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GEOREF RECORD

The hind limb of Captorhinus aguti and the step cycle of basal amniotes

Robert B. Holmes
The hind limb of Captorhinus aguti and the step cycle of basal amniotes (in Studies on the evolution of vertebrates; papers in honour of Robert Lynn Carroll--Etudes sur l'evolution des vertebres; articles en l'honneur de Robert Lynn Carroll, Hans-Dieter Sues (editor), Alison M. Murray (editor) and Jason S. Anderson (editor))
Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre (April 2003) 40 (4): 515-526

Abstract

Exquisitely preserved limb elements of Captorhinus aguti from the Lower Permian locality of Richards Spur, Oklahoma, form an excellent basis for analysing the step cycle of the hind limb of basal amniotes. An articulated composite hind limb skeleton is moved through the step cycle. These movements are constrained by the intrinsic skeletal anatomy and data from fossilized footprints attributed to Palaeozoic amniotes. Two well-defined hinge joints are evident: a distal tarsometatarsal joint, and a mesotarsal joint between the calcaneum-astragalus-centrale unit and distal tarsals. A strict homology between the latter and mesotarsal joint in lepidosaurs is uncertain. The conspicuous size disparity between the distal end of the tibia and the much larger tibial facet of the astragalus, a widespread feature of archaic amniotes, permits considerable movement between the distal end of the tibia and astragalus during the stance phase. Differential dorsoflexion, concentrated at the preaxial side of the mesotarsal joint, allows the pes to remain stationary (rather than slide laterally) on the substrate as the femur is retracted and the tarsus shifts from an anterior to lateral orientation. The distal end of the femur describes an arc of only approximately 60 degrees during the stance phase, but could rotate about 60 degrees about its long axis, a figure comparable to that recorded for living lizards.


ISSN: 0008-4077
EISSN: 1480-3313
Coden: CJESAP
Serial Title: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre
Serial Volume: 40
Serial Issue: 4
Title: The hind limb of Captorhinus aguti and the step cycle of basal amniotes
Title: Studies on the evolution of vertebrates; papers in honour of Robert Lynn Carroll--Etudes sur l'evolution des vertebres; articles en l'honneur de Robert Lynn Carroll
Author(s): Holmes, Robert B.
Author(s): Sues, Hans-Dietereditor
Author(s): Murray, Alison M.editor
Author(s): Anderson, Jason S.editor
Affiliation: Canadian Museum of Nature, Palaeobiology, Ottawa, ON, Canada
Affiliation: Carnegie Museum of Natural History, Pittsburgh, PA, United States
Pages: 515-526
Published: 200304
Text Language: English
Summary Language: French
Publisher: National Research Council of Canada, Ottawa, ON, Canada
References: 27
Accession Number: 2003-049554
Categories: Vertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendix
Illustration Description: illus.
N34°23'60" - N34°52'00", W98°49'60" - W98°04'60"
Secondary Affiliation: Canadian Museum of Nature, CAN, CanadaUniversity of Toronto at Mississauga, CAN, Canada
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200316
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