Possible Dallasaurus tooth

[ThePhysicist]

Hi y'all, I have been acid prepping some Kamp Ranch matrix for weeks and today I saw this peeking out. I'm thinking it's a Dallasaurus turneri (basal mosasaur) tooth. It's posteriorly recurved, has no mesial carina, and has a circular basal cross section. The crown height is 3 mm. I believe there's a hairline crack, so I may try a little glue before attempting to finish getting it out (if I decide to). More knowledgable eyes would be appreciated! @JohnJ @pachy-pleuro-whatnot-odon

 

 

 

 

 

 

 

 

^ from Bell & Polcyn (2005) they appear to be about 3-5 mm in height. 

 

 

Edited April 15, 2022 by ThePhysicist

[pachy-pleuro-whatnot-odon]

Unfortunately never saw a Dallasaurus-tooth, but the shape and curvature do look very similar to the teeth of another basal mosasaur I am familiar with, Tethysaurus nopscai. Below are some photographs of its dentition:

 

 

The tooth also shows a lot of superficial similarity to the teeth of another small and rather primitive mosasaur, Halisaurus esp. Halisaurus arambourgi, as well as with Russellosaurus coheni (picture below; source).

 

 

So, between Tethysaurus, Halisaurus, Russellosaurus and the photographs from Bell Jr. & Polcyn's (2005) article (very interesting, I'd say that there's indeed a good chance of this being a primitive mosasaur tooth, and by extension, possibly Dallasaurus. Very cool if it turns out to be, with their remains being so scarce!

 

The problem with these small teeth, I find, however, is that it's easy to confuse them with fish teeth, as it's often difficult to get at the distinguishing characters with sufficient detail and they can look deceptively alike. In this case, I don't think you can really see the very tip of the tooth, for example, making it hard to exclude a acrodin cap. The fact that the tooth is rooted doesn't necessarily mean fish is excluded either, as you yourself pointed out to me (albeit the root on this tooth looks very different from the examples shown in that thread) In any case, the Eagle Ford Formation being Turonian - as far as I understand - we can at least rule out Pachyrhizodus as a potential trouble-maker

 

Another issue is that all of the aforementioned mosasauroids have perfectly conical teeth with perfectly smooth enamel, which are two conditions your specimen doesn't quite have. The alternative other interpretation, therefore, and one that I think I favour - primarily for the way the root looks, as well as the slight vermiculation of the enamel and pinching that seems to be present near the anterior base of the crown - is that this is a Coniasaurus-tooth.

 

Coniasaurus sp. mandible, Eagle Ford Formation, Tarrant county, Texas (source)

 

 

Partial Coniasaurus sp. mandible, Eagle Ford Formation, Tarrant county, Texas (source)

 

 

Cf. Coniasaurus sp. (figure 1 from Shimada, Everhart and Ewell [2007])

 

One of the reasons I think we might be dealing with Coniasaurus is that there appears to be a hint of a slight constriction of the tooth crown near the transition to its base; the vermiculating enamel; the tooth being somewhat more bulbous than other early/primitive mosasauroids; and the pinching, which I see as a mechanism to force a more backward curvature/morphology in an otherwise maybe not so recurved tooth - which fits the description of Coniasaurus-teeth perfectly, if you ask me, since most of them are so bulbous, but the anterior maxillary teeth, at least in one species, seem to have been much more recurved than the rest of the dentition. See the image below from Caldwell (1999; unfortunately paywalled). So what I think we have is a Coniasaurus premaxillary or anterior maxillary tooth.

 

In any case, very neat find!

 

 

 

As to extracting the tooth from its matrix: I'd most definitely put a good layer of Paraloid on top. It's easy to remove later, but will protect your tooth during extraction

[Jared C]

Awesome find! I found a broken half vert from a coniasaur and it made my week! I can't imagine finding a tooth, that's super cool.

[JohnJ]

Interesting for sure.  A quick email to Mike Polcyn would put it in front of the most experienced eyes.  A devilish enchodus tooth is another possibility.

[ThePhysicist]

On 4/15/2022 at 4:02 AM, pachy-pleuro-whatnot-odon said:

One of the reasons I think we might be dealing with Coniasaurus is that there appears to be a hint of a slight constriction of the tooth crown near the transition to its base; the vermiculating enamel; the tooth being somewhat more bulbous than other early/primitive mosasauroids; and the pinching, which I see as a mechanism to force a more backward curvature/morphology in an otherwise maybe not so recurved tooth - which fits the description of Coniasaurus-teeth perfectly, if you ask me, since most of them are so bulbous, but the anterior maxillary teeth, at least in one species, seem to have been much more recurved than the rest of the dentition. See the image below from Caldwell (1999; unfortunately paywalled). So what I think we have is a Coniasaurus premaxillary or anterior maxillary tooth.

Thank you as always for your thorough input! I think I'm now leaning in that direction as well. 

 

On 4/15/2022 at 9:02 AM, Jared C said:

Awesome find! I found a broken half vert from a coniasaur and it made my week! I can't imagine finding a tooth, that's super cool.

Thanks! I'm super happy to find any non-fish vertebrate in this fossil-forsaken rock. I've found another tooth in POC, so anywhere you are in Turonian deposits, try sifting some micromatrix/gravel.

On 4/15/2022 at 9:25 AM, JohnJ said:

Interesting for sure.  A quick email to Mike Polcyn would put it in front of the most experienced eyes.  A devilish enchodus tooth is another possibility.

Will do. I doubt Enchodus, as positions without a mesial carina appear to have mesial striae at the base of the crown, and more of an 's' curve in my experience. The ones I have been seeing in the matrix are also much more blade-like.

[ThePhysicist]

Found another Coniasaurus, it looks much more similar to the one I've found before. Crown height 2 mm.

 

 

Time for round 2 of, "is this Dallasaurus?" Crown height 3 mm. No basal constriction, has an offset posterior carina, no mesial carina, smooth medial enamel (differing from Coniasaurus). Looks roughly like tooth 'C' in the description paper.

 

 

 

 

Edited April 20, 2022 by ThePhysicist

[pachy-pleuro-whatnot-odon]

11 hours ago, ThePhysicist said:

Time for round 2 of, "is this Dallasaurus?" Crown height 3 mm. No basal constriction, has an offset posterior carina, no mesial carina, smooth medial enamel (differing from Coniasaurus). Looks roughly like tooth 'C' in the description paper.

 

It's unfortunate that I can't find any openly accessible descriptions of Coniasaurus-teeth, as I'd really like to compare how Coniasaurus teeth are described versus those of Dallasaurus, especially when it comes to the premaxillary and anterior maxillary teeth I referred to above. Because, based on Bell Jr. & Polcyn's (2005) article, I'd have to agree that the description given there seems a good match for how the extracted tooth is characterised above:

 

Quote

posterior maxillary teeth strongly recurved posteriorly, slightly inflated at the crown and bearing only posterior carinae that is slightly offset laterally

 

Looking at the photographs, however, I'm having difficulty spotting the posterior carina mentioned, and while I do believe I can make it some sort of fold or facet, don't see anything I would associate with a typical mosasaurid carina. Rather, I still see signs if the "pinching" I mentioned earlier - depressions alongside the sides of the tooth, as well as what (in the fifth photograph) appears to be center front - that seem very unusual for mosasaur teeth, but are also present in the confirmed example of Coniasaurus-tooth given from the location. As such, my opinion remains unchanged: anterior tooth from a coniasaur upper jaw.

[JohnJ]

On 4/15/2022 at 10:25 AM, JohnJ said:

Interesting for sure.  A quick email to Mike Polcyn would put it in front of the most experienced eyes.  A devilish enchodus tooth is another possibility.

 

Mike is the guy that could enlighten us all.  

[pachy-pleuro-whatnot-odon]

1 minute ago, JohnJ said:

Mike is the guy that could enlighten us all.  

 

Yup, didn't want to repeat it too much, but fully agree. Quite interested what he'd have to say to this little puzzle

Edited April 20, 2022 by pachy-pleuro-whatnot-odon

[JohnJ]

Just now, pachy-pleuro-whatnot-odon said:

 

Yup, didn't want to repeat it too much, but fully agree. Quite interested what he'd have to say to this little puzzle

 

He is generally very helpful to collectors with good photos and geologic info.

[ThePhysicist]

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

description given there seems a good match for how the extracted tooth is characterised above:

 

Sorry, should've clarified, that tooth is a new one. I stabilized the first tooth and am now prepping it out to get a better look.

 

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

Looking at the photographs, however, I'm having difficulty spotting the posterior carina mentioned, and while I do believe I can make it some sort of fold or facet, don't see anything I would associate with a typical mosasaurid carina. Rather, I still see signs if the "pinching" I mentioned earlier - depressions alongside the sides of the tooth, as well as what (in the fifth photograph) appears to be center front - that seem very unusual for mosasaur teeth, but are also present in the confirmed example of Coniasaurus-tooth given from the location. As such, my opinion remains unchanged: anterior tooth from a coniasaur upper jaw.

Here are some better views of the 'posterior carina,' it's really hard to get decent pictures of these tiny teeth:

 

 

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

I still see signs if the "pinching" I mentioned earlier - depressions alongside the sides of the tooth

I now understand what you mean. In Caldwell (1999), he does mention similar features, I can PM the paper if you'd like. The hunt continues...

 

[pachy-pleuro-whatnot-odon]

22 hours ago, ThePhysicist said:

Sorry, should've clarified, that tooth is a new one. I stabilized the first tooth and am now prepping it out to get a better look.

 

Sorry, I had indeed not realised that both teeth in this new post are different from the one in the initial post. Now that you mention it, though, the second tooth from the second post does look somewhat different from the very first tooth you posted, if only for the constriction at the neck of the tooth or the greater degree of vermiculation in that one...

 

22 hours ago, ThePhysicist said:

Here are some better views of the 'posterior carina,' it's really hard to get decent pictures of these tiny teeth:

 

I hear you. I also always have a lot of trouble properly photographing such small teeth, especially in a way as to highlight all the relevant details However, the second batch of photographs of, lets call it tooth C (second tooth, second post), is a lot clearer and I can now see what you mean with the somewhat laterally offset distal carina. For some reason, the enamel now also looks a lot more mosasauroid to me too, in this second batch of photographs. If not for the pinching I would therefore indeed agree that this appears to be the tooth of a basal mosasauroid, or Dallasaurus.

 

22 hours ago, ThePhysicist said:

I now understand what you mean. In Caldwell (1999), he does mention similar features, I can PM the paper if you'd like. The hunt continues...

 

If you could forward me the paper, I'd be very grateful. I think it'd be very interesting to read Caldwell's description of these teeth as Bell Jr. & Polcyn's (2005) is so minimal.

[ThePhysicist]

I got the first tooth out intact ('tooth A'). Note that the lingual enamel texture is affected by glue.

 

 

Side-by-side comparison with 'tooth C;' they look very similar:

 

And a warning for future Kamp Ranch hunters, there are (Amiid?) fish teeth that superficially resemble these squamates, but have completely smooth enamel, no carinae, and a translucent acrodin cap at the tip.

 

Edited April 22, 2022 by ThePhysicist

[pachy-pleuro-whatnot-odon]

On 4/22/2022 at 4:30 AM, ThePhysicist said:

I got the first tooth out intact ('tooth A'). Note that the lingual enamel texture is affected by glue.

 

Side-by-side comparison with 'tooth C;' they look very similar:

 

Now I'm rather confused, as tooth A has a constriction around the base of the crown, what appears to be a more rugose texture to its enamel, and the sulchi described by Caldwell (1995). It's also more bulbous than tooth C, giving it a more backwards orientation that fits well with Coniasaurus. I'm therefore pretty sure this tooth can be assertive to that genus, as this morphology would be very unusual for mosasauroidae, to my knowledge even very early genera. Yet the aforementioned author makes no reference to carinae, nor do Bell Jr. & Polcyn's (2005) mention sulchi on the teeth of Dallasaurus. It may therefore be that we're dealing with a new species, although that's of course always a grand claim to make... Considering the better morphological match between tooth A and coniasaur-teeth, as well as the rarity and fragmentary nature of the latter remains and therefore our incomplete knowledge of them, however, I'm more inclined to still call tooth A Coniasaurus, possibly cf. Coniasaurus gracilodens, and by extension due to the great degree of similarity between the two teeth, tooth C as well.

 

However, John's recommendation to contact Mike Polcyn is, I think, still the best...

 

On 4/22/2022 at 4:30 AM, ThePhysicist said:

And a warning for future Kamp Ranch hunters, there are (Amiid?) fish teeth that superficially resemble these squamates, but have completely smooth enamel, no carinae, and a translucent acrodin cap at the tip.

 

That's indeed a very useful warning, and in that respect it's very lucky that the distinction can so clearly be made. Thanks for providing such a detailed description!

[ThePhysicist]

On 4/23/2022 at 4:00 AM, pachy-pleuro-whatnot-odon said:

Yet the aforementioned author makes no reference to carinae

True, but the tooth that is clearly Coniasaurus does have a posterior carina (though less pronounced), so I wouldn't be surprised if anteriors did too; I totally agree that Coniasaurus is the most parsimonious ID. I'll contact Mike with updated photos when I've got all the teeth I want him to look at so I don't pester him too much.

 

I do have another tooth on deck that looks interesting... we'll see once it's fully free from the matrix.

Edited April 24, 2022 by ThePhysicist

[ThePhysicist]

Here's 'tooth D.' It's conical with smoother enamel and a bit larger with a crown height of 4 mm. While it resembles 'A' in the description paper, it appears to be bicarinate - which precludes Dallasaurus maxillary teeth which are explicitly described as only having a posterior carina. I however don't know if anterior teeth or dentary teeth are excluded by this quality. By the positioning of the carinae, it looks like a premax or at least anterior. Could be another juvenile Mosasaurid given the size.

 

 

Enamel texture is smoother:

 

 

Size comparison with previous teeth:

 

 

Yeah... definitely looking Mosasaurid. Mosasaurus hoffmannii (anteriors):

 

^Rempert et al. (2022) 

I'm not an expert on Mosasaurine dentitions; are anteriors of Mosasaurinae distinguishable from other subfamilies? 

 

Comparison with tooth 'A' in Bell & Polcyn (2005). General morphological similarity, but don't know about the carina(e) on A:

 

 

 

[pachy-pleuro-whatnot-odon]

13 hours ago, ThePhysicist said:

Here's 'tooth D.' It's conical with smoother enamel and a bit larger with a crown height of 4 mm. While it resembles 'A' in the description paper, it appears to be bicarinate - which precludes Dallasaurus maxillary teeth which are explicitly described as only having a posterior carina.

 

This one, I'd say, does look like a mosasaurid tooth, probably some kind of plioplatecarpine. It looks way less bulbous (to me, at least); has the right curvature; lacks the sulchi Coniasaurus-teeth have; has smooth enamel and plain root-to-crown transition; and has two carinae to boot. I'd say you couldn't get any clearer than that. An awesome find!

 

13 hours ago, ThePhysicist said:

By the positioning of the carinae, it looks like a premax or at least anterior.

 

That depends on the positioning of the carinae vis-à-vis one another. I've tried to draw up a diagram below to help explain how this works. But in principle, carinae follow the shape of the jaw they are set in, meaning you can draw an imaginary outline of a mosasaur snout and place teeth along it. The curvature of the snout at the point where you place the teeth will determine the angle at which the carinae are offset from each other. Thus the angle between carinae will become smaller the more anteriorly the tooth is positioned (unfortunately my attempt at illustrating this didn't come out as clear as this can sometimes be observed in actual mosasaur teeth).

 

 

13 hours ago, ThePhysicist said:

I'm not an expert on Mosasaurine dentitions; are anteriors of Mosasaurinae distinguishable from other subfamilies?

 

Mosasaurinae is a rather large grouping of different mosasaur species, incorporating a broad range of tooth morphologies with significant variation even occurring with genera. As such, your best bet is to familiarize yourself with the teeth of individual mosasaur species and genera, as their general morphological traits hold even for anterior teeth. However, the above change in offset between carinae, of course, comes into play with anterior teeth. This may slightly affect their curvature, since it's often the carinae that determine how, within the given morphospace a tooth gets curved (tylosaurine teeth, for instance, curve distally, whereas teeth of the genus Mosasaurus do so mediodistally). Then again, there are also species - such as Prognathodon solvayi - in which the teeth become more conical anteriorly, thereby significantly changing their morphology...

 

Hope this helps. And, again, great find!

[ThePhysicist]

Thanks for your insight once again! Super psyched to find a Mosasaurid - that's what I was hoping to find! Hopefully where there's one there's more...

[ThePhysicist]

Heard from Mike, and he said the Mosasaurid looks like a young Russellosaurus. 

[JohnJ]

35 minutes ago, ThePhysicist said:

Heard from Mike, and he said the Mosasaurid looks like a young Russellosaurus. 

Congratulations!  Any opinions on the others?

[ThePhysicist]

9 minutes ago, JohnJ said:

Congratulations!  Any opinions on the others?

He didn't explicitly comment on them; sounds like he was going to check on some Dallasaurus teeth next week. 

[ThePhysicist]

Mike says teeth 'A' and 'C' are not Coniasaurus. He acknowledged their similarity to Dallasaurus, minus the differences I noted in correspondence (also in this thread). They probably are an undescribed squamate, and will be donated to the SMU collection. He also clarified on the Mosasaurid tooth, that the most conservative ID would be Russellosaurina cf. Russellosaurus given the difficulty of assigning isolated teeth.

 

[pachy-pleuro-whatnot-odon]

34 minutes ago, ThePhysicist said:

Mike says teeth 'A' and 'C' are not Coniasaurus. He acknowledged their similarity to Dallasaurus, minus the differences I noted in correspondence (also in this thread). They probably are an undescribed squamate, and will be donated to the SMU collection. He also clarified on the Mosasaurid tooth, that the most conservative ID would be Russellosaurina cf. Russellosaurus given the difficulty of assigning isolated teeth.

 

That's pretty cool, and thanks for sharing the feedback! There's not that much information online about any of these early mosasaurs, so having this information here really helps! 

 

And congrats on discovering a new squamate! That's an awesome discovery, especially since you've found multiple examples! Now I guess it'll be a waiting game to see if more complete remains can be found