Texas Shark Tooth Extravaganza Pt. 2

[GPayton]

Well, it's taken me a lot longer than I thought it would to write the second part of this trip report, mostly because I've been busy with school and several trips to other places across Texas collecting fossils, but also because I must have made about nine trips to the particular Eagle Ford formation creek site I wrote about in the first post. I've got a lot I could say, but I'll narrow it down to just the most exciting finds - I've still got another trip report covering two trips I took to Jacksboro/Mineral Wells and Post Oak Creek to write as soon as I'm done with this one! 

 

I'll link that first trip report here for anyone that wants to read it:

http://www.thefossilforum.com/index.php?/topic/126948-texas-shark-tooth-extravaganza/&tab=comments#comment-1377551

 

As I had located the specific lense in the shale with the most shark teeth on the very same day that I discovered the site, the next couple trips were spent breaking it up further and seeing what else I could find in the exposed sections. Although I came away with a respectable haul of nicely-preserved teeth I didn't find anything I hadn't already found before. Getting bored of finding the same Ptychodus and Squalicorax teeth I decided to climb up the small and now-dry waterfall that stemmed from a creekbed sitting almost on top of the shark teeth lense in the shale. I figured that it would be easier to look down and break up the rock layers than to look up at them above my head and hope they didn't land on me when ever I pulled out another chunk. Here's a picture of the site with the waterfall to the left. You can follow the bentonite seam from the right to the left with your eyes to see where the lense crops up in the creekbed (it's the sort of dark crevice just above the waterfall ledge). 

 

 

Very quickly I was rewarded for my exploration as I pulled out the largest Ptychodus tooth I had ever seen (at the time - a little hint as to what I'll be talking about in my Post Oak Creek trip report ). I'm generally pretty clueless when it comes to identifying most Ptychodus down to the species level, so if anyone could help me out I'd really appreciate it! 

 

Here's an in-situ picture:

 

 

And another picture taken after I had broken it out of its rocky prison:

 

With my enthusiasm rekindled I kept digging through the shale and was rewarded by another Ptychodus tooth, even larger than the last, that actually popped out directly into my hand before I had even seen it. I didn't get a picture at the time but it is in this photo I took after I got home. It has some really interesting surface wear that I reasoned was probably accrued during the shark's lifetime. 

 

 

Directly behind where I found the two Ptychodus teeth was the find of the day and maybe even the find of the year, although I didn't know it at the time. This is a picture of it still in-situ if anyone wants to take a guess as to what it was:

 

 

It was a mosasaur vertebra! And the largest piece of bone I had found at the site so far, many times larger than the coniasaur vert from the previous trip. This is what it looked like out of the shale back home when viewed from the bottom:

 

 

One of the transverse processes can be seen on the right as well as the two attachment points for the haemal arch, which is sort of like the spine that's on top of each vertabra but located on the bottom in the vertebrae that make up the tail. 

 

Now at the time I didn't think this individual vertebra was anything special. I had found mosasaur vertebrae before at the North Sulphur River, many of which were much larger than this one and in much better condition. I was pleasantly surprised that I had found one at this site but didn't think much of it and so it was pocketed to be looked at later. 

 

It wasn't until I got home and had a conversation with @Jared C who is much more informed when it comes to the Eagle Ford than myself that I realized this one bone might be much more important. That's because I had initially assumed that I was looking at the contact between the Eagle Ford and the Austin Chalk, making this particular shark tooth lense I had discovered the famous Atco contact. Mosasaurs are rare in Turonian age rocks but certainly not unheard of (Jared himself even found one two years ago!). But after reading several different university publications on this particular site I realized that this spot wasn't the contact between the Eagle Ford and Austin Chalk, but actually entirely Eagle Ford rock - specifically a subunit that placed it in the lower half of the formation. This meant that this one bone had come from the Cenomanian, not the Turonian, making it slightly older than the oldest known basal mosasaurines, both of which are also from Texas - Russellosaurus and Dallasaurus. 

 

Still not believing that I could have possibly been this lucky, I emailed Dr. Polcyn at SMU to get his opinion. He was the one to actually first describe both Russellosaurus and Dallasaurus and so I figured if anyone could tell me whether or not what I had found was significant it would be him. Jared has a pretty good relationship with Dr. Polcyn from his own mosasaur discovery so he was able to tell him to be on the lookout for my email. After a short exchange in which Dr. Polcyn expressed his interest in seeing the vertebra in person we arranged for me to meet him north of Dallas at a plesiosaur dig both he and Jared would be involved in. 

 

Meeting Dr. Polcyn was incredible. I've known of him for a long time since mosasaurs have always been my favorite prehistoric animal and he's definitely one of the leading researchers as far as they're concerned. I even remember seeing him interviewed for the news in 2005 when the Dallasaurus discovery was first made public and begging my grandparents to take me to the Dallas Museum to see their mosasaur skeletons. 

 

Dr. Polcyn was very interested in the vertebra when he saw it in person and asked me if I would be willing to donate it to SMU alongside the two Ptychodus teeth I had found next to it as they might be useful for dating purposes. I of course said yes as donating a fossil I had found to science has probably been my dream since I could first talk. 

 

We made plans for me to go back to the site and collect a large sample of the bentonite from the seam located beneath where I found the vertebra so it can be dated by SMU and the age of the bone confirmed. The bentonite being present at the site is extremely fortunate as it is one of the most conducive materials to dating sedimentary strata. 

 

 

Rounding out my finds for the day that I found the mosasaur vertebra was a pycnodont fish mouthplate:

 

 

And also another nice coniasaur vertebra (I actually found several more but this was the best and the only one I got a good picture of): 

 

 

Not all of the animals I saw at the site were dead and many millions of years old though. In the same vicinity as the mosasaur vertebra was a toad that I had clearly disturbed in my search for associated bones. 

 

 

I apologized for my intrusion and replaced the front door to his little hole that I had inadvertently dug up. 

 

A much less welcome sight than the toad was an absolutely massive wolf spider that I spotted on a clump of shale I had been just about to pick up.

 

 

On my way back to my car I finally spotted the pack of hogs that been so kind as to create a trail through the woods for me to follow on my first trip. I gave them a wide berth and continued on my way. 

 

 

This site has become one of my favorites, not only because of what I've found there but because I discovered it on my own after a lot of geologic map studying and old paper reading. I can finally say I understand Jared's Eagle Ford obsession! Until next time, 

 

- Graham 

 

[PaleoPastels]

Absolutely love this trip report! Also enjoyed the bonus wildlife photos. Eagle Ford has some pretty fun stuff! I love seeing older EF group stuff pulled out from down there. 
 

*Next time you hit up POC feel free to let me know next time! I recently found some cool stuff there myself, I live pretty close and frequent all those nearby creeks- company is always welcomed.  

Edited January 17, 2023 by AmmoniteDelight
Typo

[Mikrogeophagus]

Nice to see the second installment of this story! 

 

Donating specimens to a museum is a huge milestone so congratulations! Hopefully that mosasaur vert brings academia some good info. That site looks amazingly productive so don't stop hunting it, although I doubt you need me to tell you that .

 

As for the ptychodus, I'll use this as an exercise to see if I'm getting better at ID'ing them. So, take my words with a grain of salt. On the squarer tooth, I don't see any bifurcating ridges, so I'm throwing out decurrens and occidentalis. That leaves anonymous and marginalis. The pattern and number of the ridges looks closer P. anonymous so I think that's the best ID. Marginalis have circular ridging. I've found plenty anonymous in the Bouldin Flags, so it's present in cenomanian strata as well. The longer tooth is harder to gauge, but I would guess anonymous as well. Some pictures showing the crown height would be helpful for a better informed ID. Hopefully someone more knowledgeable can share their opinion.

 

I always look forward to reading your reports. Can't wait to hear how POC went!

 

 

Edited January 18, 2023 by EPIKLULSXDDDDD
Info

[PaleoPastels]

1 hour ago, GPayton said:

 

 

 

Directly behind where I found the two Ptychodus teeth

Still learning myself how to ID this genus but to me left looks like a P. anonymous (Cenonian-Turonian but reminds me a little of mammalaris at first glance which is common in the Coniacian strata) & right looks P. decurrens (Albian-Cenomanian; do the ridges have “split ends” at the sides?) if not could also be another anonymous. 

Edited January 17, 2023 by AmmoniteDelight
Yet another typo

[LSCHNELLE]

That's a fairly large-sized vert for the Eagle Ford. The site does look like either the Bluebonnet Flags or Bouldin Flags of the Eagle Ford. It's usually Upper Cenomian in age. I have found a few smaller verts in it over the years which I sent to Dr. Polcyn. They are quite rare.

 

As to the two Ptychodus teeth. A side view would be helpful if you got such pics before your donation. The second one is likely Ptychodus anonymous based on the margin showing. The first could be either P. anonymous or P. decurrens depending on crown height.

[JohnJ]

Great persistence and great finds go hand in hand.  Congratulations on your discoveries and donations, Graham. 

[Fin Lover]

Congrats on your finds and having your dream come true!

[Jared C]

So cool! It's especially exciting that this vert is ample fuel for a paper - and expanding the range of north american mosasaurs will have you starting out your career with a bang! Let's hope the samples we'll be doing this week provides the desirable results, and cheers to a helluva spot 

[pachy-pleuro-whatnot-odon]

Awesome trip report! And those coniasaur and especially mosasaur vertebra are so cool! Wish I could visit Texas some day to hunt the Eagle Ford!

[LSCHNELLE]

Graham, thanks for your help whittling down the pelvis slab of "Gracie" late last year. You were so careful in the area of the rear paddles that I think we got them both intact. It's such an exciting discovery that you made for one of the oldest mosasaur remains in the country. I hope school is going well for you now!

[Ironhead42]

Excellent trip report! Exciting finds...can't wait to see what else the site produces.

[LSCHNELLE]

On 1/17/2023 at 7:02 PM, LSCHNELLE said:

That's a fairly large-sized vert for the Eagle Ford. The site does look like either the Bluebonnet Flags or Bouldin Flags of the Eagle Ford. It's usually Upper Cenomian in age. I have found a few smaller verts in it over the years which I sent to Dr. Polcyn. They are quite rare.

 

As to the two Ptychodus teeth. A side view would be helpful if you got such pics before your donation. The second one is likely Ptychodus anonymous based on the margin showing. The first could be either P. anonymous or P. decurrens depending on crown height.

I learned something new about the Bouldin Flags member last month from Denne et al 2016. The oyster bed shell hash section at the bottom of the Bouldin Flags is actually Middle Cenomanian in age. So, it's possible Graham that the mosasaur caudal vertebra is that same age if at or below the Bluebonnet equivalent of that oyster hash. If it's from just below the uppermost part of the flaggy member, then it's more likely to be Late Cenomanian in age.