Friday mystery object #149

This Friday I have a pair of skulls (top and underside) for you to have a go at identifying. Do you think they are from the same species, or do you think they represent two different species? (N.B. You can click the image for a bigger version)

As usual you can put your questions, comments and suggestions below and I’ll do my best to reply. Good luck!

23 thoughts on “Friday mystery object #149

  1. Family is **d**t**. The spike behind the eye you get on *qu****s here, but too big. They are both old because the bit between the back of the nose and the spine bit is smooth and no cracks. The teeth on the one on the right are worn down so it could be older or eat different stuff. It had a short nose.

  2. Oh I think I might learn some really useful technical stuff this week. I need to be more ‘genned up’ on the names of all the sutures and foramen and such. I am used to telling the difference between field and bank vole teeth, so there is usually more to it than just differences in maturity and wear, and some animals may be more robust, or just male and female. Where the nasal and maxillary bones meet the frontal bone looks interesting? I don’t think I’ll get much gardening done today!

  3. The rear of the skull is more rectangular on the right hand specimen – is that enough to indicate species difference? As Jake observes, the teeth suggest different diets. Perhaps it is a difference of colour g or r but comparisions found on the web suggest g has a noticably longer snout than r.

  4. Further to my earlier comment, based on nasal length (say 15mm) I would guess both are examples of the vulgar visitor rather than resident caroline. However, that doesn’t explain the more rounded appearance of the left hand skull which makes me wonder if they are different species not found in the UK.

  5. Two little pointy teeth at the front suggest rodent but then there’s that big gap in the teeth – I know that is indicative of something but can’t remember what. The molars look like they’ve done a lot of grazing. The jaw is narrow but there’s that big zygomatic arch? to support big cheek pouches? And it looks like there’s room for big eyes. So, something tiny, nocturnal, that eats vegetation. There’s an image in my mind but I’m not sure what the name of the animal is. Lorus maybe.

    • The gap between the teeth (the ‘diastema’) is typical of herbivores, at least when it’s this large (carnivores often have a short one, just so they can slot their lower canines in). That’s likely to indicate either a rodent, a lagomorph, or an ungulate – although there are a few exceptions.

      There’s a couple of other things about the front teeth that say it’s a rodent (and not, say, a rabbit).

  6. Rodent, and large-ish as such things go (although not huge). The skull looks to be sciuromorphous, but its hard to be absolutely sure from the angle. I’m leaning towards some type of squirrely thing too.

  7. The fronto-parietal and fronto-nasal sutures are quite different, which to me suggest two different species. The tooth wear on the other hand may just be that the left animal is older or has eaten a much more abrasive diet. I have no idea what species it is, apart from some kind of rodent.

  8. Obviously rodents, and not muroid. I’d say sciurid, partly because they’ve got two maxillary premolars, which I think is fairly unusual for rodents. The shape of the postorbital bars also looks scurid-like. The snout is pretty short, but they may be immature, since the suture lines look quite distinct (although not *that* immature, as the teeth are worn down). Which would suggest one or two of the bigger ones.

    As to whether they’re the same species… the shape of suture lines is noticeably different behind the rostrum, and that’s the sort of thing that may well be diagnostic. Most of the other differences I could put down to intraspecific variation, especially if, say, one’s a male and one’s a female. But the shape of the rostral bones… yeah, I’m guessing that’s more likely to be significant.

  9. Kate mentioned cheek pouches, I have found a reference to this indicating ground s……. in which case ‘the muscles involved would leave a prominant scar just behind the upper incisors.’

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