Here's an interesting contention: until just a few thousand years ago, small crocodilians inhabited the tropical islands of the South Pacific and elsewhere. In fact, judging from recent discoveries, small terrestrial crocodilians were an ordinary component of many tropical island groups, and they presumably still would be, had they not been made extinct by people. This article originally appeared in 2006 on Tet Zoo ver 1, and here it is again...
The first of these animals to be discovered was Mekosuchus inexpectatus from New Caledonia (life restoration shown above), a species that most interested people have heard about due to its coverage in popular books (e.g., Jean-Christophe Balouet's Extinct Species of the World, Tim Flannery's The Future Eaters and Charles Ross's Crocodiles and Alligators [the big Merehurst encyclopedia]). Discovered in 1980, this species entered the literature in 1983 when Eric Buffetaut described its remains (teeth and skull bones) from a site on the Isle of Pines, just off New Caledonia. It was a small crocodilian, around 2 m long, and crushing teeth at the back of its jaws suggest that it ate molluscs on occasion. Based on the apparently archaic nature of its postorbital bar, Buffetaut (1983) speculated that this animal might be a late-surviving relict form from the Cretaceous. By 1987, Buffetaut and colleague Jean-Christophe Balouet had enough material (now from mainland New Caledonia as well as the Isle of Pines) to name the species. They regarded it as distinctive enough for its own family, Mekosuchidae, and they proposed that Mekosuchidae might be a relict group outside of the clade formed by the living crocodilian species (Balouet & Buffetaut 1987).
All of this was made more surprising by the fact that M. inexpectatus was essentially modern: its remains come from deposits that are certainly less than 4000 years old. The exact age of M. inexpectatus is unsure, but it may have been around as recently as 1670 years ago (Mead et al. 2002). Humans arrived on New Caledonia about 4000 years ago, so it is likely that M. inexpectatus was among the several New Caledonian endemics that were hunted to extinction. Beside the crocodile, these include large megapodes, rails, meiolaniid turtles and a monitor lizard. An association of M. inexpectatus remains with kitchen waste at Nessadiou (200 km north of Noumea) has been reported (Balouet 1989).
When first documented, M. inexpectatus was unique and without any apparent close relatives. Thanks to the research of Paul Willis and his colleagues however, we now know that this species was merely among the youngest of a predominantly Australasian radiation of Cenozoic crocodilians, the mekosuchines. To date this group includes generalised Kambara from Eocene Queensland and Australosuchus from Oligocene-Miocene South Australia, short-skulled Miocene Trilophosuchus from Queensland, the broad-snouted Oligocene-Miocene Baru* species, broad-snouted Pliocene-Pleistocene Pallimnarchus, and ziphodont** Miocene-Pleistocene Quinkana from Northern Territory and Queensland (Salisbury & Willis 1996, Willis 1993, 1997, Willis & Mackness 1996, Willis & Molnar 1991, Willis et al. 1990, 1993). A few unnamed Australian species, including some peculiar long-snouted, gharial-like forms, are also probably members of the mekosuchine radiation, and we'll meet more members of the group in a minute. Mekosuchines aren't regarded as a distinct 'family' anymore, incidentally (as was proposed by Buffetaut and Balouet). Rather, they seem to be a clade within the larger group Crocodylidae [adjacent image is a life restoration of Baru darrowi, by me].
* There are several Baru species, but the first one to be named is B. darrowi. The specific name honours Paul Darrow, the British actor 'best known for his role in the television series 'Blake's Seven', in recognition of his support of continuing palaeontological investigation of the Riversleigh deposits' (Willis et al. 1990, p. 522).
** Ziphodonty describes a tooth type where the teeth are recurved and laterally compressed. It is most often associated with theropod dinosaurs.
Some mekosuchines probably behaved much like living amphibious crocodiles - indeed they evolved in an Australia that was devoid of the modern Crocodylus species (these first appeared there in the Pliocene) - but others, like Quinkana, appear to have been terrestrial predators that might have behaved like giant monitor lizards [Quinkana life restoration shown here; produced by Paul Willis and borrowed from Reconstructing Dead Aussie Crocs]. Judging by its limb bone morphology and the places where its remains are found, M. inexpectatus was a terrestrial form and it has even been suggested that it might have been scansorial: that is, able to climb trees (this idea comes from Paul Willis, though I don't think he's documented it in the technical literature). This isn't regarded as likely by all fossil crocodilian experts. In the initial draft of an article I wrote about crocodilian history (Naish 2001) I mentioned that Mekosuchus might have been a tree climber. My reviewer (a noted crocodilian expert) crossed this out, writing in the margin 'Do you want to remain a credible scientist'? Anyway, it is an idea still worth considering.
So, M. inexpectatus was a member of a previously diverse group, the mekosuchines. Furthermore, discoveries from the Oligocene and Miocene of Queensland have revealed a fossil history for Mekosuchus extending well back, on mainland Australia, into the Neogene (Willis 1997). This is significant as it shows that Mekosuchus must have gotten to New Caledonia after evolving on Australia (it therefore wasn't an island endemic, unique to New Caledonia). Furthermore, M. inexpectatus is comparable in size to the Australian Mekosuchus species, so its small size probably isn't a specialisation for island life [the adjacent image depicts the Australian Mekosuchus species M. sanderi. It's one of Paul Willis' photoshop reconstructions. Visit Reconstructing dead Aussie crocs for more].
Another island-dwelling Mekosuchus species, M. kalpokasi, was described in 2002 for skull material from the archaeological Arapus site of Efate island, Vanuatu. Discovered associated with pottery fragments, bivalve shells, and bones of fish, fruit bats, turtles and birds, M. kolpokasi comes from a layer shown by radiocarbon dating to be about 3000 years old. Again, its association with human waste and evidence for hunting strongly indicates that its extinction was caused by humans. The maxilla of M. kolpokasi clearly comes from an adult individual and has a tooth row of just 88.7 mm long, so again this was a small animal perhaps less than 2 m long. The shape of the maxilla also shows that M. kolpokasi was a short-skulled species, as were probably all Mekosuchus species. So Mekosuchus wasn't just found on Australia and New Caledonia - it also got as far east as Vanuatu. Might mekosuchines prove to have been even more widely distributed?
Yes, for in 2002 Molnar et al. (2002) described another island dwelling form, Volia athollandersoni [Volia skull reconstruction shown here, from Molnar et al. (2002)]. Its name commemorates Voli Voli Cave (one of the discovery sites) and Atholl Anderson, well known for his many contributions to the prehistory and palaeoecology of south-west Pacific islands. Volia is from Viti Levu, Fiji, and again it was apparently a relatively small (2-3 m long), terrestrial form. It's Pleistocene in age, with one cave deposit that yielded it being dated at between 10,000 and 20,000 years old, though it can't be ruled out that some remains of this species are younger than this. People have been on Fiji since about 3000 years ago, so at the moment Volia seems too old to have succumbed to human hunters. I would predict, however, that it actually survived to the time of human occupation, and only then became extinct. A giant frog, a terrestrial turtle, an iguana, rails, a snipe, pigeons and megapodes all became extinct on Fiji as a result of human intervention [incidentally, Volia has been featured on a stamp: see the image below].
Mekosuchine biogeography: dispersal or vicariance?
How did mekosuchines get to these islands, and what does this mean for their total distribution? There are two competing views here. View one - the dispersal model - states the following: given that mekosuchines as a group are younger than the rifting events which separated Fiji and New Caledonia from Australia*, it seems most likely that they colonised the islands in their range by dispersal (Mead et al. 2002). That is, they swam to them. This means that the mekosuchines ancestral to the island dwelling forms must have had some marine swimming/drifting capabilities (much as do some living Crocodylus crocodiles) [here's a map, to help you with south-west Pacific geography...].
* Fiji (and Vanuatu) are of volcanic origin, but both are part of the Fijian Plateau, an area that is thought to have had emergent land since the Eocene. Until the Palaeocene/Eocene (I'm not sure which), the Fijian Plateau was adjacent to the north-west coast of Australia, and it was at this time that it began to rift away in a north-westerly direction. Prior to this rifting, it is conceivable that some faunal elements were continuous across Australia-Fiji-Vanuatu.
This dispersal model suggests that island dwelling mekosuchines might have occurred on various islands where they have yet to be discovered, such as Tonga, Samoa, Santa Cruz, the Loyalty Islands, and various of the islands that form Vanuatu and Fiji (Mead et al. 2002). We have only recently (viz, post-1980s) discovered that Fiji and Tonga were home to recently extinct big frogs, iguanas, giant pigeons and other tetrapods, so it's quite conceivable that the fossils of such mekosuchines await discovery on some of these islands. It's also worth checking native traditions and old historical accounts to see if the people who lived on, or visited, these islands ever reported anything that sounded like a terrestrial crocodile. I'm not aware of any such accounts but then I can't pretend to have checked the relevant anthropological or historical literature. Balouet (1989) did report that New Caledonian people lacked any traditions of an animal that sounded at all like Mekosuchus.
View two - the vicariance model - proposes that mekosuchines may have been present on New Caledonia, Fiji and elsewhere prior to their separation of these land masses from the Australian plate. A few pieces of evidence suggest that this is plausible. We now know that crocodilians were present on New Zealand as recently as the Miocene, and it was intimated by Molnar et al. (2002) that this might support a vicariant origin of island dwelling crocodilians in the south-west Pacific. Molnar et al. (2002) also pointed to the presence of the frog Platymantis on Fiji as evidence for a vicariant origin of at least some of the tetrapods on these islands, though it's worth noting that the old chestnut about frogs being incapable of dispersal across salt water is no longer viable (Vences et al. 2003). If vicariance was the major control on mekosuchine distribution in the south-west Pacific, then mekosuchines 'might be expected to be found on other islands in the New Zealand-New Caledonia-Fiji-Solomons region, but not as far east as Tonga or Samoa' (Molnar et al. 2002, p. 626).
So whether mekosuchines owe their distribution to dispersal or vicariance, we can be quite confident that they inhabited islands in the south-west Pacific where their presence has yet to confirmed.
This isn't the end of the story. Mekosuchines weren't the only recently extinct crocodilians that inhabited the island groups of the south-west Pacific. Furthermore, island dwelling crocodilians also inhabited islands in the Indian Ocean until very recently.
For previous Tet Zoo articles on extinct crocodilians see...
- Purussaurs: monster caimans of the Miocene
- SVPCA 2007: lepidosaurs, turtles, crocodilians, the plesiosaur research revolution continues
- Galve: giant mystery crocodyliforms and, yay, more istiodactylids
- Move over Theropoda, Sebecosuchia rules
Refs - -
Balouet, J.-C. 1989. New Caledonian crocodile (Mekosuchus inexpectatus). In Ross, C. A. (consulting ed.) Crocodiles and Alligators. Merehurst Press (London), p. 36.
- . & Buffetaut, E. 1987. Mekosuchus inexpectatus, n. g., n. sp., crocodilien nouveau de l'Holocene de Nouvelle CalÃ©donie. Comptes Rendu de l'Academie des Sciences, Paris, Serie II 304, 853-856.
Buffetaut, E. 1983. On the late occurrence of an archaic crocodilian in the Pleistocene of the Isle of Pines (New Caledonia) and its biogeographical significance. Comptes Rendu de l'Academie des Sciences, Paris, Serie II 297, 89-92.
Mead, J. I., Steadman, D. W., Bedford, S. H., Bell. C. J. & Spriggs, M. 2002. New extinct mekosuchine crocodile from Vanuatu, South Pacific. Copeia 2002, 632-641.
Molnar, R. E., Worthy, T. & Willis, P. M. A. 2002. An extinct Pleistocene endemic mekosuchine crocodilian from Fiji. Journal of Vertebrate Paleontology 22, 612-628.
Naish, D. 2001. Fossils explained 34: Crocodilians. Geology Today 17 (2), 71-77.
Salisbury, S. W. & Willis, P. M. A. 1996. A new crocodylian from the Early Eocene of eastern Queensland and a preliminary investigation of the phylogenetic relationships of crocodyloids. Alcheringa 20, 179-226.
Vences, M., Vieites, D. R., Glaw, F., Brinkmann, H., Kosuch, J., Veith, M. & Meyer, A. 2003. Multiple overseas dispersal in amphibians. Proceedings of the Royal Society of London B 270, 2535-2442.
Willis, P. 1993. Trilophosuchus rackhami gen. et sp. nov., a new crocodilian from the early Miocene limestones of Riversleigh, northwestern Queensland. Journal of Vertebrate Paleontology 13, 90-98.
- . 1997. New crocodilians from the late Oligocene White Hunter Site, Riversleigh, northwestern Queenslands. Memoirs of the Queensland Museum 41, 423-438.
- . & Mackness, B. S. 1996. Quinkana babarra, a new species of ziphodont mekosuchine crocodile from the Early Pliocene Bluff Downs Local Fauna, northern Australia with a revision of the genus. Proceedings of the Linnean Society of New South Wales 116, 143-151.
- . & Molnar, R. E. 1991. A new middle Tertiary crocodile from Lake Palankarinna, South Australia. Records of the South Australian Museum 25, 39-55.
- ., Molnar, R. E. & Scanlon, J. D. 1993. An early Eocene crocodilian from Murgon, southeastern Queensland. Kaupia 3, 27-33.
- ., Murray, P. & Megirian, D. 1990. Baru darrowi gen. et sp. nov., a large, broad-snouted crocodyline (Eusuchia: Crocodylidae) from mid-Tertiary freshwater limestones in Northern Australia. Memoirs of the Queensland Museum 29, 521-540.
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"it also got as far west as Vanuatu"
That should presumably be "as far east as Vanuatu".
I had a brief moment of perplexity when I misread that as 'Effete Island'...
Is there new information forthcoming about these highly interesting creatures (like the crocs from the Indian Ocean (Aldabra etc...) (Datrren a book like this could be an instant hit) ? I als read somewhere about a (very old) croc in New Zealand which which must be a new genus. Has anybody out there (Scully!) have more news about that strange being ?
The New Zealand croc - which may well be a mekosuchine according to Ralph Molnar - was published here...
Molnar, R. E. & Pole, M. 1997. A Miocene crocodilian from New Zealand. Alcheringa 21, 65-70.
But the remains are not yet good enough for it to be named. Ewan Fordyce has an article on the animal here.
As for the Aldabran animal, stay tuned.
Interesting! I see you started recently extinct megafauna articles!
BTW - any links to the recent rumour that saltwater crocodiles (and not nile crocodiles) were recently resident along East African coast?
I just gave a lecture this evening on Pacific Island extinctions (cribbing mostly from Steadman's book) and got home to find this posting. Wish I'd thought to say more about crocs. Plus I'd completely forgotten about Vences et al. when mentioning the strange case of the Fijian frog. Oh well. Lovely overview, well done.
I've heard about these alleged east African C. porosus but have been unable to find out anything about them: wikipedia cites Adam Britton's page as the source for this, but Adam only mentioned the Seychelles, not mainland Africa [go here]. We know that C. porosus was formerly present on the Seychelles (Gerlach & Canning 1994) - as for mainland Africa, confirmation is needed... given how close the Seychelles are to Africa (they are 1600 km off the coast of Kenya), however, it's certainly conceivable.
Ref - -
Gerlach J. & Canning, K. L. 1994, On the crocodiles of the western Indian Ocean. Phelsuma 2, 54-58.
Since Mekosuchus was terrestrial, aren't crustaceans (i.e., crabs) a more likely major food item?
On a more general note, it's fascinating that so many oceanic islands turn out to have had very diverse reptilian 'megafaunas', until practically yesterday (geologically speaking). Suddenly the GalÃ¡pagos Islands don't seem quite so special anymore.
Yes: when this article was published at ver 1, I believe land crabs (and other crabs) were suggested as possible prey for New Caledonian mekosuchines.
As for the Galapagos not being so special: yes, this is exactly what I say when I start my lectures on recently extinct fauna. Until recently, pretty much all the island groups of the world were like the Galapagos. One example: look at the big lizards and endemic passerines (one of which was flightless) formerly present on the Canaries.
Are mekosuchine limbs sprawling, or are they erect??
Thanks in advance.
Nice to see this article again on TetZoo. I once made a reconstruction drawing of Volia athollandersoni:
Thanks for the info Darren.
There is an awful lot goin' on in Kenozoic New Zealand, lots of new ducks are named so we'll be hearing more about that fascinating area.
And it still intrigues me.
There are no 'old' fossils known about these emperors of the bird-kingdom.
I wish I could transport me back into the ancient time in Australia. Running crocs with Tyranosaurus-like killing teeth competing with marsupial wolves, lions, giant monitors and archaic snakes.
There was a frog in Tonga?!? No way whatsoever to get there other than by overseas dispersal.
should actually be xiphodonty, and is in fact sometimes spelled that way. That's because it comes from Greek xiphias, "sword". Only in English is x ever pronounced the same way as z in the first place.
How terrestrial was it really?
Because until recently no terrestrial fossils between the Late Cretaceous and the Pleistocene were known from New Zealand at all.
David, there are still oceanic frogs like the Fiji Tree Frog (Platymantis vitiensis). This frogs show a tolerance towards salty water, and actually sometimes flee into the sea.
Harsh reviewer, sir! But hey, youo've since given up being credible anyway, what with your separation of rauisuchians and torvosaurs. *sorry, couldn't help it!*
Awesome article, though. It's so sad that so many awesome critters have been driven to extinction by humans. I like the idea of crocs eating land crabs. "Hit the weak point for massive damage!"
Interesting stuff. I have to admit, Ive never heard of these crocs.
On a differnt but tetrapody subject, did you see the photo of the deer swimming across Fal Harbour? I made a brief post on it today http://my.opera.com/Ukwildlife/blog/deer-in-fal-habour
Not if it had to go through the servant's entrance.
In contrast the cheloniform wyrms only started migrating into the South Pacific region some 5,000 years ago, coinciding with the spread of the early Polynesians into the same localities. The dragon turtles of the Eastern Pacific are now known to be descended from a tribe of ophidian wyrms who settled the area from North America.
A 50,000 year old shen lung specimen was discovered in the Sulu Islands of the Philippines not so long ago, and it was thought to be representative of early shen lung colonization. Until it was determined that the individual in question was a time traveler from 1965. But not our 1965.
Found with his possessions, carefully preserved in an odd container, was a newsclipping reporting the capture of a lich before he could finalize plans for the assassination of former Vietnamese President and long time US Ally Ho Chi Minh. As anyone who has lived through the Lich King's War, that is not what happened in this time line.
Oh! Instead Galapagos is unique in preserving in our time the islander reptilian megafauna biome vanished in the rest of islands......
For the oceanic frog....any species of amphibian can breed on saltwater? (sounds like a possibility for spec-evolution of marine things like large Telmatobius-like ambushers....)
I've been getting bits of Mekosuchus and Trilophosuchus as well as Baru out of a couple of late Oligocene deposits at Riversleigh over the last few years. There's particularly nice material of a small Mekosuchus whitehunterensis, associated with distinctive osteooderms (narrow and relatively smooth, except for a neck shield with huge dorsolateral crests reminiscent of an aetosaur), vertebrae, and limb and girdle elements. I have limited comparative material but the limbs, girdles and caudal vertebrae look perfectly normal to me, not supporting a view that it was much different from extant Crocodylus in locomotor abilities, but the head shape and neck shield are certainly outside the modern range. I try to keep an eye out for claws, and so far have never seen a croc ungual suggesting climbing ability (i.e. none that are strongly curved and/or laterally compressed).
I've sent Darren a rough skull reconstruction which he can post if he wants; at some point I'll try and draw the whole animal (with significant differences from the M. inexpectatus shown in the post above), but probably should get to work on describing the material first.
I don't think it's especially likely that mekosuchines swam thousands of kilometres across the open Pacific, more likely it was rare instances of passive rafting. Arboreal habits would have helped a lot with this (the reptiles Australia has received from Asia are mostly either aquatic or arboreal, including pythons, goannas, agamids, homalopsids and colubrid tree snakes) but don't seem to be necessary, because the terrestrial meiolaniids had a very similar pattern of dispersal from the mainland to volcanic Pacific islands.
I'm not a crurotarsiologist*, and someone else can no doubt give a better answer, but I'd guess that what's meant here is that Mekosuchus was terrestrial relative to extant crocodilians. In which case it could still have been an excellent swimmer and perhaps even an occasional fish-catcher, a bit like the extant Asian water monitor Varanus salvator (De Lisle, 2007).
* Is that a word? Well it is now!
Regarding the potential food sources available for Mekosuchus, it may be noted that New Caledonia has surprisingly many freshwater fish species (most of them originally marine, though).
De Lisle, H.F. 2007. Observations on Varanus s. salvator on North Sulawesi. Biawak 1, 59-66.
Supports overseas dispersal.
I knew about Fiji, just not about Tonga.
There is one whose tadpoles and adults can live in saltwater (I think Fejervarya cancrivora), but freshwater is required during metamorphosis and I think for the eggs.
Frogs on Tonga? I think David is responding to my statement: "We have only recently (viz, post-1980s) discovered that Fiji and Tonga were home to recently extinct big frogs, iguanas, giant pigeons and other tetrapods". I did not mean to imply that all of those animals were found on both Fiji and Tonga, my bad.
As for anurans (and salamanders) in saline water, go here.
re. #24: Did Tongans and Fijians bring those from Asia (like the chicken and rat), or were they clearly indigenous?
Correct. Successful spawning and metamorphosis require low salinity in the crab-eating frog (usually 'Rana cancrivora' in older publications). After hatching, tadpoles do well and grow large even in sea water, but they won't metamorphose unless the salinity drops to almost freshwater level. Gordon & Tucker (1965) suggest that in the crab-eating frog's natural habitat, this happens when torrential monsoon rains temporarily dilute the saltwater ponds where the tadpoles are developing.
Gordon, M.S. & Tucker, V.A. 1965. Osmotic regulation in the tadpoles of the crab-eating frog (Rana cancrivora). The Journal of Experimental Biology 42, 437-445.
...and by this I of course meant that the ponds the frogs spawn/develop in, and not the frogs themselves, have low salinity.
For what's worth, I've found a crab-eating frog in the middle of a mangrove swamp (no idea how saline the water was though), and I've also spotted common Asian toad (Duttaphrynus melanostictus) and banded bullfrog (Kaloula pulchra) in parks along the coast and rather close to the sea.
It's so sad that so many awesome critters have been driven to extinction by humans."
Especially since it seems like all the really awesome stuff died out first (giant lemurs, these crocs, all sorts of crazy birds, etc)...
So much for Kaloula being a microhylid, then! ;-)
How magnanimous of the reviewer to allow that you were still a credible scientist. It probably grated on him to admit it.
I suppose it will need to wait for a Witton reconstruction of a lumberjack crocodile, leaping from tree to tree, perhaps eating its lunch and wearing high heels, before such a lifestyle can be accepted by crurotarsologists.
I'm sorry. But a Mekosuchine in a pre-varanus australia would at least not have a fully round tail, maybe one convergent in some way or other. And Wroe's interpretation of Reptillian Superiority is laugable. Trilophosuchus would probably be able to climb, seeing as it's small enough, but some reconstructions showing it with a fully flattened tail is abit silly, but stanton has the right idea, and does endless redraws thankfully.
Mind you, like modern goannas Trilophosuchus would have been a good swimmer, but current crocodile paleontology would suggest that a climbing Mekosuchine crocodile would be possible through convergence, curotarsans in general are just too "plastic", notice I dont use conservative or such.