Microbatrachus pusillus Roux, 1910

ZWEIFEL, RICHARD G., 2000, Partition Of The Australopapuan Microhylid Frog Genus Sphenophryne With Descriptions Of New Species, Bulletin of the American Museum of Natural History 2000 (253), pp. 1-130 : 93-94

Microbatrachus pusillus Roux

Microbatrachus pusillus Roux, 1910: 228 (type locality, ‘‘ Pobdjetur , Terangan,’’ Aru Islands, Indonesia; holotype, NMBA 2732 , collected Feb. 6, 1908, by H. Merton and J. Roux). Van Kampen, 1923: 121. Nieden, 1926: 50. Parker, 1934: 179. Forcart, 1946: 135.

Sphenophryne pusilla : Tyler, 1978: 459.

TYPE MATERIAL: The type specimen is a juvenile 7 mm SVL that ‘‘has been extensively dissected... and very badly damaged in the process’’ (Tyler, 1978: 457).

DIAGNOSIS: The condition and immaturity of the type specimen allow diagnosis of neither the species nor of the genus of which it is the type species.

MORPHOLOGY: The following description is from van Kampen (1923: 121) and evidently is his paraphrase of the original description, as he did not examine the type specimen: ‘‘Tongue large, subtriangular, about half free behind. Head nearly as long as broad; snout broadly truncated, as long as the eye; no canthus rostralis; nostril in the middle between the orbit and the tip of the snout; interorbital space 1 times the width of the upper eyelid; tympanum hidden. Fingers obtuse; second to fifth toe with very feebly dilated tips; fingers very short, first shorter than second, which is shorter than fifth; no subarticular or metatarsal tubercles; the heel reaches the posterior border of the eye.’’

‘‘Skin smooth.’’

Roux (1910: 228) stated: ‘‘Sternal apparatus cartilaginous, extremely simple. Sternum a narrow plate. Coracoid and procoracoid present. No clavicle, no omosternum.’’ Tyler (1978) noted that as tiny a bone as the clavicle of specimen of this size might easily have been overlooked or lost in dissection. Except for the peculiar Genyophryne , no genyophrynine frog possesses a procoracoid but lacks the clavicle.

COLOR AND PATTERN: ‘‘Upper parts brown, darker on the head and the anterior part of the back; fore limbs greyish white, hind limbs yellowish brown; lower parts yellowish white, the throat a little darker, with small lighter dots. Length 7 mm ’’ (van Kampen, 1923: 121–122).

ILLUSTRATIONS: Roux (1910: pl. 14) illustrated the body in dorsal aspect (fig. 6), open mouth (fig. 6a), and pectoral girdle (fig. 6b).

HABITAT AND HABITS: ‘‘We took this tiny amphibian from wet soil at the edge of a stream’’ (Roux, 1910: 229).

DISTRIBUTION: This species is known only from the type locality (fig. 48).

REMARKS: The systematic position of Microbatrachus pusillus has elicited comments from most authors dealing with the species: ‘‘Perhaps a young Sphenophryne or Oreophryne sp. ’’ (van Kampen, 1923: 122); ‘‘almost certainly the young of an Oreophryne ’’ (Dunn, 1928: 4); ‘‘This genus may... prove to have been founded on an immature Oreophryne or Sphenophryne , more probably the latter’’ (Parker, 1934: 179). Only Tyler (1978), who placed Microbatrachus in the synonymy of Sphenophryne , has gone into the matter in detail, including examination of the type specimen. With allowance for the poor condition of the specimen, Tyler made a strong case for eliminating Cophixalus and Oreophryne from consideration, leaving Sphenophryne as the most likely candidate. The possibility that Microbatrachus represents a valid genus was given little credence by these authors.

Tyler’s (1978) allocation of Microbatrachus as a junior synonym of Sphenophryne was reasonable at the time, but with Sphenophryne (sensu Parker, 1934) now sundered into four genera, the status of Microbatrachus is more obscure than ever. In nomenclatural priority, Microbatrachus (1910) stands ahead of Austrochaperina (1912) and Oxydactyla (1913). The last is a genus of montane frogs most unlikely to be found on the Aru Islands. Austrochaperina , however, might well occur there, and I have commented elsewhere (Zweifel, 1985b: 285) that pusillus may be a senior synonym of A. adelphe (Australian) or A. gracilipes (Australian and Papuan) , either of which lowland species may occur on the Aru Islands.

My present view is that because of the paucity of the description and poor condition of the juvenile holotype, Microbatrachus pusillus cannot be identified with any known genus and species, and that future taxonomic stability will be enhanced if the name is set aside as a nomen dubium.

MORPHOLOGY