Friday mystery object #219

This week I have an unidentified skull that I found in a box of random bits of bone:


Any idea what it might be from?

As usual you can pop your questions, thoughts and  suggestions in the comments section below and I’ll do my best to respond.

Happy identifying!

43 thoughts on “Friday mystery object #219

  1. The measurements we calculated on the given skull match up perfectly to the average skull size of a Tree Squirrel.

  2. We found by the proportions of the Cephalic index, eye socket width, and teeth configuration that the friday mystery object #219 might be a Sciurus carolinensis, more commonly known as the Eastern Grey Squirrel.

    • That’s what I thought at first, but when I compared it to another Grey Squirrel skull it was considerably different in its proportions and the teeth were somewhat different. Most confusing!

  3. The bit that makes the species obvious to me is the spike at the top of the orbit, so that gets it to the two different colour options. If I found it (in the UK) I would say the duller of the two colours, and it’s up at the top end of the size so it might be from a foreign species. The spike is slightly smaller than mine as well. I’ve tried not to give it away so not to spoil the fun for others.

  4. Looking at the super-orbital arch, it protrudes out from the skull similarly to the skull of the Southern flying squirrel, and we believe the measurements are very similar.

  5. Based on the measurements, number of teeth and the size of the zygomatic arches, we would suggest that it is the skull of a Siberian chipmunk.

  6. Our measurments have also shown to us that the skull shown is closest to an Eastern Gray Squirrel. We measured the amount of teeth, the size of the orbit, and the brain cage. All of these measurements were proportionate to the skull above. Our only concern is that the bullae shown on the skull above was much larger than the Eastern Gray Squirrel.

    • You can’t rely on measurements and proportions alone, the squirrel family is pretty big and there are a lot of very similar skulls that are hard to tell apart…

  7. After thorough comparisons made between the mystery skull and other rodent skulls both around our Biology classroom and in online databases ( proved quite useful), we were able to narrow the search down to a specific genus of squirrel. We surmise that the genus is Spermophilus after comparing Cephalic Indices, ratios regarding the auditory bullae, head and teeth shape, as well as a few other measurements of the distance between the zygomatic arches and other major features on the skull.

    • After first her research specifically among the species of the genus Spermophilus, one species that matched the mystery skull extremely well, and more so than the others of the genus. We conclude that the mystery skull is a very close match to the skull of Franklin’s Ground Squirrel, originally classified in the Spermophilus genus, but re-classified in its own genus as Poliocitellus franklinii.

  8. Based upon measurements (entire skull length;6.1 cm entire skull width;3.1cm, eye socket diameter 1.8cm, etc.) of a skull of the Eastern Gray Squirrel, I agree with the numerous others that the nearest match is the Eastern Gray Squirrel.

  9. Based on the placement of the deep-set eye sockets, the protrusion of the molars from the tooth bed and the size of the jaw, we surmise that the skull belongs to a Rice Field Rat (Rattus Argentiventer).

    • Ah, but you’re missing the nature of the infraorbital foramina and the fact that there is a postorbital process rather than a supraorbital ridge. Remember to look at ALL the characters, not just a few.

  10. After looking at many species in the Spermophilus genus we thought that Spermophilus franklini is most similar in terms of proportions and features.

  11. Based on the structure of the skull and teeth, it is a rodent. In further research I think it is close to the squirrel family. My closest guess is a Fox Squirrel (Sciurus Niger).

  12. Loads of comments! And despite spending far too long looking at various squirrelly skulls this evening, I’m still not sure what it is!

    I agree that S. franklinii looks pretty close, as does Otospermophilus (to me), although the examples of these that I can find on the web seem to have rather more flared zygomatic arches than the specimen above. I don’t know if that’s just variation or being on the wrong track. To be honest, the only thing I can say for sure is that they all look very very similar!

    If those suggestions are on the right track, there’s quite a useful open access paper with lots of good photographs of for comparison here:

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