Please help me identify this bone.

[reefer_man_kz]

Hello everyone Please help me identify this bone. It was found in a layer of Cenomanian sediments of western Kazakhstan (Mangyshlak peninsula). According to the description of this area, there are fossils of plesiosaurs, ichthyosaurs and sharks of the Cretaceous period. There are a lot of finds from this place that I periodically post on my Instagram account. Later I found another fragment of the same bone, but twice as large and it was just fragments of something whole. I looked through almost the entire forum carefully, found nothing or was inattentive..

[rocket]

not easy..., I would say this is a jawbone from Platypterygius. 

We worked on this type of Ichthyo many years ago and the lower jaw bones look "similar"

Edited May 23 by rocket

[reefer_man_kz]

14 minutes ago, rocket said:

непросто... я бы сказал, что это челюстная кость Platypterygius. 

Мы работали над этим типом Ихтио много лет назад, и кости нижней челюсти выглядят «похожими».

Thanks for the reply. I was also inclined to think that it had to do with the jawbones. The only question was, was he without teeth?

[pachy-pleuro-whatnot-odon]

Indeed not an easy one, but certainly not plesiosaur, as these have socketed teeth (thecodont tooth condition). This, as stated, reminds me more of the aulacodont tooth implantation of ichthyosaurs, i.e., teeth set in grooves. Compare to the below, which is a section of jaw from the older ophthalmosaurine ichthyosaur Brachypterygius extremus from Abingdon in the UK.

 

 

 

What I find a bit strange and confusing in that respect, though, is that your section seems to have two grooves, rather than a single one. Could be a generic difference, maybe...?

[reefer_man_kz]

8 hours ago, pachy-pleuro-whatnot-odon said:

Indeed not an easy one, but certainly not plesiosaur, as these have socketed teeth (thecodont tooth condition). This, as stated, reminds me more of the aulacodont tooth implantation of ichthyosaurs, i.e., teeth set in grooves. Compare to the below, which is a section of jaw from the older ophthalmosaurine ichthyosaur Brachypterygius extremus from Abingdon in the UK.

 

 

 

What I find a bit strange and confusing in that respect, though, is that your section seems to have two grooves, rather than a single one. Could be a generic difference, maybe...?

It seems to me that your fragment also had two grooves, and then the bone was simply flattened.

[Mike from North Queensland]

many Ichthyosaurs mandibles have two main bones each side to allow for flexibility the Angular and the Surangular that holds the teeth.

I would assume yours is a section of the Angular the fits into the underside of the Surangular

[pachy-pleuro-whatnot-odon]

3 minutes ago, Mike from North Queensland said:

many Ichthyosaurs mandibles have two main bones each side to allow for flexibility the Angular and the Surangular that holds the teeth.

I would assume yours is a section of the Angular the fits into the underside of the Surangular

 

That would certainly help explain the absence of foramina. Still, I'm a bit confused as to how this would fit together. If this were a section of angular, than the top groove would supposedly hold the surangular? However, what about the bottom groove in that case?

 

Reconstructed ophthalmosaurid ichthyosaur skull (Fig. 3; Tyborowski, Skrzycki and Dec, 2018)

[Mike from North Queensland]

Like everyone most of my specimens are fragmentary but here are two photos of a Angular and the larger piece in the cluster are part of the Surangular unfortunately one comes from the left the other the right side of the jaw and different specimens so can not fit together. In the hand it is easy to see how they fit together with the photos of the angular from the top showing the groove where they fit and the surangular in the group photo with the bottom to the bottom. These I might add are from platypterygius australis so expect some variation from the specimen in this topic

[Mike from North Queensland]

Here are some more photos of the angular so you can see the side view

[reefer_man_kz]

I'll go there again soon-I'll look more carefully, maybe I'll come across more fragments..

[pachy-pleuro-whatnot-odon]

Thanks, @Mike from North Queensland! Those are some very informative photographs! Haven't ever been able to have as good a look at ichthyosaur mandibles before! 🙌🏻