A redescription of the Late Jurassic (Tithonian) turtle Uluops uluops and a new phylogenetic hypothesis of Paracryptodira

Yann Rollot,Serjoscha W Evers,Walter G Joyce

doi:10.1186/s13358-021-00234-y

Abstract

We study the Late Jurassic (Tithonian) turtle Uluops uluops using micro-computed tomography scans to investigate the cranial anatomy of paracryptodires, and provide new insights into the evolution of the internal carotid artery and facial nerve systems, as well as the phylogenetic relationships of this group. We demonstrate the presence of a canalis caroticus lateralis in Uluops uluops, the only pleurosternid for which a palatine artery canal can be confidently identified. Our phylogenetic analysis retrieves Uluops uluops as the earliest branching pleurosternid, Helochelydridae within Pleurosternidae, and Compsemydidae including Kallokibotion bajazidi within Baenidae, which suggests at least two independent losses of the palatine artery within paracryptodires. We expect future studies will provide additional insights into the evolution of the circulation system of paracryptodires, as well as clarifying relationships along the turtle stem.

Highlights

Uluops uluops Carpenter and Bakker, 1990 is a poorly understood turtle known from a single skull from the Late Jurassic of North America
Basicranium and circulation system The clade Paracryptodira was originally defined by Gaffney (1975) based on the location of the foramen posterius canalis carotici interni, the posterior entrance of the internal carotid artery into the skull, midway along the parabasisphenoid–pterygoid suture
We here describe the skull of the Late Jurassic (Tithonian) paracryptodire Uluops uluops based on μCT scans

Summary

Introduction

Uluops uluops Carpenter and Bakker, 1990 is a poorly understood turtle known from a single skull from the Late Jurassic of North America. Carpenter and Bakker (1990) initially described Uluops uluops as a baenid paracryptodire closest to Plesiobaena, Baena, and Eubaena and diagnosed it as a new taxon based on a novel combination of primitive features found in non-baenid paracryptodires, e.g., a more rectangular, plate-like basitubera region, and derived features, such as the presence of a strongly curved maxillary cutting edge and a ventral muscle scar located along the basioccipital–basisphenoid suture. Paracryptodires were initially thought to have an extremely short canalis caroticus internus that splits into the canals for the cerebral and palatine arteries (respectively, the canalis caroticus basisphenoidalis and canalis caroticus lateralis sensu Rollot et al, 2021) upon entry to the skull midway along the parabasisphenoid–pterygoid suture (Gaffney, 1975). Using micro-computed tomography (μCT), Rollot et al (2018) showed that the canal initially identified as the canalis caroticus lateralis in the

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Conclusion