COMPARATIVE OSTEOLOGY AND EVOLUTIONARY RELATIONSHIPS IN THE AFRICAN RANINAE (ANURA RANIDAE)

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Abstract
SUMMARY Boulenger'S 1920 monograph on South Asian Rana provided a stimulus for utilizing osteological characters to interpret evolutionary relationships within the African Raninae. The existence, in the British Museum (Natural History) library, of Boulenger'S unpublished manuscripts on African and Eurasian Rana is noted. The skeletons of 62 specimens representing 33 of the 75 species of African ranine frogs were examined to determine the validity of their current generic assignment, and to attempt to infer a phylogeny for the group. Information on larger samples, rare and type specimens was obtained by x-raying 152 specimens representing a further 31 species. Detailed examination of the skeletons revealed 22 characters varying between supraspecific groups. These characters are analysed chiefly by applying the «commonality principle of character state distribution» of Schaeffer et al. (1972), and also by using outgroup comparison, where available, to determine the primitive state; the direction of change within the character state series is suggested for each of the 22 characters. Osteological definitions are provided for each of the genera recognised, and a phylogeny suggested for the African members of the subfamily. Three groups are recognised within the subfamily: (i) Aubria, Pyxicephalus, Conraua and Rana («Euphlyctis»); (ii) Tomopterna., (iii) Rana, Hylarana, Rana (Strongylopus group), Ptychadena, Hildebrandtia and H.(?) largeni Lanza, 1978. Aubria and Pyxicephalus are recognised as being very closely related, possibly congeneric; Conraua and Rana («Euphlyctis») are recognised as distinct, valid, generic groups. Tomopterna is considered to be only distantly related to the other African ranines, and more closely related to Asian and Madagascan Tomopterna. Rana, Hylarana and Rana (Strongylopus group) are considered to be closely related but in need of further investigation; Strongylopus is recognised as the most derived of the group, and possibly generically distinct. Ptychadena, Hildebrandtia and H.(?) largeni are considered to be the most advanced (derived) monophyletic group in the African Raninae, and only distantly related to the other members of the group. Hildebrandtia(?) largeni is considered to belong to a distinct, new monotypic genus (CLARKE, in preparation).

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