New cladid crinoid (phylum echinodermata) from the Middle Devonian Delaware Limestone, Franklin County, Ohio (1).

ABSTRACT. A new species of Goniocrinus, G. saettii, is described from the Delaware Limestone of Franklin County, OH. This is the first crinoid described from the Delaware Limestone and the first cladid crinoid described from Devonian limestones of Ohio. This new occurrence suggests that additional new echinoderm specimens may be found in Devonian limestones of Ohio with a directed search for strata conducive to complete echinoderm preservation, that is, rapidly deposited, fine-grained facies.

OHIO J SCI 103 (2):19-24, 2003

INTRODUCTION

The Lower Devonian Columbus and Delaware limestones record the last middle Paleozoic carbonate platform deposition prior to transgression of the siliciclastic wedge from the Acadian Orogeny. These are relatively thick, shallow-water carbonates throughout the northern two-thirds of the central portion of the state and are relatively thick in the northern half of the state. They contain a diverse and abundant fauna dominated by brachiopods, corals, stromatoporoids, bryozoans, trilobites, and echinoderms. Despite considerable study of this fauna relatively few echinoderm species are known. Only two blastoid species and six crinoid species have been described from the Columbus Limestone of central Ohio (Table 1), and no identified echinoderms have been described previously from the Delaware Limestone. Thus, discovery of a new crinoid from the Delaware Limestone is especially noteworthy. Furthermore, this new crinoid belongs to the subclass Cladida, whereas previously described crinoids include only members of the subclass Camerata.

The majority of the older collections of the Columbus Limestone fauna was from insoluble residues of silicified specimens from terra rossas, rather than from material collected in situ with documented stratigraphic and sedimentologic context. Faunas preserved and collected in this manner, here and elsewhere (for example, the Salem Limestone of southern Indiana [Beede 1906]), are commonly dominated by camerate crinoids and blastoids. This tendency may be controlled by either the ecology of the facies that supported organisms, which as fossils were susceptible to this type of preservation, crinoid taphonomy, or both. Among crinoids, camerates have a much more robust calyx than cladids (Meyer and others 1989; Ausich and Sevastopulo 1994), which makes them more resistant to the taphonomic process of disarticulation and more likely to be preserved. Blastoids commonly are taphonomically similar to camerate crinoids (Meyer and others 1989; Ausich 2001).