PALEOCENE ECHINOIDS OF THE GULF COAST OF THE UNITED STATES

The Paleocene was a period of transition in echinoid faunas, with a distinctly Cretaceous character and only a few tantalizing glimpses of the genera that came to dominate the remaining Cenozoic. The spottiness of Gulf Coast Paleocene (Midway Group) outcrops, the wide range in lithologies (and associated paleoecologies), and the relatively poor collection record have made any study of these faunas especially sensitive to the Signor-Lipps effect. An on-going project of new collection, curation, and taxonomic re-evaluation of the echinoids of the Midway Group from Texas to Georgia will help correct these deficiencies. The Paleocene echinoids of the Gulf Coast are a more diverse group than previously documented, with cidaroids, stomopneustoids, phymosomatoids, cassiduloids, and spatangoids. The faunas appear to lack the holasteroids found in the slightly younger Vincentown Formation (New Jersey), and no evidence of clypeasteroids has been found. Much of the new material comes from recent collections from bryozoan-dominated carbonate units in the Clayton Formation in the Chattahoochee River valley of western Georgia. Collections to date have still not adequately tested the Tehuacana Limestone in Texas, although preliminary work has found evidence of echinoids as unidentifiable spines and scattered plates.