Literaturdatenbank
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Bramble, D. M. (1974). Emydid shell kinesis: biomechanics and evolution. Copeia, 1974(3), 707–727.
Added by: Sarina Wunderlich (28 Feb 2010 12:07:05 UTC) |
| Resource type: Journal Article BibTeX citation key: Bramble1974 View all bibliographic details  |
Categories: General Keywords: Morphologie = morphology, Schildkröten = turtles + tortoises, Systematik = taxonomy Creators: Bramble Collection: Copeia |
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| Abstract |
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Mechanisms of shell closure in box turtles of the family Emydidae have been analyzed with respect to functional anatomy, evolution and phylogenetic significance. Structural requirements essential to the box turtle morphotype are: 1) plastral kinesis; 2) mechanisms for displacement (accommodation) of the limb girdles as the shell is closed; 3) additional space in the shell for displacement of the forelimbs; 4) musculature to effect shell closure. Girdle accommodation is structurally and evolutionarily the most "difficult" requirement; plastral kinesis is the least. In typical box turtles of the subfamily Batagurinae, the anterior plastral lobe is elevated by the hypertrophied testoscapularis muscle. The scapulocarapacial articulation is modified to allow dislocation of the joint during shell closure. A portion of the main cervical retractor (M. retrahens capitis collique) raises the front end of the plastron in all hinged turtles of the subfamily Emydinae. In this group a unique, segmented scapula permits both effective accommodation of the girdle and a passive locking mechanism that stabilizes the girdle in locomotion. An enlarged M. testoilìacus is chiefly responsible for closure of the rear portion of the shell in box turtles of both subfamilies. Excluding Notochelys, the box turtle specialization has arisen independently once each in the Batagurinae and Emydinae. Among batagurines, members of the Cyclemys Group (Cyclemys, Pyxidea, Cuora) share a common closing mechanism. This generic complex probably derives from a Heosemys-like ancestry, suggesting all four genera may be united in a Heosemys Complex. The batagurine, Notochelys, has evolved shell kinesis separately from the Cyclemys Group and is not closely related to members of this group. A shared closing system and other morphological similarities warrant the inclusion of all hinged emydines (Emys, Emydoidea, Terrapene) in a single Emys Group. Within the group, Emys is most primitive with Emydoidea in most respects structurally and probably phyletically intermediate between it and Terrapene. Emydoidea is unrelated to Deirochelys, but is convergent with it in several features related to similar feeding systems. The Emys Group originates from a Clemmys-like ancestor and its members are joined with Clemmys in a distinct Clemmys Complex.
Added by: Sarina Wunderlich |