Ichthyosaur tooth

[Notidanodon]

Hi guys just wanted to see if anyone could identify it past the current label   thanks! @pachy-pleuro-whatnot-odon @Praefectus

[pachy-pleuro-whatnot-odon]

Unfortunately, the label seems correct to me. It's not Stenopterygius spp., as these have teeth that lack ornamentation, same as with Temnodontosaurus crassimanus. Can't be Eurhinosaurus longirostris either, as that species' teeth also lack the typical plicidentine enamel folds, instead exhibiting horizontal banding and a pinching towards the tooth apex. This, I believe, leaves just Ichthyosaurus itself as a genus within the appropriate time-frame...

[Praefectus]

Thanks for the tag. I think @pachy-pleuro-whatnot-odon is better suited to answering this. He knows ichthyosaurs much better than me. 

[Notidanodon]

On 7/9/2023 at 4:23 PM, pachy-pleuro-whatnot-odon said:

Unfortunately, the label seems correct to me. It's not Stenopterygius spp., as these have teeth that lack ornamentation, same as with Temnodontosaurus crassimanus. Can't be Eurhinosaurus longirostris either, as that species' teeth also lack the typical plicidentine enamel folds, instead exhibiting horizontal banding and a pinching towards the tooth apex. This, I believe, leaves just Ichthyosaurus itself as a genus within the appropriate time-frame...

Thanks! I have become a bit confused by ichthyosaur nomenclature, because we refer to them all as icthyosaurs, so that is a family, but here it is a genus as well, is that correct?

[pachy-pleuro-whatnot-odon]

17 hours ago, Notidanodon said:

Thanks! I have become a bit confused by ichthyosaur nomenclature, because we refer to them all as icthyosaurs, so that is a family, but here it is a genus as well, is that correct?

 

That's correct. Although I should be quick to add that the genus Ichthyosaurus has become somewhat of a wastebucket-taxon over the years, and we generally refer to all ichthyopterygia as ichthyosaurs...

[Notidanodon]

On 4/12/2024 at 10:57 AM, pachy-pleuro-whatnot-odon said:

 

That's correct. Although I should be quick to add that the genus Ichthyosaurus has become somewhat of a wastebucket-taxon over the years, and we generally refer to all ichthyopterygia as ichthyosaurs...

Ok thanks that makes sense

[Aman]

Unfortunately the label is about as specific as it can be; Stenopterygius and its kin don't appear in the fossil record until the Toarcian, almost 20 million years after the owner of this tooth died. The same is true of species like Eurhinosaurus and the Temndomtosaurus species T. crassimanus and T. trigonodon.

 

The tooth cannot be narrowed down to the specific level; it is impossible to distinguish which of the five species of Ichthyosaurus known from the Blue Lias that this came from with just one tooth. The tooth does not have any carinae so it cannot be a juvenile Temnodontosaurus platyodon, and it has to wide a diameter to be either Excalibosaurus or Wahlisaurus. The crown also appears to be too short and uncurved to be Protoichthyosaurus.

 

On another note:

On 4/12/2024 at 10:57 AM, pachy-pleuro-whatnot-odon said:

 

That's correct. Although I should be quick to add that the genus Ichthyosaurus has become somewhat of a wastebucket-taxon over the years, and we generally refer to all ichthyopterygia as ichthyosaurs...

While Ichthyosaurus was a massive wastebasket taxon at one point, with there being over 50 species at one point, there is now a much more reasonable six (possibly seven, although the last one is doubtful). The taxonomy of this genus has been broadly sorted for a while now, with new species mostly being ones that were synonymized with I. communis at some point but have been found to be distinct.

[pachy-pleuro-whatnot-odon]

4 hours ago, Aman said:

Unfortunately the label is about as specific as it can be; Stenopterygius and its kin don't appear in the fossil record until the Toarcian, almost 20 million years after the owner of this tooth died. The same is true of species like Eurhinosaurus and the Temndomtosaurus species T. crassimanus and T. trigonodon.

 

True, I should've probably checked the geology of the location - though I never exclude a species appearing in the palaeontological record before the start of its chronological range - or to extend past that. The palaeontological record quite spotty, and it wouldn't be the first time species is marine reptile have been recovered from the geological record pre- or post-dating their supposed temporal range. At the same time, Lilstock apparently being 

Rhaetian Triassic changes things, making me agree the species I mentioned aren't really good candidates.

 

Now that I'm looking at the tooth again, by the way, I see that it has horizontal banding and might be slightly prismatic, both of which are features I've observed in the teeth of Eurhinosaurus longirostris from both Germany (Holzmaden area) and France (Essay-les-Nancy). As such, while this tooth is older and doesn't have the clear apical constriction seen in teeth of Eurhinosaurus and Excalibosaurus, I'd argue there are enough similarities to warrant identification as "leptonectidae indet.", a family that would've been around at the time...

[Notidanodon]

Thanks @Aman and @pachy-pleuro-whatnot-odon very informative!