Nusaviichthys nerivelai gen. et sp. nov., an Albian crossognathiform fish from the Tlayúa lagerstätte, Mexico

Abstract

The fish Nusaviichthys nerivelai gen. et sp. nov. is described here based on well-preserved fossils from the Albian deposits of the Tlayúa quarry, near Tepexi de Rodríguez, Puebla, central Mexico. The occurrence of this new fish from Tlayúa expands the taxonomical and morphological diversity of the crossognathiformes of the Caribbean region of America during the Early Cretaceous. The inclusion of the osteological features of this species into comparative and phylogenetic analyses reveal its belonging to the order Crossognathiformes, suborder Pachyrhizodontoidei, and family Notelopidae; some of the most significant of these features include the presence of a large extrascapula bone; circumorbital bones forming a completely closed ring; medioparietal condition of the skull; posterior infraorbitals hypertrophied, covering the entire cheek, and extended up to the anterior part of the opercular bones; the relative short uroneural 1 anteriorly restricted to the preural 1; and the cycloid scales with a crenulated posterior edge. This new species differs from its relatives in the presence of numerous and small conic teeth in both jaws and vomer; the large triangular gular plate, and the numerous radiating grooves ridges present in the supraorbital, dermosphenotic, skull roof bones, opercular bones, and jaws; and the almost horizontal position of the neural and hemal spines of the last caudal centra. Despite the weak support, the naturalness of this extinct teleost order is recovered in the phylogenetic analysis performed here, which includes this new Mexican fossil fish as well as other crossognathiform genera not included in previous studies.