Variation in the foot muscles of frogs of the family Myobatrachidae

Abstract

The hind-foot musculature of representatives of all myobatrachid frog genera was examined with a view to finding phylogenetic characters and characters correlated with the burrowing habit. Despite much intraspecific variation, evidence was found to support the monophyly of Mixophyes(possession of a fibrous section in the tendon of insertion of the m. lumbricalis longus digiti V, tendinous insertion of the m abductors brevis dorsalis digiti V), Rheobatrachus (threefold insertion of the m. extensor longus digiti IV), Neobatrachus +Heleioporus (possession of the m. lumbricalis longus digiti II), Pseudophryne + Metacrinia(loss or reduction of medial slip of the m. lumbricalis brevis digiti V), Adelotus + Heleioporus +Limnodynastes (minus L. ornatus-group) +Neobatrachus+Notaden (possession of a transversus-like muscle between the first metatarsus and the prehallux), and Rheobatrachus + Myobatrachinae (reduction of the m. plantaris brevis plantaris digiti V). Differences were found in the musculature associated with the metatarsal tubercles between (a) rear-foot-burrowing frogs of the genera Notaden, Neobatrachus,Heleioporus and Limnodynastes (minus L. ornatusandL. spenceri); (b)L. ornatus and L. spenceri; and (c)Uperoleia. The differences indicate separate evolution of burrowing in these taxa. A new muscle, the m. adductor praehallucis, is described. From its structure and distribution among species, this muscle appears to be associated with the burrowing habit.