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Re-description of 'Steneosaurus' obtusidens Andrews, 1909, an unusual macrophagous teleosaurid crocodylomorph from the Middle Jurassic of England

Re-description of 'Steneosaurus' obtusidens Andrews, 1909, an unusual macrophagous teleosaurid crocodylomorph from the Middle Jurassic of England
Re-description of 'Steneosaurus' obtusidens Andrews, 1909, an unusual macrophagous teleosaurid crocodylomorph from the Middle Jurassic of England

Teleosaurids were a clade of crocodylomorphs that attained near-global distribution during the Jurassic Period. Within Teleosauridae, one particular sub-clade of durophagous/macrophagous taxa achieved large body sizes and were apex predators in shallow marine environments during the Late Jurassic and Early Cretaceous in Europe and around the coast of the Tethys Seaway. Unfortunately, the origins of this clade are still poorly understood. 'Steneosaurus' obtusidens is a little-studied macrophagous species from the Oxford Clay Formation (Callovian, Middle Jurassic) of the UK and near Migné-les-Lourdines (Middle Callovian) in France. Despite being considered a sister taxon of the Late Jurassic taxon Machimosaurus, the taxonomy of 'S.' obtusidens remains unclear. Although three different synonymies have been proposed (variously a subjective synonym of other taxa), these taxonomic hypotheses have not been based on detailed anatomical comparisons and thus have not been tested. Here, we re-describe the holotype of 'S.' obtusidens, demonstrate that it is indeed a valid taxon, restrict the referred specimens to a fragmentary skeleton, nearly complete skull, and partial rostrum, and establish a new monotypic genus, Lemmysuchus. Our re-description reveals five autapomorphies for Lemmysuchus obtusidens and nine apomorphic characters that support the tribe Machimosaurini (Lemmysuchus + Machimosaurus).

Crocodylomorpha, Lemmysuchus, Machimosaurus, Steneosaurus, Teleosauridae, Thalattosuchia
0024-4082
385-418
Johnson, Michela M.
788dd560-8228-453b-8dfd-8622ec03636c
Young, Mark T.
d9880973-1dd1-4b1c-81a8-7494170dbac2
Steel, Lorna
661f272f-fa0c-45bb-89a3-3036cc85c703
Foffa, Davide
a0a5e738-a340-4b36-b4c7-39e44994f22e
Smith, Adam S.
def177b6-3970-450c-a0ee-6f475908033d
Hua, Stéphane
efa4fb2e-f338-491d-a3af-10f7f52e7b78
Havlik, Philipe
4b9ec2a1-91c4-40f2-9ec9-f23d9800b203
Howlett, Eliza A.
e7763a3f-c367-4398-9b57-d6a34f46bc31
Dyke, Gareth
600ca61e-b40b-4c86-b8ae-13be4e331e94
Johnson, Michela M.
788dd560-8228-453b-8dfd-8622ec03636c
Young, Mark T.
d9880973-1dd1-4b1c-81a8-7494170dbac2
Steel, Lorna
661f272f-fa0c-45bb-89a3-3036cc85c703
Foffa, Davide
a0a5e738-a340-4b36-b4c7-39e44994f22e
Smith, Adam S.
def177b6-3970-450c-a0ee-6f475908033d
Hua, Stéphane
efa4fb2e-f338-491d-a3af-10f7f52e7b78
Havlik, Philipe
4b9ec2a1-91c4-40f2-9ec9-f23d9800b203
Howlett, Eliza A.
e7763a3f-c367-4398-9b57-d6a34f46bc31
Dyke, Gareth
600ca61e-b40b-4c86-b8ae-13be4e331e94

Johnson, Michela M., Young, Mark T., Steel, Lorna, Foffa, Davide, Smith, Adam S., Hua, Stéphane, Havlik, Philipe, Howlett, Eliza A. and Dyke, Gareth (2018) Re-description of 'Steneosaurus' obtusidens Andrews, 1909, an unusual macrophagous teleosaurid crocodylomorph from the Middle Jurassic of England. Zoological Journal of the Linnean Society, 182 (2), 385-418. (doi:10.1093/zoolinnean/zlx035).

Record type: Article

Abstract

Teleosaurids were a clade of crocodylomorphs that attained near-global distribution during the Jurassic Period. Within Teleosauridae, one particular sub-clade of durophagous/macrophagous taxa achieved large body sizes and were apex predators in shallow marine environments during the Late Jurassic and Early Cretaceous in Europe and around the coast of the Tethys Seaway. Unfortunately, the origins of this clade are still poorly understood. 'Steneosaurus' obtusidens is a little-studied macrophagous species from the Oxford Clay Formation (Callovian, Middle Jurassic) of the UK and near Migné-les-Lourdines (Middle Callovian) in France. Despite being considered a sister taxon of the Late Jurassic taxon Machimosaurus, the taxonomy of 'S.' obtusidens remains unclear. Although three different synonymies have been proposed (variously a subjective synonym of other taxa), these taxonomic hypotheses have not been based on detailed anatomical comparisons and thus have not been tested. Here, we re-describe the holotype of 'S.' obtusidens, demonstrate that it is indeed a valid taxon, restrict the referred specimens to a fragmentary skeleton, nearly complete skull, and partial rostrum, and establish a new monotypic genus, Lemmysuchus. Our re-description reveals five autapomorphies for Lemmysuchus obtusidens and nine apomorphic characters that support the tribe Machimosaurini (Lemmysuchus + Machimosaurus).

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More information

Accepted/In Press date: 14 May 2017
e-pub ahead of print date: 7 August 2017
Published date: 1 February 2018
Keywords: Crocodylomorpha, Lemmysuchus, Machimosaurus, Steneosaurus, Teleosauridae, Thalattosuchia

Identifiers

Local EPrints ID: 420857
URI: https://eprints.soton.ac.uk/id/eprint/420857
ISSN: 0024-4082
PURE UUID: ac72e6ce-190c-444d-8cf8-fe228c0a0e14

Catalogue record

Date deposited: 17 May 2018 16:30
Last modified: 13 Mar 2019 18:28

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