Abstract
Late Cretaceous members of Peritresius belong to a diverse clade of marine adapted turtles currently thought to be some of the earliest representatives of the lineage leading to modern hard-shelled sea turtles (Pan-Cheloniidae). Prior studies have suggested that Peritresius was monospecific, with a distribution restricted to Maastrichtian deposits in North America. However, new Peritresius specimens identified from Alabama and Mississippi, USA, show that the genus contains two taxa, Peritresius ornatus, and a new species Peritresius martini sp. nov. These two taxa are characterized by the presence of a generally cordiform carapace with moderately serrated peripherals, well-developed ventral flanges beginning at the third peripheral, squarish umbilical and lateral plastral fontanelles, and a narrow bridge formed by the contact between the hyoplastron and hypoplastron. Peritresius martini sp. nov. can be distinguished by its lack of dermal ornamentation and the presence of a ‘rib-free’ 10th peripheral. These new specimens represent the first occurrences of Peritresius from the Late Cretaceous Mississippi Embayment and extend the temporal range of this genus back to the early Campanian. When tested within a global phylogenetic context, Peritresius is placed on the stem of Cheloniidae (Pan-Cheloniidae) along with Ctenochelys and Allopleuron hofmanni. The heavily vascularized and uniquely sculptured dermal elements of P. ornatus are interpreted here as potentially relating to thermoregulation and therefore may have been one of the key factors contributing to the survival of Peritresius into the Maastrichtian, a period of cooling when other lineages of Campanian marine turtles (e.g., Protostegids, Toxochelys, and Ctenochelys) went extinct.
Highlights
Cretaceous marine turtle fossils are abundant within Santonian to Campanian marine deposits in the southeastern United States, and have been reported from Alabama, Arkansas, Georgia, Mississippi, and Tennessee [1,2,3,4]
As part of this study, two additional marine turtles have been identified within this formation, Peritresius ornatus (Baird, 1964 [4]) and a new taxon described Peritresius martini sp. nov. This new taxon is currently known only from the type locality, here we report the occurrence of P. ornatus from nine additional late Campanian to lower Maastrichtian localities within Alabama and Mississippi
A new species of Cretaceous marine turtle from the southeastern United States (Peritresius martini sp. nov.) is described based on material collected from the upper Campanian of Alabama, USA
Summary
Cretaceous marine turtle fossils are abundant within Santonian to Campanian marine deposits in the southeastern United States, and have been reported from Alabama, Arkansas, Georgia, Mississippi, and Tennessee [1,2,3,4]. The most frequently recovered Cretaceous marine turtle taxa from the Cretaceous of the southeastern U.S are Toxochelys Cope, 1873 [7], Ctenochelys Zangerl, 1953 [2] and Prionochelys Zangerl 1953 [2], with each genus represented by dozens, or in the case of Toxochelys, hundreds of specimens. Despite their abundance in the southeastern U.S, these genera appear absent from the Maastrichtian components of the Hornerstown and Navesink formations along the Atlantic Coast, and are seemingly absent entirely from Maastrichtian deposits in North America (Zangerl 1953 [2]). The relative paucity of Maastrichtian pan-chelonioids (i.e., P. ornatus, Catapleura Cope, 1868 [8], Euclastes Cope, 1867 [9]) and their relationship to well-known Santonian and Campanian taxa (i.e. Toxochelys latiremis Cope, 1873 [7] and Ctenochelys stenoporus Zangerl, 1953 [2]), are both issues of particular interest to any attempt to resolve the phylogeny and biogeography of Late Cretaceous Pan-Chelonioidea
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