New early Campanian characiform fishes (Otophysi: Characiformes) from West Texas support a South American origin for known Late Cretaceous characiforms from North America

Abstract

Fossil characiform dentaries from the “Lowerverse locality” in the lower Campanian portion of the Aguja Formation of West Texas represent a rare Late Cretaceous occurrence of characiform fishes in North America. Two morphotypes are represented. Both of them exhibit ventrally encased, mandibular laterosensory canals and distinctive anterior lobes unique to the characiform symphyseal ‘hinge’. The first, dentigerous morphotype closely resembles fossil characiform dentaries from the Campanian Dinosaur Park Formation of Alberta, Canada. All of these are collectively referred herein to Primuluchara laramidensis gen et sp. nov. The second morph is edentulous as in extant curimatids and pertains to a different new species herein referred to Eotexachara malateres gen et sp. nov. Numerous Weberian vertebral centra recovered at Lowerverse suggest that characiforms were abundant in the coastal, subaquatic paleoenvironment here. The early Campanian age of the Aguja Formation characiforms supports previous temporal estimates regarding the arrival of characiforms in North America from either Europe or South America as inferred from previous molecular and/or paleontological studies. The presence of morphologically related, but geotemporally divergent species in Campanian strata of West Texas and Alberta indicates a south-to-north radiation among Laramidian characiforms and points to a southerly origin for ancestral forms. Santonian – Maastrichtian occurrences of characiforms in Europe suggests that they reached the limit of their dispersal there and were unable to invade southern Laramidia by the early Campanian. Whether the likely dispersal of characiforms from South America occurred via an archaeo- or telolimnitic progression remains unclear. However, it is plausible that euryhalinity played some role in their coastal dispersal.