Fossil Friday – bison jaw fragments

Some of the species in the Diamond Valley Lake deposits are common enough that it’s actually possible to get some idea of intraspecies variability, including growth-based (ontogenetic) differences. Bison are not as common at DVL as horses, but there are still enough specimens to look a bit at age profiles. 

The specimen above is the anterior end of the lower jaw, with portions of both dentaries. This is a dorsal view, with anterior to the left. Below is a lateral view of the left dentary:

…and here’s right dentary in lateral view:

Three teeth are preserved, the right 2nd premolar and the left 2nd and 3rd premolars, none of which have any strong indications of wear. The jaw sections are also quite small compared to other bison in our collection. That raises a question: are these teeth permanent premolars, indicating an animal that was maybe 3 or 4 years old, or are they deciduous premolars, in which case it was probably only a few months old? The small size of the jaw actually makes me suspect the latter. I hope at some point to get x-ray images to see if the permanent premolars are present inside the jaw, although this animal could be so young that they hadn’t started to develop yet.


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