Cretaceous dicynodont is not a dicynodont

[Halichoeres]

In 2003, a few small fragments of bone thought to be from Cretaceous rocks were described as a dicynodont, which would make the specimen by far the most recent dicynodont, which otherwise went extinct by the end of the Triassic. More recently, another paper suggested it could be a baurisuchid stem-crocodile. This paper re-examines the specimen and concludes that not only is it not from the Cretaceous, it's a proper mammal. Specifically, it seems to belong to a marsupial related to Diprotodon, along with wombats, koalas, and kangaroos.

Summed up graphically:


Paper (open access, I think, in Gondwana Research): https://www.sciencedirect.com/science/article/pii/S1342937X19302254

[suspsy]

Always knew there was something wrong there. Good that they finally figured it out!

[Ravonium]

Thanks for sharing this. I wonder though; how did the original researchers even mess up that badly in the first place?

[Funk]

Hehe, reminds me of that "Thalassodromeus" bone that turned out to just be part of a turtle shell, but was originally used to justify a huge ghost lineage as well, and even as basis for a new species.

It should be apparent by now that almost unidentifiable fragments should never be enough to base such far reaching conclusions on... At most, mention the possibility, but don't make it your main hypothesis.

Those late surviving Cretaceous temnospondyls are pretty solidly founded though, no?

[Halichoeres]

Thanks for sharing this. I wonder though; how did the original researchers even mess up that badly in the first place?

I don't know, I think it's just really hard to be sure what you're looking at when the specimens are highly eroded fragments. Australia's Mesozoic record is mostly crap--remember how the Vickers-Rich team decided they were looking at a  ceratopsian based on a single ulna?

Those late surviving Cretaceous temnospondyls are pretty solidly founded though, no?

Yeah, I think so. Koolasuchus seems to be a perfectly good temnospondyl, and of course Jurassic Gondwana is replete with exemplars (not so for dicynodonts). Of course, if temnospondyls are paraphyletic with respect to lissamphibians, which they probably are, then frogs, salamanders, and caecilians are also temnospondyls.

[Newt]

To be fair, diprotodontids are really just the marsupial versions of dicynodonts.


I've been reading a lot on Early Permian vertebrates lately, and there are tremendous numbers of such misidentifications based on scrappy or damaged material, many originating with good old Eddy Drinker Cope, who seems to have worked with more enthusiasm than care at times and would attach a name to any material, no matter how meager. But many of these misidentifications survived inspection by later, more careful workers for years before being corrected, so it's unfair to pin it all on Cope's hasty speed-science. For example, the amniote genus Otocoelus and family Otocoelidae were considered a remarkable case of convergence between a reptile and the armored temnospondyl Dissorophus. Otocoelus was extensively discussed as a potential turtle ancestor. Turns out Otocoelus really was just a specimen of Dissorophus with some damage to the skull creating the impression of an amniote-style occiput.


Many other misidentifications become apparent only after recovery of more complete remains - witness the many Triassic "ornithischians" that have turned out to be silesaurids and revueltosaurs, clades of herbivorous Triassic archosaurs with ornithischian-like teeth that were entirely unknown until recently.


My point, if any, is that misidentifying bone scraps is easy, and usually only obvious in hindsight, so we should be forgiving of such mistakes. Remember that in science, getting things wrong is the first step to getting them right!

[Funk]

Not to mention Marsh's Bison alticornis which turned out to be Triceratops, but of course, modern scientists should be held at much higher standards than the pioneers...

[Papi-Anon]

Well, time to change the little Cretaceous flashback in my WIP scifi story:

The mammalians' endurance, while not impossible to fathom, still surprised Cuga, and rekindled his interest in the former heirs of his first servant. Even some of the ancient, more derived group of synapsids that had soldiered through the previous purge had lingered on up until several million years ago. Truly the synapsids were unrelenting in their survival as a clade.