PaleoBios

Toxochelys latiremis Cope, 1873 is currently thought to be one of the oldest members of the clade originating from the last common ancestor of all extant species of marine-adapted turtles (Chelonioidea). Fossil material of this species has been reported from numerous lower Campanian marine formations across North America; however, reported occurrences have been conspicuously absent from the upper Santonian-to-lower Campanian Mooreville Chalk of Alabama and Mississippi, USA, the type stratum for the only other valid species within the genus, Toxochelys moorevillensis Zangerl, 1953. The apparent absence of T. latiremis from the Mooreville Chalk, and from the southern expanse of the Mississippi Embayment, has made T. latiremis one of the few outliers in previously proposed paleobiogeographic models for marine turtles in the Late Cretaceous Western Interior Seaway. This absence also confounded attempts at reconciling the distribution and phylogeny of these taxa. Here we report the first material of T. latiremis identified from the Mooreville Chalk of Alabama, which represents the southern-most occurrence of this taxon. The discovery of this species in the Mooreville Chalk of Alabama helps to reconcile the previously hypothesized paleobiogeography of North American Late Cretaceous chelonioids with their fossil occurrence and provides the first evidence for overlapping ranges of the only two currently recognized species of Toxochelys.