Document Detail

Olecranon orientation as an indicator of elbow joint angle in the stance phase, and estimation of forelimb posture in extinct quadruped animals.
MedLine Citation:
PMID:  19378290     Owner:  NLM     Status:  MEDLINE    
Reconstruction of limb posture is a challenging task in assessing functional morphology and biomechanics of extinct tetrapods, mainly because of the wide range of motions possible at each limb joint and because of our poor knowledge of the relationship between posture and musculoskeletal structure, even in the extant taxa. This is especially true for extinct mammals such as the desmostylian taxa Desmostylus and Paleoparadoxia. This study presents a procedure that how the elbow joint angles of extinct quadruped mammals can be inferred from osteological characteristics. A survey of 67 dried skeletons and 113 step cycles of 32 extant genera, representing 25 families and 13 orders, showed that the olecranon of the ulna and the shaft of the humerus were oriented approximately perpendicular to each other during the stance phase. At this angle, the major extensor muscles maximize their torque at the elbow joint. Based on this survey, I suggest that olecranon orientation can be used for inferring the elbow joint angles of quadruped mammals with prominent olecranons, regardless of taxon, body size, and locomotor guild. By estimating the elbow joint angle, it is inferred that Desmostylus would have had more upright forelimbs than Paleoparadoxia, because their elbow joint angles during the stance phase were approximately 165 degrees and 130 degrees , respectively. Difference in elbow joint angles between these two genera suggests possible differences in stance and gait of these two mammals.
Shin-Ichi Fujiwara
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of morphology     Volume:  270     ISSN:  1097-4687     ISO Abbreviation:  J. Morphol.     Publication Date:  2009 Sep 
Date Detail:
Created Date:  2009-08-17     Completed Date:  2010-02-23     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0406125     Medline TA:  J Morphol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1107-21     Citation Subset:  IM    
Copyright Information:
Copyright 2009 Wiley-Liss, Inc.
The University Museum, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
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MeSH Terms
Biomechanics / physiology
Elbow Joint / anatomy & histology,  physiology*
Forelimb / anatomy & histology,  physiology*
Olecranon Process / anatomy & histology,  physiology*
Posture / physiology*
Ulna / anatomy & histology,  physiology*

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