A new species of Sphenacanthid (Chondrichthyes, Elasmobranchii) from the Rio do Rasto Formation (Paraná Basin), southern Brazil

Abstract

The chondrichthyan skeletal structures with the greatest potential for fossilization are teeth, scales, fin and cephalic spines. In the Rio do Rasto Formation, the Chondrichthyes are represented by finspines and teeth attributed to sphenacanthids, hybodontids and xenacanthids. Herein is presented new finspines collected from an outcrop of the Serrinha Member of the Rio do Rasto Formation, in the Municipality of Jacarezinho, Parana State. The studied material consists of two finspines that are gradually tapered distally, with convex anterior and lateral faces. The posterior proximal face is strongly concave forming a furrow; absence of pronounced median ridge in the posterior distal face; the lateral faces have non-pectinated ribs separated by intercostal grooves, some of them bifurcated and beaded with rows of rounded closely spaced tubercles are the features that allow the finspines to be ascribed to a new species of Sphenacanthidae.