Connexions of the Pterygoquadrate in the Tadpole of Philautus variabilis (Anura)

Abstract

WHILE examining the chondrocranium of Ranid and Rhacorphorid (Polypedatid) genera of frogs, the connexions of the pterygoquadrate with the cranium were found to vary considerably. It is well known since the time of Parker¹ and Gaupp² that in the anuran larvæ, the pterygoquadrate gains attachment with the cranium normally in three regions, namely, an anterior ligamentary or, in the majority of cases, a cartilaginous quadrato-ethmoidal connexion; the second connexion is in the posterior orbitotemporal region, called the processus ascendens, which bears definite relationship with the three branches of the Vth. cranial nerve. When the tadpole undergoes metamorphosis, this larval connexion is lost (say in the case of R. fusca larva (S. temporaria) 29 mm., de Beer³) and the adult is without one. There is no anuran larval form described where, in the larval stages prior to metamorphosis, the absence of a processus ascendens is described. The last connexion is the oticus one; the posterior portion of the pterygoquadrate unites with the dorsal wall of the otic capsule over the cranioquadrate passage. This connexion, however, may be absent from some tadpoles.