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Giant extinct caiman breaks constraint on the axial skeleton of extant crocodylians


Scheyer, Torsten M; Hutchinson, John R; Strauss, Olivier; Delfino, Massimo; Carrillo-Briceño, Jorge D; Sánchez, Rodolfo; Sánchez-Villagra, Marcelo R (2019). Giant extinct caiman breaks constraint on the axial skeleton of extant crocodylians. eLife, 8:1-19.

Abstract

The number of precaudal vertebrae in all extant crocodylians is remarkably conservative, with nine cervicals, 15 dorsals and two sacrals, a pattern present also in their closest extinct relatives. The consistent vertebral count indicates a tight control of axial patterning by Hox genes during development. Here we report on a deviation from this pattern based on an associated skeleton of the giant caimanine Purussaurus, a member of crown Crocodylia, and several other specimens from the Neogene of the northern neotropics. P. mirandai is the first crown-crocodylian to have three sacrals, two true sacral vertebrae and one non-pathological and functional dorsosacral, to articulate with the ilium (pelvis). The giant body size of this caiman relates to locomotory and postural changes. The iliosacral configuration, a more vertically oriented pectoral girdle, and low torsion of the femoral head relative to the condyles are hypothesized specializations for more upright limb orientation or weight support.

Abstract

The number of precaudal vertebrae in all extant crocodylians is remarkably conservative, with nine cervicals, 15 dorsals and two sacrals, a pattern present also in their closest extinct relatives. The consistent vertebral count indicates a tight control of axial patterning by Hox genes during development. Here we report on a deviation from this pattern based on an associated skeleton of the giant caimanine Purussaurus, a member of crown Crocodylia, and several other specimens from the Neogene of the northern neotropics. P. mirandai is the first crown-crocodylian to have three sacrals, two true sacral vertebrae and one non-pathological and functional dorsosacral, to articulate with the ilium (pelvis). The giant body size of this caiman relates to locomotory and postural changes. The iliosacral configuration, a more vertically oriented pectoral girdle, and low torsion of the femoral head relative to the condyles are hypothesized specializations for more upright limb orientation or weight support.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Paleontological Institute and Museum
Dewey Decimal Classification:560 Fossils & prehistoric life
Uncontrolled Keywords:General Biochemistry, Genetics and Molecular Biology, General Immunology and Microbiology, General Neuroscience, General Medicine
Language:English
Date:27 November 2019
Deposited On:13 Jan 2020 11:33
Last Modified:06 Mar 2020 15:15
Publisher:eLife Sciences Publications Ltd.
ISSN:2050-084X
OA Status:Gold
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.7554/elife.49972
Project Information:
  • : FunderSNSF
  • : Grant ID31003A_149506
  • : Project TitleSensory Palaeoecology in Secondary Aquatic Reptiles - The Radiation of Independent Triassic Marine Reptile Lineages following the Earthâ��s Largest Mass Extinction Event
  • : FunderSNSF
  • : Grant ID205321_162775
  • : Project TitleProtorosaur phylogeny and palaeobiogeography: marine versus arboreal, dispersal versus vicariance

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