Partial Rhomaleosaurus tooth from UK?

[Alston Gee]

This partial tooth is sold as Eurycleidus sp. tooth from the Westbury Formation, Penarth Group of Blue Anchor, Somerset, UK. The tooth is 5mm in height. Thoughts on it?

[Alston Gee]

@pachy-pleuro-whatnot-odonI have my doubts because the pattern of the ridges on the lingual side of this tooth rarely occurs in Rhomaleosaurus teeth. I once saw similar patterns of ridges on fish tooth fossils, but not quite sure if it is the same thing.

Edited October 16, 2023 by Alston Gee

[Alston Gee]

Also, here is another Triassic plesiosaur tooth from Rhaetic Bone Bed, Westbury Formation, Aust Cliff, Aust, South Gloucestershire, England that is labeled as “Rhomaleosaurid indet.”. What’s your thoughts? The general shape and lingual ornamentation make me believe it's a Thalassiodracon sp. tooth rather than a Rhomaleosaur tooth because you once mentioned that most Rhomaleosaur teeth lack striation on the lingual side of the tooth. Nevertheless, I failed to find relevant journal articles involving the description of the striation patterns of Thalassiodracon teeth. @pachy-pleuro-whatnot-odon

 

 

 

Edited October 16, 2023 by Alston Gee

[Alston Gee]

@paulgdls Hi Paul, do you have any thoughts on these fossils?

[Alston Gee]

@RuMert

[RuMert]

Thank you, I guess we need opinion from British experts

[Alston Gee]

@pachy-pleuro-whatnot-odon any thoughts?

[Alston Gee]

@fossils-uk

[Alston Gee]

22 hours ago, Alston Gee said:

Also, here is another Triassic plesiosaur tooth from Rhaetic Bone Bed, Westbury Formation, Aust Cliff, Aust, South Gloucestershire, England that is labeled as “Rhomaleosaurid indet.”. What’s your thoughts? The general shape and lingual ornamentation make me believe it's a Thalassiodracon sp. tooth rather than a Rhomaleosaur tooth because you once mentioned that most Rhomaleosaur teeth lack striation on the lingual side of the tooth. Nevertheless, I failed to find relevant journal articles involving the description of the striation patterns of Thalassiodracon teeth. @pachy-pleuro-whatnot-odon

 

 

 

@Welsh Wizard are two fossils mentioned above possibly fish teeth?

Edited October 17, 2023 by Alston Gee

[Welsh Wizard]

At first glance it looks like a plesiosaur/pliosaur tooth but if you look at what’s left of the root, I think it’s a big ichthyosaur tooth.

[Alston Gee]

1 hour ago, Welsh Wizard said:

At first glance it looks like a plesiosaur/pliosaur tooth but if you look at what’s left of the root, I think it’s a big ichthyosaur tooth.

Are you referring to the first or second tooth in the post? The second tooth is weakly curved and has a sub-circular cross-section, which makes me to believe it is a pliosaur or plesiosaur tooth rather than an ichthyosaur tooth. Nevertheless, I found a tooth with similar striation patterns and shape as the second tooth from this post(http://www.thefossilforum.com/topic/124672-id-teeth-from-triassic-aust-uk/), so the second tooth could also be a fish tooth. It's challenging for me to distinguish the plesiosaur tooth and fish tooth from Aust Cliff. The first tooth is also more likely to be a fish tooth, but I am still uncertain about its identity. 

Edited October 17, 2023 by Alston Gee
I was unable to embed a link.

[pachy-pleuro-whatnot-odon]

On 10/16/2023 at 8:39 PM, Alston Gee said:

This partial tooth is sold as Eurycleidus sp. tooth from the Westbury Formation, Penarth Group of Blue Anchor, Somerset, UK. The tooth is 5mm in height. Thoughts on it?

 

On 10/16/2023 at 8:39 PM, Alston Gee said:

I have my doubts because the pattern of the ridges on the lingual side of this tooth rarely occurs in Rhomaleosaurus teeth. I once saw similar patterns of ridges on fish tooth fossils, but not quite sure if it is the same thing.

 

The pattern of striations is consistent with rhomaleosaurid teeth, like those of Eurycleidus arcuatus. In fact, plesiosaur teeth usually have more striae on the lingual than buccal side of the tooth. In his chapter on tetrapods in Swift and Martill's (eds.) 1999 volume "Fossils of the Rhaetian Penarth Group" Storrs (p. 228) mentions that "[plesiosaur] teeth [from Aust Cliff] are large, sharp, curved and striated".

 

Have a look at the below photographs and posts for comparison:

 

 

 

Storrs (ibid.) further observes that

 

Quote

[a]lthough no plesiosaur genus can be recognized on the basis of the currently known Penarth Group fossils, the short cervical vertebrae and the large, robust teeth typically encountered suggest that big-headed, relatively short-necked forms similar to the British Rhaetian-Lower Jurassic genus Eurycleidus Andrews, 1922 may have been their source.

 

So, while this tooth is without a doubt a plesiosaur tooth, it's rather its attribution to Eurycleidus arcuatus that's in question...

 

 

On 10/16/2023 at 9:34 PM, Alston Gee said:

The general shape and lingual ornamentation make me believe it's a Thalassiodracon sp. tooth rather than a Rhomaleosaur tooth because you once mentioned that most Rhomaleosaur teeth lack striation on the lingual side of the tooth.

 

If I did state that, this is in error, since rhomaleosaurid teeth, like those of most other types of plesiosaurs, are more heavily ornamented on the lingual rather than labial side. That having been said, I too, unfortunately, don't have any usable reference material for Thalassiodracon sp. teeth, so wouldn't know how to differentiate them - if this is at all possible (it's already hard for most pliosaurids, for which patterns of striations have been extensively studied, let alone for genera and species where such a study has not been performed yet). As Storrs (ibid.) suggests, however, Eurycleidus arcuatus may be one of the few species recognised from the Penarth Group...

 

On 10/16/2023 at 9:34 PM, Alston Gee said:

 

1 hour ago, Welsh Wizard said:

At first glance it looks like a plesiosaur/pliosaur tooth but if you look at what’s left of the root, I think it’s a big ichthyosaur tooth.

 

I agree. The tooth looks a bit too stubby for a plesiosaur tooth. And when you look at the cross-section of the root, you can make out the dentine folding that mirrors the plicidentine that would've been present in the crown. So, this is an ichthyosaur tooth. In fact, Storrs (ibid.) mentions that ichthyosaur remains might actually be more common in these deposits than are plesiosaur remains, with Leptonectes sp. being the most common - and a large bodies - ichthyosaur...

[Welsh Wizard]

1 hour ago, Alston Gee said:

Are you referring to the first or second tooth in the post? The second tooth is weakly curved and has a sub-circular cross-section, which makes me to believe it is a pliosaur or plesiosaur tooth rather than an ichthyosaur tooth. Nevertheless, I found a tooth with similar striation patterns and shape as the second tooth from this post(http://www.thefossilforum.com/topic/124672-id-teeth-from-triassic-aust-uk/), so the second tooth could also be a fish tooth. It's challenging for me to distinguish the plesiosaur tooth and fish tooth from Aust Cliff. The first tooth is also more likely to be a fish tooth, but I am still uncertain about its identity. 

this one

 

[Alston Gee]

33 minutes ago, pachy-pleuro-whatnot-odon said:

 

 

The pattern of striations is consistent with rhomaleosaurid teeth, like those of Eurycleidus arcuatus. In fact, plesiosaur teeth usually have more striae on the lingual than buccal side of the tooth. In his chapter on tetrapods in Swift and Martill's (eds.) 1999 volume "Fossils of the Rhaetian Penarth Group" Storrs (p. 228) mentions that "[plesiosaur] teeth [from Aust Cliff] are large, sharp, curved and striated".

 

Have a look at the below photographs and posts for comparison:

 

 

 

Storrs (ibid.) further observes that

 

 

So, while this tooth is without a doubt a plesiosaur tooth, it's rather its attribution to Eurycleidus arcuatus that's in question...

 

 

 

If I did state that, this is in error, since rhomaleosaurid teeth, like those of most other types of plesiosaurs, are more heavily ornamented on the lingual rather than labial side. That having been said, I too, unfortunately, don't have any usable reference material for Thalassiodracon sp. teeth, so wouldn't know how to differentiate them - if this is at all possible (it's already hard for most pliosaurids, for which patterns of striations have been extensively studied, let alone for genera and species where such a study has not been performed yet). As Storrs (ibid.) suggests, however, Eurycleidus arcuatus may be one of the few species recognised from the Penarth Group...

 

 

 

I agree. The tooth looks a bit too stubby for a plesiosaur tooth. And when you look at the cross-section of the root, you can make out the dentine folding that mirrors the plicidentine that would've been present in the crown. So, this is an ichthyosaur tooth. In fact, Storrs (ibid.) mentions that ichthyosaur remains might actually be more common in these deposits than are plesiosaur remains, with Leptonectes sp. being the most common - and a large bodies - ichthyosaur...

The ridges on the labial side of the first tooth seem weird to me compared with the rhomaleosaurid teeth from the photos you posted because the ridges on the first tooth are way too deep and coarse. 

Edited October 17, 2023 by Alston Gee

[Alston Gee]

10 minutes ago, Welsh Wizard said:

this one

 

I agree with you that this tooth probably belongs to a large ichthyosaur. Sometimes these ichthyosaur look very much like the plesiosaur/pliosaur teeth. 

[pachy-pleuro-whatnot-odon]

5 minutes ago, Alston Gee said:

The ridges on the labial side of the first tooth seem weird to me compared with the rhomaleosaurid teeth from the photos you posted because the ridges on the first tooth are way too deep and coarse. 

 

They often seem more pronounced on smaller teeth...

[paulgdls]

The infolding of the base enamel shouts ichthyosaur to me too. Definitely not pliosaur or plesiosaur. Could be amphibian though ... How long is the preserved section? 

[Alston Gee]

2 minutes ago, paulgdls said:

The infolding of the base enamel shouts ichthyosaur to me too. Definitely not pliosaur or plesiosaur. Could be amphibian though ... How long is the preserved section? 

Hi Paul. The second tooth is approximately 3cm. What’s your thoughts on the first tooth? Do you also agree that the first tooth probably belongs to certain plesiosaur species?

[fossils-uk]

Both ichthyosaur teeth. 

[Alston Gee]

1 hour ago, fossils-uk said:

Both ichthyosaur teeth. 

Any specific features of the first tooth mark it as an Ichthyosaur tooth? Agree that the second tooth probably belongs to a large Ichthyosaur.

[Alston Gee]

@pachy-pleuro-whatnot-odon Is the first tooth possibly a partial Ichthyosaur tooth? I do see some UK Ichthyosaur teeth with coarse striation like this, but the interspaces between ridges of Ichthyosaur teeth are usually narrower than the first tooth. 

[pachy-pleuro-whatnot-odon]

8 hours ago, Alston Gee said:

@pachy-pleuro-whatnot-odon Is the first tooth possibly a partial Ichthyosaur tooth? I do see some UK Ichthyosaur teeth with coarse striation like this, but the interspaces between ridges of Ichthyosaur teeth are usually narrower than the first tooth. 

 

While the photographs are not clear enough to entirely rule out the first tooth also being an ichthyosaur tooth, I'd say that it isn't based on how densely packed the striations are compared to how tall and slender the tooth is. Simply put, this ichthyosaur teeth are usually either more stubby or more pointy, and don't have parallel edges over such stretches as this particular tooth. Also, take a look at the below overview of cross-sections of marine reptile teeth taken from McCurry et al. (2019; fig. 4), especially comparing A (pliosaur) and E (ichthyosaur). As you'll be able to tell, pliosaurs - as do plesiosaurs, though in a less pronounced way - bear very strong enamel ridges with triangular cross-section, which, however, lay on top of the enamel, rather than interact with the underlying dentine. This is not the case for ichthyosaur teeth, which plicidentine enamel folds affect the underlying dentine, something that is visible in broken cross-sections of the teeth as well.

 

A = brachauchenine pliosaur ('Polyptychodon interruptus'); B = Globidens alabamaensis; C = Goniopholis crassidens; D = Spinosaurus aegypticus; E = Ichthyosaurus communis; F = Zygorhiza kochii.

 

 

Cross-section through ichthyosaur jaw with teeth from Holzmaden, albeit mainly through their roots. Species is either Stenopterygius sp. or Temnodontosaurus trigonodon, which have teeth without or relatively minimal enamel folds respectively, with the latter species being more likely (see also photograph underneath for a comparable jaw section with the outside of the teeth still visible. Above all, observe how the enamel folds run all through the teeth, including through cross-sections.

 

 

Also compare to the cross-sections through teeth of Aegirosaurus leptospondylus from figures 2 and 5 of Scheyer and Moser (2011).

 

 

 

E = enamel; OD = orthodentine; IGZ = interglobular zone of orthodentine

 

Just to clarify how orthodentine shows on the outside of ichthyosaur teeth, here's an schematic representation:

 

 

Since the first tooth you showed has both bold striae and doesn't show evidence of enamel folding in its broken cross-section, as well as having relatively long parallel edges, I'd still say this is a plesiosaur tooth. Compare with these more clearly exposed sections of a Early Cretaceous plesiosaur teeth (Hastanectes valdensis):

 

 

I hope this helps.