Callulops mediodiscus, Oliver, Paul, Richards, Stephen & Tjaturadi, Burhan, 2012

Oliver, Paul, Richards, Stephen & Tjaturadi, Burhan, 2012, Two new species of Callulops (Anura: Microhylidae) from montane forests in New Guinea, Zootaxa 3178, pp. 33-44 : 40-42

Callulops mediodiscus sp. nov.

( Figs. 1 b–2c,d)

Holotype. SAMA R66016 (field number SJR 8853), adult male, Moran Oilfield, Southern Highlands Province, Papua New Guinea (6 o14.817’ S, 143 o 07.523’ E, 1750 m asl) collected by S. Richards, C. Dahl and J. Hiaso, 13 November 2004. Liver tissue sampled and stored in ethanol at the South Australian Museum.

Paratopotypes. SAMA R66010 (SJR8559), SAMA R66012 (SJR8827), 66013–15 (SJR8850–8852), UPNG 10071 (SJR 8848) and UPNG 10072 (SJR8849) all with same locality and collector details as holotype, collected 13–18 November 2004.

Diagnosis. Distinguished from all congeners and from species in the genera Metamagnusia and Pseudocallulops by the combination of moderate size (males 42.0–49.0 mm SVL), moderately enlarged digital discs on fingers and toes (up to approximately twice width of penultimate phalanx), discs on toes approximately same width as discs on fingers (3FD/4TD = 0.89–1.12), hind limbs moderately long (TL(fold)/SVL = 0.41–0.47, TL(knee)/SVL = 0.46–0.48), snout truncate in dorsal aspect, hands and feet relatively long (HandL/SVL = 0.28–0.30, FootL/SVL = 0.48–0.54), skin on dorsum and lateral surfaces relatively smooth, dorsum uniform brown with darker head, ventral and lower lateral colouration uniform light brown without light mottling or flecking, and advertisement call a series of four harsh barking notes lasting a total of 2.1– 2.4 s with a dominant frequency of 1529–1661 Hz.

Comparisons with other species. Callulops mediodiscus sp. nov. is distinguished from both species of Metamagnusia by having finger discs narrower than or equal to width of toe discs (vs finger discs much wider than toe discs), and uniform dark-brown or two-tone dorsal pattern (vs obvious spotting, marbling or thick longitudinal striping both dorsally and laterally, Günther 2009). It is distinguished from both species of Pseudocallulops by its larger size (adult SVL> 41 mm vs <36 mm) and uniform dark-brown dorsal colouration (vs light-brown with extensive darker brown spotting and blotching, Günther 2009).

The presence of distinctly expanded digital discs distinguishes Callulops mediodiscus sp. nov. from all congeners except C. boettgeri and C. omnistriatus , and especially from four species that lack digital discs entirely ( C. glandulosus , C. sagittatus , C. stictogaster and C. wilhelmanus ). It differs from the geographically distant C. boettgeri in having finger discs not conspicuously wider than the toe discs ( Zwefel 1972); and from C. omnistriatus in being smaller (male SVL <50 mm vs 55.0– 59.6 mm), having a narrower head (HW/SVL 0.31–0.34 v 0.34–0.39), darker head than body (vs uniform), including a darker gular region than the belly, and in having finger and toe discs of approximately equal width (3FD/4TD 0.89–1.12 vs 0.62–0.99) ( Kraus and Allison 2009).

In addition to having wider finger discs (approximately twice width of penultimate phalanx vs less than twice width of penultimate phalanx), C. mediodiscus sp. nov. can be distinguished from the remaining Callulops species as follows: from C. comptus , C. doriae , C. marmoratus and C. personatus by its two-tone brown dorsal colouration (vs marbled, spotted or blotched with grey, dark brown or black); it is also significantly smaller than C. doriae and C. personatus (SVL <55 mm vs> 65 mm); from C. comptus , C. humicola , C. fuscus and C. kopsteini it also differs in having a relatively uniform light-brown venter (vs boldly mottled with yellow and brown in C. comptus and C humicola , flecked with light grey or white in C. fuscus and C. kopsteini ); from C. eremnosphax and the type series of the geographically distant species C. fuscus and C. dubius by its significantly larger size (male SVL 42–49 mm vs <40 mm); from C. fojaensis sp. nov. in having much longer legs (TL(knee)/SVL 0.46–0.48 vs 0.34) and in having an advertisement call with 4 (vs 6–7) notes; and finally from topotypic C. robustus from Misima island by its much smaller size (SVL of adult male robustus 60.6–64.9 mm) and smooth (vs rugose) dorsal and lateral skin.

It differs from a number of nominal taxa currently synonymised with C. robustus in the combination of more greatly expanded toe and finger discs (all synonyms), presence of distinct terminal groove on the first finger and absence of light flecks on the thighs and lateral surfaces (vs C. microtis ), absence of yellow flecks and pigmentation across the body (vs Pomatops valvifera ), in having a truncate (vs rounded) snout tip and smaller size (42– 49mm vs 54.6mm) (vs Liophyrne kampeni ) ( Zweifel 1972, Kraus and Allison 2009).

Description of holotype. Key measurements are given in Table 1. Body moderately slender, somewhat pearshaped, head wide (HW/SVL 0.33), broader than long (HL/HW 0.96) not distinct from body, nares closer to tip of snout than to eye, directed laterally. Internarial distance greater than distance from eye to nares (EN/IN 0.82), eyes moderately large (EYE/SVL 0.12). Snout truncate in dorsal view and rounded in lateral view. Canthus rostralis rounded, not sharply defined; loreal regional very slightly concave, labial region near vertical but slightly inflated and convex. Tongue rounded; anterior palatal ridge long, smooth, posterior palatal ridge with approximately eleven distinct denticles. Mandibular symphysis forming a small hook at tip of lower jaw. Supratympanic fold moderately distinct, extending from posterior edge of eye across dorsal edge of tympanum, curving around posterior edge of tympanum to a point approximately level with jaw, then extending over dorsal edge of axilla. Dorsum, lateral surfaces, and venter smooth without any obvious tuberculation or folds in preservative.

Limbs long (TL(knee)/SVL 0.46) and moderately robust. Hands long (HandL/SVL 0.29), fingers unwebbed, with very low, rounded, indistinct and unpigmented subarticular tubercles; relative lengths 3>4>2>1, tips with expanded digital discs approximately twice width of penultimate phalanx, all discs with distinct terminal grooves; palm smooth except for three indistinct low metacarpal tubercles, largest and most distinct at the base of finger 1. Feet long (FootL/SVL 0.49), toes unwebbed, with low, rounded, indistinct and unpigmented subarticular tubercles; relative lengths 4>3>5>2>1, tips with expanded digital discs approximately twice width of penultimate phalanx, all discs with distinct terminal groove, heel smooth with oval inner metatarsal tubercle at base of toe 1.

In preservative dorsum, lateral surfaces and exposed surfaces of limbs and digits brown, notably darker on the head, lighter posteriorly and towards tips of fingers. Venter light brown without obvious pattern; much darker on throat and limbs, and lighter towards posterior of torso and tips of digits. Metacarpal pads unpigmented, lighter than brown palmar regions.

Variation. Summary data for the type series are presented in Table 1. The type series is relatively uniform in appearance and colouration. All types are predominantly brown with noticeably darker heads. Intensity of brownish pigmentation varies as follows: dorsal and lateral colouration varies from medium-brown to greyish-brown; gular region (extending from anterior tip of lower jaw to posterior edge of forelimb insertion) of all specimens light to medium-brown and distinctly darker than light-brown of posterior venter; approximately half of type series with indistinct lighter buff mottling across posterior two thirds of venter. Under-surface of limbs always darker brown than venter; in a few specimens faint buff blotching is present on the hind limbs; under-surface of digits varies from light to medium-brown, always becoming lighter and less densely pigmented towards tips.

Appearance in life. The following description is based on a photograph of paratype SAMA R66014 taken at night ( Fig. 1 ). Overall dorsal colouration of body light yellowish-brown, lateral surfaces more strongly tinged with yellow than dorsum; dorsal and lateral surfaces of head, including eyes and lower and upper jaw darker brown than rest of body. Exposed surfaces of forelimbs yellowish-brown proximally, becoming medium brown distally; exposed surfaces of hindlimbs relatively uniform yellowish brown; digits lighter and less densely pigmented than limbs and tending towards off-white. Iris silvery-grey, with thin to moderately thin dark-brown reticulations; sclera brown.

Advertisement call. The advertisement call of C. mediodiscus sp. nov. is a series of four loud, barking notes. A single call is illustrated in Figure 3A. We analysed eight complete call sequences from the holotype (SAMA R66016) recorded at a temperature of 18o C. Calls were produced at intervals of 54–84 s (mean = 71.42, SD = 11.76, n = 7), and had a dominant frequency of 1529–1661 Hz (mean = 1590, SD = 37.30, n = 8). Individual notes lasted 0.18– 0.24 s (mean = 0.21, SD = 0.01, n = 32) and were produced at a rate of 1.42–1.59 notes/s (mean = 1.51, SD = 0.05, n = 8). Each note contained 31–37 pulses (mean = 34.83, SD = 1.60, n = 29) produced at a pulse rate of 141–176 pulses/s (mean = 160.18, SD = 8.71, n = 29).

Etymology. In reference to the most distinctive feature of this species, the moderately enlarged discs, which are large for a Callulops , of similar size to those of Pseudocallulops , and small for Metamagnusia . The epithet is used here as an invariable noun in apposition to the genus name.

Natural history and distribution. Callulops mediodiscus sp. nov. is known only from extremely wet, mossy lower-montane rainforest (~ 1750 m asl) on karst limestone in the upper Kikori Basin of Southern Highlands Province. The type series was found on the ground on leaf litter or calling from slightly elevated perches on mossy rocks and logs after rain at night. No other species of Callulops was collected at the type locality.

Figures

FIGURE 1. A) Callulops fojaensis sp. nov. (holotype MZB Amph. 11958) in life. B) Callulops mediodiscus sp. nov. (paratype SAMA R 66014) in life. Photographs Stephen Richards.