Some Rare Sharks from the Border

[Mikrogeophagus]

Earlier this week, I lucked out with a couple of calls to some landowners who I previously thought were unreceptive to my inquiries. One of them happened to live along the Mexican border, close by to some spots I had been wanting to check out. The property in question contained a large exposure of an elusive formation- one that I imagine not many on this forum have ever hunted (if anyone at all)! The Upson Clay is an Early Campanian member of the Taylor Group and is about equivalent to the Ozan and Sprinkle Formations farther north. As expected for this age, the owner, John, reported a strange presence of huge seashells, some which were bigger than a fist! Any Texas hunter can tell you that these are undoubtedly oysters of the species Exogyra ponderosa. Following the thin band of Campanian strata from the border all the way to Arkansas, these giants are a guiding light for collectors who seek the monsters of the Late Cretaceous. John reported that he had hunted fossil shells there for many decades, and it was indeed totally full of them as promised. As for shark teeth, he hadn't seen one yet and the same could be said in regards to the literature I read.

 

Upon arriving to the ranch, I was greeted and taken on a tour by the very kind foreman, Paul. He gave me a little bit of the history on the ranch and showed off the livestock. After circling the property, he left me to it. I took a little drive over to the main outcrop I had studied so closely through Google Earth in recent months. The mound was composed of a mixture of Upson Clay and the ever unproductive Uvalde Gravel. The air was a little chilly as I put on the backpack and left the car, unlocked. Pretty quickly I ran into numerous Exogyra ponderosa, but a closer inspection of the ground yielded some smaller finds.

 

Gastropod

 

Hamulus squamosus worm tube

 

Echinoid plate

 

After hunting for about an hour and a half, I ventured to the far end of the outcrop, where I finally escaped the mound and was met with freshly eroding and undisturbed Upson Clay. Most of it was comprised of a grayish sandy mudstone. At some intervals, reddish seams of oyster hash spanned the outcrop. I spent most of my time crawling around the platy chunks of that seam, hoping to find something shiny amongst the countless purple shells. Luck came my way when I spotted a serrated age sticking out of one.

 

Squalicorax yangaensis

 

Although only a fragment of a tooth was present, there is just enough of a crown to detect a strong constriction towards the base. The curve is simply too much for the typical Squalicorax lindstromi (S. kaupi) and seems to align better with Squalicorax yangaensis. This species of crow shark is pretty atypical for the state of Texas. It does occur with some regularity way far west in the Aguja Formation (MIddle Campanian), but for the Ozan and Sprinkle Formations, I haven't noticed a presence. So it's a first for me and an unusual find for sure.

 

While meticulously picking through a field of washed out purple shells, I crawled nose-first into another tooth. This time it was a more common Squalicorax lindstromi, just like the many I had bagged across the state over the past few years. This specimen shared a similar violet complexion to it's molluscan neighbors. 

 

Squalicorax lindstromi

 

On that high note, I wrapped up the brief excursion into the Upson. John thought the shark teeth were pretty neat and said I'd need to visit again when he was back in town and after a rain. That sounded like a pretty good deal to me. So little is written about this formation. I do wonder what other sorts of sharks could be present. Hopefully I'll find out not so far in the future.

 

Upson Clay

 

 

 

As I mentioned before, there were some other prospective sites I intended to visit in the area. They didn't prove fruitful in terms of quantity of finds. However, the rarity made up for it in full. Schizorhiza stromeri is without a doubt one of the scarcest micros to be found in the state. I first read up on the sawskate when browsing Welton and Farish's shark book a couple years ago. I believe only a single specimen was documented from Texas back in 1948. I knew beforehand that I was retracing the steps of the great Dunkle, so the possibility of rediscovering this alien creature was certainly on my radar. Pretty quickly at the first Escondido site, I saw a shiny black tooth poking out of chunk of stone.

 

Schizorhiza stromeri

 

And quickly after, another smaller tooth popped up as well!

 

Both S. stromeri

 

Just like that, the number of Schizorhiza in Texas tripled (unless there are others I am not aware of). The preservation of both teeth was a bit shoddy, but that is not such a big deal to me. For those unfamiliar, these teeth usually have a series of finger-like projections jutting out from the basal margin of the root. They are extremely delicately and can only be found in well-preserved specimens extracted directly from matrix.

 

All in all, these made for a respectable trip down to the border. There's still more work to be done over there and much more fun trips lined up elsewhere around the state, so keep an eye out for future posts! I think I'm starting to figure out the dynamic of coordinating with landowners, but I just have to wait out hunting season!

[Yoda]

@Mikrogeophagus

 

Nice finds, especially the teeth 

[Jared C]

Another excellent repot, from one of the most neglected high potential areas of Texas, love to see it

I am greatly looking forward to your shark field guide. Is it something you'll just be posting to the forum, or potentially publishing in academic literature, or even publishing as a purchasable book one day?

[Mikrogeophagus]

@Jared C Just something for the forum like my last guide! I've thought about doing a book some day, but I'd need to build up a lot more experience. I am still regularly surprised by Texas fossils with most trips out, so clearly there is a lot left to learn and plenty of state to explore.

[JohnJ]

You have made some interesting contacts in an area that could prove just as interesting.

 

Looking forward to your next report!