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High diversity, low disparity and small body size in plesiosaurs (Reptilia, Sauropterygia) from the Triassic-Jurassic boundary.
PLoS One. 2012; 7(3):e31838.Plos

Abstract

Invasion of the open ocean by tetrapods represents a major evolutionary transition that occurred independently in cetaceans, mosasauroids, chelonioids (sea turtles), ichthyosaurs and plesiosaurs. Plesiosaurian reptiles invaded pelagic ocean environments immediately following the Late Triassic extinctions. This diversification is recorded by three intensively-sampled European fossil faunas, spanning 20 million years (Ma). These provide an unparalleled opportunity to document changes in key macroevolutionary parameters associated with secondary adaptation to pelagic life in tetrapods. A comprehensive assessment focuses on the oldest fauna, from the Blue Lias Formation of Street, and nearby localities, in Somerset, UK (Earliest Jurassic: 200 Ma), identifying three new species representing two small-bodied rhomaleosaurids (Stratesaurus taylori gen et sp. nov.; Avalonnectes arturi gen. et sp. nov) and the most basal plesiosauroid, Eoplesiosaurus antiquior gen. et sp. nov. The initial radiation of plesiosaurs was characterised by high, but short-lived, diversity of an archaic clade, Rhomaleosauridae. Representatives of this initial radiation were replaced by derived, neoplesiosaurian plesiosaurs at small-medium body sizes during a more gradual accumulation of morphological disparity. This gradualistic modality suggests that adaptive radiations within tetrapod subclades are not always characterised by the initially high levels of disparity observed in the Paleozoic origins of major metazoan body plans, or in the origin of tetrapods. High rhomaleosaurid diversity immediately following the Triassic-Jurassic boundary supports the gradual model of Late Triassic extinctions, mostly predating the boundary itself. Increase in both maximum and minimum body length early in plesiosaurian history suggests a driven evolutionary trend. However, Maximum-likelihood models suggest only passive expansion into higher body size categories.

Authors+Show Affiliations

Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom. rbb27@cam.ac.ukNo affiliation info availableNo affiliation info available

Pub Type(s)

Historical Article
Journal Article
Research Support, Non-U.S. Gov't
Review

Language

eng

PubMed ID

22438869

Citation

Benson, Roger B J., et al. "High Diversity, Low Disparity and Small Body Size in Plesiosaurs (Reptilia, Sauropterygia) From the Triassic-Jurassic Boundary." PloS One, vol. 7, no. 3, 2012, pp. e31838.
Benson RB, Evans M, Druckenmiller PS. High diversity, low disparity and small body size in plesiosaurs (Reptilia, Sauropterygia) from the Triassic-Jurassic boundary. PLoS One. 2012;7(3):e31838.
Benson, R. B., Evans, M., & Druckenmiller, P. S. (2012). High diversity, low disparity and small body size in plesiosaurs (Reptilia, Sauropterygia) from the Triassic-Jurassic boundary. PloS One, 7(3), e31838. https://doi.org/10.1371/journal.pone.0031838
Benson RB, Evans M, Druckenmiller PS. High Diversity, Low Disparity and Small Body Size in Plesiosaurs (Reptilia, Sauropterygia) From the Triassic-Jurassic Boundary. PLoS One. 2012;7(3):e31838. PubMed PMID: 22438869.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - High diversity, low disparity and small body size in plesiosaurs (Reptilia, Sauropterygia) from the Triassic-Jurassic boundary. AU - Benson,Roger B J, AU - Evans,Mark, AU - Druckenmiller,Patrick S, Y1 - 2012/03/16/ PY - 2011/10/11/received PY - 2012/01/12/accepted PY - 2012/3/23/entrez PY - 2012/3/23/pubmed PY - 2012/8/14/medline SP - e31838 EP - e31838 JF - PloS one JO - PLoS One VL - 7 IS - 3 N2 - Invasion of the open ocean by tetrapods represents a major evolutionary transition that occurred independently in cetaceans, mosasauroids, chelonioids (sea turtles), ichthyosaurs and plesiosaurs. Plesiosaurian reptiles invaded pelagic ocean environments immediately following the Late Triassic extinctions. This diversification is recorded by three intensively-sampled European fossil faunas, spanning 20 million years (Ma). These provide an unparalleled opportunity to document changes in key macroevolutionary parameters associated with secondary adaptation to pelagic life in tetrapods. A comprehensive assessment focuses on the oldest fauna, from the Blue Lias Formation of Street, and nearby localities, in Somerset, UK (Earliest Jurassic: 200 Ma), identifying three new species representing two small-bodied rhomaleosaurids (Stratesaurus taylori gen et sp. nov.; Avalonnectes arturi gen. et sp. nov) and the most basal plesiosauroid, Eoplesiosaurus antiquior gen. et sp. nov. The initial radiation of plesiosaurs was characterised by high, but short-lived, diversity of an archaic clade, Rhomaleosauridae. Representatives of this initial radiation were replaced by derived, neoplesiosaurian plesiosaurs at small-medium body sizes during a more gradual accumulation of morphological disparity. This gradualistic modality suggests that adaptive radiations within tetrapod subclades are not always characterised by the initially high levels of disparity observed in the Paleozoic origins of major metazoan body plans, or in the origin of tetrapods. High rhomaleosaurid diversity immediately following the Triassic-Jurassic boundary supports the gradual model of Late Triassic extinctions, mostly predating the boundary itself. Increase in both maximum and minimum body length early in plesiosaurian history suggests a driven evolutionary trend. However, Maximum-likelihood models suggest only passive expansion into higher body size categories. SN - 1932-6203 UR - https://www.unboundmedicine.com/medline/citation/22438869/High_diversity_low_disparity_and_small_body_size_in_plesiosaurs__Reptilia_Sauropterygia__from_the_Triassic_Jurassic_boundary_ L2 - https://dx.plos.org/10.1371/journal.pone.0031838 DB - PRIME DP - Unbound Medicine ER -