North Sulphur River, TX - Coprolite of the Month

[Searcher]

I headed to the North Sulphur River last Friday and found a magnificent coprolite in situ in the otherwise soft gray shale. I cleaned it up a bit, but as with most fossils from the NSR, the surrounding shale largely flaked away leaving the nearly 15 pound coprolite a fairly solid mass. Coincidentally, I had found a large isolated mosasaur tooth only a few feet from the spot two weeks prior. I positioned the tooth in one of the empty sockets and it would appear to be a fit. There had been a fairly good rain in the interim that looks to have dissolved a good portion of the matrix previously surrounding the chunk.

 

My original instinct was that it had been deposited by a mosasaur, but the teeth marks in the jaw section look more shark-related to me.

 

Too bad there's not a Coprolite of the Month. I am guessing that I might have a pretty good shot at it. Not quite the distinction of Vertebrate of the Month, but it's a start.

 

 

 

 

 

 

 

[doushantuo]

Awesome find!!!

[Macrophyseter]

Nice coprolite and jaw fragments! and I want that mosasaur tooth

[bone2stone]

Where is coprolite?

I see the jaw fragment and a mass of whatever.

What makes you think it is a coprolite?

 

Jess B.

[JarrodB]

Definitely not a coprolite but it's a very nice Tylosaur jaw section. Here's one I found there recently.  Many pieces from there have shark scavenging marks. Nice find!

[John S.]

Very nice. That is a massive jaw section. How long is that?

[Searcher]

Thanks for the input, Jarrod, that certainly would have been my first impression. But in my 100 or so trips there you get a sense of pieces that are different.

 

I have many jaw pieces like your example, but this is not quite like my other finds. One difference between this fossil and yours is that mine has the same jawbone wrapped around another 5 sides. The jawbone shot in my last photo can be seen along the top of the chunk in the second photo. You can see the scale in the fourth photo using the quarter placed in the bottom right. I took the photo of it in situ to show that the matrix surrounding the chunk was the usual soft shale, including the matrix beneath it. That is one of the beautiful things about the NSR is that the vertebrate fossils weather out so perfectly, like the one piece you are holding. So the fact that this matrix was much, much harder than the matrix on all sides was interesting. I have never found a mosasaur bone in that river that I could not pry out with a screwdriver and then clean with some water and a brush.

 

You'll also note that the much of the mass has been coated with a thin layer of what appears to be matrix. The pieces are all literally glued together. If you will examine a large number of the verts that you have been picking up you'll note a certain number with either a gray or yellowish layer coating the fossil which is inseparable, unlike the surrounding matrix. It's not really surprising that a large number of bones found in the NSR passed through an animal's intestines first. Much of the wear on many of the mosasaur bones found is always assumed to be from tumbling in the river, when instead it was actually due to a good dose of stomach acid before being passed. My guess would be that of the bones found it would be much more likely that they were excreted as opposed to belonging to an animal that died and was then untouched.

 

I will certainly grant that I have never seen anything like it before, and will probably never again, but I am sticking with my original appraisal.

 

 

[JarrodB]

I kindly disagree but congrats on the find either way. 

[Xiphactinus]

Many large sharks now and in the past will bite off a huge chunk of flesh and bone and regurgitate the indigestible parts. They get stomach acid etched, but don't pass through the intestines. I have a Xiphactinus skull that has Cretoxyrhina tooth marks, and embedded fragment and lots of etching.  No way that passed all the way through a shark. That may be what you have.

 

Here's a page from Oceans of Kansas talking about sharks taking bites of mosasaurs.  http://oceansofkansas.com/bite.html

[John S.]

1 hour ago, Xiphactinus said:

Many large sharks now and in the past will bite off a huge chunk of flesh and bone and regurgitate the indigestible parts. They get stomach acid etched, but don't pass through the intestines. I have a Xiphactinus skull that has Cretoxyrhina tooth marks, and embedded fragment and lots of etching.  No way that passed all the way through a shark. That may be what you have.

 

Here's a page from Oceans of Kansas talking about sharks taking bites of mosasaurs.  http://oceansofkansas.com/bite.html

This would make sense good call!

[Miocene_Mason]

Looks kinda like a jaw too me as well, either way the tooth is real nice! I always admire the fossils that come out of the NSR!

[Searcher]

You'll notice that the matrix coating the jaw is yellowish, while the surrounding matrix was the typical NSR flaky gray shale. It had not been redeposited that I could tell. The site was too small to be attributed to ocean current concentrating the bones, I think, so it becomes a question as to what would have caused the anomalous pocket.

 

The idea of regurgitation could make sense. The viscosity of the decaying flesh would serve the same purpose as the fecal material to hold the ball of bones together. The mouth could also have compacted the jaw so that it would be folded on all sides like that.

 

Thanks.