On Friday I gave you this skull to identify:
I used this skull because the shape really appealed to me when I stumbled across it in one of my office drawers – here are another couple of views of the same specimen:
Most of you quickly worked out that this skull belongs to a rodent – and a big rodent at that. The inflated nasal region was also quickly picked up by some of you and I think that’s what led Jonpaulkaiser to the correct answer first, followed by Neil who also managed a species level identification. Well done to everyone though, there were lots of very close attempts, with several of you missing out by a quill’s breadth – if you’ll excuse the frankly awful pun. This is of course (if you didn’t guess from the bad pun) a Crested Porcupine Hystrix cristata Linnaeus, 1758.
These prickly African mammals are the third largest rodents (after Capybara and Beaver) and they are decidedly odd looking beasties. Their nasal region is greatly inflated and their infraorbital foramen (the hole in front of their eye) is huge and allows one of the muscles used in chewing (called the masseter) to pass through and attach to the maxillary bone on the side of the snout region (the maxilla is the piece of the skull that the back teeth are embedded in). Usually this muscle is attached to the cheekbone (sometimes called the zygoma – which is the cheeky namesake of this blog). If you look at the second image above you can just make out the scar along the snout where the masseter muscle was attached.
Some of you may have mistaken the diagnostic large infraorbital foramen as an enclosed forward-facing eye socket, which would understandably cause some confusion – after all, porcupines have tiny eyes on the sides of their head and they rely more on their sense of smell, hearing and touch (via long whiskers) to find their way about and detect hazards in the darkness (they’re nocturnal).
Porcupines are pretty cool animals – they can see off a Leopard using their modified hairs and they can even act as accumulators of fossil cave-fill deposits by virtue of their habit of dragging bones back to their dens, where they gnaw them to keep their teeth from overgrowing and for the calcium they contain.
I keep referring to the generic name “Porcupine” but there are over two dozen species of rodent called “Porcupine” and they fall into two quite distinct families that are not closely related. The spiny defence mechanism these animals use is so effective that it has arisen several times (in different forms) in various groups of mammals – from the primitive Echidna through Spiny Bandicoots to Hedgehogs, Spiny Tenrecs and Porcupines. Some humans have even tried it.
I hate to be one of those freudian zoologist but isn’t the Mara was the third largest rodent?
SJG wrote a good article about sizes in zoology. Maybe the subject needs revisiting.
EDIT: Pedantry corner too! I meant third largest extant rodent.
I suppose it depends on what measure of size you use. Mass is the unit of size that I was thinking of, in which case Mara’s are fourth:
Capybara usually up to about 65kg
Beavers usually up to about 25kg
Porcupine usually up to about 23kg
Mara usually up to about 11kg
Pingback: Friday mystery object #142 answer « Zygoma