Bone fragment from a creek in austin, + a mosasaur tooth (species?)

[Jared C]

Hey ya'll

Today the unexpected happened - I decided that instead of letting my young life waste away in front of a calculus textbook, I should treat my self to a "brief" fossil hunt. I halfheartedly used google maps to find an possible area for some shark teeth (more with the hope of just exploring rather than anything -finding teeth feels like an impossible task here in austin). On arrival, I had no expectations  - shark teeth seemed more like a pipe dream, but then instead I found something 100x better. Out in the gravel was what could only be a mosasaur tooth, and I found afossilized bone fragment as well.

 

I'm a bit unsure of the formation I found it on - the USGS pocket map is confusing for the area. If a moderator, or someone who's experienced on the site personally messages me, I can tell them the location for help identifying the formation.  

 

I would like an ID on the species of mosasaur, if possible, and also an ID of the bone fragment, if possible.

 

All I could find to measure was a dinged up ruler - the measurements are in inches.

 

 

 

(base of the tooth)

 

 

Here comes the bone fragment next:

 

Edited May 10, 2021 by Jared C
fixing typos

[pachy-pleuro-whatnot-odon]

Wow! That's a nice find! A beautifully preserved specimen!

 

Guess that goes to show the old saying that you always make the best finds when you least expect them!

 

To me it looks like there are larger facests - areas demarcated by ridges that start at the base and taper out towards the tip - all around the tooth, as well as may be some finer tertiary striae - stripes or lines - towards the base? Somewhat stronger on the inner side of the tooth - the slightly concave lingual, or tongue, side - and less pronounced on the other, buccal/labial (or mouth/lip) side? The tooth is somewhat flattened, mildly elliptical in cross-section with the tip bending mesiodistally - from front to back - rather than mediodistally - towards the middle and back, and the curve being restricted to the upper two-thirds of the tooth... Seems to me you've found yourself a very nice anterior lateral Tylosaurus sp. tooth, probably T. proriger! Congratulations! An awesome tooth!

 

As to the bone fragment, although rolled, it's conservation looks rather sub-recent to me. Hard to say for sure what it could be as so little of it remains. But the acute angle shown in one of the photographs suggests one of the flat bones: rib, scapula, pelvic or pectoral bones. My guess would be rib...

[PrehistoricWonders]

@Praefectus could likely confirm the species on that Mosasaur tooth.

[Jared C]

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

Wow! That's a nice find! A beautifully preserved specimen!

 

Guess that goes to show the old saying that you always make the best finds when you least expect them!

 

To me it looks like there are larger facests - areas demarcated by ridges that start at the base and taper out towards the tip - all around the tooth, as well as may be some finer tertiary striae - stripes or lines - towards the base? Somewhat stronger on the inner side of the tooth - the slightly concave lingual, or tongue, side - and less pronounced on the other, buccal/labial (or mouth/lip) side? The tooth is somewhat flattened, mildly elliptical in cross-section with the tip bending mesiodistally - from front to back - rather than mediodistally - towards the middle and back, and the curve being restricted to the upper two-thirds of the tooth... Seems to me you've found yourself a very nice anterior lateral Tylosaurus sp. tooth, probably T. proriger! Congratulations! An awesome tooth!

 

As to the bone fragment, although rolled, it's conservation looks rather sub-recent to me. Hard to say for sure what it could be as so little of it remains. But the acute angle shown in one of the photographs suggests one of the flat bones: rib, scapula, pelvic or pectoral bones. My guess would be rib...

Wow! Thank you for sharing your expertise so freely, I'm very grateful. I'll definitely be using this as a reference for future finds as well!

 

[JohnJ]

Although informative, I am not seeing what our friend, @pachy-pleuro-whatnot-odon, is seeing.  Further, since there are overlaps in tooth characteristics between different mosasaur species, I am reluctant to assign a species to a fragmentary, unassociated tooth.  Additional complications to an ID are added when pterygoid teeth or juveniles are factored.

 

Here are a few quick phone photos of Tylosaurus prorigor teeth from a partial skull I found in 2010.

 

 

Congratulations on your find, @Jared C.

[Praefectus]

Beautiful mosasaur tooth. I am not as familiar with American mosasaurs, but I second @pachy-pleuro-whatnot-odon in saying Jared's tooth has a morphology very reminiscent of Tylosaurus. Do you know the age of the formation where the tooth came from. That may help determine which species it could be. 

 

 

1 hour ago, JohnJ said:

Although informative, I am not seeing what our friend, @pachy-pleuro-whatnot-odon, is seeing.  Further, since there are overlaps in tooth characteristics between different mosasaur species, I am reluctant to assign a species to a fragmentary, unassociated tooth.  Additional complications to an ID are added when pterygoid teeth or juveniles are factored.

 

Here are a few quick phone photos of Tylosaurus prorigor teeth from a partial skull I found in 2010.

 

Congratulations on your find, @Jared C.

Nice find!

Edited May 10, 2021 by Praefectus

[Jared C]

39 minutes ago, Praefectus said:

Do you know the age of the formation where the tooth came from. That may help determine which species it could be. 

 

I do know that the formation is late cretaceous, however I'm still a bit of a newbie, so it's hard for me to dial down on the exact formation of the area. However, in the same creek, there are some very large Exogyra oysters (maybe Exogyra ponderosa?), and the same creek has yielded the occasional scapanorychus tooth before for others, about a mile up stream. I'm going to message the head of the local paleo society for a better understanding of the formation, and get back to you when I have a reply.

 

 

 

Edited May 10, 2021 by Jared C

[pachy-pleuro-whatnot-odon]

3 hours ago, JohnJ said:

Although informative, I am not seeing what our friend, @pachy-pleuro-whatnot-odon, is seeing.  Further, since there are overlaps in tooth characteristics between different mosasaur species, I am reluctant to assign a species to a fragmentary, unassociated tooth.  Additional complications to an ID are added when pterygoid teeth or juveniles are factored.

 

John makes some very valid points here, as assigning disassociated mosasaur teeth a genus, let alone species, is very complicated, and far from fully accepted academically. Mosasaurs are strongly heterodont, which means their teeth can vary significantly along the jaw. But not just that: between the number of mosasaur species that existed (mosasauroidae was a very prolific group with different species adapted to a great variety of niches) and their heterodonty, there is indeed a degree of overlap in teeth of certain species. This can make identification of single mosasaur teeth very difficult. Typically one would want associated skull material - the quadrate, if possible - to aid identification, as this material can be identified with a lot more certainty.

 

The problem is exacerbated by the fact that mosasaurs had teeth in their throats, the so-called pterygoidal teeth - which, arguably, could be an interpretation for this tooth too, as the tooth is more laterally compressed than is typically for teeth of Tylosaurus, while, to my knowledge, lateral compression is not an uncommon trait of pterygoidal teeth - as well as ontogeny (that is, growth stages in life). For there are some suggestions that the facets and prism faces that ornament mosasaur teeth became less prominent as the animals aged, with various authors have proposed synonymy of mosasaur species for reasons of the one being juveniles of the other - see, for example, Zietlow (2020), Hornung and Reich (2014, p. 66) and Wikipedia.

 

That having been said, the last couple of years have seen an academic move towards researchers using tooth morphology to identify and even define new mosasaur species (with a lot of these species definitions seemingly pertaining to Moroccan finds). This trend is far from generally accepted, however.

 

Overall, this uncertainty is actually the reason why I was so explicit when explaining how I arrived at my conclusion on the genus that seemed the most likely candidate for the tooth to me, and why I phrased all my observations as assumptions and questions rather than as fact. The photographs, unfortunately, left me with some doubt as to whether the features I thought I was seeing are indeed present, and we'd either need better pictures that could bring out these features or physical inspection to verify my assumptions. Another reason for being so explicit, by the way, is that, following scientific method, it makes my thought-process reproducable, open for debate, and will allow me to learn from any possible mistakes as well (in the end we're all here to learn ) - for my experience with American mosasaur teeth is admittedly rather limited. The benefit, of course, is that others can learn from it as well The species identification, by the by, was more of an inference based on the genus, since, as far as I know, T. proriger is the only Tylosaurus that occurs (that far south) in Texas.

 

 

5 hours ago, JohnJ said:

Here are a few quick phone photos of Tylosaurus prorigor teeth from a partial skull I found in 2010.

 

 

 

Wow! That's an amazing specimen! I can barely begin to imagine how it must have been to find something as spectacular as that...!

 

I'm a bit surprised by such light coloured teeth having come out of the Austin Chalk, though, as all mosasaur teeth I've seen up until now are all rather dark in colour, either black or brown.

[JohnJ]

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

That having been said, the last couple of years have seen an academic move towards researchers using tooth morphology to identify and even define new mosasaur species (with a lot of these species definitions seemingly pertaining to Moroccan finds). This trend is far from generally accepted, however.

 

Let's hope this "trend" is more of an anomaly given the ambiguous evidence and confusion this could generate.  I always wince at most definitive identifications of isolated mosasaur teeth.

[pachy-pleuro-whatnot-odon]

4 hours ago, JohnJ said:

Let's hope this "trend" is more of an anomaly given the ambiguous evidence and confusion this could generate.  I always wince at most definitive identifications of isolated mosasaur teeth.

 

Yeah, I've noticed that (no offence)

 

However, while I do to large extent share your concerns as to not being able to confidently identify single mosasaur teeth, and retain my scepticism as to species that have solely been defined based on teeth or, at most, minimal jaw elements only (such as Carinodens minalmamar, Xenodens calminechari, Harranasaurus khuludae and Igdamanosaurus aegypticus from Morocco, for example), I share Hornung and Reich's (2014) opinion that much of the confusion seems to stem from inconsistently applied terminology. Compare the two below definitions of M. hoffmanni, for example. Purely based on their descriptions, you might not think they're actually describing the same species, if not the same actual specimen, while the terminological confusion in this case is still very minimal, as one can easily spot which terms have been exchanged for which other ones. Bigger problems arise when authors begin to arbitrarily apply terminology that is inconsistent even within their own descriptions, or if teeth have more complex ornamentation.

 

From Street and Caldwell (2017, p. 541):

Quote

In M. hoffmannii the anterior marginal teeth tend to have two or three lateral facets, two being more common on the anterior dentary teeth and three being more common on the anterior maxillary teeth of the holotype. The medial facets are more numerous and less distinct, but there are usually at least five. The number of lateral facets increases posteriorly along the tooth row as the facets get narrower, and, perhaps more importantly, the lateral surface gets larger as the posterior carina shifts posteriorly.

 

From Bardet et al. (2013, p.72):

Quote

The high and slender shape of the crown, as well as a labial surface bearing 3 prisms and a lingual face with indistinct ones are typical characters of Mosasaurus hoffmanni (Lingham-Soliar, 1995).

 

[Jared C]

23 hours ago, Praefectus said:

Do you know the age of the formation where the tooth came from

It feels like we've beaten this dead horse already, but I found that the formation is the Ozan formation, AKA the lower taylor marl. However, for a specific age I couldn't find anything dating the Ozan anymore specifically than just "late cretaceous".

[Praefectus]

15 minutes ago, Jared C said:

It feels like we've beaten this dead horse already, but I found that the formation is the Ozan formation, AKA the lower taylor marl. However, for a specific age I couldn't find anything dating the Ozan anymore specifically than just "late cretaceous".

Thanks for the information. I'm not super familiar with that formation, but I think pachy-pleuro-whatnot-odon already got the identification for you. 

 

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

The species identification, by the by, was more of an inference based on the genus, since, as far as I know, T. proriger is the only Tylosaurus that occurs (that far south) in Texas.

 

[Jared C]

1 hour ago, Praefectus said:

Thanks for the information. I'm not super familiar with that formation, but I think pachy-pleuro-whatnot-odon already got the identification for you. 

 

 

thank you, and I only realized just now how my last reply must have sounded! I should've rather said " sorry to beat this dead horse, because I found the formation"... it was not directed at you or your helping. My apologies

[Thomas.Dodson]

3 hours ago, Jared C said:

It feels like we've beaten this dead horse already, but I found that the formation is the Ozan formation, AKA the lower taylor marl. However, for a specific age I couldn't find anything dating the Ozan anymore specifically than just "late cretaceous".

Can't speak for Central Texas but in NE Texas the Ozan is aged approximately the first 1/3 to 1/2 of the Middle Campanian. The NE portion of the state with the North Suphfur River sections of the Ozan have no doubt been given more stratigraphic attention and so are more easily found in literature.