A large non‐marine turtle from the Upper Cretaceous of Alabama and a review of North American “Macrobaenids”

Abstract

The abundant record of marine turtles from the Late Cretaceous of Appalachia contrasts with the relatively poor record of contemporaneous terrestrial and freshwater species. A new taxon from the Santonian‐Campanian of Alabama, Appalachemys ebersolei gen. et sp. nov., is described here and assigned to a grade of freshwater turtles known as “macrobaenids.” Appalachemys can be differentiated from other “macrobaenids” by the presence of a nearly round carapace, deep nuchal emargination, and nine pairs of costals. With a carapace more than 80 cm in length, Appalachemys is among the largest freshwater turtles to ever inhabit North America. The absence of pre‐Campanian “macrobaenids” from Laramidia indicates that the North American distribution of this grade may have been restricted to Appalachia prior to the recession of the Western Interior Seaway. Phylogenetic analysis places Appalachemys as the sister taxon to all post‐Santonian “macrobaenids.” Although the phylogeny lacks statistical support, it demonstrates morphological similarities between the K/Pg boundary species Osteopygis emarginatus and Maastrichtian‐Danian species referred to Judithemys. We, therefore, refer all but the Campanian type species of Judithemys to the genus Osteopygis. A review of all North American “macrobaenid” occurrences reveals that despite originating in Asia, the record of the grade (as defined here) is predominantly North American. Future studies can test whether late Paleocene records in Asia and Europe resulted from dispersal from North America.

New findings on the evolution of turtles: A symposium in honor of Marcelo S. de la Fuente

“…Appalachemys ebersolei gen. et sp. nov. is a large "macrobaenid" from the Upper Cretaceous of Alabama, USA (Gentry et al, 2023) and one of the few records of a nonmarine turtle in the Late Cretaceous of Appalachia. Chelydropsis aubasi sp.…”

Two new plioplatecarpine mosasaurs (Mosasauridae; Plioplatecarpinae) of the genus <i>Ectenosaurus</i> from the Upper Cretaceous of North America

“…Until recently, the Mooreville Chalk was subdivided into a thick lower unnamed member and the thin upper Arcola Limestone Member. Gentry et al (2022) recognized a basal member of the Mooreville Chalk, informally designated the Erie Bend member. In this paper "unnamed member" refers specifically to the portion of the Mooreville Chalk that overlies the contact with the Erie Bend member and underlies the Arcola Limestone Member.…”