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’ (image to follow… once an alternative camera has been acquired).
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