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Cranial turtle musculature:
WERNEBURG

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Multilingual  Abstracts

Abstract

Introduction

Materials and Techniques

New Nomenclature and the Synonymy of Cranial Musculature in Turtles

The Cranio-Cervical Skeleton of Emydura subglobosa

Cranium Associated Musculature in Emydura subglobosa

Nomenclature of Turtle Cranial Musculature

Hierarchy of Homology

Dynamic Model of Muscle Evolution and Development

Homology of Particular Muscular Structures in Turtles

Conclusions

Acknowledgments

References

Appendix 1

Appendix 2

Appendix 3

Appendix 4

Appendix 5

Appendix 6

Appendix 7

 

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HIERARCHY OF HOMOLOGY

In the presented study, I homologised muscular units mainly based on spatial characters in adult anatomy. In most cases, the origin and insertion patterns were used to decide between particular structures. However, Rieppel (1990, 2007), Mabee (2000), Haas (2001), and others have shown that there are different levels of homology to consider. A muscular structure such as the anterior head of m. adductor mandibulae posterior is to be mentioned (Rieppel 1990: ampa; homologue to No. 30), which develops as a part of the pseudotemporalis Anlage; ontogenetically it belongs to the m. adductor mandibulae internus complex, while in adult anatomy it has separated from that complex and shifted spatially. Finally, it has to be considered as a part of m. adductor mandibulae posterior (No. 29-30). Rieppel (1990) refers to the dynamics of developmental processes. That may involve spatial and temporal plasticity as well as intraspecific variability (Werneburg 2009a; see below).

Paraxial head mesoderm – the material source of the anterior parts of head musculature (No. 1-48) – is initially patterned by streams of cranial neural crest cells (cNCC) (Maier et al. 2004) and shows intermixtures with cNCC derivates (Grenier et al. 2009). Mitgutsch et al. (2009) have shown a high interspecific variability of very early cNCC migration in frogs. At later stages, their timing may contain a phylogenetic signal; and the pattern of tissue differentiation bears specific information for higher and lower taxonomic levels (Köntges and Lumsden 1996, 2000; Olsson et al. 2001). In different taxa different timing of the cNCC / mesoderm (muscle-Anlagen) interaction may result either in a different or comparable adult topology of cranial muscles.

In addition to origin / insertion of adult muscles, I propose also considering the innervation pattern and the pattern of the tendinuous framework (sensu Iordansky 1990, 1994) – both structures directly derived from NCC – to define homologies. As in every homology discussion, a consideration of several homology criteria has to be performed parallel due to heterotopic shifts of anatomical elements.

A comparable situation to paraxial mesoderm is recognisable in the postcranial region. The myotom parts of the somites form epaxial and hypaxial muscle Anlagen (Gilbert 2006). Steiner (1977) stated that there are several fusions and separations in developing muscles of tetrapods resulting in a shore leave adapted twisting of posthatching / postnatal muscle anatomy. Both cranial and postcranial musculature information on developmental patterns – as far as they are available – must not be disregarded, as they may expose homologies of structures that are intermixed or blurred in adult anatomy (e.g., the discussion on the homology of the parts of "m. cervico-hyo-capitis" of Ogushi 1913b).

 

Next Section

Cranial turtle musculature
Plain-Language & Multilingual  Abstracts | Abstract | Introduction | Materials and Techniques
New Nomenclature and the Synonymy of Cranial Musculature in Turtles
The Cranio-Cervical Skeleton of Emydura subglobosa  | Cranium Associated Musculature in Emydura subglobosa
Nomenclature of Turtle Cranial Musculature | Hierarchy of Homology
Dynamic Model of Muscle Evolution and Development
Homology of Particular Muscular Structures in Turtles | Conclusions
Acknowledgments | References |
Appendix 1 | Appendix 2 | Appendix 3 | Appendix 4 | Appendix 5 | Appendix 6 | Appendix 7
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