title: A temnospondyl trackway from the early Mesozoic of western Gondwana and its implications for basal tetrapod locomotion.
abstract: BACKGROUND
  Temnospondyls are one of the earliest radiations of limbed vertebrates. Skeletal remains of more than 190 genera have been identified from late Paleozoic and early Mesozoic rocks. Paleozoic temnospondyls comprise mainly small to medium sized forms of diverse habits ranging from fully aquatic to fully terrestrial. Accordingly, their ichnological record includes tracks described from many Laurasian localities. Mesozoic temnospondyls, in contrast, include mostly medium to large aquatic or semi-aquatic forms. Exceedingly few fossil tracks or trackways have been attributed to Mesozoic temnospondyls, and as a consequence very little is known of their locomotor capabilities on land.
  
  
  RESULTS
  We report a ca. 200 Ma trackway, Episcopopus ventrosus, from Lesotho, southern Africa that was made by a 3.5 m-long animal. This relatively long trackway records the trackmaker dragging its body along a wet substrate using only the tips of its digits, which in the manus left characteristic drag marks. Based on detailed mapping, casting, and laser scanning of the best-preserved part of the trackway, we identified synapomorphies (e.g., tetradactyl manus, pentadactyl pes) and symplesiomorphies (e.g., absence of claws) in the Episcopopus trackway that indicate a temnospondyl trackmaker.
  
  
  CONCLUSIONS
  Our analysis shows that the Episcopopus trackmaker progressed with a sprawling posture, using a lateral-sequence walk. Its forelimbs were the major propulsive elements and there was little lateral bending of the trunk. We suggest this locomotor style, which differs dramatically from the hindlimb-driven locomotion of salamanders and other extant terrestrial tetrapods can be explained by the forwardly shifted center of mass resulting from the relatively large heads and heavily pectoral girdles of temnospondyls.
authors.affiliation: Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Claudia A
authors.initials: CA
authors.lastname: Marsicano
authors.affiliation: Museum of Paleontology and Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan, United States of America.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Wilson
authors.affiliation: Department of Karoo Paleontology, Iziko South African Museum, Cape Town, South Africa; Department of Geological Sciences, University of Cape Town, Cape Town, South Africa.
authors.forename: Roger M H
authors.initials: RM
authors.lastname: Smith
mesh_terms: D000818:Animals; D005580:Fossils; D008124:Locomotion / Q000502:physiology*; D014426:Turtles / Q000033:anatomy & histology / Q000502:physiology*
references.citation: J Exp Biol. 2004 Jan;207(Pt 3):553-63
references.pmid: 14691103
references.citation: J Exp Biol. 2004 Jan;207(Pt 3):461-74
references.pmid: 14691094
references.citation: PLoS One. 2012;7(12):e50743
references.pmid: 23227204
references.citation: PLoS One. 2014 May 02;9(5):e96516
references.pmid: 24788982
references.citation: Biol Rev Camb Philos Soc. 2003 May;78(2):251-345
references.pmid: 12803423
references.citation: J Exp Zool A Ecol Genet Physiol. 2009 Apr 1;311(4):240-57
references.pmid: 19266497
references.citation: J Anat. 2009 Apr;214(4):607-19
references.pmid: 19422431
references.citation: Integr Comp Biol. 2013 Aug;53(2):283-94
references.pmid: 23667046
references.citation: J Exp Biol. 2001 Mar;204(Pt 6):1099-122
references.pmid: 11222128
references.citation: Proc Natl Acad Sci U S A. 2011 Dec 27;108(52):21146-51
references.pmid: 22160688
references.citation: Integr Comp Biol. 2013 Aug;53(2):209-23
references.pmid: 23624864
references.citation: Anat Rec (Hoboken). 2009 Sep;292(9):1442-61
references.pmid: 19711477
references.citation: J Exp Biol. 2007 Jul;210(Pt 14):2401-2
references.pmid: 17601942
references.citation: J Exp Biol. 1994 Aug;193(1):255-83
references.pmid: 9317755
references.citation: Proc Biol Sci. 2006 Jun 22;273(1593):1563-8
references.pmid: 16777753
references.citation: J Neurophysiol. 1997 Aug;78(2):638-50
references.pmid: 9307101
references.citation: PLoS One. 2009 Oct 06;4(10):e7331
references.pmid: 19806213
references.citation: Nature. 2012 Jun 28;486(7404):523-6
references.pmid: 22722854