January 29th

2015 – Koshisaurus Described

On this day in dinosaurs, Masateru Shibata and Yoichi Azuma announced the discovery of a primitive hadrosaur found in Japan. The dinosaur dates back to the early Cretaceous and the remains of the individuals found appear to be from sub-adults, so its adult size is not yet known.


Kochisaurus is named after the original title for the Fukui Prefecture, where the fossils were first unearthed. The holotype specimen includes a partial maxilla with teeth, along with additional post-cranial skeletal elements.

Differences in Kochisaurus (namely the addition of an antorbital fossa–a depression that marks the closure of a structural gap called a fenestra–in the skull, as well as signature ridges on its teeth) separate this hadrosaur from several others who lived at the same time in Japan. This hadrosaur diversity is intriguing for paleontologists who want to understand the proliferation of the group.

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