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PointyKnight

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Hey everyone!

 

I recently got a few marine reptile teeth from various formations in the UK, including this partial plesiosaur tooth from the Oxford Clay. The enamel is only partially preserved, but appears unworn and allows for a good look at the enamel ridges of this section.

 

Plesiosaur_00.thumb.png.4f0e6797e97f6501adb8cace7f79f262.png

 

The curved, rather robust shape of the tooth and the irregular distribution of the pretty prominent enamel ridges made me move away from ichthyosaur or machimosaurid as an ID, and seemed more in line with the many plesiosaurs from this formation. But that's where it got more tricky.
 

Since it's a small tooth (about 21mm in total) excluding taxa based on size alone isn't possible. I couldn't find much literature on the ontogenetic changes in enamel structure for most plesiosaurs from this formation, so assuming similar condiditions in both adult and juvenile individuals has to suffice (though I'm always open for more info!).

 

Starting with the plesiosauroids, all Oxford Clay taxa are part of Cryptoclididae and have at times very detailed descriptions of their teeth available. Therefore we're able to use these as a reference point to compare this tooth against. BROWN 1981 describes teeth from all available species in detail: Cryptoclidus possesses teeth with greatly reduced ornamentation, to the point where usually labial ridges are missing entirely. Also, all lingual ridges in these teeth originate basally, neither of which is the case here. Muraenosaurus is described to have a higher number of labial ridges apically than basally and no prominent axial ridges, conditions that don't apply here: The ridge count is highest basally and is reduced apically, and axial carinae are seperate and distinguishable from the other ridges. OTERO et al. 2020 recovers Picrocleidus as the sister taxon to Muraenosaurus, so since there is no dental material assigned to Picrocleidus we have to assume a similar condition. Lastly, Tricleidus is supposed to possess teeth similar to Muraenosaurus, only with stronger and more numerous labial ridges than lingual ones. Again, neither of these conditions apply here: Ridges are more numerous lingually, and don't appear to be obviously different in strength (though I will have to examine and describe them individually in more detail). Overall, the relatively short, robust nature doesn't fit as well with Plesiosauroidea (though position is important), and the sometimes mentioned labio-lingually compressed shape of their teeth doesn't seem to apply here either, at least not in the parts preserved.

 

Looking at the other resident plesiosaur group, the pliosaurids, the round cross-section and offset carinae are found in various taxa. Still, we can again exclude some from the start: According to KETCHUM & BENSON 2010, Peloneustes possesses teeth in which all ridges around the crown originate basally, which like mentioned before isn't the case. 'Pliosaurus' andrewsi likely represents a new taxon closest related to Peloneustes, but with no known dental material, so assuming a similar condition is the most resonable option for now. Descriptions of the teeth of Pachycostasaurus in NOÈ 2001 describe the enamel ridges as broad and sparse, but don't go into much detail. Yet, these conditions don't really seem to sit well with the structure of this tooth, in which ridges are at least in one region somewhat tightly grouped together. KETCHUM & BENSON 2011 describe a diagnostic condition in the teeth of Marmornectes, in which the enamel ridges only start in some distance to the carinae - this is somewhat true for one carina, but not the other, in which the carina is clearly distinguishable from the other ridges, yet isn't particularly spaced further away from the the ridges than they are from one another. This leaves Liopleurodon and Simolestes, neither of which typically show much labial ornamentation, yet this appears to be highly dependent on position and ontogeny. For example, ANDREWS 1918 describes teeth of Simolestes with comparatively extensive labial ornamentation even at considerable size. 

 

Overall, I know this ID is hard to pin down. I'd really like to hear your thoughts, and I can of course provide more detailed pictures if necessary. If anyone knows someone I could contact over this, I'd really appreciate it! 

 

Thank you for your help!

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Not sure where to start on this, as it seems you definitely did your homework - and game me some to boot! :P Will have to try and track these publications down!

First off, you're definitely right in this not being an ichthyosaurian tooth. Ichthyosaurian teeth have rounded enamel ridges, which this tooth definitely doesn't have. I also agree that this doesn't look particularly like a Machimosaurus-tooth (compare to the Machimosaurus hugii below), since the striae on your tooth appear interrupted.

 

5ffb48549972d_MachimosaurushugiitoothonmatrixLourinhFormationPortugal02.thumb.jpg.7579d92ddebf07976b6b9c1e4dc7aa15.jpg

 

I myself still need to do some research on a couple of teeth from the Oxford Clay myself, which I suspect of being teleosaurid. As such, you may find a reference to an article describing crocodilian tooth ornamentations in my thread below. I wouldn't want to rule out a teleosaurid origin for the pattern of striations on your tooth quite entirely yet, as there seems to be a lot of variation amongst crocodiles. The article is in French, though, and I'm not sure when I'll get around to working myself through it.

 

 

I don't believe your tooth is a plesiosauromorph plesiosaurian, as these are indeed slightly compressed and the ornamentation of their teeth less pronounced (see below images).

 

601de60e87bca_oxfordclayplesiosaurteeth.jpg.f8aa95899493a585be843e6c31ce2ff9.jpgTeeth of Muraenosaurus leedsi (left), Cryptoclidus oxoniensis (middle) and Tricleidus seeleyi. Modified from figure 5 of Noè, Taylor and Gómez-Pérez, 2017. An integrated approach to understanding the role of the long neck in plesiosaurs

 

 

 

 

 

 

 

601de6ac57d5c_Muraenosaurusleedsiplesiosaurtooth.jpg.df2ebe37b7a5f42f71422a27ebecfba8.jpgMuraenosaurus leedsi lingual face. Oxford Clay of Peterborough

 

 

 

 

 

 

 

 

 

 

 

 

 

If not a teleosaurian tooth, I'd then be more inclined to indeed think of pliosaur. The below image - figure 8 from Madzia 2016's "A reappraisal of Polyptychodon (Plesiosauria) from the Cretaceous of England" and reproduced after Tarlo's (1960) original publication - shows a number of pliosaurid tooth morphologies, including those of (B) Simolestes vorax, (C) Liopleurodon ferox, (D) Liopleurodon pachydeirus, (E) Pliosaurus andrewsi, and (F) Peloneustes philarchus. (A) was originally Simolestes nowackianus, but has since been reassigned as the machimosaurid (thus teleosaurid) M. nowackianus.

 

peerj-04-1998-g008.jpg.03466509aecf45566c9aaf6cbf605c1e.jpg

 

As you yourself already concluded, it seems less likely your tooth matches P. philarchus. However, as the striae seem rather thin, and as some of them appear to start halfway up the tooth crown, I'd say it most matches S. vorax. While teeth of the latter indeed often have less labial ornamentation, some of them may be fully ornamented all around. Thus, I'd say it's quite possible your tooth can be attributed to S. vorax. However, for a proper answer, I think you'd better wait for @paulgdls to pop by.

 

In a way, I think we're currently in a rather similar position, you and I, as I'm struggling with exactly the same issues as you're facing with this tooth.

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'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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Excellent analysis above which it's difficult to add to. I can confirm that in Peloneustes the ridges all start at the base of the enamel and that in Simolestes a few start some way up the enamel. This condition is also present in MarmonectesAlso in Simolestes there are often quite numerous and strong ridges on the convex side, contrary to some opinion (except that is in a lunate area of enamel near the base of the convex side where the ridges are absent). 

 

Your tooth looks very similar in morphology and size to those of Marmonectes depicted in the Ketchum and Benson description of the genus. Please see below. 

 

DSCF3864.thumb.JPG.ce66467505fb0315717052db49c0d3bb.JPG

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@pachy-pleuro-whatnot-odon 

Thank you! It's good to know I'm not alone in this struggle, haha! But yes, I was thinking about teleosaurids as well - My problem remains that I haven't been able to find conclusive information on the placement of carinae in teleosaurs, and how consistent those characters are? As for literature I'd be happy to send any PDFs I've found so far!

 

@paulgdls

Thank you! That's a great help, as I wasn't able to access the original Marmornectes description so far! If you don't mind, I'd like to ask about some characters that I haven't been able to confirm as important or not yet:

 

In their description of Liopleurodon sp., SACHS & NYHUIS 2018 mention that all ridges remain separate along their length, only in one point do two lingual ridges fuse apically near a carina. This is mirrored in ANDREWS 1913 description of Liopleurodon as well as the description of Simolestes in GODEFROIT 1994. Similarly, all ridges on this tooth remain seperate as well, only in one case do three lingual ridges fuse apically near a carina. Is this is of any significance or a common trait among all pliosaurs?

 

And lastly: It's hard to make out on the photos, but there are three light, transverse bands that at points split and remerge along the circumference of the crown. Are these in any way important or simply part of the normal enamel coloration?

 

Thank you again!

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32 minutes ago, PointyKnight said:

@pachy-pleuro-whatnot-odon 

Thank you! It's good to know I'm not alone in this struggle, haha! But yes, I was thinking about teleosaurids as well - My problem remains that I haven't been able to find conclusive information on the placement of carinae in teleosaurs, and how consistent those characters are?

I'd say you've already been able to get into this to much greater extent then I have. And, of course, I'm just trying to figure this question out myself right now as well. But, as far as I'm aware, teleosaurids (and thalattosuchians in general) always have exactly two carinae, placed on the mesial and distal edges of the tooth. That, at least, is my observation from teeth belonging to Steneosaurus spp. and Machimosaurus spp. - as well as Metriorhynchus spp., including Dakosaurus.

 

40 minutes ago, PointyKnight said:

As for literature I'd be happy to send any PDFs I've found so far!

I'd be very glad for them! Not that I find myself having too much time to read these days, but I will get to them eventually ;) Feel free to PM me ;)

 

43 minutes ago, PointyKnight said:

In their description of Liopleurodon sp., SACHS & NYHUIS 2018 mention that all ridges remain separate along their length, only in one point do two lingual ridges fuse apically near a carina. This is mirrored in ANDREWS 1913 description of Liopleurodon as well as the description of Simolestes in GODEFROIT 1994. Similarly, all ridges on this tooth remain seperate as well, only in one case do three lingual ridges fuse apically near a carina. Is this is of any significance or a common trait among all pliosaurs?

 

And lastly: It's hard to make out on the photos, but there are three light, transverse bands that at points split and remerge along the circumference of the crown. Are these in any way important or simply part of the normal enamel coloration?

It's indeed these kinds of features that made me wonder about some of the teeth I have / am currently working on, as I've come to associate horizontal banding with crocodilian teeth - irrespective of whether fully aquatic or not - whereas striae merging or disappearing when they reach a carinae is also rather something I've observed on teleosaurid teeth, but not on pliosaurian ones. That is, as my knowledge currently stands, pliosaurian teeth don't actually have carinae in the traditional sense, but may instead have striae that span the full apicobasal length of the tooth. Then again, my reference collection / reference material for pliosaur teeth is rather limited. Which is what prompted my own questions in the first place...

 

Ah, I've still got so much reading to do...! :o

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'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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6 hours ago, pachy-pleuro-whatnot-odon said:

teleosaurids (and thalattosuchians in general) always have exactly two carinae, placed on the mesial and distal edges of the tooth

And that's what's making me move away from croc, too, since in all my croc teeth the carinae are on opposing sides of the tooth, while in this one the two more prominent ridges are closer labially.

 

6 hours ago, pachy-pleuro-whatnot-odon said:

striae merging or disappearing when they reach a carinae

 

6 hours ago, pachy-pleuro-whatnot-odon said:

pliosaurian teeth don't actually have carinae in the traditional sense, but may instead have striae that span the full apicobasal length of the tooth

It's not as much striae merging into the carina (which I think you're right is actually a teleosaurid trait), but merging into one another as they run parallel to the carina. Also you're correct with them not being true 'carinae', they really should be best referred to as axial ridges/striae, yet most literature I've seen either primarily refers to them as carinae or treats the two as interchangeable.

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ALRIGHT, so:
I've contacted Dr Ketchum over her 2010 paper on the description of Marmornectes. She kindly sent over the document and had some quick feedback.

 

First off, I have to correct myself on my original post: 'Pliosaurus' andrewsi does in fact have dental material assigned to it (NHMUK R389) (ANDREWS 1913, FOFFA et al. 2018); The teeth are generally similar to those of Peloneustes, yet lack labial ornamentation entirely (ANDREWS 1913, TARLO 1960). This is a trend seen in many pliosaurs, where dental ornamentation becomes reduced as the animal matures and also in positionally larger teeth.

 

Also on the point of ornamentation, apical fusion of striae is apparently not known to occur in Marmornectes, nor is it present in the teeth of related taxa like Peloneustes or 'Pliosaurus' andrewsi (FOFFA et al. 2018, KETCHUM & BENSON 2010a, 2010b). Then again, it is common in and sometimes even considered charactersitic of more derived thalassophoneans like Liopleurodon and Simolestes specifically (ANDREWS 1913, GODEFROIT 1994, SACHS & NYHUIS 2018). This structure is also directly mentioned to occur in the same region as it does in this tooth. Other aspects like mesio-distal striation distribution seem to fit less with Marmornectes as well, but appear highly variable positionally and are probably unreliable. Overall I think the first point holds much more weight, and still makes me sceptical...

 

On a related note @paulgdls, if you don't mind me asking: Do you know what represents the largest individual of Simolestes vorax? I've read there's at least some undescribed remains from the Oxford Clay, and I was wondering whether the described specimens are a good indicator of its size.

 

 

 

ANDREWS, C.W. (1913): A Descriptive Catalogue Of The Marine Reptiles Of The Oxford Clay - Part II

FOFFA, D., YOUNG, M.T., BRUSATTE, S.L. (2018): Filling The Corallian Gap: New Information On Late Jurassic Marine Faunas From England

GODEFROIT, P. (1994): Simolestes keileni sp. nov., Un Pliosaure (Plesiosauria, Reptilia) Du Bajocen Supérieur De Lorraine (France)

KETCHUM, H.F. & BENSON, R.B.J. (2010a): The Cranial Anatomy And Taxonomy Of Peloneustes philarcus (Sauropterygia, Pliosauridae) From The Peterborough Member (Callovian, Middle Jurassic) Of The United Kingdom

KETCHUM, H.F. & BENSON, R.B.J. (2010b): A New Pliosaurid (Sauropterygia, Plesiosauria) From The Oxford Clay Formation (Middle Jurassic, Callovian) Of England: Evidence For A Gracile, Longirostrine Clade Of Early-Middle Jurassic Pliosaurs

SACHS, S., NYHUIS, C.J. (2018): Plesiosaurier-Funde Aus Dem Mittleren Jura Von Hildesheim

TARLO, L.B. (1960): A Review Of The Upper Jurassic Pliosaurs

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Well done on getting the Ketchum paper.

 

Noe calls the fusion reticulation. He says its rare in Simolestes but occurs quite commonly near the base of the enamel in Liopleurodon. Here are a few quotes from his thesis:

 

"`Ridgelets' on the bottom of the enamel are infrequent, and reticulations are exceedingly rarely observed. In other respects the length
of the enamel ridges in Simolestes vorax is similar to Liopleurodon."

 

"In Pachycostasaurus dawni (PETMG R338; figures 171a, 172) the longitudinal enamel ridges
do not reach the bottom of the enamel on the `convex' surface of the tooth; some of the larger
teeth are almost devoid of ornamentation on the `concave' surface (figure 173). In the figured
tooth, reticulations frequently occur close to the bottom of the enamel and occasionally further
up the crown (e. g. figures 171 a 2,171 a4). In other respects the length of the enamel ridges is
similar to that displayed by Liopleurodon."

 

On Simolestes again: "The bottom of the enamel ridges very infrequently displays reticulations, and the
enamel is rarely vermiculated."

 

On Liopleurodon: "Occasionally the enamel ridges bifurcate or
reticulate close to the bottom of the enamel, and rarely additional enamel ridges are added
between the existing ornamentation, some distance above the bottom of the enamel (figure 24)."

 

A general point Noe makes about carinae  and terminology:

 

"The term enamel ridges is adopted here as the ornamentation is raised above the surface of the tooth, elongate and restricted to the enamel of the tooth crown (Owen, 1841: 272). Enamel ridges, extending from the bottom of the enamel to the apex of the tooth, have occasionally been referred to as `carinae' (Sauvage, 1873: 379; Bardet et al., 1993: 12), but this is incorrect usage of the term which suggests opposing enamel ridges with associated flattening of the tooth between them as found in crocodiles (Romer, 1956: 441). As such `carinae' are not found in the Plesiosauria, the term is not applicable and should not be used."

 

@PointyKnight Specimens of S. vorax listed in Noe's Phd thesis are:

 

NHM R3319
NHM R3170
NHM R10145
PETMG R188
PETMG R296
GPIT 3

 

I can't find out the relative size of these at present but the maximum skull length is given by Noe as 1m. The following figure shows the maximum and minimum size of the skull:

 

6023b4f4592ca_Sskull.thumb.jpg.feca111666d6c97f2277819819951df2.jpg

 

Re. the size of the NHM symphysis animal the following calculations are from McHenry (Kronosaurus, 'devourer of Gods')

 

6023b9363a25e_Stewartbysymphysissizecalculations.jpg.0480b6f9f3d113ca5ef872f1789c6198.jpg

 

This data indicates that there was a far more massive pliosaur present in the Oxford Clay age, 10 to 15 metres in total length and with a truly massively built skull. Dave Martill coined the name Megaliopleurodon for this as yet relatively unknown predator. The possible scapula that I have would have been from a similar sized animal.

 

Paul 

 

The Stewartby synmphysis from Bedford is from a much larger animal than those described in current papers. . 

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@paulgdls Thank you very much, Paul! This is very intriguing: Seeing how apparently reticulation occurs far more commonly in Liopleurodon than it does in Simolestes, and SACHS & NYHUIS 2018 identify a tooth with the exact feature in the very same region as belonging to Liopleurodon sp., might Liopleurodon actually present a viable (tentative) identification for this tooth?

 

As for the terminology, I'll avoid the term 'carinae' in this context from here on out. Aside from being incorrect it's probably better as to avoid confusion in general.

 

As for the specimens: Thank you for all this information! I'll have to read through McHenry's paper (unfortunate that he doesn't seem to picture the symphysis, and no teeth are preserved), but it's exciting to know that there are still large pliosaurs to be described from this formation!

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Indeed you are right. Liopleurodon is probably the most likely ID for your tooth given our discussion. 

 

Its worth bearing in mind that pliosaurs were probably akin to crocodiles in that they just kept growing and growing until they died. A very small proportion of individuals would have survived long enough to reach giant size. Then there are the size variations over millions of years of evolution and then the different genera. Our studies have only just begun but the Stewartby symphysis is deserving of much more study. It hasn't even been prepared properly. 

 

 

Stewartby pliosaur snout diagram.jpg

Stewartby symphysis addx#5.jpg

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@paulgdls Thank you! That symphysis is indeed very impressive! Here's to hoping that it'll be properly reexamined soon!

 

Also indeed, in the research for this I've found an even deeper appreciation for plesiosaurs. Their evolution and ecology truly are fascinating, and I hope we can continue to further our understanding of them.

 

I really appreciate all the help! But I have to ask one final question: I have just removed the label on the case supplied by the seller

to archive it. Underneath there are handwritten lines reading 'Plesiosaur, Oxford Clay,

BEDFORD'.

 

IMG_20210210_201131.jpg.a77450cf21ce5bb176cb67e919e0fb37.jpg

 

I have reason to believe that these are the original details given by the original collector, and the true location of this tooth, as other Oxford Clay material recently listed by this seller also stems from Bedford rather than Peterborough. But does this actually change anything about what we concluded?

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Hi. Glad you share the interest in this! 

 

I imagine that your tooth was collected from the Peterborough formation (Callovian) at Stewartby pit, Bedford, which has the same fauna as that in Peterborough, as far as we know. So I don't think it should change our conclusions. 

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@paulgdls Thank you! After looking at some remains recovered from Stewardby pit, I think this might very well be the case! I'm glad we were able to get this far into the ID, thanks again for all the help!

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