On Friday I gave you this unidentified object from the Horniman’s collections and asked for your help in identifying it:
Suggestions ranged from the Easter Bunny (topical) to Dangermouse (fantastic), but there was a remarkably fast convergence of opinion on what this is.
Jamie Revell, Barbara Powell, henstridgesj and Jake all came to the conclusion that this is the skull of a Grasscutter or Cane Rat Thyryonomys sp. (Fitzinger, 1867). There opinion divided somewhat, as there are two species of Cane Rat, the Lesser and the Greater. I personally lean towards the Lesser Cane Rat Thryonomys gregorianus (Thomas, 1894) rather than the Greater Thryonomys swinderianus (Temminck, 1827), but how did we all get to Cane Rat in the first place?
First of all the skull is large. Most rodents are smaller than this, which helps restrict the possibilities. Next, the cheek teeth are distinctive. There are four of them and they have a shape that marks them as belonging to a member of the Hystricomorpha.
The large and distinctive infraorbital foramen (they’re the holes in front of the eyes that you can just make out in the middle picture of the specimen – I’ve talked about them before) tell us that this animal is also a Hystricognath. This narrows down the possibilities to a point where it becomes fairly easy to start comparing this specimen with other skulls, especially when many of the possibilities have been narrowed down by looking at the teeth above.
It didn’t take long to narrow the choices down to one of the Cane Rats and the excellent Mammals of Tanzania skull key provided the information to select the Lesser Cane Rat over the Greater – apparently it’s all about how the degree to which the skull arches at the front. Thanks to everyone for helping confirm the identification!
Zygoma 
Another fun FMO. Thanks, Paolo!
I’d like to be able to say that, yes, that’s exactly how I came to that identification. But, no, I don’t know enough about the differences in cheek teeth and foramen. So, it was more a case of trawling through the rodent families with largish species and looking for a match. I couldn’t find a picture of a Lesser Cane Rat skull, but now that I’ve seen the one on the Tanzania site, yes definately the Lesser. But those differences in the cheek teeth are subtle; even knowing what it is, I still don’t think I could ID it as a Hystricomorpha!
Sorry, probably didn’t make it clear – all those teeth belong to members of the Hystricomorpha and they generally look quite similar to each other.
Ah, that makes more sense! 🙂 Thanks.
Congrats and amazing work as always, Jamie Revell, Barbara Powell, henstridgesj and Jake! In the same way that I love to watch Olympians competing in their sport, or dancers in Swan Lake perform, or professional harpists play their instruments I have such a good time seeing you all work on the FMOs. To top it all off, I admire how much expertise you must have, Paolo, to be able to oversee everyone’s guesses so that you can confirm or nudge them in the right direction.