Coenholectypus?

[madness]

Found this little guy while hunting today with my kids. I haven't found something like this since I was young. I swore I would find one soon...and there it was!

 

I would have just called this a "sea urchin" but I'm trying to learn more. I also don't want to simply just be told what it is, so I'm looking in books and doing internet searches. However, I'm either confronted with terrible printed images (old books) or precise scientific descriptions like "all ambulacra identical with elongate and weakly conjugate pore-pairs adapically; subpetaloid" ....  So I'm sure I'll be checking here quite often on new things we find!

 

Anyway, this was in Austin, Glen Rose formation (or similar - cretaceous limestone, no doubt). It's ~3 cm in diameter. (I need to get the lens fixed on my camera so I can do better macro shots than an iphone...)

 

I've also never "prepped" a fossil before. This had more limestone over the top surface that I cleared off. I need some serious work in this area, but I'm willing to learn the right way!

 

[madness]

Thought I'd throw in the photo from when I pulled it out of the creek.

 

[bone2stone]

Not sure that these are found in the Glen Rose material.

It is most likely Main Street formation.

> Google up:  "Main Street formation".

The holectypus may occur in the Del Rio material as well which is very much like the Grayson.

 

[Uncle Siphuncle]

I’ve taken a few C. planatus from the Glen Rose, and a ton ub ‘em from the Walnut fm, mostly from the Bee Cave Marl if not mistaken.  C. ovatus hails from the same timeframe, and differs by having a proportionally larger periproct, not visible in this specimen.  Good find.  And yes, the genus does range to the top of the Albian in TX, as noted by Jess.

[madness]

So much to learn! I was researching the different formations to try to get a better understanding, and not just blindly follow what was on the map. I had just come to the conclusion that this specimen was actually found in Bee Cave Marl. And Uncle Siphuncle confirms it...again! I found an old post of yours describing the Walnut formation and mentioning "The index fossil is the distinctive oyster Ceratostrean texanum, quite abundant in this zone." with specific reference to Central Texas Bee Cave Marl. I also just identified the many oysters we found at the same spot as that species. We were near a boundary between the Glen Rose and the Bee Cave Marl, but it looks like our finds fit better into the latter formation.