Nyctimystes cheesmani

Kraus, Fred, 2012, Identity of Nyctimystes cheesmani (Anura: Hylidae), with description of two new related species, Zootaxa 3493, pp. 1-26 : 4-7

Nyctimystes cheesmani

Fig. 1 A, B

Nyctimystes montana Parker, 1936: 80 . Type locality: Mondo [approximately 8.5909˚ S, 147.1280˚ E, Central Province, Papua New Guinea].

Nyctimystes cheesmani — Tyler, 1964: 268.

Nyctimystes cheesmanae — Menzies, 1976: 45.

Litoria cheesmani — Frost et al., 2006: 362.

Diagnosis. Nyctimystes cheesmani is unique in its combination of medium body size (male SV = 47.6–56.5 mm, female SV = 54.7–65.0 mm); presence of a small tubercle on heel; webbing on hand extending up to or below base of penultimate tubercle on fourth finger; tympanum exposed; palpebral reticulum well-developed, with an obliquely vertical orientation but with relatively few horizontal cross-connections; snout relatively broad (EN/IN = 0.98–1.36); iris pale tan or russet in adults; rear of thighs barred, blotched, or unicolor brown, caramel, or bluegray; males with vocal slits; and call a slow (0.289– 0.365 s), single-note, pulsed croak delivered relatively slowly (1.03–1.36 calls/s) in trains of 2–200+ and with a dominant frequency of 1.84–1.96 Hz.

Comparisons with other species. Nyctimystes cheesmani differs from N. avocalis , N. disruptus , N. oktediensis , N. papua , N. trachydermis , and N. tyleri in having (vs. lacking) vocal slits in males; from N. foricula , N. granti , N. gularis , N. humeralis , N. kubori , N. kuduki , N. montanus , N. narinosus , N. persimilis , and N. zweifeli in having (vs. lacking) a distinct tubercle on the heel; from N. obsoletus in having an exposed tympanum (hidden in N. obsoletus ); from N. pulcher in its smaller size (female SV to 84 mm, male SV to 65 mm in N. pulcher ) and small tubercle (vs. large lappet) on heel; from N. fluviatilis in lacking (vs. having) a row of pale-colored tubercles on outer edge of tarsus, having a thinner palpebral reticulum, and lacking bright orange on rear of thighs (present in N. fluviatilis ); from N. daymani in its greater size (male SV to 42 mm, female SV to 48 mm in N. daymani ), shorter snout (EN/IN = 1.17–1.39 in N. daymani ), and tan or pale russet iris (dark brown in N. daymani ); from N. perimetri in its smaller size (male SV to 61 mm, female SV to 76 mm in N. perimetri ) and shorter snout (EN/IN = 1.23–1.56 in N. perimetri ); and from N. semipalmatus in having less finger webbing (extending to or past penultimate tubercle of fourth finger in N. semipalmatus ), brown or blue-gray on rear of thighs (bright orange in N. semipalmatus ), and a brown dorsum sometimes mottled or freckled with dark brown or black but without distinct black spots (light tan or gray with rounded black spots in N. semipalmatus ).

Description. This description is based only on the holotype and 17 specimens collected by me from within 5 km of the type locality: Vomeropalatines with two patches of teeth between internal nares, approximately five teeth in each patch. Vocal slits and sac present. Head moderately wide (HW/SV mean = 0.34 ± 0.0016, range = 0.32–0.35), slightly longer than wide (HL/SV mean = 0.32 ± 0.0013, range = 0.31–0.34, HL/HW mean = 0.96 ± 0.0048, range = 0.93–1.01); loreal region oblique; canthus rostralis sharp, concave; nostrils closer to tip of snout than to eyes; internarial distance less than distance from external naris to eye (EN/IN mean = 1.07 ± 0.0119, range = 0.98–1.18, IN/SV mean = 0.084 ± 0.0005, range = 0.078–0.87, EN/SV mean = 0.090 ± 0.0007, range = 0.085–0.097); snout slightly rounded to truncate when viewed from the side, rounded at lip but pointed between nares when viewed from above; eyes of moderate size (EY/SV mean = 0.11 ± 0.0015, range = 0.10–0.12), not especially protuberant, eyelid approximately two-thirds width of interorbital distance; tympanic ring distinct but top margin covered by supratympanic skin fold, horizontal diameter less than half width of eye (TY/EY mean = 0.38 ± 0.0077, range = 0.34–0.48). Skin of dorsal surfaces finely granular; ventral surfaces of body and thighs coarsely granular, less so on chest, and smooth under arms and tibiae. Fingers less than one-half webbed between F3 and F4, web reaching no farther than base of penultimate tubercle of F4; webbing less extensive between F2 and F3 but sometimes reaching top of penultimate tubercle of F2; only basal webbing present between F1 and F2; relative lengths 3>4>2>1; tips flattened into discs bearing circum-marginal grooves; discs approximately twice width of penultimate phalanges on F2–F4 but only 1.5 times wider than penultimate phalanx on F1; single subarticular tubercle present at base of each phalanx; each metacarpal with series of 2–4 tubercles; low outer metacarpal tubercle present, inner a long, low oval. First finger of males with nuptial pad of fine, light-brown dermal asperities in approximately an L shape, with main body of pad lying between and dorsal to penultimate phalangeal tubercle and inner metacarpal tubercle, and with a ventral tail extending posteriorly along the dorsal margin of inner metacarpal tubercle. Toes well webbed, webbing stopping at or reaching past subarticular tubercle at base of penultimate phalanx of T4 and to bases of discs on remaining toes; relative lengths 4>5≈3>2>1; tips flattened into discs with circum-marginal grooves; discs slightly wider than penultimate phalanges; inner metatarsal tubercle a prominent oval, outer absent. Hind legs moderately long (TL/SV mean = 0.54 ± 0.0027, range = 0.52–0.56), with a small tubercle at the heel. Mensural variation among features frequently diagnostic for Papuan hylids is not great ( Table 1 ).

In preservative, dorsal ground color medium tan to darker orange brown or gray brown, with scattered freckles of darker brown; scars black. Some specimens have a more mottled color pattern, a few have scattered light-tan flecks or spots. Rear of thighs dark brown (in darker animals) or gray brown (in lighter animals), often with a vaguely barred pattern incorporating some of the dorsal ground color. Venter light to dark brown, sometimes lighter anteriorly or mid-ventrally; two specimens with amelanic patches in the pectoral region. Series of low white or pale-brown tubercles along outer margin of forearm. Webbing of hands and feet brown. Heel tubercle frequently tipped with white. Iris light brown or silver brown; pale tan or pale russet in life ( Fig. 1 A, B); that of the holotype pale tan. Palpebral reticulum of obliquely vertical lines that are frequently bifurcating but with few horizontal cross-connections; lines pale tan to medium brown.

In life, color notes for BPBM 18293 ( Fig. 1 A) state: “Dorsum muddy yellow brown with obscure dark-brown mottling. Venter dirty white with a bluish-purple cast. Fore and rear of thighs, groin, rear of tibiae, and under feet and hands with a bluish-gray wash. Palpebral reticulum of gold vertical lines. Skin granular; tympanum distinct and granular. Iris light brass/silvery with faint green cast.” BPBM 18295 was the same. In contrast, most animals were like BPBM 18294 ( Fig. 1 B): “Dorsum dark olive brown with a few scattered cream flecks. Venter dirty white, largely suffused except for anterior abdomen with dark purple brown. Hidden surfaces dark purple brown.” BPBM 18296 was the same but with a few small red-brown dorsal blotches; BPBM 18299 had russet blotches and brass flecks dorsally; and BPBM 18298 had several clusters of brass flecks dorsally. BPBM 18303 was noted to have a dark-blue wash on rear of thighs. Iris color was generally pale tan ( Fig. 1 A), but several specimens had a more russet or copper color ( Fig. 1 B).

Call. The call of Nyctimystes cheesmani consists of a single-note, unmodulated, pulsed croak ( Figs. 2 A, 3A) delivered at long, irregular intervals in series ranging from 2 to more than 200 calls, with delivery rates varying from 0.74–0.97 calls/s. The call is rather quiet and slow ( Fig. 2 A, C). The interval between two call series measured by me was 130 s. Duration of call notes varied from 0.289– 0.365 s ( Table 2 ). Intervals between successive notes were longer than call notes, varying from 1.029– 1.979 s ( Table 2 ). Calls increase and decrease rather gradually in amplitude, providing a rounded waveform ( Fig. 3 A). Dominant frequency was very uniform, varying from 1840–1960 Hz overall ( Fig. 2 B, Table 2 ).

Ecological notes. Animals were common along a fairly large (5–10 m wide), high-energy, forested stream open to the sky and with trees, shrubs, and large herbs along its banks. Forest at the collection locality was obviously disturbed but mostly closed. Frogs were calling either on boulders or vegetation along or in the stream, typically at the sites with greatest water noise. Nearby smaller forested streams (1–2 m wide) of lower energy contained only N. gularis , but no N. cheesmani , so the species may be restricted to larger forested streams.

Remarks. As indicated above, the call of Nyctimystes cheesmani is a series of slow, raspy croaks. Parker (1936), in describing this species, stated that its call is “a clicking sound such as can be imitated by the tongue on the palate”. That is certainly not an accurate description of the call of this species, and I presume it inadvertently refers to the call of Litoria arfakiana , which occurs syntopically with N. cheesmani in the region of the type locality and whose call fits the description provided by Parker. That species also calls on average from higher in the trees and shrubs than does N. cheesmani , consistent with Parker’s statement that N. cheesmani is found in the foliage of high trees. This is presumably true during the day, but at night, when the males are calling, they are typically doing so from streamside boulders or from relatively lower positions on adjacent trees and shrubs. The call information that Parker reported came from Evelyn Cheesman, the collector, who apparently erred in inferring the proper call for the species.

It is worth noting that a second species of Nyctimystes that may belong to the N. cheesmani complex occurs syntopically with N. cheesmani at Fane. I collected only a single female of this species, but it differs from N. cheesmani in its dark-brown iris, largely horizontal palpebral reticulum, and absence of a heel tubercle. I did not hear this species to call. Lest it be thought that the recording I assigned to N. cheesmani belongs inadvertently to this species, I note that I observed several of the male N. cheesmani I collected to utter the same call as that which I recorded.

Figures

FIGURE 1. Portraits in life of (A) Nyctimystes cheesmani, BPBM 18293, Fane, Central Province; (B) N. cheesmani, BPBM 18294, Fane, Central Province; (C) male N. bivocalis, BPBM 15206, Cloudy Mts., Milne Bay Province; (D) female N. bivocalis, BPBM 15209, Cloudy Mts., Milne Bay Province; (E) N. intercastellus, BPBM 16481, Fergusson Is., Milne Bay Province; (F) N. intercastellus, BPBM 37765, Normanby Is., Milne Bay Province.

FIGURE 2. (A) Waveform, (B) power spectrum, and (C) spectrogram of six calls of an uncaptured Nyctimystes cheesmani recorded near Fane, Central Province, 3 October 2003, air temperature 20.0 C.

FIGURE 3. Expanded waveforms and spectrograms showing note structure for (A) Nyctimystes cheesmani from Fane, Central Province (uncaptured), (B) N. bivocalis (BPBM 15202) from Cloudy Mts., Milne Bay Province, and (C) N. intercastellus (BPBM 17938) from Normanby Island, Milne Bay Province.

Tables

TABLE 1. Mensural variation among adults of Nyctimystes cheesmani. Sample includes the holotype (male) and 17 specimens from nearby Fane.

Character	mean	Males (n = 18) SD	range
SV (mm)	49.5	0.3841	46.3–52.4
TL/SV	0.54	0.0027	0.52–0.56
EN/SV	0.090	0.0007	0.085–0.097
IN/SV	0.084	0.0005	0.078–0.087
SN/SV	0.15	0.0010	0.14–0.16
TY/SV	0.043	0.0005	0.040–0.047
EY/SV	0.11	0.0015	0.10–0.12
HW/SV	0.34	0.0016	0.32–0.35
HL/SV	0.32	0.0013	0.31–0.34
EN/IN	1.07	0.0119	0.98–1.18
HL/HW	0.96	0.0048	0.93–1.01

TABLE 2. Call data for a specimen of Nyctimystes cheesmani from Fane, 1400 m, within 5 km of the type locality. Numbers for call parameters are mean ± SD (range).

Call series	Temperature (˚C)	Number of calls	Duration of call sequence (s)	Call rate (calls/s)	Note duration (s)	Interval between notes (s)	Dominant frequency (kHz)
a	20.0	3	3.1	0.97	0.307 ± 0.0095 (0.289–0.321)	1.079 ± 0.0500 (1.029–1.129)	1.890 ± 0.0182 (1.857–1.920)
b	“	2	2.7	0.74	0.318 ± 0.0075 (0.311–0.326)	1.979	1.862 ± 0.0225 (1.839–1.884)
c	“	6	8.0	0.75	0.352 ± 0.0044 (0.336–0.365)	1.157 ± 0.0311 (1.062–1.239)	1.911 ± 0.0093 (1.893–1.956)