THE PHYLOGENY OF THE SALIENTIA

Summary 1. The essentially recent skeletal patterns of fossil Salientia indicates that the evolutionary relationships of the order must continue to be assessed on evidence obtained chiefly from a study of recent forms. 2. The morphology and morphogenesis of the more important criteria employed in taxonomic analyses are described. Definitive and developmental features of pectoral and vertebral elements are particularly detailed. It is concluded that: ( a ) neither the nature of the vertebral articulation nor the arrangement of the thigh complex is a reliable character on which to define major salientian categories; and ( b ) criteria based on degree of freedom of epicoracoid cartilages are incapable of exact taxonomic application. The Arcifera and Firmisternia are redefined according to the presence or absence of epicoracoid horns. The importance of certain morphogenetic patterns in the analysis of phylogenetic trends is suggested. 3. A new scheme is proposed for the definition of recent salientian families. This hinges chiefly on the number of presacral vertebrae, the nature of the definitive centrum and the epicoraco‐sternal complex. 4. The status of Protobatrachus (L. Trias) is reviewed. It is concluded that the proanuran stock stemmed from temnospondylid ancestors and that the so‐called ‘saltatory’ trends of modern Salientia evolved primarily for swimming. Fossil footprints from the Ecce formation of South Africa may indicate that the Proanura were already established by the Permian. The role of the urostyle in facilitating the pro‐anuran‐salinetian transition is considered. 5. On the evidence of the vertebral column it is suggested that the Salientia are at least diphyletic and that all non‐ascaphid forms stemmed from a pipoid stock. Interrelationships between the non‐ascaphid families are considered. 6. The geographic history of the order is reviewed. It is concluded that early salientian evolution was rapid and radiative and that, skeletally at least, the essential features of all the recent families had been established by the Tertiary or, possibly, by the Mesozoic. Discoglossidae, Pipidae and Pelobatidae are interpreted as eco‐1 ogically isolated and the Atelopodidae as Neotropical in both origin and range. Whilst the main ranoid and bufonid stocks almost certainly originated in and radiated from the Old World tropics (as Darlington suggested) some of their derived lines (Rhaco‐phoridae and Microhylidae in particular) may equally well have evolved polycentrically without much subsequent radiation. 7. It is suggested that radiation or isolation, in the different families, is a function of locomotory specializations and that these are reflected particularly in the variations of the vertebral centrum and the shoulder girdle. I wish to thank Miss A. G. C. Grandison, Professor Georg Haas, Professor J. P. Lehman, Dr H. W. Parker, the late Dr Malcolm Smith and Dr L. C. Stuart who have assisted me either with helpful discussions and information or with gifts of material. I am also indebted to Dr A. W. Crompton for photographs of the fossil footprints from the Ecce formation.