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| Honghesaurus longicaudalis Xu, Ren, Zhao, Liao & Feng. 2022 |
Abstract
Pachypleurosaurs (Pachypleurosauroidea) are a group of small to medium-sized, lizard-like marine reptiles in the Early to Middle Triassic, including Pachypleurosauridae, Keichousauridae and closely related taxa. The group is generally considered as a sauropterygian radiation, but its phylogenetic interrelationships remain highly debated. Here, we present a new pachypleurosaurid, Honghesaurus longicaudalis gen. et sp. nov., from the early Middle Triassic (Anisian, ~ 244 Ma) marine deposits in Luxi, Yunnan, China. The discovery documents the first really long-tailed pachypleurosaur with totally 121 (69 caudal) vertebrae, providing new evidence for the vertebral multiplication and ecological adaption of this group. The long trunk associated with an incredibly long tail could provide Honghesaurus the advantage of maneuverability and energy efficiency for lateral undulatory swimming. Honghesaurus, although possessing a series of autapomorphies, fills the morphological gap between Qianxisaurus from the Ladinian Xingyi Biota and Wumengosaurus from the Anisian Panxian Biota. Phylogenetic studies unite these three pachypleurosaurids as a monophyletic clade above European pachypleurosaurid clades and provide new insights into the interrelationships of this group. Our scenario of pachypleurosaurian phylogeny combined with the stratigraphic data imply that the Tethys Ocean was a west–east corridor for dispersal of pachypleurosaurids from Europe into South China.
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Skull and mandible of Honghesaurus longicaudalis gen. et sp. nov., IVPP V30380. Photo before (a) and after (b) dusted with ammonium chloride. (c) Line- drawing. (d) Reconstruction in dorsal view. an, angular; ar, articular; at, atlas; ax, axis; c, cervical vertebra; den, dentary; en, external naris; eo, exoccipital; f, frontal; j, jugal; m, maxilla; n, nasal; op, opisthotic; p, parietal; pat, proatlas; pm, premaxilla; po, postorbital; pof, postfrontal; prf, prefrontal; pt, pterygoid; q, quadrate; sa, surangular; so, supraoccipital; sq, squamosal; stf, supratemporal fossa. Honghesaurus longicaudalis gen. et sp. nov., Holotype (IVPP V30380). Photo (a) and line-drawing (b) of whole specimen. c, cervical vertebra; ca, caudal vertebra; d, dorsal vertebra; s, sacral vertebra. |
Systematic paleontology
Sauropterygia Owen, 1860
Eosauropterygia Rieppel, 199
Pachypleurosauroidea Huene, 1956
Pachypleurosauridae Nopcsa, 1928
Honghesaurus longicaudalis gen. et sp. nov.
Holotype: A complete skeleton in the collection of the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences (IVPP V30380).
Diagnosis: A pachypleurosaurid distinguishable from other members of this family by the following autapomorphies: snout longer than postorbital portion of skull, 47.8% of skull length; external naris longitudinally retracted, 47.7% of orbital length; supratemporal fossa oval, 46.2% of orbital length; about ten teeth in anteriorly pointed premaxilla; two fossae in retroarticular process; 20 cervical, 29 dorsal, three sacral, and 69 caudal vertebrae; single ossified carpal; and phalangeal formula 2-3-2-4-1 for manus and 2-3-4-5-2 for pes.
Etymology: The genus name refers to Honghe Prefecture, where the holotype was located; the species epithet is derived from longi plus caudalis (Latin for long tail), referring to its incredibly long tail.
Locality and horizon: Luxi, Honghe, Yunnan, China; Second (Upper) Member of Guanling Formation, Pelsonian (~ 244 Ma), Anisian, Middle Triassic.
Guang-Hui Xu, Yi Ren, Li-Jun Zhao, Jun-Ling Liao and Dong-Hao Feng. 2022. A Long-tailed Marine Reptile from China provides New Insights into the Middle Triassic pachypleurosaur Radiation. Scientific Reports. 12, 7396. DOI: 10.1038/s41598-022-11309-2
