12 March 2010

Maybe a fox jaw—I don't know


This pair of jaws are from a field trip back in January during which I also found a deer skeleton. Each jaw is about 9 cm long. Both are missing the incisors and the canines.

I found them in a hedgerow on one side of which was a farm field and on the other side a hill leading up to a residential building. I am suspecting that they belonged to either a small fox or a small dog. Raccoons seem to have a more curved lower jaw. I don't have enough expertise to tell the lower jaw of a fox from that of a dog. In fact, it may not be possible to reliably distinguish the 2 species from each other only from lower jaws unless large samples are available to do a statistical comparison.


pascal said...

I suspect you've got the lower jaw of the Virginia opossum (Didelphus virginiana).

Most mammals can be diagnosed via their molar formula. The other skeletal features are often very similar. Especially, as you noted, among similarly-sized members of the same family (such as canines).

Note that the molars are all nearly equidimensional. Foxes and other canines typically have a very large first molar compared to the others. The molars of this specimen are nearly the same size.

Also, there appear to be four molars, which indicates a marsupial (placentals only have three). The dental formula for an opossum's lower jaw is (four incisors, one canine, three pre-molars, four molars). The red fox (Vulpes vulpes has three molars and four pre-molars.

Also, look at the curvature of the lower jaw of the fox. compared to the opossum.

The jaw shows a more angular curvature, whereas the opossum has a more smooth curve throughout the length of the jaw. Also the openings for blood vessels (towards the distal end of the mandible) are deeper and more distinct on the fox.

fred schueler said...


Neil said...

Yep, those four molars are very distinctive. Definitely opossum.


Opossum it is! Thank you all for correcting me.

Anonymous said...

iv got a identified fox scull, this has a simular jaw structure, but the teeth are not the same, so id bet on it being a opossum...