Id for Central Texas echinoid?

[rickeclectic]

Howdy,

 

Found this in central Texas last week and not sure how to id it. From my research it looks a bit like a tetragramma or some such, but it looks to have a pretty clear pentagon shape, like a codiopsis but not the markins?  Any help appreciated.

 

[JamieLynn]

Both Phymosoma texana and Tetragramma texanum look very similar, but the way to tell them apart is if the tuburcles are perforate. Unfortunately, on a worn specimen like this, it's sometimes hard to discern if there is indeed a perforation or it's just worn.  I have many Phymos that I THOUGHT were Tetras but on closer inspection, there were enough unperforate tuburcles for me to lean towards Phymo.  I can't quite see this one close enough to tell if they are indeed perforate, but if they are, I would say Tetragramma texanum.  The Pentagonal shape is not a very good indicator, as both of the above mentioned echinoids are sometimes more round, sometimes very pentagonal. But you are correct, definitely not a Codiopsis. 

[rickeclectic]

Thanks Jamie! (fellow clubber). I did not realize they could sometimes be pentagon shaped.