APPARATUS COMPOSITION AND STRUCTURE OF THE PENNSYLVANIAN CONODONT GENUS GONDOLELLA BASED ON ASSEMBLAGES FROM THE DESMOINESIAN OF NORTHEASTERN ILLINOIS, USA

Gondolella pohli new species assemblages, from the Desmoinesian of Ill inois, confirm that the initial apparatus reconstruction of the conodo nt genus Gondolella was incomplete and support later reconstructions b ased on discrete elements. Gondolella pohli is the first species of a biostratigraphically important conodont genus to be based primarily on assemblages and to be placed within a known phylogeny. The 43 assembl ages confirm the presence of seven distinct element types in the Gondo lella apparatus and permit the reconstruction of each of these to a gr eater degree than previously possible. Because the assemblages are pro bably all fecal, the apparatus of the closely related Neogondolella is used to interpret the apparatus plan-the position and identity of the 15 elements-single pairs of Pa, Pb, M, Sb-1, and Sb-2 elements, two p airs of Sc elements, and an unpaired bilaterally symmetrical Sa elemen t in the Gondolella apparatus. Using the similarity of the latter to t he apparatuses of the better known ozarkodinids, we infer a three-dime nsional fanlike apparatus architecture for the prioniodinid Gondolella . Gondolella is apparently restricted to the Pennsylvanian and probabl y evolved in the Early Pennsylvanian from the Idioprioniodus-Embsaygna thus lineage by loss of the Pa element posterior process and by remode lling of the other apparatus elements. Some species in the Idioprionio dus-Gondolella lineage are atypical among prioniodinids in having deve loped a Pa element platform; the lineage is also noteworthy because bo th ancestor and descendant inhabited low-energy, low pH environments d uring the Pennsylvanian.