Last week we had a guest mystery object from Rohan Long, Curator of the Harry Brookes Allen Museum of Anatomy & Pathology at the University of Melbourne:
It is not an easy one. This part of the mammalian skull contains very few helpful diagnostic features – as pointed out by Kenny Travouillon:
Plus this is from a juvenile animal, and we all know how that can cause problems when making an identification.
Thanks to everyone for your comments – Rohan was keeping and eye on them here and on Twitter, so I’ll hand over to him to wrap this one up:
Well, it’s been a week, and many identifications for the mystery skull were offered on Twitter and in the Zygoma comments. Some suggestions were silky anteater, marsupial mole, pangolin, armadillo – but the focus quickly turned to marsupials. On Twitter, mammal curator Kenny Travouillon said it was not peramelemorphian or macropod, zooarchaeologist Jillian Garvey said that it could be macropod. Early on, biology lecturer Robin Beck said that it was definitely a phalangerid, and that it was probably a juvenile common brushtail possum (Trichosurus vulpecula). Robin identified the specimen as phalangerid based on the restriction of the mastoid exposure to a ventral strip on the occiput, and then narrowed down to trichosurine, rather than a phalangerine, due to the relatively flat dorsal profile of the skull. The bone texture indicates a juvenile specimen. (Richard came to the same conclusion in the Zygoma comments.)
I went digging around in our comparative anatomy collection to investigate this and then clouded matters a bit, as I found a partial skull of a juvenile common ringtail possum (Pseudocheirus peregrinus) which was superficially similar to the mystery skull. I thought this was the real identity of the skull, but Robin pointed out that the ventrally restricted mastoid exposure, more recessed stylomastoid foramen, and a well-developed pterygoid fossa all point to Trichosurus rather than Pseudocheirus.
I think this partial skull is conclusively identified to genus. I have already identified a number of (less ambiguous) Trichosurus specimens within the comparative anatomy collections. Although it would take more work to definitively ID the species, I think it is likely to be vulpecula – a very common and widely distributed species in Australia. As you may have noticed from the original images, the specimen has sand grains adhering to it. Based on this, I’d say that this was collected in the field, probably by Frederic Wood Jones (or members of the McCoy Society for Research and Investigation, which he founded) in the 1930s.
Thank you all for your suggestions and discussion!
Finally, I’d like to add my thanks to Rohan for giving us this mystery object to mull over. If anyone else fancies doing a guest mystery object, please do get in touch.