Discodeles

Brown, Rafe M., Siler, Cameron D., Richards, Stephen J., Diesmos, Arvin C. & Cannatella, David C., 2015, Multilocus phylogeny and a new classification for Southeast Asian and Melanesian forest frogs (family Ceratobatrachidae), Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 174 (1), pp. 130-168 : 150-151

SUBGENUS DISCODELES BOULENGER, 1918

Type species

Rana guppyi Boulenger, 1884 .

Diagnosis

The sole species of the subgenus Discodeles is easily diagnosed from species of the genus Cornufer by having (1) an extremely large body size [females up to 250 mm SVL (mass of up to 1 kg) vs. most species with female SVL ≤ 65 mm]; (2) moderately expanded terminal discs of fingers and toes (vs. widely or non-expanded); (3) fully webbed feet (vs. interdigital webbing absent, limited to basal vestige, or present but with one or two terminal phalanges free of web); and (4) aquatic microhabitat preference (vs. terrestrial or arboreal). We consider its body size and full interdigital foot webbing to be synapomorphies of this distinct lineage ( Fig. 2, Clade H).

Phylogenetic definition

Discodeles is the apomorphy-based name for the clade ( Fig. 2, Clade H) originating in the ancestor in which the following apomorphies, synapomorphic with that in the known populations of D. guppyi , originated: extremely large body size and fully webbed feet.

Content

Composed of highly divergent isolated allopatric and insular lineages of the nominal species, Co. (D.) guppyi is most likely a complex of evolutionary lineages (species) from New Britain, Bougainville, and various Solomon Islands populations ( Table 3).

Comment

Two species of Ceratobatrachidae have the specific epithet guppyi : Rana guppyi Boulenger, 1884 (the type species of the aquatic genus Discodeles ) and Cornufer guppyi Boulenger, 1884 (a tree frog native to the Solomon Islands). Our inclusion of the two species in the resurrected genus Cornufer creates homonymy between the names. Under the principle of priority (ICZN, 1999) we normally would retain the senior homonym, the older available name. However, both species were named in the same year, in the same work and on the same page ( Boulenger, 1884: 211), an extremely unusual situation.

Under the Code, the preferred and most conservative action would be the substitution of a valid junior synonym of one of these species. Rana guppyi Boulenger, 1884 , purportedly has a junior synonym; Zweifel (1960) treated Rana bufoniformis cognata Hediger, 1933 (NHMB 4605, holotype; Forcart, 1946) as a synonym of R. guppyi Boulenger, 1884 . However, we reject cognata as a junior synonym of R. guppyi because its type locality, ‘Iriu’, Admiralty Islands, falls within the known geographical range of ‘ D. ’ vogti and not within that of D. guppyi . Hediger’s (1933) description additionally lists morphological character states (narrowly expanded toe discs, relatively small body size) that lead us to believe that this species is not referable to Co. (D.) guppyi . We therefore consider R. bufoniformis cognata Hediger, 1933 , as a junior subjective synonym of D. vogti ( Hediger, 1934) . Thus, there is no junior synonym that can be substituted for R. guppyi Boulenger, 1884 .

The second species in this conundrum is Co. guppyi Boulenger, 1884 , which also lacks any junior synonyms. However, the Code provides for a resolution in such cases. Article 24.2 of the Code states that the principle of first reviser (ICZN, 1999:30) is to be used in situations in which the precedence between names cannot be determined and an available junior synonym does not exist. Acting as first reviser, we fix precedence of R. guppyi Boulenger, 1884 , over Co. guppyi Boulenger, 1884 . This action maintains the name of the well-known species D. guppyi (= Rana guppyi Boulenger, 1884 ), which is also the type species of Discodeles . We provide a new replacement name for Co. guppyi Boulenger, 1884 , below (see under subgenus Aenigmanura ).

Etymology

Although Boulenger (1918b) provided no etymology for Discodeles , he distinguished it from other Papuan and Melanesian forms on the basis of the ‘horseshoeshaped groove’ ( Boulenger, 1918b:238) evident on the tips of fingers and toes. Thus, we assume that the name is derived from the Latin ‘discus’, meaning a flat and round shape, and the Greek ‘delos’, meaning visible or evident, in reference to presence of the digital discs. Suggested common name: giant Pacific water frogs.