French Plesiosaur Tooth?

[Othniel C. Marsh]

Shown below is a marine reptile tooth from the early Jurassic of Nancy, France. It is being sold as that of Stenopterygius, but the tooth appears to be much more gracile than what I'd expect from such an ichthyosaur based on my very limited knowledge of Jurassic marine reptile dentition. Moreover, there are only striae on one face of the tooth, which is again not something I have seen on any ichthyosaur teeth thus far. This has led me to the conclusion that the tooth is from a plesiosaur, perhaps Muraenosaurus or a relative.
I will take the liberty of "tagging in" @pachy-pleuro-whatnot-odon, and thank them for tolerating my constant questions.

 

 

Thanks in advance,
Othniel

[pachy-pleuro-whatnot-odon]

Initially, I thought this could indeed be a plesiosaur tooth, seeing most of the striae are located on the lingual side, with only some short striations being present on the labial. However, the second photograph shows a clear carina, which wouldn't be present on cryptoclidid plesiosaur teeth. Moreover, this angle also makes it clear that the striations run up to, but don't interact with, the carina, which is another characteristic that indicates this is a teleosaurid crocodile tooth, rather than a plesiosaur. Probably the vendor got confused between Stenopterygius, which is an ichthyosaur and a misnomer in this case, and the correct label of Steneosaurus (if we ignore the fact that this genus is now a nomen dubium).

[Othniel C. Marsh]

The "steneosaurs" are the one's with diagnostic teeth, aren't they?

 

Edit: All the "steneosaur" teeth described in this thread have vertical striations across the tooth's surface. I assume, therefore, that this tooth would be best labelled as Teleosauroid indet.

Edited December 14, 2024 by Othniel C. Marsh

[pachy-pleuro-whatnot-odon]

There is some morphological distinction between the various species in the former genus, and also a lot of intraspecific variation, complicating ascription of these kinds of teeth. At Essay-les-Nancy, I think I've mostly recognised Macrospondylus 'Steneosaurus' bollensis and cf. Seldsienean 'Steneosaurus' megistorhynchus. This, I'd classify as the former.

 

Source: Mueller-Töwe (2006)

[rocket]

I would assume it is a ?Steneosaurus-type. We have had some of them from famous Posidonia-slate and they looked "similar".

Nice find!