Oldest Teleostean Otolith Assemblage from North America (Pawpaw Formation, Lower Cretaceous, upper Albian, northeast Texas, USA)

Abstract

The oldest-reported otoliths in North America are Late Cretaceous (Cenomanian) in age. However, an otolith assemblage from the Pawpaw Formation, northeastern Texas, USA, extends otolith occurrence to the Early Cretaceous (late Albian). The 729 otoliths from the Pawpaw Formation represent 10 taxa with 8 identified to species level including 2 new genera and 7 new species: Genartina princeps sp. nov., Elopothrissus pawpawensis sp. nov., Argentina? texana sp. nov., Ichthyotringa? cuneata sp. nov., Paraulopus wichitae sp. nov., Texoma cyclogaster gen. et sp. nov., Allocyclostoma alienus gen. et sp. nov. The diversity of the Pawpaw Formation assemblage is characterized by fairly low richness (10 species) and low evenness with Genartina princeps accounting for approximately 67% of the total specimens. The Pawpaw Formation otoliths are dominated by the “Genartina Group” (unknown taxonomic affinity), Albuliformes, and Aulopiformes. Although rare, two monospecific fossil otolith-based genera are postulated to be related to the Polymixiiformes, which moves the most recent common ancestor back approximately 8 Ma. Teleost evolution from an otolith perspective appears to confirm the rapid increase in diversity known in the late Albian and Cenomanian, which is postulated to be instrumental in crown teleost evolution. Comparison of the Pawpaw Formation otoliths with Albian skeletal remains is hindered with only one Albian fish known with in situ otoliths. Thus, otoliths are largely unknown from many of the large and extinct Albian teleostean groups known from skeletons. Selachian remains (8 taxa) were also obtained from the Pawpaw Formation and provided additional information regarding the paleoecology and paleogeography.