Last week I gave you this skull from the Grant Museum of Zoology to identify:
I thought it was a fairly easy one and, from the slew of correct cryptic answers, I think many of you spotted what it was quite quickly. However, if you’re not familiar with this sort of abstract critter, you probably found it more of a challenge.
In terms of physical characteristics, the vacuities (holes) in the palate are a sure indicator that this is a marsupial – as Allen Hazen pointed out. He also recognised that it has a broad head and short rostrum (nose) for a marsupial, narrowing down the possibilities – particularly for an animal of this size – Wombats or Koalas.
For me these two main options can be quickly distinguished by looking at the zygomatic arch, which is high at the rear and runs downward in the Koala, but which runs horizontally in Wombats. The skull of the Koala is also very square and flat on top, whereas Wombats have a more domed braincase.
Many of the cryptic clues referred to bears, since these animals are often called a Koala Bear for some bizarre reason – I must say that I’ve never seen much similarity between a Koala and a Bear, although once upon a time people thought Red Pandas were bearlike as well and I suppose the two species have some fuzzy, tree climbing and specialist-diet type similarities.
Koala climbing a tree. Photo by DAVID ILIFF. License: CC-BY-SA 3.0
So well done to everyone who managed to identify the specimen and provide some great cryptic clues, especially Chris who was first on the scene with a reference to bears and the obscure ‘pap’ which is the first solid food of Koala joeys, which is partially broken down eucalyptus released from the caecum of the mother.
A special mention for palfreyman1414 who was tenacious is working out the mystery and who also managed to provide a reference to a story I’d not heard before about a man in New Zealand who reported an unlikely incident to Police and got in some trouble for it.
Zygoma 
Ha ha ha! You actually bothered to look it up. Nice one.
Now can I please have “awkward large anthropoid” explained? Please?
I also seem, in my travels through the interwebs, to have gained the impression that koalas, but perhaps not wombats, have teeth behind their incisors (diprtotodon) that in wombats are totally diastemas, or some such? Or have I interpreted that incorrectly?
Palfreyman–
In the piccies Paolo has posted (maybe others, since Iooked for skull images of both “cousins”… but the ones I found may have been the same specimens that Paolo has posted!) it looks as if
(i) wombat has an uninterupted upper diastema between the incisors and the “molar” row
(ii) the koala has a small tooth maybe 40% of the way back… though, since I can’t see where the premaxila ends and the maxilla begins, I have no idea whether it is another incisor, or maybe a vestigial canine. Curious.
Rabbits, of course, have a second pair of upper incisors, but they are close enough behind the main pair that they look as if they had a special function. (Maybe, to nip something off very neatly and carefully — the local hare took a bud off the top of my 3-year-old oak tree so neatly this past spring that I initially thought some human with clippers had been vandalizing it — the lower incisors get put BETWEEN the first and second uppers?) But the extra tooth in the koala’s upper jaw looks too far away from the front incisors to be used in the same way. Curious.
Any ideas, Paolo? Do you have other Wombat and Koala skulls to compare to see if this is really a difference between the species and not just individual variation?
Good points. I do not know about the wombat diastema except for perhaps the same pic we all seem to have seen. But with Koalas, I seem to recall that this second set of incisors (or whatever they are) are a feature of the species. Perhaps Paolo know?