A small short-necked hupehsuchian from the lower Triassic of Hubei Province, China.

Xiao-Hong Chen,Long Cheng,Olivier Rieppel,Ryosuke Motani,Da-Yong Jiang,Andrew A Farke

doi:10.1371/journal.pone.0115244

Xiao-Hong Chen, Long Cheng + Show 4 more

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https://doi.org/10.1371/journal.pone.0115244

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Abstract

Hupehsuchia is a group of enigmatic Triassic marine reptiles that is known exclusively from two counties in Hubei Province, China. One of the common features of the group was a modestly long neck with nine to ten cervical vertebrae. We report a new species of Hupehsuchia, Eohupehsuchus brevicollis gen. et sp. nov., which for the first time shows a short neck in this group, with six cervicals. The configuration of the skull roof in Eohupehsuchus is also unique among Hupehsuchia, with narrow frontals and posteriorly shifted parietals, warranting recognition of a new species. The taxon superficially resembles Nanchangosaurus in retaining hupehsuchian plesiomorphies, such as low neural spines and small body size. However, its limbs are well-developed, unlike in Nanchangosaurus, although the latter genus is marginally larger in body length. Thus, the individual is unlikely to be immature. Also, Eohupehsuchus shares a suite of synapomorphies with Hupehsuchus, including the second and third layers of dermal ossicles above the dorsal neural spines. A phylogenetic analysis suggests that the new species is not the most basal hupehsuchian despite its short neck, and instead forms the sister taxon of Hupehsuchidae. Until recently, Hupehsuchia contained only two monotypic genera. Now there are at least four genera among Hupehsuchia, and the undescribed diversity is even higher. The left forelimb of the only specimen is incomplete, ending with broken phalanges distally. The breakage could only have occurred pre-burial. The individual may have been attacked by a predator and escaped, given that scavenging is unlikely.

Highlights

The Mesozoic saw the emergence of multiple marine reptile groups including Hupehsuchia, which is only known from the Spathian (Lower Triassic) of Hubei Province, China [1]
Hupehsuchians have been known to science for more than half a century since the discovery of Nanchangosaurus suni Wang, 1959 [2], the name Hupehsuchia was not coined until Hupehsuchus nanchangensis was described by Young in 1972 [3]
It is firstly important to consider the possibility that the type and only specimen of Eohupehsuchus brevicollis may represent a growth stage of another taxon

Summary

Introduction

The Mesozoic saw the emergence of multiple marine reptile groups including Hupehsuchia, which is only known from the Spathian (Lower Triassic) of Hubei Province, China [1]. Hupehsuchians have been known to science for more than half a century since the discovery of Nanchangosaurus suni Wang, 1959 [2], the name Hupehsuchia was not coined until Hupehsuchus nanchangensis was described by Young in 1972 [3] Until recently, their anatomy and diversity have been poorly understood despite the notable pioneering work by previous authors [2,3,4,5]. Two monotypic genera and a third unnamed genus represented by an impression fossil (IVPP V4070, Institute of Vertebrate Paleontology and Paleoanthropology, Academia Sinica) [4] were known, and none of the specimens were well-preserved This left their affinities within Diapsida ambiguous, a close relationship with ichthyosaurs was suspected [4, 6]. The suggested phylogenetic affinities with ichthyosaurs [4] are strongly supported based on cladistic analyses [7]

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