Last week I gave you this really difficult, but incredibly cool mystery object to identify:

Definitely not a simple one for the uninitiated, but most of you got impressively close.

It looks a bit like ancient chewed gum at first glance (hey, it’s a thing!):

A nearly 6,000 year old piece of chewing gum, found in Scandinavia, perfectly preserved the DNA of its chewer. She was a young, hunter-gatherer girl, with dark skin, brown hair & blue eyes, who had recently eaten a meal of hazelnuts & duck. Archaeology is amazing. pic.twitter.com/kfav9PkonE

— Dorsa Amir (@DorsaAmir) July 13, 2023

However, on closer inspection, some of the features start to emerge – including teeth:

Obviously, this is the fossilised skull or some critter, but what kind of critter is harder to determine.

The length suggests it’s something about the size of a rabbit:

And if you’re looking for a good fossil rabbit, you can’t beat Palaeolagus:

As you can see, the mystery object has a few differences, but due to the various missing parts, it’s a little hard to be confident exactly how different they are – although the shape of the orbital margin (the front of the eyesocket) gives a bit of a hint.

But, even more useful, is the curve in the maxilla (the upper jaw bone) that traces the root of the first incisor. In lagomorphs (rabbits, hares and even pikas), the incisor roots terminate with quite a big gap before the orbital margin, often with a triangular fenestrated region of cancellous bone (a sort of window of bony struts) in between.

The mystery specimen doesn’t have that – in fact the end of the incisor root is very close to the orbital margin. This is something you see in rodents.

I would have been impressed if you got that far, since the overall shape and size of this specimen definitely gives off a rabbity vibe, but believe it or not, this a dormouse. More specifically, it’s the Gigantic Dormouse Leithia miletensis (Adams, 1863) or if you want to go with the commonly used and more technically accurate, but nomenculatorily incorrect, L. melitensis, since Adams made a spelling error in his original description.

In fact, this is one of the specimens collected and figured by Adams in that original work describing the species, making this part of the type series for the species (although the holotype is more likely to be a very well preserved half mandible from the same site).

The fact that this is a fairly large and intact part of the type series means that it is of great interest to researchers. The reason I had this specimen to hand for the mystery object, is because I was preparing it for a research loan to some of my old colleagues in UCL, where it’s being MicroCT scanned.

This research will help refine an understanding of the morphology of the Gigantic Dormouse and offer some clues to what happens on islands that leads to the development of giants, building on work that they’ve been doing on this fascinating species, which is an interesting read that you can find here (you may even recognise Fig. 1B).

Virtual Cranial Reconstruction of the Endemic Gigantic Dormouse Leithia melitensis (Rodentia, Gliridae) from Poggio Schinaldo, Sicily, By Jesse J. Hennekam , Victoria L. Herridge, Loïc Costeur, Carolina Di Patti, Philip G. Cox – CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=92037373