Niobrara Formation Mosasaur

[Othniel C. Marsh]

Below is a tooth from the Niobrara Formation being sold as that of Platecarpus tympactinus, and I am reasonably confident this is a plioplatecarpine based on @pachy-pleuro-whatnot-odon's comments concerning an Ozan Formation mosasaur tooth (said comment can be found here). However, Plesioplatecarpus and Selmasaurus are also known from the Niobrara Formation and I am not sure how to differentiate the three species.

 

 

Thanks in advance,
Othniel

[rocket]

cool specimen! Could you post a pic of the cross-section, please? Thanks

[Othniel C. Marsh]

I've not purchased the specimen yet, as I've been caught out more times than I'd like to admit when it comes to non-dinosaurian reptile teeth, and the seller hasn't provided an image of the base but I will buy it and take one if it would be diagnostic.

[pachy-pleuro-whatnot-odon]

I really need to defer to @Praefectus for this level of identification of American mosasaurs, as he's much more versed in them at this point then I am, with the inverse being true for European specimens (or so I'd like to believe! 😋).

 

Plioplatecarpine mosasaur does generally seem correct, though.

Edited December 11, 2024 by pachy-pleuro-whatnot-odon

[Othniel C. Marsh]

It would appear that the teeth of Selmasaurus johnsoni are characterised by prominent basal ridges, which this tooth lacks, reducing the number of potential species to two.