Head Skeleton

Miscellaneous and Personal Stuff I Must Share
1

I first saw the term “Head Skeleton” on a poster of an Allosaurus Skull out in Utah. It was a reproduction from some scientific paper, and it was the first time I saw the use of “head skeleton” rather than “skull”. I thought it odd and affected at the time. I see it occasionally, almost always in zoological contexts.
Looking it up via Google N-Gram, I see no uses before about 1875, but quite a lot after that, with occasional rapid rises and falls.

The only reason I can see for its use is that it might be specifying some creatures (lampreys, maybe, or early jawless fish) that don’t have what we would properly call a “skull”, because they lack certain parts. But then, why use it for something as advanced as a dinosaur, which certainly has all the parts that I’m happy to see in a Skull?

Certainly it’s a precise term for am assembly of bones, but what is gained by the use of this coinage rather than the familiar “skull”?

2

This is just a WAG but you didn’t post this in GQ so I assume you’re inviting such speculation.

In many cases a “skull” is synonymous with the “cranium”. But in humans (and many animals) the cranium is only part of the head, another major part of the skeletal structure of the head is the jaw bone, the “mandible”, which is a totally separate bone from the cranium/skull. Between those two major bones you have a complete “head skeleton”.

Of course other times the mandible seems to be considered part of the skull so I might be totally off with my guess. But I’m thinking that if a museum has only a cranium on display in one place labeled as a “skull” then they’d differentiate a separate display including the mandible as a “head skeleton”.

Again just a WAG from a non-paleontologist who is also otherwise not an expert on bones.