THE JURASSIC BELEMENITE SUBORDER BELEMNOTHEUTINA

Abstract

The Belemnotheutina is a monophyletic group of mostly late Jurassic belemnites that possess largely plesiomorphic characters of ten subequal arms with hooks, a simple, conical, rostrum, a narrow breviconic phragmocone and a spatulate pro-ostracum. Although some of the best-preserved belemnites with soft parts have been described from this group, until recently, its status has been in question. A new genus from the Upper Jurassic of Antarctica, Antarctiteuthis is described which, like Acanthoteuthis (= Belemnotheutis of authors), possesses unique rostral surface morphology of raised ridges with accompanying grooves unknown in other true belemnites. This is an important apomorphy for the group, which is considered to be a monophyletic suborder of the Belemnitida.