Oldest evidence of bramble sharks (Elasmobranchii, Echinorhinidae) in the Lower Cretaceous of southeast France and the evolutionary history of orbitostylic sharks

Two shark teeth from the Early Cretaceous limestone (Late Hauterivian, Pseudothurmannia ohmi Zone, Pseudothurmannia catulloi Subzone) of Nyons (Drôme) in southeast France are reported here as Echinorhinus sp. They represent the oldest record of the family Echinorhinidae (Elasmobranchii), an enigmatic and primitive branch of living deep-sea sharks. This discovery has allowed completion of the fossil record of this family and revival of the debate about its origin as a result of recent advances in selachian phylogeny. The fossil record is now consistent with the assumption that the Echinorhinidae is the stem group of Squaliformes s.l. and the modern morphology of the first representatives does not support alternative hypotheses. Although the phylogenetic position of living bramble sharks remains unclear, the peculiar enameloid histology of fossil and extant echinorhinids is globally similar to those of some basal neoselachian sharks (e.g., Synechodontiformes). Considered as a plesiomorphic feature of modern Neoselachian sharks, this supports a basal position among the orbitostylic sharks. Although the precise origin of echinorhinids remains obscure, the environmental settings of the fossil discoveries suggest that the first representatives frequented the deep sea.