North Texas Echinoid Identification 3 Or More Scecies

[Gary T]

Hi All, Guess you can't edit the title. Go figure a biologist that can't spell species. LOL

I have at least 3 obvious morphologies of echinoids found from about a 30 yard stretch of the Trinity and maybe some not so obvious morphologies. I think the round one may be Phymosoma texanum but that is only a slightly educated guess. I think the majority of the others (The top ten) may be Macraster sp.?, but again I am unsure. I see a lot of conflicting stuff on the net. The lower 4 echies on the right have very differing morphologies than all the others. They are much harder to find, possibly 1 in 300. Their star pattern is very different, the 3 upper arms are much longer than the 2 lower arms (this can be seen in the close-up), additionally the upper most arm is combined with a very deep and wide grove but the other arms have almost no groves associated with them at all when compared to the other echinoids I have found.

There may be other differences in the top ten when compared with one another but none that jump out at you. I have noticed some have a bowing of the little dashes that make the star while on others the dashes are mostly straight.

I found a website that has photos of Macraster elegans and Heteraster adkinsi and it appears that this may be one of the things that distinguishes them.

If anyone out there would like to school a feller on how to ID these guys give me a shout back.

[MikeD]

This one must have rolled off of the New Posts list. Usually, someone would be all over this. I'll reply to bump it back up. I agree that there are at least 3 different types, but I have a long way to go before I can start identifying these babies. For now, the best I can do is "round and flat like a donut" and "heart urchins".

[Guest bmorefossil]

wow how did this post get past us......im no good with echinoids sorry

[LanceH]

Can I ask where along the Trinity you found them? What section of what county? That assortment of echinoids smells like Goodland formation but not sure. You have any ammonite pics you can post?

I think the irregular (heart shape) echinoids with one long wide groove would be Heteraster. The regular (round) echinoid maybe Tetragramma. The pic below is Tetragramma.

[Roz]

I don't remember ever seeing your post before.. great echs, so hard to find

one that are as intact as yours.