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The integumentary skeleton of tetrapods: origin, evolution, and development
Matthew K Vickaryous1, Jean-Yves Sire
1Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Canada. mvickary@uoguelph.ca
Journal of Anatomy
|May 9, 2009
Summary
The tetrapod integumentary skeleton includes osteoderms, dermal scales, and lamina calcarea, all derived from neural crest cells and ancestral scales. Their evolution and development reveal deep homologies within the dermis.
Area of Science:
- * Evolutionary developmental biology
- * Comparative osteology
- * Integumentary system research
Background:
- * The tetrapod integumentary skeleton, often overlooked, comprises diverse skeletal elements.
- * These elements are thought to derive from the dermal skeleton of stem-gnathostomes, but evolutionary details are unclear.
- * Existing knowledge on the evolution and development of these integumentary structures is limited and uncertain.
Purpose of the Study:
- * To re-evaluate the tetrapod integumentary skeleton.
- * To integrate comparative developmental and tissue structure data.
- * To clarify the evolutionary origins and developmental pathways of integumentary skeletal elements.
Main Methods:
- * Comparative analysis of developmental and tissue structure data across tetrapod lineages.
- * Re-evaluation of existing literature and data on integumentary skeletal elements.
- * Histological and developmental studies (implied).
Main Results:
- * Three types of integumentary elements recognized: osteoderms, dermal scales (gymnophionans), and lamina calcarea (anurans).
- * All elements are considered derivatives of the ancestral cosmoid scale and originate from neural crest cells.
- * Osteoderms are plesiomorphic, variable, and develop through various ossification modes, originating in the dermis from neural crest cells.
- * Gymnophionan dermal scales resemble teleost elasmoid scales and are hypothesized to be odontogenic.
- * Lamina calcarea is also proposed as odontogenic, requiring further research.
Conclusions:
- * Osteoderms, dermal scales, and lamina calcarea share a common origin from ancestral scales and neural crest cells.
- * Osteoderms exhibit deep homology related to dermal skeletogenic competence, with varied developmental processes.
- * Gymnophionan scales and lamina calcarea likely represent distinct, possibly odontogenic, integumentary skeletal structures.
- * All integumentary skeletal elements maintain a fundamental relationship with the integument, linking to ancestral rhombic scales.
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