Abstract
Sharpey’s fibres are known mainly as providing anchorage between tooth and the periodontal ligament but they occur also in other types of bones. In the postcranial skeleton these fibres are usually present at the muscle or tendon attachment sites. They were reported in all major groups of extant vertebrates, as well as in putative lissamphibian ancestors—temnospondyls and lepospondyls. However, it was recently stated that their presence was very rarely described in extant amphibians. In limbs, they were reported predominantly from proximal bones. They have not yet been reported from phalanges, which are the most commonly sectioned amphibian bones. Here, we describe phalangeal histology of nine species representing most major clades of lissamphibians. These results show that Sharpey’s fibres occur commonly in lissamphibian phalanges. In shaft, they are radially oriented and occur in the periosteal bone, at sites of tendon attachment. They can also occur in the metaphysis and contact the cartilage. This may provide a basis for foot muscle reconstructions in fossil amphibians.
Highlights
Sharpey’s fibres (SF) are poorly mineralised fibres of the connective tissue, composed mostly of several types of collagen, elastin or tenascin (e.g. Francillon-Vieillot et al 1990; Aaron 2012)
Most of them have tendinous attachment sites, where SF are usually abundant. For this purpose we investigated bone histology of nine species which belong to several major clades of extant amphibians (Lissamphibia) and represent different modes of life and locomotion (Table 1)—factors which may affect bone histology (e.g. Laurin et al 2004; Canoville and Laurin 2009)
Presence of SF is well documented in many types of bones of Palaeozoic and Mesozoic amphibians, including both temnospondyls and lepospondyls
Summary
Sharpey’s fibres (SF) are poorly mineralised fibres of the connective tissue, composed mostly of several types of collagen, elastin or tenascin (e.g. Francillon-Vieillot et al 1990; Aaron 2012) They are known primarily as providing attachment between tooth and a periodontal ligament Ho et al 2007) They occur in other body parts, where they most commonly attach muscles, ligaments or tendons to collagen fibres present in the periosteal bone (Francillon-Vieillot et al 1990; Aaron 2012) but can be present in osteoderms, in which they probably serve as anchorage to the skin The aim of our study was to find out whether SF occur commonly or rarely in lissamphibian phalanges This could provide an experimental basis for inferring muscle attachment sites in fossil amphibians. Most of them have tendinous attachment sites (entheses), where SF are usually abundant
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