On Friday I gave you this skull as a mystery object, dredged as it was from the memory card of my severely concussed camera:

This was a slightly sneaky object, because I had a feeling that quite a few of you would make the same mistake as I did when I first saw this skull, by assuming that it’s from a large rodent. The large front teeth (the incisors) support this, since enlarged first incisors are a feature of the rodents.
Rodents also have a large gap behind those incisors called a ‘diastema’ – which this skull has for the lower jaw (or mandible), but you may notice that the upper jaw has three incisors in the pre-maxilla (that’s bone in the front bit of the upper jaw) before the diastema. This is easier to see in a side (or lateral) view:

You might notice that there’s a small tooth behind the third incisor in the upper jaw – that’s a canine. You might also notice the faint wiggly line in the bone of the jaw just above the canine – that’s the junction (or suture) between the maxilla and the pre-maxilla bones. The canine is the first tooth in the maxilla and all the incisors are in the pre-maxilla (this is the same for all mammal teeth).
Rodents only have two teeth in the pre-maxilla, not six. They also have no canine teeth in the maxilla. That means this mystery object cannot be a rodent. Here’s what a rodent’s diastema looks like (the suture between maxilla and pre-maxilla is really clear in this photo):

Lagomorphs (rabbits and hares) have teeth similar to rodents, except they have an extra pair of incisors behind the front pair in the maxilla – these are called ‘peg teeth’:

Peg-teeth in a Rabbit skull
Clearly the mystery object has more incisors than this, plus those canines, so it can’t be a lagomorph either.
So what beastie has six upper and two lower incisors? Several of you worked out that this was a marsupial from the dentition (namely Cromercrox, jonpaulkaiser, David Craven and Zigg), but only Prancing Papio and Jamie Revell managed to get it to species, namely the Continue reading →