Rana megalonesa, Inger & Stuart & Iskandar, 2009

Inger, Robert F., Stuart, Bryan L. & Iskandar, Djoko T., 2009, Systematics of a widespread Southeast Asian frog, Rana chalconota (Amphibia: Anura: Ranidae), Zoological Journal of the Linnean Society 155 (1), pp. 123-147 : 136-137

RANA MEGALONESA SP. NOV.

(Previously referred to as Borneo Large morphotype)

Rana chalconota (part) Boulenger, 1920: 201; van Kampen, 1923: 217.

Rana chalconota raniceps Inger, 1966: 177 .

Rana cf. chalconota Stuart et al., 2006: 473 .

Holotype

FMNH 267821 , an adult female from Bukit Sarang (2°39′N / 113°03′E), Bintulu Division, Sarawak (Borneo), Malaysia. Collected in a freshwater swamp forest (20 m a.s.l.) 1 m above ground on a shrub, 11.xi.2004, by Freddy Paulus and Patrick Francis.

Paratypes

From type locality FMNH 267814-15 , 267818 , 267825 adult males with nuptial pads , FMNH 267816 , 267819 , 267824 adult females with convoluted, enlarged oviducts ; FMNH 267817 , 267820 , 267822- 23 subadult females .

Etymology

Specific name from megalo-, Gr., large, and nesos, Gr., island, referring to its distribution on the large island of Borneo.

Referred material

Sarawak: Belaga District , Sg. Segaham (2°44′N / 113°55′E) FMNH 220474 , 220477-78 , 220484 , 220492 , 220512-13 , 220526 , 220541-43 , 220547 , 220549 , 220551-52 , 220554 ; Kapit District , Nanga Tekalit (1°37′N / 113°35′E) FMNH 220264 , 220267-68 , 220286 , 220297 , 220379 , 220381 , 220383 , 220396 , 220399 , 220404 , 220417 , 220434 , 220447 , 220559-60 , 220563- 64 , 220568 , 220570 , 220572-74 , 220576-77 , 220579 , 220581 , 220586 , 222955-56 ; Bintulu Division, Labang Forest Reserve (3°21′N / 113°27′E) FMNH 148203-07 ; Bintulu Division, Sg. Pesu camp (3°07′N / 113°48′E) FMNH 156607 , 156610-11 , 156622 , 156627 , 156631 , 156634-35 , 156638 , 156640 , 156643 , 156653-56 , 156658 , 156660 , 156666 , 156668 , 156674-77 , 156680- 84 , 156687 , 156709-13 , 156716 , 156718 , 156720 , 156729-31 , 156735 , 156741 , 156747 , 156749 , 156756- 59 , 156762 , 156765-68 . Sabah: Kota Marudu District , Marak Parak (6°18′N / 116°42′E) FMNH 235639-45 ; Lahad Datu District, Danum Valley Research Centre (5°12′N / 117°50′E) FMNH 203953-62 , 203965 , 203969- 71 , 203974-78 , 203980 , 203983 , 203985 , 203987-88 , 203991-92 ; Sipitang District , Mendolong (4°54′N / 115°42′E) FMNH 128334 , 238336 , 238348 , 238362 , 242797-98 , 242801 , 242804 , 242806-07 , 242811 ; Tawau District , Bukit Tawau Park (4°37′N / 117°54′E) FMNH 248339-42 , 248345-46 , 248348-49 ; Tawau District , Kalabakan (4°25′N / 117°30′E) FMNH 76694 , 76696 , 76702 , 76705 , 76715-16 , 76718 , 76722 , 76733 , 76738 , 76742-43 , 76753 , 76762-64 , 76770 , 76779 , 76781-82 , 76784-86 , 76789 .

Diagnosis

A large-sized member of the R. chalconota group; distinguished from other forms by combination of females usually> 50 mm, males> 35 mm; T / SVL usually> 0.56, HW / SVL usually> 0.30, DF3/ SVL > 0.06; males with nuptial pad constricted or divided and with weak humeral gland discernible only upon dissection.

Description

Habitus moderately slender, head slightly wider than trunk, legs long. Head triangular; snout obtusely pointed, projecting beyond lower jaw, longer than diameter of eye; nostril on side of snout, closer to tip of snout than to eye; canthus angular, not constricted; lores concave, weakly sloping; interorbital wider than upper eyelid and wider than internarial; pineal body faintly visible, between anterior corners of upper eyelids; tympanum distinct, about two-thirds eye diameter in female, slightly larger in males, slightly depressed relative to surface of temporal region; vomerine teeth in short, oblique groups between choanae, distance between groups shorter than distance from choanae.

Fingers long, length of third finger equal to distance from rear of eye to nostril; fingers without webbing; second and third fingers with narrow, movable fold of skin on medial margins; tips of three outer fingers with wide discs, that of third finger about two-thirds diameter of tympanum in female, disc of first finger about half width of disc of second finger, all discs with circummarginal grooves; subarticular tubercles conspicuous, rounded; base of third finger with one or two supernumerary tubercles, bases of second and fourth fingers with one supernumerary tubercle. Tips of toes expanded into discs smaller than those of fingers, but with circummarginal grooves; webbing extensive, to base of discs on lateral margins of three inner toes and on medial margin of fifth, to base of disc on medial margin of fourth toe or between disc and distal subarticular tubercle; a narrow ridge of skin medially along first toe and a similar one along outer edge of last joint of fifth toe; a low, oval inner metatarsal tubercle and a distinct, round outer one.

Skin of back weakly granular with scattered colourless spinules in females; males with densely crowded, taller spinules on all dorsal surfaces including head and eyelid, similar spinules on lores; a distinct, but low dorsolateral fold; ventral surface of body smooth, weakly rugose at rear of abdomen; a ridge-like rictal glandular swelling followed after a narrow gap by a glandular swelling above the axilla.

Colour in preservative brown above and on sides, darker on side of head, upper lip white; many scattered dark spots on back and usually on head; ventral surfaces white, throat and chest with or without small dark spots; hind limb without dark crossbars in most preserved individuals; rear of thigh brown with faint, round lighter markings.

Measurements (mm) of holotype: SVL 53.8, T 28.4, HW 16.6, HL 21.1, TYM 4.4, DF3 3.4.

Variation

Females 45.4–65.6 mm, mean 53.66 ± 0.45 mm (N = 115); males 33.3–48.2 mm, mean 39.21 ± 0.34 mm (N = 113). DF3/ SVL 0.054 –0.076, median 0.064 (N = 104). TYM/ SVL of males 0.089 –0.135, median 0.112 (N = 76). Humeral gland in males usually detectable only by dissection. Frequency of dark spotting on back varies among samples. In two samples from eastern Sabah dorsal spots were present in 18 of 28 frogs; in two samples from western Sabah dorsal spots were present in only seven of 29. The spots were present in two-thirds of frogs from the Bintulu Division of westcentral Sarawak but in only four of 90 from southeastern Sarawak. Frequency of constriction of the nuptial pad of males also varies. In frogs from eastern Sabah (three localities) the nuptial pad was constricted or divided in 22 of 28 males. The frequency of constriction in males from western Sabah (two localities) was five of 13. In males from south-eastern Sarawak (three localities) the frequency of constricted or divided nuptial pads was 24 of 51 individuals. The nuptial pad was constricted or divided in four of eight males from the Bintulu Division, west-central Sarawak .

Comparisons

The difference between this species and the cooccurring R. raniceps in size is striking. The mean SVL of males of R. megalonesa is roughly 10 mm larger than that of R. raniceps and the difference between means of females is almost 15 mm ( Table 2). Individuals of Rana megalonesa that co-occur with R. raniceps differ from the latter in higher frequency of dark spots on the back.

Although it is a large form of the chalconota group, females of R. megalonesa are smaller than those of both R. rufipes (see below) and Javan R. chalconota and its males smaller than those of R. rufipes ( Tables 2 and 6). In addition to the size difference, the new species also differs from R. rufipes in having a relatively larger tympanum ( Tables 2 and 6) and in the form of the nuptial pad (not constricted or divided in R. rufipes ). Both males and females of R. megalonesa are larger than those of R. labialis , R. eschatia and R. parvaccola (see below). Relative head width ( HW / SVL) of R. megalonesa is larger than that of R. labialis and R. parvaccola . Relative width of the tympanum ( TYM / SVL) of R. megalonesa is larger than that of R. labialis in both sexes ( Tables 2 and 6).

The uncorrected pairwise sequence divergence between R. megalonesa and the co-occurring R. raniceps is 13.11–13.97% (Table 4).