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…
I usually offer up a mystery object on Friday, but here’ a bonus object that landed on my desk this morning.
Apparently it was found in a horsefield in Kent, I have narrowed down the likely species of the animal that ‘donated’ the bone to a couple of options, but thought you might like to have a go as well, before the specimen is handed over to our Anthropologists to inspect the engraved designs.
As usual can can leave your comments below. Have fun!
Last Friday I gave you these bits of mystery forelimb (scapula and humerus) to identify:
I thought it would be an easy one, since it’s from a very common species with a near global distribution – plus the humerus has quite a characteristic crest along the proximal end, from the shoulder articulation to the middle of the bone.
Most people who commented noticed this crest and Jake suggested that it had adaptive features (along with the scapula), maybe for a specialised way of life.
As it turns out, these bones come from an animal that is probably best described as a specialist generalist – a Brown Rat Rattus norvegicus (Berkenhout, 1769).
These versatile and intelligent animals are very good climbers and brilliant swimmers, using their forelimbs to both get around and manipulate food.
My reasons for suspicion were the nature of the post-orbital constriction (the narrowing of the braincase behind the eyes), the nature of the zygomaticotemporal suture between the temporal process of the zygomatic and the zygomatic process of the temporal bone (the bit where two bones meet to make the arch of the cheek) and the shape of the nasal bones where they meet the frontals (the V shaped bones above the nose area).
The observation by henstridgesj that the skull was similar to the previous mystery object (Leopardus tigrinus) was a good one, so I decided to research the genus Leopardus in a bit more detail, to see if there was a better match.
It turns out that the skull I found that matched this one most closely – especially with regard to the relative lack of a post-orbital constriction and the nasal-frontal junction – was the highly arboreal Margay Leopardus wiedii (Schinz, 1821) [link opens pdf].
Of course, the real identification may be even more complicated, since the South American cats have a bit of a track record for hybridising to the point of masking distinct species, so any identification I make will be laden with disclaimers and caveats. The joy of real-world animals when contrasted against nice simple biological concepts…