Cenozoic asteroids and ophiuroids from Florida: An understudied fossil component

Howe (1942) pointed out that despite the abundant fossil remains of sea stars (asteroids) and briftle stars (ophiuroids), reports of these Tertiary Gulf Coast echinoderms were nearly non-existent. Today, the same holds true for reports of sea star and brittle star occurrences from Cenozoic strata of Florida. Rapid post-mortem disarticulation and quick dispersal of the ossicles that comprise these echinoderms' skeleton make their fossil record difficult to interpret. Occasionally however, through exceptional events of rapid burial, some specimens are preserved intact. Thus far only two Florida faunas have been reported. Ivany et al. (1990) published an undescribed, and for the most part, unidentifiable middle Eocene Avon Park Formation fauna associated with sea grass, and Oyen and Portell (2001) reported on the lower Pliocene Tamiami Formation of southern Florida. The latter fauna contained Heliaster microbrachius Xantus, 1860 (first reported by Jones and Portell, 1988), Luidia sp., and an unknown ophiuroid. Recent surveys of the FLMNH Invertebrate Paleontology Collection and several private collections reveal a substantial number of other unreported asteroid occurrences but only a few new ophiuroid occurrences. These occurrences consist primarily of disarticulated ossicles but some are of partially articulated specimens. Fossil asteroids are now known from at least eleven stratigraphic units in Florida ranging in age from middle Eocene to early Pleistocene. Ophiuroids are now known from at least three stratigraphic units of middle Eocene, early Miocene, and early Pliocene age. Our present study is a first attempt to compile a complete database for all of these neglected and understudied Florida echinoderm fossils. Each stratigraphic unit in which these taxa occur as well as a discussion of their abundance and taxonomic assignment will be presented.