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Morphological and phylogenetic aspects of the dentition of Megacephalosaurus eulerti, a pliosaurid from the Turonian of Kansas, USA, with remarks on the cranial anatomy of the taxon

Madzia, Daniel ; Sachs, Sven and Lindgren, Johan LU (2019) In Geological Magazine 156(7). p.1201-1216
Abstract

Megacephalosaurus eulerti is a large macropredatory plesiosaur representing one of the last members of the diverse pliosaurid clade Brachaucheninae. The taxon was established upon a nearly complete skull including the mandible and fragments of the postcranial skeleton originating from the lower middle Turonian (Upper Cretaceous) of Kansas, USA. Owing to its age, reasonable completeness and its state of preservation, M. eulerti bears important anatomical details regarding the last brachauchenines. Here we assess the dentition of the taxon, compare the teeth to those of other thalassophonean pliosaurids and comment on the utility of these results for inferences of the phylogenetic relationships of the last brachauchenines. Additionally,... (More)

Megacephalosaurus eulerti is a large macropredatory plesiosaur representing one of the last members of the diverse pliosaurid clade Brachaucheninae. The taxon was established upon a nearly complete skull including the mandible and fragments of the postcranial skeleton originating from the lower middle Turonian (Upper Cretaceous) of Kansas, USA. Owing to its age, reasonable completeness and its state of preservation, M. eulerti bears important anatomical details regarding the last brachauchenines. Here we assess the dentition of the taxon, compare the teeth to those of other thalassophonean pliosaurids and comment on the utility of these results for inferences of the phylogenetic relationships of the last brachauchenines. Additionally, we provide remarks on the cranial anatomy of M. eulerti, revise character scores of this taxon used in current phylogenetic studies and address the phylogenetic relationships within Brachaucheninae. Parsimony analyses, aimed to test different character sampling and tree-search strategy, inferred only a single unambiguous synapomorphy uniting a clade formed by mid- to Late Cretaceous brachauchenines: presence of subcircular rather than subtrihedral/trihedral cross-sectional shape of the teeth. Still, the last brachauchenines (Brachauchenius and Megacephalosaurus) can be roughly characterized by a switch from anisodont to subisodont dentition and reduction of their tooth count. Nevertheless, the overall knowledge of the origin, phylogenetic relationships and distinguishability of brachauchenine pliosaurids remains poor and represents a subject for further extensive studies and modifications in taxon and character sampling.

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author
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organization
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type
Contribution to journal
publication status
published
subject
keywords
Brachaucheninae, Cretaceous, Megacephalosaurus, phylogeny, Pliosauridae, Teeth, Turonian
in
Geological Magazine
volume
156
issue
7
pages
1201 - 1216
publisher
Cambridge University Press
external identifiers
  • scopus:85052649451
ISSN
0016-7568
DOI
10.1017/S0016756818000523
language
English
LU publication?
yes
id
9703ee51-95ca-44fb-b70d-5e7a062c9ab5
date added to LUP
2018-10-05 09:53:18
date last changed
2025-04-04 14:44:20
@article{9703ee51-95ca-44fb-b70d-5e7a062c9ab5,
  abstract     = {{<p>Megacephalosaurus eulerti is a large macropredatory plesiosaur representing one of the last members of the diverse pliosaurid clade Brachaucheninae. The taxon was established upon a nearly complete skull including the mandible and fragments of the postcranial skeleton originating from the lower middle Turonian (Upper Cretaceous) of Kansas, USA. Owing to its age, reasonable completeness and its state of preservation, M. eulerti bears important anatomical details regarding the last brachauchenines. Here we assess the dentition of the taxon, compare the teeth to those of other thalassophonean pliosaurids and comment on the utility of these results for inferences of the phylogenetic relationships of the last brachauchenines. Additionally, we provide remarks on the cranial anatomy of M. eulerti, revise character scores of this taxon used in current phylogenetic studies and address the phylogenetic relationships within Brachaucheninae. Parsimony analyses, aimed to test different character sampling and tree-search strategy, inferred only a single unambiguous synapomorphy uniting a clade formed by mid- to Late Cretaceous brachauchenines: presence of subcircular rather than subtrihedral/trihedral cross-sectional shape of the teeth. Still, the last brachauchenines (Brachauchenius and Megacephalosaurus) can be roughly characterized by a switch from anisodont to subisodont dentition and reduction of their tooth count. Nevertheless, the overall knowledge of the origin, phylogenetic relationships and distinguishability of brachauchenine pliosaurids remains poor and represents a subject for further extensive studies and modifications in taxon and character sampling.</p>}},
  author       = {{Madzia, Daniel and Sachs, Sven and Lindgren, Johan}},
  issn         = {{0016-7568}},
  keywords     = {{Brachaucheninae; Cretaceous; Megacephalosaurus; phylogeny; Pliosauridae; Teeth; Turonian}},
  language     = {{eng}},
  number       = {{7}},
  pages        = {{1201--1216}},
  publisher    = {{Cambridge University Press}},
  series       = {{Geological Magazine}},
  title        = {{Morphological and phylogenetic aspects of the dentition of Megacephalosaurus eulerti, a pliosaurid from the Turonian of Kansas, USA, with remarks on the cranial anatomy of the taxon}},
  url          = {{http://dx.doi.org/10.1017/S0016756818000523}},
  doi          = {{10.1017/S0016756818000523}},
  volume       = {{156}},
  year         = {{2019}},
}