Vergleichende Morphologie der Kiefermuskulatur der Beloniformes (Teleostei, Atherinomorpha)
The taxon Beloniformes represents a heterogeneous group of teleost fishes including distinct forms as ricefishes (Adrianichthyidae), flying fishes (Exocoetidae), halfbeaks (Hemiramphidae), needlefishes (Belonidae), and sauries (Scomberesocidae) which show an extraordinary diversity of their jaw morphology. Beside the monophyly of Beloniformes, the relationships of its major taxa are disputed resulting in the proposal of several conflicting phylogenetic hypotheses. In order to investigate the contribution of cranial soft tissue elements to this debate the morphology of the jaw apparatus of five representatives of Beloniformes and four related species were comparatively analysed based on manual dissections, Azan-stained serial sections and 3d reconstructions. The 37 cranial soft tissue characters described in this study were mapped onto the alternative topologies and supported at best the monophyly of Beloniformes. Although Oryzias latipes shows numerous autapomorphic characters, Beloniformes are characterised by a derived reduction of the intramandibular portion of m. adductor mandibulae and the specific course of truncus maxillaris, which separates near the jaw joint. Within Beloniformes a sister group relationship of Adrianichthyidae to a clade consisting of ((Exocoetidae + Hemiramphidae) + (Belonidae + Scomberesocidae)) is supported by the reduction of the external section of m. adductor mandibulae and the shift of the m. levator arcus palatini origin to the sphenotic. These different observed characters could be correlated altogether to the reduced mobility between the elongated beak-like jaw bones evolved within this group.
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