Pyritized Disk Mystery and Some Nice Shark Teeth

[Mikrogeophagus]

Hey everyone! I thought I'd share a few of my finds from the past couple months and get yall's opinions. Over winter break, I went back home to North Texas and did some searching around Ammonite Beach at Texoma and the NSR with my family. At Texoma I had a nice time hammering out a few ammonites, collecting teeth, and surprisingly finding lots of smaller, pyritized ammonites that I did not expect to be there. The NSR was a bit slower, but I at least got a nice Squalicorax as shown in the pics below. Since school has started, I've been down in Austin. I've been finding the usual stuff, but the pyritized disk I've attached is new to me. I'd love to hear what you guys think!

 

Austin Finds:

Pictured above is the pyritized disk and a pyritized clam found in a gravel bar next to what I believe to be an Ozan exposure. The area has a decent amount of the pyritized clams and other marine fossils that I assume are cretaceous in age given the local geology. My initial reaction was that it could be a vertebrae, but the bulging center and distorted shape throws me off. It has very apparent concentric rings on both its faces. In pics 1 and 3, you can see that underneath that outside layer there is a lot of pyrite. Parts of the edges are also pyritized while other sections have an iron concretion look to them. The face shown on pic 2 resembles and feels like petrified wood. I suppose this could be a pyrite sun, but I'm not seeing anything too similar to what I have on google images. Super interested in what you guys have to say!

 

Texoma Tooth (left) and NSR Tooth (right)

Left (Leptostyrax macrorhiza?): Pretty tooth found by my little brother at Texoma in the Duck Creek Formation. Did some quick googling and found that Leptostyrax macrorhiza was in that formation and saw some pictures that were similar to what I have.

Right (Squalicorax): Had a bit of a slow day at the NSR, but managed to at least find this at the end of my cold, muddy adventure there. It's preserved very nicely. Looks like Squalicorax to me. Would love to know the species.

 

 

If you guys would like any additional closeup pics feel free to let me know! I might share some of my other finds later on, but I don't want to inundate the forum with my rocks lol. Thanks for reading.

 

 

[abyssunder]

Maybe the pyritized disc it's an intervertebral disc.

[Mahnmut]

If found close to shark teeth, maybe shark vertebrae?

Any traces of holes around the circumference?

Intervertebral disks are normally not heavily mineralized, as their function is to provide flexibility between the rigid centra. They may become calcified in old individuals though. Rarely fossilized as far as I know.

Best Regards,

J

[Mikrogeophagus]

I have found Ptychodus, Cretoxyrhina, and a few other sharks teeth in the same area. I would've also thought this to be a shark vert because of that, but the protruding shape of the centrum confuses me. An intraverbal disc would be cool. I'm not sure how common it is for softer tissue like that to be found in this formation, but I guess if cartilaginous shark verts can be found, why not other cartilaginous parts?

 

Some more closeups:

The only "hole" I could find around the circumference is the shallow indention seen in the third pic. Relative to the rest of the disk, it's located on a flatter portion of the circumference. About a third of the circumference is ridged like what is shown in pic 3 and 4 on the right side. Also, I noticed in pic 1 that there are very small, but noticeable notches/grooves radiating from the center and perpendicular to the concentric rings. They are faint on camera, but you can see them near where the pyrite and outer surface material meet. Their regularity seem noteworthy to me.

 

Thanks for the insights!

 

[pachy-pleuro-whatnot-odon]

Just for those looking for a continuation of the discussion concerning the vertebra - which I believe to indeed be a shark vertebra, albeit in very poor state of preservation, without intervertebral disk, and highly pyrite affected to the extent of deformation, in turn leading to the observed "oddities" in the piece's interpretation as a shark vertebra - this can be found here:

 

 

[siteseer]

I think it needs to be cleaned more to rule out a bony fish vertebra.  However, if you can see that has just two holes on one edge of the disk and then two more on the opposite edge of the disk, then it probably is a shark or a ray vertebral centrum and certainly if it shows no signs of vertebral process attachment.  In a shark or ray vertebra, the hemal and neural arches are cartilaginous and they dissolve shortly after death leaving those holes.  In a bony fish vertebra, the processes are also bony so they often preserve.  They can be chipped or worn off but you can usually see some evidence of them.

[pachy-pleuro-whatnot-odon]

11 minutes ago, siteseer said:

I think it needs to be cleaned more to rule out a bony fish vertebra.  However, if you can see that has just two holes on one edge of the disk and then two more on the opposite edge of the disk, then it probably is a shark or a ray vertebral centrum and certainly if it shows no signs of vertebral process attachment.  In a shark or ray vertebra, the hemal and neural arches are cartilaginous and they dissolve shortly after death leaving those holes.  In a bony fish vertebra, the processes are also bony so they often preserve.  They can be chipped or worn off but you can usually see some evidence of them.

 

Sounds like if the vertebra does indeed turn out to be elasmobranch with the cartiligenous arches dissolved away, this would be another argument to preclude the intervertebral disc... But it also looks like the vertebra being this thin isn't as diagnostic for elasmobranch/shark vertebrae as I thought it was