The Recessus Scalae Tympani and Its Bearing on the Classification of Reptiles

Abstract

The scalae has recently become an important character in the re- construction of the phylogenetic relationships of higher taxa of reptiles. The subdivision of an originally undivided fissura metotica during ontogeny lends itself particularly well to cladistic analysis. The present paper is an attempt to review the differentiation of the scalae in reptiles in order to elucidate problems of topographic homology and convergent evolution. The term recessus scalae tympani was introduced into the biological lit- erature by Hasse (1873) and his collab- orators. With this term, Hasse designat- ed in the skull of birds a ventral and posterior part of the recessus cavi tym- pani, separated from the recessus cavi sensu strictiori by the mem- brana secundaria but com- municating with the tympani, i.e., with that part of the osseous laby- rinth which houses the lagena sur- rounded by the scala of the perilymphatic system. What Hasse (1873) referred to is obviously the an-