A NEW PALAEOSPINACID SHARK (CHONDRICHTHYES, NEOSELACHII) FROM THE UPPER JURASSIC OF SOUTHERN GERMANY

摘要

The Palaeospinacidae are a highly diverse clade (> 30 species) within the Synechodontiformes, which are considered to be a monophyletic group of basal galeomorph sharks. Four genera. Macrourogaleus, Paraorthacodus, Palidiplospinax, and Synechodus are included in the Palaeospinacidae, ranging in age from the Early Permian to the Paleogene. So far, the only described palaeospinacids from the Upper Jurassic lithographic limestones of southern Germany are several specimens of Macrourogaleus from the Solnhofen area. and a single one of Paraorthacodus jurensis from Nusplingen. The presence of Synechodus in the Upper Jurassic of southern Germany was only indicated by a single figured but undescribed tooth. An incomplete and disarticulated skeleton of a small neoselachian shark and additional isolated teeth from the Kimmeridgian of Baden-Wurttemberg represent the first record of Synechodus in the Upper Jurassic lithographic limestones of Germany. The skeleton includes parts of the vertebral column, the left palatoquadrate, the right Meckel's cartilage, several fragments of calcified cartilage of the cranial skeleton, 32 teeth, and several placoid scales. The dental features unique to this species include a slender and sub-triangular main cusp, a crown ornamentation consisting of long ridges, a basal reticulation pattern that does not extend basally to the crown-root boundary, and a basal labial depression of the main cusp in anterior teeth.