A new non-marine osteichthyan fauna from the Upper Cretaceous (Campanian) of West Texas: Additional evidence for latitudinal segregation among bony fish in the Western Interior

Abstract

A new osteichthyan fauna from the lower Campanian Aguja Formation of West Texas represents a critical southern datum regarding the interpretation of faunal differences observed among Upper Cretaceous, non-marine fish assemblages of the Western Interior. Bony fish are represented within the “Lowerverse” local fauna by as many as 21 primitive and advanced species. The Lowerverse locality is situated at the southern end of a geographic range of paracontemporaneous localities in Laramidia that have produced a number of similarly well-sampled osteichthyan assemblages. A comparison of the Lowerverse bony fish fauna with those of southern Utah and southern Alberta supports previous hypotheses regarding the latitudinal segregation of some species in the Western Interior. Given their ubiquity throughout Late Cretaceous North America in both time and space, the north-south geographical segregation of garfishes in the Western Interior is especially revealing in this regard and reveals that some species were markedly provincial during the Campanian. Taxonomic inconsistencies among these regional faunas are observed even at higher taxonomic ranks and infer that such differences are sending meaningful ecological signals.