Late Cretaceous sturgeons (Acipenseridae) from North America, with two new species from the Tanis site in the Hell Creek Formation of North Dakota

Abstract Although the Cretaceous is widely regarded as a time of great evolutionary transition for freshwater fish fauna North America, fossil record this period notoriously poor, consisting mostly fragments and isolated skeletal elements. Exceptions include acipenseriforms, discussed in paper, some exceedingly rare teleosts. Here we describe two new species well-preserved sturgeons (Acipenseridae) from Tanis site Late Hell Creek Formation Dakota. The type referred materials were preserved loosely consolidated matrix. † Acipenser praeparatorum n. sp. represented by multiple body fossils (including head relatively complete postcranial remains) specimen an intact, three dimensionally skull pectoral girdle. This taxon can be diagnosed based on features opercular elements (exceptionally tall narrow branchiostegal). second species, anisinferos sp., partially skull, elongate preorbital region (i.e., snout) absence thorn-like spines roofing bones. Most known sturgeon are only undiagnosable fragmentary remains scutes pectoral-fin spines) or poorly partial skeletons (e.g., Protoscaphirhynchus ), with Priscosturion Anchiacipenser (both monotypic) being exceptions. Therefore, newly discovered give glimpse into evolution Acipenseridae at critical phylogenetic history suggest significant morphological taxonomic diversity early group. UUID: http://zoobank.org/375b586a-2dd8-4a31-b6c4-42151e6e8fc8