Pliosaur or Ichthyosaur Tooth?

[Alston Gee]

[RuMert]

I'd say pliosaur judging by the ridges

[pachy-pleuro-whatnot-odon]

The presence of sharp intermittently spaced striations rather than rounded regularly placed plicidentine enamel folds marks this as a pliosaur rather than ichthyosaur tooth. Do you know where it's from? Preservation initially suggests Faringdon in the UK, in which case I propose it's Liopleurodon ferox, many similar teeth of which have been find at that location...

[Alston Gee]

This tooth was found in the UK. The seller told me that it’s Simolestes vorax. 

[pachy-pleuro-whatnot-odon]

3 hours ago, Alston Gee said:

This tooth was found in the UK. The seller told me that it’s Simolestes vorax. 

 

Yeah, so probably Faringdon and with that likely Liopleurodon ferox, though true species determination would be neigh impossible based on such a fragmentary specimen... In any case, there is no indication that this would be Simolestes vorax. For that exact locality and possibly even find layer would be needed (in absence of any diagnostic traits on the tooth itself).

Edited August 15, 2022 by pachy-pleuro-whatnot-odon

[Alston Gee]

@pachy-pleuro-whatnot-odon Is this tooth more likely to be Liopleurodon forax or Polyptychodon (see here)? I have a hard time distinguishing the tooth crown from these two species.

[pachy-pleuro-whatnot-odon]

With pliosaur tooth material it can be very difficult to tell. However, Polyptychodon, which is a nomen dubium following the very 2016 article by Madzia ýou referenced and would more correctly be referred to as "brachaucheninae indet.", is a Cretaceous species, with traditional understanding limiting the range of Liopleurodon ferox to the Jurassic. Its based on this that a distinction between the two can be made, whereas amongst Middle Jurassic species differentiation depends much more on the nature of the striations (see here). With this tooth being reworked Jurassic in age, however, and given the multitude of precedents from the same site, this tooth can be established as Liopleurodon ferox (compare with the second tooth posted here).

[Alston Gee]

@pachy-pleuro-whatnot-odon I really appreciate your reply! However, my concern was that the striations on this tooth do not perfectly match to the traditional tooth crown morphology of Liopleurodon ferox (see Fig. 8). When I scanned Madzia's (2016) article, the striations on this tooth crown do share some similarities with the sample TN 3770.2.1 from figure 3. How did you identify this tooth as Liopleurodon ferox rather than "brachaucheninae indet" based on its morphological features (i.e., the striations)?

[pachy-pleuro-whatnot-odon]

I'd say that's a very valid question. However, there's plenty of variation in L. ferox tooth crown morphology when it comes to striations, where striations may be variedly more or less densely packed, or the tooth may lack striae on the labial side entirely. In this sense L. ferox teeth can indeed look very similar to brachauchenine teeth. Have a look at the below images to see what I mean:

 

L. ferox tooth from Hildesheim in Germany as described by Sachs and Nyhuis (2015).

 

 

 

Liopleurodon ferox tooth from the Oxford Clay at Whittlesey in the Peterborough area, now held by the Wollaton Hall (sources: Jed Taylor & Sven Sachs).

 

 

 

L. ferox from the Peterborough area in the UK.

 

 

Liopleurodon ferox tooth from Faringdon.

 

 

L. ferox misidentified as Simolestes vorax.

 

 

Due to these similarities, it can be very difficult to differentiate between brachauchenine teeth and those of L. ferox. It's just part of the issue of ascribing species labels to isolated teeth, and one of the main reasons for many marine reptile palaeontologists to have their reservations on the topic. Thus, it again boils down to provenance, the deposit a tooth was found in, to help determine the species that may be involved.

Edited August 24, 2022 by pachy-pleuro-whatnot-odon