Tetrapod Zoology

Tetrapod Zoology

Amphibians, reptiles, birds and mammals - living and extinct

The Freshie: Australian crocodile, seemingly from the north (crocodiles part V)


Freshwater crocodile, photographed in captivity by Richard Fisher. Licensed under Creative Commons Attribution 2.0 Generic license.

It’s time to carry on once more with the Tet Zoo crocodile series – for previous parts, see the list of links below. In the previous article we looked at the New Guinea crocodile Crocodylus novaeguineae and Philippine crocodile C. mindorensis, and before that the Saltwater, Indopacific or Estuarine crocodile C. porosus.

Dorsal osteoderm compliment of Freshwater crocodile, from Ross & Mayer (1983). Note that the cervical and dorsal shields are nearly contiguous and that there are typically two rows of ovate scutes between the cervical shield and the back of the skull. Greg Mayer kindly points out that I've been citing the wrong Ross brother when referencing Ross & Mayer (1983) - apologies!

This last species famously occurs in (but is not unique to) Australia where it’s definitely the largest, most formidable and most feared crocodile. For it’s not the only one there: Australia is also home to the Freshwater or Johnston’s crocodile C. johnstoni or C. johnsoni, also called the Freshie [photo of captive Freshie above by Richard Fisher]. Most people interested in crocodilians know that G. Krefft mis-spelt the specific name when naming this species (in 1873) after Robert A. Johnston; the incorrect spelling johnsoni has been used widely ever since. According to the ICZN, incorrectly spelt names have to be retained for reasons of stability so – technically – C. johnsoni is ‘right’, even though it’s definitely wrong. Despite this, many authors (including most Australian herpetologists) have used the correct, but ‘wrong’ C. johnstoni, mostly since Cogger et al. (1983) argued that it deserves precedence.

It’s difficult today to work out which name appears more frequently in the literature, though it has been said that C. johnstoni is "most commonly applied in the scientific and general literature" (Webb & Manolis 2010, p. 66). If you work on the basis that language exists to serve us, not the other way round, it seems most sensible to use the ‘wrong’ spelling C. johnstoni, and I’ll follow many others in doing that here.

Oh, it's not directly relevant to the content of this article but - if you're wondering - here's how that montage of fossil crocodyliforms is coming along (for the previous version go here). Still numerous taxa left to add...

Some of crocodyliform diversity, by Darren Naish. We'll be seeing lots more of this image later on.

The Freshie is a particularly long-snouted member of Crocodylus, with a snout that’s about three times longer than it is wide at its base. In contrast to the Saltwater croc, the Freshie lacks unarmoured bands between its dorsal and cervical osteoderm shields. At maximum it perhaps reaches 3 m in length. Freshies are (so far as we know, read on) uniquely Australian, being found only in northern Western Australia, Northern Territory and Queensland. The species is of course mostly associated with rivers, billabongs and (during the wet seasons) flooded grasslands and forests; it generally avoids areas frequently by the Saltwater crocodile, but the two are known to be sympatric in places. When Saltwater crocs declined due to hunting, Freshwater crocs moved in, but when the Saltwater crocs recovered, Freshwater crocs retreated. In other words, competitive exclusion seems to be in operation between the two species. The Freshie appears to be at healthy population levels overall, though its sensitivity to Cane toad poison is a cause for concern and the topic of ongoing research. [Photo below by Guillaume Blanchard].

Another captive Freshie; photo by Guillaume-Blanchard, licensed under Creative Commons Attribution-Share Alike 1.0 Generic license.

In terms of ecology, it’s a fish predator that uses rapid lateral strikes of the open jaws to grab passing prey; frogs, mammals (bats and murid rodents), snakes, turtles, birds and other vertebrates are on record as prey items as well (Tucker et al. 1996). An ontogenetic shift from invertebrates to vertebrates occurs (Tucker et al. 1996).

The historical view

Hypothesis of crocodile phylogeny, shown in simplified form but mostly based on Oaks (2011). The Freshwater crocodile is a member of the 'reduced' Indopacific assemblage. 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. Click to enlarge.

How does C. johnstoni fit into the crocodile radiation? Meganathan et al. (2010) found the Freshwater crocodile to be the sister-taxon to a C. mindorensis + C. novaeguineae clade in several of their trees, and Oaks (2011) supported this position as well. Oaks (2011) put the divergence between C. johnstoni and the C. mindorensis + C. novaeguineae lineage in the Serravalian or Tortonian part of the Miocene (somewhere round about 13-11 million years ago or so), so the Freshie might not be an especially young species... but, then again, it might, since we don’t know much, if anything, about the extinct populations that form the stem of its lineage. We might regard them as separate species if only we had better fossils of them – all we have are a few fragments.

Willis & Archer (1990) described an isolated, incomplete dentary from Pleistocene deposits at Riversleigh that they referred to C. johnstoni. Intriguingly, it's exceptionally large for this species (preserved total length 183 mm; when complete, it would have been several cm longer - this is dentary length, not whole jaw length). This might show that modern Freshies are ‘unnaturally’ small due to human hunting pressures, or it could show that Pleistocene Freshies were larger on average than Holocene ones. The specimen, however, also differs from modern C. johnstoni individuals in being relatively narrower, and in having a noticeable gap between the 5th and 6th alveoli (Willis & Archer 1990). Maybe these differences are inconsequential, but maybe they hint at the presence of a distinct Pleistocene member of the C. johnstoni lineage.

From Willis & Archer (1990). The big Pleistocene Freshie jaw is visible as the data point at extreme right.

If you’ve read the previous articles in this series (or if you know a lot about crocodiles already), you’ll know that the clade that contains C. johnstoni, C. mindorensis and C. novaeguineae can be regarded as a pared-down version of the ‘Indopacific assemblage’ hypothesised in previous studies (e.g., Brochu 2000). With the Saltwater croc removed (as discussed previously, it seems to be part of the same clade as the Siamese crocodile C. siamensis and Mugger C. palustris), this group can be imagined as a ‘reduced' Indopacific assemblage, as shown in the simplified cladogram above.

Given that the Freshwater crocodile is exclusively Australian, it’s difficult to know what these results mean in terms of biogeographical history. It obviously seems sensible to conclude that the ‘reduced' Indopacific assemblage clade originated in the Indopacific region (as, maybe, did crown-group Crocodylus crocodiles as a whole), but did it diversify in Australasia before one lineage dispersed to the Philippines, or did the two Australasian taxa (the New Guinea and Freshwater crocodile) reach Australasia independently after originating further north? If the latter possibility is true, we should expect fossil Freshwater crocodiles (or stem members of the Freshwater crocodile lineage) to be discovered north of Australia.

There’s a lot left to find out.

Non-standard taxonomic proposals, and the Hoser Problem

Galloping Freshwater croc, photo by Adam Britton. This is a McKinlay River Freshie - the sort suggested to represent the new species Philas webbi by Wells & Wellington (1985).

In recent decades, the Freshie has been universally included within the genus Crocodylus, and molecular and morphological data shows it to be deeply nested within a clade that has long been associated with this name. For the sake of completeness, however, it’s only right to note that Wells & Wellington (1983, 1985) sought to reinstate the generic name Philas, coined by John Gray in 1874, for both this crocodile and the New Guinea crocodile. Furthermore, Wells & Wellington (1985) also suggested (as they did with the Saltwater crocodile) that the Freshie might represent a species complex rather than a single species. According to these authors, a Northern Territory population (the holotype is from the McKinlay River) that reaches a smaller maximum size than Freshies elsewhere warrants recognition as the distinct species Philas webbi. As with the other ‘new’ Australian crocodile named by Wells & Wellington (1985) (C. pethericki), the idea that “P. webbi” might deserve recognition has not been accepted by other workers. [Adjacent photo of a galloping McKinkay River Freshie by Adam Britton; from McKinlay River Freshwater Crocodile Project page at the invaluable Crocodilians: Natural History & Conservation.]

I should also note that Raymond T. Hoser – a notorious individual who has published tens of new taxonomic names for Australian reptiles in his self-published, strangely written, non-technical works – has also just (within the last week or two) proposed some revisions to the taxonomy of Freshwater crocodiles as well as for crocodiles in general (Hoser 2012a).

Two of the crocodile taxa affected by Hoser's recommendations: Saltwater croc (conventionally Crocodylus porosus) and New Guinea crocs (conventionally C. novaeguineae). Photos by Darren Naish and Wilfried Berns. New Guinea croc photo licensed under Creative Commons Attribution-Share Alike 2.0 Germany license.

For starters, he argues that Crocodylus as currently conceived should be split into several genera: Crocodylus Laurenti, 1768 is retained for C. niloticus alone, Oxycrocodylus Hoser, 2012 is coined for the African species C. suchus, Motina Gray, 1844 is resurrected for the New World species, and Oopholis Gray, 1844 is also resurrected for Asian and Australasian species. If you’re wondering, Oxycrocodylus is named after Hoser’s dog, Oxyuranus – itself named after the Australian snake. A lengthy etymology section explains why Hoser’s dog, nicknamed ‘Oxy’, has provided a sterling contribution to Australian herpetology (Hoser 2012a, p. 13).

Within Oopholis, Hoser (2012a) regards Philas as a subgenus for the Australasian species. If you read the previous article on the New Guinea crocodile C. novaeguineae, you might recall the discussion of distinct northern and southern forms, neither of which have been granted taxonomic separation. Hoser acts on this, naming the southern one O. adelynhoserae. It’s named after one of his daughters (Hoser 2012a, p. 13). [New Guinea croc photo here by Wilfried Berns.]

Among Australian crocodiles, he also names the Liverpool River crocodiles of Northern Territory as the new species O. jackyhoserae. The etymology isn’t given, but I assume the name honours his other daughter. These crocodiles – Hoser (2012a) says that males “average under 1.5 m” (versus 1.7 m for an average male Freshie) – have otherwise been identified as a population of C. johnstoni. Hoser (2012a) doesn’t provide any comprehensive measurement data, nor any skeletal or molecular data – their separate species status is based on scute and scale number, small overall size, and proportionally longer limbs. If there really is data confirming the validity of these supposedly diagnostic features, then frankly the case for species status doesn’t sound unreasonable. Alas, the data – if it exists – is not presented, so all we have is an assertion or, at best, a very poorly presented hypothesis of separate taxonomic status.

Photo of Liverpool River freshwater crocodile, by Grahame Webb.

I’d rather this didn’t become the time or place to discuss what has become known as ‘Hoser taxonomy’, but it does need to be said that Hoser’s works are decidedly unprofessional, the numerous taxonomic changes he proposes are typically highly questionable and without adequate support, and few – if any – working experts agree with his proposals. Of the allegedly new Liverpool River crocodile, Grahame Webb, their discoverer, said that “They are stunted because of a lack of food; they are a clinal variation and not a new species”. Of Mr Hoser, Webb added “The guy’s a f*****g idiot” (I’m not kidding, this quote was genuinely reported in an online news article from the Northern Territory News).

Hoser is so prolific and has self-published so many new names (including species, subgenera, genera and tribes - the count was c. 60 new taxa as of May 2012) that he’s been accused of ‘taxonomic vandalism’. The ICZN seemingly refuses to impart any kind of blanket ban on the names Hoser proposes, since it argues that the maintenance of ‘taxonomic freedom’ - that is, the right of researchers to make taxonomic changes as they see fit, so long as they operate within the rules - is important. However, this ignores the fact that Hoser’s works (which aren’t peer-reviewed, nor written in the style or tone expected of technical contributions) contain undoubted examples of unethical behaviour (e.g., knowingly scooping other authors because their work was preceding too slowly (Hoser 2000)) and frequently include personal rants directed at professional herpetologists, officials, politicians and judges. In other words, he isn’t operating within the normal rules. Hoser, incidentally, writes at length about alleged corruption in the Victorian police force and legal profession and he has been found guilty of (and fined for) "scandalising the court". Wikipedia's page on him is pretty good.

Raymond Hoser, one of many photos available online. His venomous snakes have their venom glands surgically removed.

Hoser’s main response to those who criticise his herpetological articles is that they are “truth haters” who reject his work due to personal vendettas or biases. It should be clear to any outside party that Hoser’s works are woefully inadequate as pieces of honest scholarship: if you don’t believe me, look at any of pp. 3-13 in Hoser (2009a) or pp. 16-18 in Hoser (2009b). It should also be noted that his proposed nomenclatural acts are not trivial and irrelevant if you’re interested in conservation, ethics and welfare, since many of them concern venomous snakes – a group of animals for which a stable nomenclature, accessible via a clearly authoritative literature, is something of a must (for reasons related to law, medicine and communication).

I’m hardly the first to bring attention to the Hoser issue and I definitely won’t be the last. As you’ll know if you follow Hoser’s Australasian Journal of Herpetology, a group of qualified herpetologists recently put together a manuscript in which they argue why Hoser’s work qualifies as taxonomic vandalism, and why his output necessitates the creation of some sort of ICZN-approved vetting system for new herpetological names. This manuscript was leaked to Hoser, and he has published it in full, together with a lengthy response that includes screenshots of facebook pages and chains of email correspondence (Hoser 2012b). I think it’s time that as many of us as possible stand up and denounce Hoser’s work. Taxonomic freedom is all very well and good, but due process, conservatism and appropriate levels of scholarship, rigour and evidence are essential if a researcher’s output is to be taken seriously.

I didn’t realise we’d end up here, giving that this article was meant to be about crocodiles. More soon.

For previous Tet Zoo articles on crocodiles, see...

Refs - -

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

Cogger, H. G., Cameron, E. E. & Cogger, H. M. 1983. Amphibia and Reptilia In Zoological Catalogue of Australia. Vol. 1. Australian Government Publishing Service, Canberra.

Hoser, R. 2000. A new species of snake (Serpentes: Elapidae) from Irian Jaya. Litteratura Serpentium 20, 178-186.

- . 2009a. Creationism and contrived science: a review of recent python systematics papers and the resolution of issues of taxonomy and nomenclature. Australasian Journal of Herpetology 2, 1-34.

- . 2009b. A reclassification of the rattlesnakes; species formerly exclusively referred to the genera Crotalus and Sistrurus. Australasian Journal of Herpetology 6, 1-21.

- . 2012a. A review of the taxonomy of the living crocodiles including the description of three new tribes, a new genus, and two new species. Australasian Journal of Herpetology 14, 9-16.

- . 2012b. Robust taxonomy and nomenclature based on good science escapes harsh factbased criticism, but remains unable to escape an attack of lies and deception. Australasian Journal of Herpetology 14, 37-64.

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

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.

Tucker, A. D., Limpus, C. J., McCallum, H. I. & McDonald, K. R. 1996. Ontogenetic dietary partitioning by Crocodylus johnstoni during the dry season. Copeia 1996, 978-988.

Webb, G. J. W. & Manolis, S. C. 2010. Australian Freshwater Crocodile Crocodylus johnstoni. In Manolis, S. C. & Stevenson, C. (eds) Crocodiles. Status Survey and Conservation Action Plan. Third Edition. Crocodile Specialist Group, Darwin, pp. 66-70.

Wells, R. W. & Wellington, C. R. 1983. A synopsis of the Class Reptilia in Australia. Australian Journal of Herpetology 1, 73-129.

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

Willis, P. M. A. & Archer, M. 1990. A Pleistocene longirostrine crocodilian from Riversleigh: first fossil occurrence of Crocodylus johnstoni Krefft. Memoirs of the Queensland Museum 28, 159-163.

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

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