Cophixalus nexipus, Kraus, Fred, 2012

Kraus, Fred, 2012, Papuan frogs of the genus Cophixalus (Anura: Microhylidae): new synonyms, new species, and a dichotomous key, Zootaxa 3559, pp. 1-36 : 13-17

Cophixalus nexipus , sp. nov.

Fig. 7 , 8 A

Holotype. BPBM 19323 (field tag FK 9108), collected by F. Kraus and B. Iova, W slope Mt. Obree, 9.4601º S, 148.0304º E, 1800–2040 m, Central Province, Papua New Guinea, 7 February 2004.

Paratypes (n = 21). BPBM 19320–21, same data as holotype except collected 4 February by F. Kraus; BPBM 19322, same data as holotype except collected 5 February by F. Kraus; BPBM 19324–37, PNGNM 24108–11, same data as holotype.

Diagnosis. A species characterized by its unique combination of modest size (male SV = 18.9–22.7 mm, female SV = 27.2–27.5 mm); basal webbing between toes; finger discs larger than toe discs (3rdF/4thT = 1.07–1.37); first finger of normal size, bearing a disc; dorsum pustulose, irregularly smudged/mottled with dark brown; and venter straw yellow densely and evenly flecked with dark brown.

Comparisons with other species. The new species differs from all other Papuan members of the genus except C. kethuk and C. tagulensis in having webbing between the toes. Both of those species are of smaller size (SV 12.4–15.0 mm in C. kethuk and 13.5–18.5 mm in C. tagulensis ) and have finger discs smaller than toe discs. Further, C. kethuk lacks a disc on the first finger and has a smooth dorsum, and C. tagulensis has the toes halfwebbed and the venter evenly stippled, not flecked, with dark brown.

Description of holotype. An adult male with small right-lateral incision, vocal slits. Head moderately wide (HW/SV = 0.39), with oblique loreal region; canthus rounded, straight when viewed from above ( Fig. 7 A); nostrils directed laterally, closer to tip of snout than to eyes; internarial distance larger than distance from naris to eye (EN/ IN = 0.90, IN/SV = 0.093, EN/SV = 0.084); snout truncate when viewed from the side ( Fig. 7 B), shallowly angulate when viewed from above; eyes of moderate size (EY/SV = 0.12); eyelid approximately 2/3 width of interorbital distance; tympanum small (TY/SV = 0.026) and indistinct. Dorsal and lateral surfaces pustulose; ventral surfaces granulose; supratympanic fold small but distinct. Fingers with trace of basal webbing; relative lengths 3>4>2>1; first finger well developed ( Fig. 7 C). Third finger disc approximately twice width of penultimate phalanx (3rdF/SV = 0.077); that of first finger barely wider than penultimate phalanx. Subarticular and metacarpal tubercles low and poorly developed but distinct. Toes with basal webbing and fringes along T3 and T4 that extend to the disc, bearing discs with terminal grooves; relative lengths 4>3>5>2>1 ( Fig. 7 D). Toe discs smaller than those of fingers (3rdF/4thT = 1.30); disc of fourth toe less than 1.5 times width of penultimate phalanx (4thT/SV = 0.059); disc of first toe approximately same width as penultimate phalanx. Subarticular tubercles poorly developed; inner metatarsal tubercle low and elongate, outer lacking. Hind legs moderately long (TL/SV = 0.48).

Dorsal ground color dark tan, irregularly mottled, smudged, and freckled with dark brown, this concentrated dorsolaterally, on snout, on posterior of head, and in a suprascapular chevron. A vaguely defined tan postocular stripe runs below the darker supratympanic fold. Rear of thighs tan mottled with dark brown; front of thighs same but with less dark mottling. Ventral surfaces straw yellow densely and evenly flecked with dark brown and with scattered gray-white punctations across abdomen. Iris black flecked with silver.

Measurements (in mm). —SV = 22.7, TL = 11.0, HW = 8.8, HL = 7.4, IN = 2.1, EN = 1.9, SN = 3.0, EY = 2.7, TY = 0.6, 3rdF = 1.75, 4thT = 1.35.

Variation. Mensural variation for the type series is shown in Table 5 . Adult males and juveniles appear to have slightly larger snouts than do adult females ( Table 5 ), but the difference is not great. Otherwise, no clear ontogenetic or sexually dimorphic differences are apparent in the type series. All specimens have clearly developed basal webbing between the toes, with that of the largest females appearing only slightly more conspicuous than what is seen in the other specimens.

There is little color variation. Most specimens have the gray-brown appearance of the holotype, but three are lighter brown. Most have the dark suprascapular chevron, but this is often indistinct. The dark ventral flecking varies only slightly in intensity, with only four specimens having less contrast with the ground color than does the holotype.

Color in life. From field notes for holotype BPBM 19323 ( Fig. 8 A): “Dorsum mud-brown, reddish middorsally, with gray suprascapular chevron and dark brown flecks all over. Iris mud-brown. Venter pale purple, except chin and throat, which are pale straw; entire venter speckled with dark brown flecks. Rear of thighs mudbrown with dark-brown mottling. One dark band across the forearm, another above the wrist.” BPBM 19321: “Dorsum green-gray with gray scapular mark and irregular gray or black flecking, with pustules, which are tan. Limbs tan with black flecking; rear of thighs same. Venter flecked light and dark gray with scattered white flecks on abdomen. Posterior belly and under legs light straw. Iris light brown.” BPBM 19320 was yellow-brown above; BPBM 19330 had a narrow, tan mid-dorsal stripe.

Call. This species calls at night from the edges of streams. Most calling animals were perched on leaves 4–30 cm above ground, but one specimen was calling from under a rock.

The call is a single, relatively long (0.99– 1.35 s), highly pulsed note lacking harmonic structure and frequency modulation ( Fig. 9 C) and delivered at intervals of 2.7 to 50 s apart ( Table 6 ). To the human ear the call sounds similar to a squeaky door hinge or a throaty snore. The number of pulses/call varied from 44–63, and pulse rate varied from 41.5–57.4/s. Notes increase in amplitude relatively rapidly and maintain approximately maximum amplitude for most of the note before decreasing again relatively rapidly ( Fig. 9 A). Notes have lesser-amplitude pulses at the beginning and end of the note, giving the waveform a rounded rectanglar shape, with most notes showing approximately equal-amplitude pulses for most of their duration ( Fig. 10 A), but for the holotype notes frequently increase to peak amplitude more gradually than they decrease, giving the amplitude envelope a slight skew to the left ( Fig. 10 B). Pulsing is invariably slower at the beginning, and quicker at the end, of each note. Dominant frequency varies from 2.80–3.96 kHz ( Table 6 , Fig. 9 B).

Etymology. The trivial epithet is a masculine latinized Greek adjective meaning “web-footed”.

Range. Known only from a single mid-elevation site at 1800–2040 m on the western slope of Mt. Obree, Central Province, Papua New Guinea ( Fig. 2 ).

Ecological notes. Animals were moderately common along the edges of a small, first-order stream having a bed of ca. 1–3 m width and containing water ca. 2–15 cm deep. Streambed consisted mostly of gravel and small rocks and occurred in relatively open forest with a canopy of approximately 30 m height. Only one animal was found higher than 30 cm above the ground or farther than 1 m from the edge of the stream. When disturbed, animals jumped to the rocks or gravel beneath and pressed themselves close to it. In such instances, their color matched the substrate well. This is the only Cophixalus I have seen leap into a stream in an attempt at escape. This and the partially webbed feet suggest the species spends some amount of its time in streams, if only to escape predators.

The smallest mature male is 18.9 mm SV; an immature male is 16.5 mm. The smallest mature female is 27.2 mm; four immature females range from 19.9–22.4 mm. Three unsexed juveniles range from 13.4–14.8 mm SV.

Syntopic microhylids include Callulops doriae , Cophixalus ateles , Cophixalus iovaorum , Hylophorbus sp., and Liophryne magnitympanum .

Figures

FIGURE 2. Map of southeastern New Guinea and adjacent islands showing type localities for Cophixalus ateles (filled star), C. sisyphus and C. nexipus sp. nov. (filled circle), C. verrucosus (stars), C. albolineatus sp. nov. (filled square), C. clapporum and C. amabilis (filled triangle), and an additional locality for C. albolineatus sp. nov. (open square). Five additional numbered localities from which call samples of C. verrucosus were obtained for this study are: 1 = Sudest Island, type locality for C. aimbensis; 2 = Cloudy Mts.; 3 = N slope of Mt. Simpson; 4 = W slope of Mt. Dayman; and 5 = Fane. Elevational contours are at 1000 m (light gray) and 1500 m (dark gray).

FIGURE 7. (A) Top of head, (B) side of head, (C) palmar view of left hand, and (D) plantar view of left foot of holotype of Cophixalus nexipus sp. nov. (BPBM 19323). Scale bars = 5 mm.

FIGURE 8. Portraits in life of (A) Cophixalus nexipus sp. nov., holotype BPBM 19323; (B) C. albolineatus sp. nov., paratype BPBM 18429; (C) C. clapporum sp. nov., paratype BPBM 37718; (D) C. clapporum sp. nov., paratype BPBM 37721; (E) C. amabilis sp. nov., holotype BPBM 37730; and (F) C. amabilis sp. nov., paratype BPBM 37740.

FIGURE 9. (A) Waveform, (B) power spectrum, and (C) spectrogram of two calls of Cophixalus nexipus sp. nov. (BPBM 19323) recorded at Mt. Obree, 7 February 2004, air temperature 16.7 C.

FIGURE 10. Expanded waveforms of (A) typical note of Cophixalus nexipus sp. nov., uncaptured animal, showing rectangular shape of amplitude envelope; (B) note from C. nexipus sp. nov. (BPBM 19232) showing left-handed skew in amplitude envelope common to this individual; and (C) typical note of C. amabilis sp. nov. (BPBM 15840).

Tables

TABLE 5. Mensural data for type series of Cophixalus nexipus sp. nov. Characters showing non-overlapping ranges among at least two of the samples are shown with an asterisk.

Character	Males (n = 10) mean range	Females (n = 4) mean range	Immatures (n = 8) mean range
SV (mm)	21.5 18.9–22.7	27.3 27.2–27.5	17.8 13.4–22.4
TL/SV	0.48 0.47–0.50	0.44 0.42–0.46	0.47 0.44–0.50
EN/SV*	0.086 0.081–0.090	0.080 0.077–0.081	0.088 0.081–0.097
IN/SV*	0.093 0.090–0.095	0.087 0.084–0.088	0.098 0.093–0.105
SN/SV	0.14 0.13–0.15	0.13 0.13–0.13	0.14 0.14–0.16
TY/SV	0.030 0.026–0.036	0.034 0.029–0.040	0.035 0.027–0.050
EY/SV	0.13 0.12–0.13	0.12 0.12–0.12	0.12 0.11–0.13
HW/SV	0.41 0.39–0.43	0.38 0.37–0.39	0.40 0.36–0.41
HL/SV	0.34 0.32–0.35	0.31 0.31–0.32	0.34 0.32–0.36
3rdF/SV	0.071 0.063–0.077	0.071 0.066–0.076	0.062 0.052–0.076
4thT/SV	0.056 0.053–0.059	0.056 0.053–0.064	0.051 0.044–0.058
EN/IN	0.92 0.86–1.00	0.92 0.88–0.96	0.90 0.86–0.95
3rdF/4thT	1.28 1.14–1.35	1.26 1.20–1.37	1.21 1.07–1.31
HL/HW	0.82 0.76–0.88	0.83 0.81–0.84	0.85 0.80–0.91

TABLE 6. Call parameters for Cophixalus nexipus sp. nov. from the west slope of Mt. Obree, Central Province, PNG. Numbers for call parameters are mean ± SD (range).

Individual	Number of calls	Temperature (˚C)	Call duration (s)	Interval between calls (s)	Pulses/note	Pulse rate (pulses/s)	Dominant frequency (kHz)
uncaptured	16	15.8	1.15 ± 0.022 (0.99–1.29)	3.74 ± 0.143 (2.68–4.61)	58.4 ± 0.598 (54–63)	50.98 ± 0.783 (47.29–57.43)	3.32 ± 0.086 (2.80–3.96)
BPBM 19323	14	16.7	1.19 ± 0.020 (1.06–1.35)	9.57 ± 3.452 (3.83–49.99)	53.5 ± 1.325 (44–63)	45.09 ± 0.499 (41.51–47.01)	2.93 ± 0.015 (2.80–3.00)