A New Euteleostean Fish from the Lower Cretaceous of Tucano Basin, North-Eastern Brazil

Abstract

A new euteleostean fish, Britoichthys marizalensis gen. and sp.nov. is described from the Lower Cretaceous of Tucano basin, North-eastern Brazil, based on various almost complete and articulate specimens preserved in a yellowish siltstone yielded from Marizal Formation. This taxon is recognised by an unique combination of characters: an ethmoidean commissure on rostrodermethmoid bone; well- developed premaxilla with fang-like teeth; presence of a sinuous maxilla with oral border garnished of aligned conical teeth; massive mandible with straight oral border; reduced orbit bordered by large infraorbital bones; seven branchiostegals rays; three uroneurals, the first not extending forward beyond the preural centrum 1; ural centra not fused; membranous outgrowth (stegural) of first uroneural; leaf- like plates of bone associated with rudimentary neural arches of the first preural and ural vertebrae; non bifurcate epineurals, pattern 2 supraneurals, cycloid scales, and 36 vertebrae. The reduced number of vertebrae and branchiostegal rays, premaxilla shape, caudal endoskeleton pattern, simple epineurals, supraneural type, and the presence of a retroarticular in the corner of the lower jaw suggest affinities with euteleostean fishes. In so far as known, Britoichthys is unique in its combination of features and cannot be included in any known family.