Marine reptile tooth ID Lyme Regis

[pachy-pleuro-whatnot-odon]

Hi all,

Bought this tooth online a while back. It was sold to me as "Ichthyosaurus platyodon" (which I understand to mean Temnodontosaurus platyodon) from Lyme Regis. Likely found by the seller themselves, as I know they occasionally collect fossils there. However, for the following reasons, I'm not sure about this attribution:

 

1. Overall, the tooth doesn't look like your typical ichthyosaur tooth to me:
   • It has more of an oval rather than round cross-section
   • It's labolingually flattened
   • Messial and distal carinae run the full length of the crown and divide the tooth into labial and lingual parts
   • While fine striations can be seen on one side of the tooth (presumably the lingual side), the other side (which would be the labial) seems entirely smooth - though some traces of rare striations can be seen on the photographs
   • The striations are much more similar to those of crocodile or pliosaur teeth than to the plicidentine condition so typical of ichthyosaurs
2. The horizontal banding on the tooth surface is unfamiliar to me with respect to most marine reptile teeth I have seen, but occurs much more frequently on crocodile teeth of various species
3. I also bought another tooth with the same attribution from the seller, more or less around the same time. This one has no striations whatsoever, has a more rounded base, is less flattened and has a more rounded tip. It also has carinae. I therefore reclassified it as a probable Goniopholis sp. crocodile tooth.

 

Now I know that not having the root makes it more difficult to identify this particular specimen, but I was hoping someone on this forum might be able to help me, as currently it goes without label. I've considered crocodile, plesiosaur and even pliosaur, but all of these have some reservations that prevent final classification. For one, none of these groups have teeth that are typically flattened like this, nor do plesiosaurs (sensu lato, thus including pliosaurs) have carinae. Crocodiles, then again, would either have or not have striations all around the tooth. And what to make of the banding: is this just preservational, or does it reflect the internal structure of the tooth - i.e. outcome of the tooth's ontological growth?

 

Tooth measures 18 mm and is missing the tip.

 

Thanks in advance for your help!

 

 

 

 

[Paleoworld-101]

I can't give you a definitive ID but i'll just point out that there aren't any marine crocodiles in the Lyme Regis fauna (which constitutes the Blue Lias and Charmouth Mudstone formations, from the Hettangian to the Pliensbachian of the Early Jurassic). The marine crocodiles of the UK are associated with later Jurassic deposits such as the Oxford and Kimmeridge clays. You mentioned another tooth from the same seller that may be Goniopholis . I'm assuming by the way you worded it, that tooth was also a Lyme Regis specimen? In which case it can't be that taxon, which didn't appear until the Late Jurassic. As for your pictured tooth: there is a considerable diversity of plesiosaurs from the Blue Lias Formation in particular. If you are certain this tooth comes from Lyme Regis (although you'll probably just have to take the sellers word for it), i would suggest tracking down some of the original papers that describe those plesiosaur taxa, and see if they figure any of the teeth that you could compare with. Same with the ichthyosaurs. 

[pachy-pleuro-whatnot-odon]

1 hour ago, Paleoworld-101 said:

I can't give you a definitive ID but i'll just point out that there aren't any marine crocodiles in the Lyme Regis fauna (which constitutes the Blue Lias and Charmouth Mudstone formations, from the Hettangian to the Pliensbachian of the Early Jurassic). The marine crocodiles of the UK are associated with later Jurassic deposits such as the Oxford and Kimmeridge clays. You mentioned another tooth from the same seller that may be Goniopholis . I'm assuming by the way you worded it, that tooth was also a Lyme Regis specimen? In which case it can't be that taxon, which didn't appear until the Late Jurassic. As for your pictured tooth: there is a considerable diversity of plesiosaurs from the Blue Lias Formation in particular. If you are certain this tooth comes from Lyme Regis (although you'll probably just have to take the sellers word for it), i would suggest tracking down some of the original papers that describe those plesiosaur taxa, and see if they figure any of the teeth that you could compare with. Same with the ichthyosaurs. 

Hmmm... Good points about the Goniopholis identification. Guess this would indeed not really be possible. Mainly I based my conclusions on the fact that the tooth (pictured below) really reminds me of a croc-tooth rather than ichthyosaur and that this genus has been found along the Jurassic coast. But, as you pointed out, the deposits at Swanage are of much later age. All the same, I find it odd that there are no marine crocodiles in Lyme Regis, since they occur so often in later Jurassic deposits, such as the frequent Steneosaurus sp. in the Posidonia Shale of Holzmaden. Especially as teleosaurids have been around since the Early Jurassic... On the other hand, the fact that it doesn't seem likely to find a crocodile-tooth out of Lyme Regis is part of what makes we wonder whether this could not be some kind of plesiosaur.

 

 

 

 

 

As to your proposal of checking these teeth against all species know to occur at Lyme Regis, @The Amateur Paleontologist actually wrote up a nice overview of the ichthyosaurian and plesiosaurian species present at the locality/Dorset coast:

Unfortunately, having a list of species is but a first step. Finding useful and reliable material to compare against will be a lot trickier. Hence my asking here...

[pachy-pleuro-whatnot-odon]

1 hour ago, Paleoworld-101 said:

If you are certain this tooth comes from Lyme Regis (although you'll probably just have to take the sellers word for it), i would suggest tracking down some of the original papers that describe those plesiosaur taxa, and see if they figure any of the teeth that you could compare with. Same with the ichthyosaurs. 

Actually, based on your comment and unless anybody manages to come up with an answer to this "riddle", I actually think that the vendor information on locality might not be reliable, i.e. that these teeth do no come out of Lyme Regis. For one, the type of preservation (banding, colours) is not what I'm used to seeing from that location either...

[RuMert]

I don't think plesio/ichthyosaurs have carinae, wrong location is more likely

[pachy-pleuro-whatnot-odon]

18 minutes ago, RuMert said:

I don't think plesio/ichthyosaurs have carinae, wrong location is more likely

Neither ichthyosaur teeth, nor plesiosaur teeth typically have carinae, frequently either sticking with striations or polygony, or both. Though these may appear as carinae, they are not. However, Temnodontosaurus spp., as the name suggests (i.e. "cutting-tooth lizard"), did, in certain species (most notably T. platyodon), have carinae.

 

 

Temnodontosaurus platyodon tooth from Holzmaden

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Temnodontosaurus platyodon from Lyme Regis

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Other ichthyosaurs, to my knowledge, do not have carinae, however.

 

The same goes for plesiosaur teeth. Normally, these would not have carinae, but it appears that some form of carinae might be present on polycotylid teeth, such as those of Dolichorhynchops osborni, figured below (taken from Oceans of Kansas):

 

When checking my own specimens, however, I did not find any carinae - though some striations had the superficial look of them.

 

Hence, the presence of carinae can't be used to entirely rule out plesiosaur or ichthyosaur, though croc would be much more likely. Same goes for the ovoid shape, which is not typical for plesiosaur teeth, but does occur.

 

But I agree, misidentified locale is the more likely cause for me not being able to identify these teeth with more confidence.

[RuMert]

Interesting exceptions

[Paleoworld-101]

I agree these are probably not Lyme Regis teeth, in which case without any solid provenance information, the chance of getting a good ID will be low. You could always probe the seller for more information but unless they were self-collected, i doubt they would know anything more than what was originally sold to them. Your second tooth does look rather crocodile-like to my eye. 

[pachy-pleuro-whatnot-odon]

7 hours ago, Paleoworld-101 said:

I agree these are probably not Lyme Regis teeth, in which case without any solid provenance information, the chance of getting a good ID will be low. You could always probe the seller for more information but unless they were self-collected, i doubt they would know anything more than what was originally sold to them. Your second tooth does look rather crocodile-like to my eye. 

Hmm... May be I'll look into getting in touch with the original seller, then. But I doubt it'd be worth it. Not just for the fact that these teeth might not have been self-collected, but also because I already bought them a year ago. Pity!

[pachy-pleuro-whatnot-odon]

I recently came to a conclusion concerning the tooth I originally posted, and will answer my own question here so others may profit from it

 

As many of you have said, the tooth doesn't look anything like reptile teeth from Lyme Regis, so I've accepted that the seller's provided information was a complete miss when it comes to both provenance and identity. It initially also didn't look convincingly crocodilian to me, though it does have the carinae typical for crocodilians, as well as fine striations sometimes also seen on crocodile teeth (but then, often, on both sides rather than just the one. However, when doing some research on Thalattosuchia (marine crocodiles) recently, I came across the below metriorhynchid crocodile teeth (first two pictures represent the same specimen), which seem a very close match to my tooth. As you can see, they have a round, but somewhat compressed cross-section; fine striae on the lingual side of the tooth, but none on the labial side; the horizontal banding I've come to associate with crocodilian teeth; and, of course, the obvious carinae. Therefore, these specimens add the information I lacked to classify my tooth as crocodilian after all, and specifically metriorhynchid. I had not picked up on this before, as the other major group of Thalattosuchia, the Teleosauridae, have more traditional looking crocodilian teeth - probably due to their lesser adaptation to a fully marine life-style. Further confirmation came from a couple of metriorhynchid teeth I recently picked up. As such, I'm now firmly in the believe that what I've got is a Metriorhynchidae indet. tooth.

 

 

Where the tooth actually comes from is an entirely different matter. But seeing at these teeth are generally Middle to Late Jurassic in age, assuming the vendor had at least the origin as being from the British Isles correct, and comparing the degree and type of preservation with the rightmost tooth, I'm thinking Peterborough would not be a bad match.

[RuMert]

Very nice, but it was obvious from the beginning I badly need to find something like this

[pachy-pleuro-whatnot-odon]

3 hours ago, RuMert said:

Very nice, but it was obvious from the beginning I badly need to find something like this

True, though not originally voiced as such. Now I found some supporting evidence to do so

[D.N.FossilmanLithuania]

I would say that your tooth specimen belongs to ichthyosaur marine reptile

 

[paulgdls]

I wouldn't rule out Lyme Regis or Charmouth as a location for your first tooth. A couple of years ago a semi-complete crocodile skeleton was unearthed between the two. It's being studied professionally at present. 

[pachy-pleuro-whatnot-odon]

Wow! Thanks, @paulgdls! I wasn't aware! That quite changes things. However, as that find is still being studied, I guess there's no reference material on that specimen yet, right? That makes it difficult to determine whether the state of preservation and tooth morphology (if teeth were found with it, that is) could match. Or to say whether the crocodile that was found has the same conservation as is typical for other Lyme Regis material, for that matter - as my tooth seems to differ from that. All the same, I guess I'll leave the provenance at Lyme Regis for now then

[pachy-pleuro-whatnot-odon]

Thanks to @PointyKnight's excellent description of Oxford Clay metriorhynchid crocodiliforms, I'm now quite confident that the first tooth I mentioned at the start of this thread can be attributed to Thalattosuchus superciliosus (what used to be known as Metriorhynchus superciliosus), and thus now has a species name, rather than the more generic metriorhynchidae indet..

 

 

Edit:

With some further information on the distinction between the teeth of the closely related species of T. superciliosus and G. leedsi in the above thread, it now actually seems more likely that this specific tooth belongs to Gracilineustes leedsi.

Edited April 30, 2021 by pachy-pleuro-whatnot-odon

[pachy-pleuro-whatnot-odon]

On 11/19/2020 at 5:42 PM, paulgdls said:

I wouldn't rule out Lyme Regis or Charmouth as a location for your first tooth. A couple of years ago a semi-complete crocodile skeleton was unearthed between the two. It's being studied professionally at present. 

 

This new crocodilian has just been described:

 

 

[pachy-pleuro-whatnot-odon]

In an addendum to this topic, with my current knowledge, I now consider the below tooth to be Temnodontosaurus trigonodon:

 

On 7/8/2020 at 7:24 PM, pachy-pleuro-whatnot-odon said:

 

While I now know that the below tooth belongs to Temnodontosaurus eurycephalus (see also here):

 

On 7/8/2020 at 7:24 PM, pachy-pleuro-whatnot-odon said: