On the anuran musculus pulmonum proprius

Abstract

The present contribution provides a systematic survey on the variation of the musculus pulmonum proprius within Anura. Evidence is contrary to previous works that presented the muscle as an enigmatic feature present only in the family Pipidae. Although having different sites of origin, the m. pulmonum proprius was observed in all examined anurans. The muscle originates at the level of the transverse processes of the fourth vertebra in the neobatrachian families Bufonidae, Calyptocephalellidae, Ceratophryidae, Cycloramphidae, Dendrobatidae, Hylidae, Hylodidae, Leiuperidae, Leptodactylidae, Mantellidae, Microhylidae, Ptychadenidae and Ranidae. In Bombina variegata (Bombinatoridae) the origin of the muscle shifts caudally at the level of the transverse process of the sacral vertebra and, in Pipidae, it originates either at the ilium (Xenopus) or the femur (Pipa). Features of the m. pulmonum proprius do not vary in species with different modes of locomotion within Neobatrachia and there is no sexual dimorphism in this muscle. It is absent in the genera Salamandra (Caudata) and Chthonerpeton (Gymnophiona). Pending verification in Leiopelmatidae, the presence of m. pulmonum proprius may be considered as a previously unknown anuran synapomorphy.