Last Friday I gave you a variety of mandibles to have a go at identifying. They lacked a scale bar and represented a range of different species that have similarities in mandible shape.
There were some great cryptic suggestions of identities, but it must be said that Jake came through with a really clear and pretty much spot-on list of suggestions. So here are the answers in a handy form that might be useful for reference:
The Sheep and Cow have a distinctive upward inflexion at the end of the mandible, with the Cow’s being so strong that the incisors start above the level of the top of the molar tooth row – unlike the Sheep’s.
This inflexion is much less marked in the Red Deer, which has a narrower body of the mandible, presumably relating to the less intensive chewing of a browser compared to grazers (grass is tough stuff). The Deer also has a notch along the bottom of the jaw, which Jake pointed out as a useful feature.
The Pig mandible tapers less overall, but is thicker at the end with the articulation – presumably because the omnivorous Pig is chewing differently, using the temporal muscles more than the masseter muscles and therefore needing a different area of the jaw for muscle attachment. The teeth are also pretty distinctive. Like the Pig, the Donkey mandible lacks the long and hooked coronoid process, but is also very triangular in shape with quite squared teeth – features typical of an equid.
So hopefully that gives you some pointers for telling some common herbivore mandibles apart when you don’t have a scale bar – a more common problem for some of us than you might think…
Donkey, eh|? Wow!
Well, it was actually labelled “Ass”, but I thought some of the American readers might take that the wrong way…
The profiles of the tops of the molariform teeth are interesting: the equid’s look much flatter. I assume that this reflects the different structure of the teeth (which, in an occlusal view, would have made the non-artiodactyl D stand out immediately, I hope).