Austrochaperina rivularis, ZWEIFEL, 2000

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 : 52-54

Austrochaperina rivularis , new species Figure 31E

Sphenophryne macrorhyncha : Zweifel, 1967: 6. Hyndman and Menzies, 1990: 272.

HOLOTYPE: AMNH A130551 (Field No. RZ 12802 ), collected by Fred Parker and Papuan assistants at Finalbin, 840 m, 5 km N, 2 km W Tabubil, Western Province , Papua New Guinea, on July 27, 1987.

PARATYPES (all from Papua New Guinea): Western Prov. : AMNH A130552–130559 , UPNG 8273 , same data as holotype ; AMNH A84541 , A84542 ; MCZ A81000 , 81224– 81230 , 81451 , 81452 , Imigabip, 1280 m, collected by Fred Parker, Dec. 1969 ; AMNH A84543 ; MCZ A81002 , 81003 , Bolangon, 1280 m, collected by Fred Parker, Dec. 1969 ; MCZ A81001 , Migalsimbip, 790 m, collect- ed by Fred Parker, Dec. 1969. West Sepik Prov.: QM J67247 , 67255 , Mt. Stolle, 1600 m, collected by Stephen Richards and G. R. Johnston, July 4, 1993. East Sepik Prov.: AMNH A77550 –77588 , A84445 (C&S), A129514–129558, Mt. Hunstein , 1220 m, collected by Ru Hoogland Aug. 14–15, 1966. Southern Highlands Prov.: AMS R122164 , R122165 , Namosado, collected by S. Donnellan.

ETYMOLOGY: The specific name is a Latin adjective pertaining to small brooks or streams, in reference to the habitat of this species.

DIAGNOSIS: A moderate- to large-sized Austrochaperina , maturing at 35 mm SVL or larger (geographically variable), with relatively large finger discs (FD/SVL ± 0.035), moderate leg length and eye size (TL/SVL Ṩ 0.46, EY/SVL Ṩ 0.116), and a dorsal pattern of small, dark markings on a slightly paler ground.

DESCRIPTION OF HOLOTYPE: Adult female with the following measurements and proportions: SVL 49.0, HW 17.1, TL 21.8, EY 4.8, EN 3.4, IN 4.8, HD 12.6, FT 23.8, third finger disc 1.95, fourth toe disc 2.3; HW/ SVL 0.349, TL/SVL 0.445, EY/SVL 0.098, EN/SVL 0.069, IN/SVL 0.098, EN/IN 0.708, HD/SVL 0.257, FT/SVL 0.486, FD/SVL 0.040, TD/SVL 0.047.

Head narrower than body. Snout rounded to almost subacute seen from above, rounded and slightly projecting in profile; loreal region moderately steep, slightly concave, canthus rostralis rounded but distinct; nostrils lateral, just visible from above, slightly clos- er to tip of snout than to eye. Eyes relatively large, outline visible from beneath, lid almost as wide as interorbital span. Tympanic outline scarcely visible, diameter less than half that of eye. Relative lengths of fingers 3> 4> 2> 1, first more than half length of second, all with expanded, rounded, grooved discs, that of third finger twice width of penultimate phalanx or a little less; subarticular and metacarpal elevations indistinct. Toes unwebbed, relative lengths 4> 3> 5> 2> 1, all with discs larger than those of fingers, that of fourth toe about twice width of penultimate phalanx; subarticular elevations low, rounded, scarcely evident; inner metatarsal elevation small, elongate, rounded. Skin smooth above and below except for very weak, diagonal postorbital fold.

Purplish brown above in preservative with a few darker flecks, weak, convergent dark lines in the scapular region, and an ill-defined dark stripe above the postocular fold. The fingers and toes are marked with dark and light in no particular pattern. The ventral ground color is pale tan with gray-brown mottling from chin to posterior tip of abdomen as well as beneath the limbs. The intensity of the mottling is slightly less on the abdomen than elsewhere.

VARIATION IN TYPE SERIES: Populations referred to A. rivularis have different maximum body sizes. The sample from Western Province includes apparently immature males (no vocal slits) of 30.2 and 31.5 mm, mature males of 35.7 and 36.5 mm, females just maturing at 35.9 and 36.9 mm, and adult females of 39.1 to 49 mm. Several males from Mt. Hunstein, East Sepik Province, in the range of 39–45 mm lack vocal slits whereas others 42– 45 mm have them. Whether this indicates variability in the vocal apparatus of adult males or variability in size at maturity is not evident, but the greater size of males in this sample is clear. The series of females from Mt. Hunstein includes a juvenile as large as 44.0 mm, one maturing at 44.8 mm and adults 47.6–51.5 mm. Proportions of specimens in the two major samples are quite similar (table 2). Regression data are in table 3.

In life, frogs from Western Province were scarcely more distinctively colored than in preservative, being olive-brown above with darker brown markings, a faint lumbar ocellus, and the tympanic area pale yellowish tan. Undersides were gray-brown with faint dark- er mottling most evident on the chin. The iris is dark golden brown above and below the horizontal pupil, little differentiated from the dorsal color.

REFERRED SPECIMENS: SAMA 6385–6403, 6409–6414, 6416–6418, collected by Barry Craig at Busilmin, West Sepik Province, on May 7, 1965. I lack a complete suite of measurements on these specimens and thus could not make critical comparisons. Although I exclude them from paratype designation, it is likely that they represent this species.

ILLUSTRATIONS: 3rd finger terminal phalanx, fig. 71O; premaxilla, fig. 63F; sacral region, fig. 73A; vomer, fig. 65N; skull, fig. 68A; hand and foot, fig. 56A.

CALL: Through the courtesy of Stephen Richards, I have tape recordings of the calls of two individuals of this species and have examined one of the voucher specimens. The call (fig. 79B, table 5) is a series of harsh notes each about 0.06–0.08 sec long, composed of six to eight pulses, and repeated at a rate of about three notes per second. Individual notes characteristically begin with a long pulse, followed by others half its length (fig. 80C), although occasional notes have all the pulses approximately the same length (see Vocalizations). The dominant frequency is approximately 2600 Hz in one instance and 2700 in the other. One complete call (i.e., initiated after recording began and terminat- ed voluntarily) lasted 1 min 25 sec; the other (presumably incomplete) call was at least 38 sec long. Both frogs called from beside small creeks. The air temperature recorded for one call was 21.3°C.

Stephen Richards recorded one of the frogs at 1600 m on Mt. Stolle, West Sepik (Sanduan) Prov., the other about 5 km west of Tabubil (elevation about 600 m by my estimate and close to the type locality), Western Prov. The localities are about 75 km apart.

COMPARISONS WITH OTHER SPECIES: Austrochaperina rivularis is compared with two similar species— macrorhyncha and palmipes —in the accounts of those species. The two species basipalmata and derongo are smaller, with maximum male and female sizes approximating the sizes at which rivularis matures. Presence of toe webbing distinguishes basipalmata , and average tibia length, eye, hand, and disc sizes are smaller in derongo .

HABITAT AND HABITS: The frogs found at Finalbin, when uncovered from beneath leaves lying beside small streams in mossy, hilly forest, jumped into the water and swam well in attempting escape. Except for the note above on a recorded individual, nothing else is known about the habits of this species.

DISTRIBUTION: The known localities are in or on the fringe of the central mountainous region of western Papua New Guinea in Western, West Sepik, East Sepik, and Southern Highlands Provinces (fig. 29). The species undoubtedly occurs in eastern Irian Jaya, as the type locality is only 22 km from the border. The known range in elevation is about 600 to 1600 m. For locality records and specimens examined, see above under Holotype, Paratypes, and Referred Specimens.

REMARKS: The question of whether A. rivularis is a species distinct from A. derongo is answered by their distinction in sympatry in Southern Highlands Province of Papua New Guinea as well as by differences in advertisement calls. See the account of A. derongo for details of the sympatric locality.

Another question is whether rivularis includes more than one species. The larger body size seen in the Mt. Hunstein sample is suggestive, but there are no other morphological characters sufficiently trenchant to mark species lines. Also, geographic variation in body size is seen in the related species derongo and palmipes . Information on advertisement calls might be helpful in resolving the question if more populations can be sampled.

Figures

Fig. 31. Examples of Austrochaperina, Liophryne, and Sphenophryne. A. S. cornuta, AMNH A130544, adult. B. A. brevipes, AMNH A130534, SVL 21.9 mm. C. A. guttata, QM J67256, SVL 43.2 mm. D. A. macrorhyncha, MZB 3564, SVL 36.8 mm. E. A. rivularis, holotype, AMNH A130551, SVL 49.0 mm. F. A. palmipes, AMNH A130550, adult. G. L. similis, AMNH A130564, SVL 40.0 mm. H. A. derongo, MZB 3563, SVL 36.7 mm. Photos C, D, and H by S. Richards.