Rhinophrynidae

Note: this taxon list is still under construction. It does not yet contain all known Rhinophrynidae subgroups.

Introduction

The Mexican Burrowing Toad (Rhinophrynus dorsalis) is the only living member of this family. This toad's type of tadpole (Orton Type 1) is evidence of a close phylogenetic relationship between Rhinophrynidae and Pipidae. The larger group to which these two families, and the fossil family Palaeobatrachidae, belong is called the Pipoidea.

Definition of the name Rhinophrynidae and thus a listing of synapomorphies for the taxon is problematic because the name Rhinophrynidae has been applied consistently to several fossil taxa (Henrici, 1991) that are related to the single living taxon Rhinophrynus dorsalis. Association of the name Rhinophrynidae or even Rhinophrynus with living taxa only would render those names redundant with the name of the living species. Because the living taxon has a widely used name, we use the more inclusive names Rhinophrynus and Rhinophrynidae for taxa that incorporate fossils. This also has the advantage of stabilizing those names with their common usage. Therefore, Rhinophrynidae is defined to be a stem-based name for those pipoids that are more closely related to the taxon dorsalis than to †Palaeobatrachidae + Pipidae. Rhinophrynus is defined as a stem-based name for rhinophrynids that are more closely related to the living taxon dorsalis than to †Eorhinophrynus or †Chelomophrynus.

Maxson and Daugherty (1980) reported MC'F distances of 170 between Ascaphus and Rhinophrynus dorsalis, more than 190 between Rhinophrynus and Bombina, and more than 200 between Rhinophrynus and Xenopus, Scaphiopus, Pelobates, and three neobatrachians. From these data they tentatively concluded that "... Rhinophrynus appears to have shared a common ancestor more recently with Ascaphus than with other salientian lineages..." (p. 279). This is in contrast to the conclusions reached by Cannatella (1985) and Hay et al. (1995).

Characteristics

By the above definition, synapomorphies of Rhinophrynidae include (1) the division of the distal condyle of the femur into lateral and medial condyles, (Henrici, 1991), and three others that we derived from Henrici's work: (2) modification of the prehallux and distal phalanx of the first digit into a spade for digging, (3) tibiale and fibulare short and stocky, with distal ends fused, and (4) an elongate (at least as long as wide) atlantal neural arch. The first three of these are unknown in †Eorhinophrynus. Synapomorphies of Rhinophrynus are given by Henrici (1991).

References

Cannatella, D. C. 1985. A phylogeny of primitive frogs (archaeobatrachians). Ph.D. Dissertation, The University of Kansas, Lawrence.

Hay, J. M., I. Ruvinsky, S. B. Hedges, and L. R. Maxson. 1995. Phylogenetic relationships of amphibian families inferred from DNA sequences of mitochondrial 12S and 16S ribosomal RNA genes. Mol. Biol. Evol. 12(5):928-937.

Henrici, A. C. 1991. Chelomophrynus bayi (Amphibia, Anura, Rhinophrynidae), a new genus and species from the Middle Eocene of Wyoming: Ontogeny and relationships. Ann. Carnegie Mus. 60:97-144.

Maxson, L. R., and C. H. Daugherty. 1980. Evolutionary relationships of the monotypic toad family Rhinophrynidae: a biochemical perspective. Herpetologica 36:275-280.