GONDOLELLID CONODONT ELEMENTS FROM THE LOWER AND MIDDLE PENNSYLVANIAN: SUBTLE APPARATUS RELATIONSHIPS

Gondolella is an unusual Pennsylvanian conodont genus, bearing a Pa element that lost its posterior process, emphasizing instead an anterior process that is commonly, though not always, developed into a platform. Highly restricted by paleoecologic controls, Gondolella is usually recovered from only a few lithofacies in lower paleolattitude settings. These characters help make the idioprioniodinid Gondolella distinctive from its more common ozarkodinid cohorts. A detailed reconstruction of its apparatus by von Bitter and Merrill (1998), based on bedding plane specimens of mid-Desmonesian Gondolella pohli, suggests a septimembrate construction of paired Pa, Pb, M, Sb₁, and Sb₂ elements, plus two pair of Sc elements and a single Sa element. For this study, ramiform elements representing other Gondolella species scattered through the lower and middle Pennsylvanian are compared to the von Bitter and Merrill model. These include Atokan platformless (“naked”) gondolellids and mesogondolellids, as well as a succession of species through the Desmoinesian. Subtle differences in proportion and symmetry are seen to exist among the elements of platformless gondolellids, smooth gondolellids, and crenulated gondolellids. Interestingly, Mesogondolella from elsewhere in the Pennsylvanian and from the Permian are not as similar as previously interpreted. We analyze those differences with regard to temporal succession and interpreted genealogy, then explore the implications for gondolellid taxonomy.