New chondrichthyans characterised by cladodont-like tooth morphologies from the Early Cretaceous of Austria, with remarks on the microstructural diversity of enameloid

Abstract

ABSTRACT Cladodontomorphii represents an archaic clade of chondrichthyan fishes characterised by distinct tooth morphologies referred to as the cladodont type. This group of cartilaginous fishes first occurred during the early Palaeozoic Era as revealed from the fossil record and were long thought to have gone extinct at the Permian-Triassic mass extinction event. However, a recently reported chondrichthyan tooth assemblage from the Early Cretaceous of France suggests that cladodontomorphs might have survived the catastrophic events at the Permian-Triassic boundary, probably by occupying deep-sea refuge environments. Here, we describe two new chondrichthyan genera based on isolated teeth recovered from Valanginian (Early Cretaceous) deep-water deposits of Austria, including a total of three new species tentatively assigned to the cladodontomorph families Falcatidae (Cretacladoides ogiveformis gen. et sp. nov. and C. noricum sp. nov.) and Ctenacanthidae (Natarapax trivortex gen. et sp. nov.). In addition, an enameloid microstructure analysis had led to the identification of a distinct multilayered enameloid including a parallel-, tangled-, and radial-bundled enameloid, whose phylogenetic distribution within Chondrichthyes is here discussed in detail, leading to the conclusion that the herein described cladodont-like taxa, together with those reported from the French Early Cretaceous might be closely related to ancient Palaeozoic taxa. The ZooBank electronic publication LSID is: urn:lsid:zoobank.org:pub:C06FD718-F54F-4C57-A45E-8C0D7CC8EB83