Generous Central Texas Rock

[Jackito]

School starts next week and my 10 yr old kiddo and I are both trying to extend summer as much as possible. We decided to go on a hunt yesterday afternoon. His focus was on the ever shrinking pools within the creek for turtles, snakes, and frogs, and my focus is on finding a mosasaur.

It’s frustrating because I’m finding all sorts of shark and fish material but I have yet to stumble upon marine reptile. There seems to be several types of rock that yields teeth within the creek. The rocks range from dense shell mass, crumbly bits of pulverized things, light shell hash and shale, dark shale, sandy shale mix, and sandstone.

 

After a bit of prospecting on loose rocks in the creek bed, I went to my go-to rock. This one rock is the most productive rock ever. It’s a big slab that was previous covered in water. It moves each time it rains, and teeth erode out from the bottom. Yesterday I loped off a 2ft section of the slab and explored it.

 

At one point I uncovered a nice tooth that I was trying to gently break free. In doing so, I uncovered several additional teeth. In total, I probably found 15 ptychodus and 30 shark teeth.

 

I've also posted a picture of a previous find of two teeth stacked, and of the various teeth we've found in a couple of trips. Most of the teeth are in the matrix so it takes some patience to work them free. Luckily the material is soft and crumbly, and can be worked with fairly easily. 

 

I might shift my focus to Dallas and try to do a road-trip hunt to a few spots along I-35 in Ellis, Tarrant, and Collin County for mosasaur. I'll read the old geology publications, paleontology papers, geology apps, and google maps, and jot down addresses to hunt. Probably a lot getting skunked but maybe one will pan out and I'll get that mosasaur tooth I'm after.

 

 Feel free to send a direct message if you can point us in the direction of the elusive marine reptile, or if you'd like to meet up and do some hunting. 

[Ironhead42]

Generous rock indeed! Nice finds!

 

[Jared C]

A honey hole like that is a rare gem! Especially in centex 

 

Keep it safe, and best of luck on your quest for giant lizards!

Edited August 4, 2022 by Jared C

[Jared C]

5 hours ago, Jackito said:

 

 

Also.. is that an Archaeolamna I spy in there?

Edited August 4, 2022 by Jared C

[pachy-pleuro-whatnot-odon]

That's one productive spot! Very rare to come across a site as productive as this, and even more so over here in Europe!  One thing I've learned, though, is that you rarely get what you're looking for, but should always take what you get...!  What you've got there is something some of us would need to work years for! 

Edited August 4, 2022 by pachy-pleuro-whatnot-odon

[Jared C]

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

One thing I've learned, though, is that you rarely get what you're looking for, but should always take what you get

 

True actually - none of my bigger finds were expressly my targets the day I found them.

 

The Eagle Ford mosasaur site was co- discovered while I was looking for Ptychodus - and when Christian started flipping slabs in the pit he was hoping for shark teeth too

The Eagle Ford Plesiosaur was co-discovered - I was looking for nothing in particular (being a scouting trip for me) and Joe was looking for Pyrite

The Eagle Ford Coniasaur was found while I was looking for nothing in particular (but I was daydreaming about Ptychodus decurrens...)

The Ozan Hadrodus hewletti was found while I was scouting for shark teeth

The Austin Chalk Cidarids were found while I was daydreaming about finding a Ptychodus mortnoni mouth plate

 

So, as you can see, a lot of it has been luck - and my luck with the Eagle Ford reptiles has been unusual, as usually the Eagle Ford (especially the Turonian eagle ford) isn't great for reptiles compared to other formations

 

The reason why is because the Cenomanian-Turonian represent an intense transitional time in the western interior seaway. Ichthyosaurs don't really make it into the Turonian - their final stand is the cenomanian, and there were very few of them at that point, so they're quite rare. Folks like @facehugger have seen some Texas Ichthyosaur materiel but it's hard to find.

 

Pliosaurs make their final stand in the Turonian as well - these animals were also dwindling up until this point so Pliosaur materiel is also rare in Turonian strata, and uncommon in cenomanian strata. 

 

The fossil record of Texas suggests that mosasaurs here were starting to radiate around the middle Turonian, though it's very reasonable that lower turonian mosasaurs should exist here too (none of have been found yet, as far as I'm aware). For this reason Mosasaur materiel in Turonian strata is rare

 

So - the awkward transitional gap where these reptile groups were replacing each other (but none had diverse populations yet/anymore) occured right as the Eagle Ford was deposited. The only thing the Eagle Ford has going for it in the reptile realm are the three foot coniasaurs, who had their time to shine during the cenomanian and pulled through into at least the middle Turonian. 

 

I should mention that there are also the long-necked plesiosaurs  - they survived just fine until the end cretaceous, so I'm not sure why they're so rare in the Eagle Ford. Check out this exquisite plesiosaur specimen found in the Eagle Ford of north Texas sometime before the 40's.

 

Libonectes morgani:

 

 

So, the Eagle Ford captures a very unique time period, and that's why I think it's still worth looking for reptiles in it, despite their comparative rarity, because the few reptiles there tell an interesting evolutionary story. However, if you're feeling rather indiscriminate and you're looking for any mosasaur you can get - I suggest younger formations where the quantity of mosasaurs is greater and more diverse. Unfortunately, the coniacian and santonian rocks of Texas are dominated by the relatively unfossiliferous Austin Chalk. Cool mosasaurs can be seen, like @JohnJ's Tylosaur, or the "Duck Creek Mosasaur" that made the news not too long ago, but they're rare since they don't preserve well in the formation. Therefore, your best bet is the campanian Ozan formation - since the Maastrichtian stuff in Texas seems hard to find things in as well.

 

Central Texas was a lot deeper than North Texas, so in terms of quantity, NTX has more to offer - though the deep water creatures are interesting on their own. For example - large adult Hadrodus seem to have spent their time in deeper water - so it's no wonder that central texas is where the H. hewletti specimen came from. It's why the Ozan of central texas is a lot more barren than in the north Texas, but in central texas it produces weird stuff now and then. 

 

Regardless, best of luck! See if you can find the rare NSR basal Globidens before it gets dammed.