Fossil Friday – bite marks on a camel skull

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One of the specimens we have on display at the Western Science Center is a cranium and partial vertebral column including the neck of the camel Camelops hesternus. A closer examination of the skull reveals some surprising features. 

The parietals (the bones that make up the back half of the top of the braincase) have a series of holes and apparent scrapes:

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At first I thought the two back holes might be an anatomical feature called the parietal foramen. However, parietal foramina are uncommon, usually forming as a developmental abnormality. I’ve been unable to find images or reports of parietal foramina in Camelops or any other camel. The holes in this specimen are not symmetrical in their position (each one is located in a different position on its respective parietal), and there are cracks in the parietals leading to the holes. Finally, if these were parietal foramina, it doesn’t help to explain the presence of the other hole located at the front of the parietal.  Taken together, this suggests that the holes are not an anatomical feature but instead are bite marks from another animal.

I originally envisioned a carnivore grabbing the camel by the top of the head, with its head held almost parallel to the camel’s head, and then dragging the camel’s head and neck away from the rest of the carcass. This would mean that the four parietal marks (three punctures and one scrape) were made by the four canines of the carnivore in a single bite. Darla and I pulled out cast skulls of several different carnivores to try this out, but we couldn’t get it to work. If we assume that the four marks were made in a single bite, then the spacing is about right for a small dire wolf, a black bear, or a jaguar. However, when we tried to simulate the bite the predator’s incisors would always hit the sagittal crest (the ridge of bone along the top of the skull) long before the canines reached the parietals. If we went with larger animals with longer canines like a short-faced bear or an American lion, the canines would reach the parietals but the spacing was far to close for such a large animal.

I now think that it’s more likely that the punctures were caused by multiple bites, by a carnivore coming at the skull from an oblique angle (possibly multiple angles), something like this:

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This actually may be more consistent with the behavior of modern carnivores; if you want gory confirmation, do an image search for “hyena carrying head” for examples of how scavenging carnivores transport prey. There is also some evidence that there may be additional bite marks all over this skull, consistent with multiple bites. There are two unusual depressions in the top of the frontal bone, several holes along the edge of the right lambdoidal crest at the back of the skull, and damage to part of the right squamosal. To be fair, none of these additional marks are sure things; if not for the four bite marks on the parietal I would have never considered these as likely candidates for bite marks.

Another observation I would not have thought twice about except for this context is the damage at the front of the skull. The nasal bones are damaged, and the premaxillary bones are missing entirely. The premaxillae can loosen and fall off as a skull dries out, and that’s normally how I would explain this. But if this skull was being chewed up by carnivores it raises another possibility. It seems that the nose is one of the choice bits of meat on the skull for a carnivore. There’s a lot of meat and blood in the nose, and it’s easier to get to than the brain. Moreover, while cats such as lions usually kill their prey with a bite to the neck, closing the windpipe, an alternate method used on occasion is to bite down on the nose. Is it possible that the missing premaxillae in this specimen is another predation feature?

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