the sand dollar Astrodapsis coalingaensis

Mystery Fossil #51

This sand dollar, Astrodapsis coalingaensis, is a representative of the echinoidea, a diverse and successful group of echinoderms. Echinoids first appear in the fossil record in the Ordovician, but their numbers and diversity donít really begin to increase until late in the Triassic. Sand dollars make their appearance in the Paleocene, though this particular specimen is Miocene in age; itís from the Santa Margarita Formation, Fresno County, CA. To learn more about echinoids in general, look here.


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