The first Pan-Carettochelys turtle in the Neogene of the American continent and its paleobiogeographical relevance

Abstract

Turtles of the clade Pan-Carettochelys have a broad fossil record, from the Early Cretaceous to the late Miocene in the Old World, and some records in the Paleogene of North America; however, its distribution in the Neogene of the American continent was unknown. Here we describe a new species of Pan-Carettochelys, Allaeochelys liliae sp. nov., based on an incomplete single specimen from the Los Pocitos mine, Mazantic Shale (Lower Miocene, Aquitanian), near Simojovel, State of Chiapas, southern Mexico. A midline keel, plastral kinesis, and a single suprapygal, suggest that the new turtle belongs to Pan-Carettochelys, and the loss of plastral scutes includes it in Carettochelyidae. The new fossil is referred to Allaeochelys based on the loss of carapacial and plastral scutes and a large plastron. It differs from other Allaeochelys by the following unique combination of characters: carapacial ornamentation slighty marked with small and shallow tubercules and pits, xiphiplastron and hypoplastron ornamented with pits and vermicular grooves uniformly distributed in all the bone surface, single suprapygal with general triangular shape but with five contact edges, and costal eight in contact with the peripherals nine and ten. Allaeochelys liliae sp. nov., represent the first record of Pan-Carettochelys in the Neogene of the American continent, and it is the first Allaeochelys described for the Aquitanian (Early Miocene) worldwide.