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A new long‐necked archosauromorph from the Guanling Formation (Anisian, Middle Triassic) of southwestern China and its implications for neck evolution in tanystropheids


Wang, Wei; Spiekman, Stephan N F; Zhao, Lijun; Rieppel, Olivier; Scheyer, Torsten M; Fraser, Nicholas C; Li, Chun (2023). A new long‐necked archosauromorph from the Guanling Formation (Anisian, Middle Triassic) of southwestern China and its implications for neck evolution in tanystropheids. The anatomical record:Epub ahead of print.

Abstract

A long neck is an evolutionary innovation convergently appearing in multiple tetrapod lineages, including groups of plesiosaurs, non-archosauriform archosauromorphs, turtles, sauropodomorphs, birds, and mammals. Among all tetrapods both extant and extinct, two Triassic archosauromorphs, Tanystropheus and Dinocephalosaurus, have necks that are particularly elongated relative to the lengths of their trunks. However, the evolutionary history of such hyperelongated necks in these two archosauromorph clades remains unknown, partially because known close relatives such as Macrocnemus and Pectodens possess only moderately elongated necks. Here, we describe a newly discovered early diverging archosauromorph, Gracilicollum latens gen. et sp. nov., based on a specimen comprising a partial neck and an incompletely preserved skull. The long neck is composed of at least 18 cervical vertebrae. The dentition suggests that this new taxon most likely represents an aquatic piscivore, similar to Dinocephalosaurus and Tanystropheus hydroides. Despite possessing a high number of cervical vertebrae, Gracilicollum gen. nov. is recovered as a tanystropheid in an evolutionary grade between Macrocnemus and Tanystropheus rather than as a close relative of Dinocephalosaurus, a result that is primarily attributable to the presence of palatal teeth and the anatomy of the cervical vertebrae in Gracilicollum gen. nov. Considering the information provided by the new specimen, we provide a detailed discussion of the cervical evolution in dinocephalosaurids and tanystropheids, which is shown to be highly complex and mosaic in nature.

Abstract

A long neck is an evolutionary innovation convergently appearing in multiple tetrapod lineages, including groups of plesiosaurs, non-archosauriform archosauromorphs, turtles, sauropodomorphs, birds, and mammals. Among all tetrapods both extant and extinct, two Triassic archosauromorphs, Tanystropheus and Dinocephalosaurus, have necks that are particularly elongated relative to the lengths of their trunks. However, the evolutionary history of such hyperelongated necks in these two archosauromorph clades remains unknown, partially because known close relatives such as Macrocnemus and Pectodens possess only moderately elongated necks. Here, we describe a newly discovered early diverging archosauromorph, Gracilicollum latens gen. et sp. nov., based on a specimen comprising a partial neck and an incompletely preserved skull. The long neck is composed of at least 18 cervical vertebrae. The dentition suggests that this new taxon most likely represents an aquatic piscivore, similar to Dinocephalosaurus and Tanystropheus hydroides. Despite possessing a high number of cervical vertebrae, Gracilicollum gen. nov. is recovered as a tanystropheid in an evolutionary grade between Macrocnemus and Tanystropheus rather than as a close relative of Dinocephalosaurus, a result that is primarily attributable to the presence of palatal teeth and the anatomy of the cervical vertebrae in Gracilicollum gen. nov. Considering the information provided by the new specimen, we provide a detailed discussion of the cervical evolution in dinocephalosaurids and tanystropheids, which is shown to be highly complex and mosaic in nature.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Paleontology
Dewey Decimal Classification:560 Fossils & prehistoric life
Scopus Subject Areas:Health Sciences > Anatomy
Life Sciences > Biotechnology
Health Sciences > Histology
Life Sciences > Ecology, Evolution, Behavior and Systematics
Uncontrolled Keywords:Ecology, Evolution, Behavior and Systematics, Histology, Biotechnology, Anatomy, Archosauromorpha, Dinocephalosauridae, fossil, marine reptile, neck evolution, South China, Tanystropheidae, Triassic, vertebral column
Language:English
Date:7 April 2023
Deposited On:08 May 2023 08:44
Last Modified:29 Jun 2024 01:35
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:1932-8486
OA Status:Closed
Publisher DOI:https://doi.org/10.1002/ar.25216
PubMed ID:37029530
Project Information:
  • : FunderYouth Innovation Promotion Association of the Chinese Academy of Sciences
  • : Grant ID
  • : Project Title