosis.

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  45. 45. John Harshman 5:26 pm 06/23/2012

    By the way, is the title a reference to The Iron Giant?

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  46. 46. naishd 6:35 pm 06/23/2012

    John… yes, well done (smiley).

    D

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  47. 47. vdinets 10:06 pm 06/23/2012

    Lars: thank you. I’d be surprised if naive migrants from outside the croc’s range do not accidentally walk into the mouth of a basking crocodile in search of food on some occasions… it sucks to be a naive migrant.

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  48. 48. Lars Dietz 10:37 am 06/24/2012

    vdinets: Yes, that might of course happen. Another case would be the Common Sandpiper that was observed doing this in South Africa by J. J. Player according to the article on the Nile croc in Grzimek’s Tierleben (written by Bernhard Grzimek himself). Grzimek also mentions that Guggisberg observed a marabou picking a small fish out of a croc’s open mouth, which even was filmed. Unfortunately there are no references, so I don’t know when either of this happened or where it was published.
    By the way, it’s strange that all the accounts that I found refer to Nile crocodiles. Does anyone know if there are any reports that involve other crocodile species?

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  49. 49. David Marjanović 6:53 pm 07/9/2012

    Yay for Tet Zoo 2!

    Alfred Brehm [...] I am also not aware of him ever being caught lying…

    He did retell plenty of tall tales and anthropomorphized a lot, AFAIK.

    Link to this

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