Lepidosaurian remains from the Lower Cretaceous Kirkwood Formation of South Africa

ABSTRACT

New lepidosaurian material is reported from the Lower Cretaceous (middle to upper Valanginian) Kirk-wood Formation, South Africa. The material includes fragmentary jaws of a new sphenodontian and a well-preserved squamate braincase. The braincase is attributable to Squamata based on its possession of a complete abducens canal, a vidian canal that is fully enclosed posterodorsally, a divided metotic fissure, laterally directed basisphenoid processes, and distally expanded paroccipital processes. The prominent anterodorsally directed alar process is a similarity shared with Scleroglossa and some Iguanidae, and the presence of an open fenestra “rotunda” excludes the specimen from the Chameleontidae. The long posterior process of the dentary behind the coronoid process and enlargement of the palatine toothrow support reference of the jaws to the Rhynchocephalia. The open Meckelian groove, the addition of teeth at the back of the jaw, and the possession of at least some degree of acrodonty confirm their sphenodontian affinities. These specimens help to fill a large gap in the fossil record of lepidosaurs from Gondwana and document that squamates and sphenodontians were not confined to northern Gondwana during the Early Cretaceous.