Cophixalus gigiraensis, Günther & Dahl & Richards, 2023

Guenther, Rainer, Dahl, Chris & Richards, Stephen J., 2023, Another giant species of the microhylid frog genus Cophixalus Boettger, 1892 from the mountains of Papua New Guinea and first records of procoracoids in the genus, Zoosystematics and Evolution 99 (1), pp. 173-183 : 173

publication ID	https://dx.doi.org/10.3897/zse.99.97006
publication LSID	lsid:zoobank.org:pub:A2B9BC7F-5CF6-40DF-A3A8-A3A2F7A02644
persistent identifier	https://treatment.plazi.org/id/125B2D49-E0B0-4459-9F06-5C912E695326
taxon LSID	lsid:zoobank.org:act:125B2D49-E0B0-4459-9F06-5C912E695326
treatment provided by	Zoosystematics and Evolution by Pensoft
scientific name	Cophixalus gigiraensis
status	sp. nov.

Treatment

Cophixalus gigiraensis sp. nov.

Oreophryne ? sp. 5 'loud grunter’ (Richards & Armstrong, 2017).

Cophixalus sp. 5 'loud grunter’ (Richards & Armstrong, 2018).

Cophixalus sp. 4 'loud grunter’ ( Richards et al., 2021).

Type material.

Holotype: SAMA R71740 (SJR 15394), adult male from Gigira Ridge, Hela Province, Papua New Guinea (5.9725°S, 142.7532°E; 2160 m a.s.l.) collected on 22 May 2017 by S. Richards and C. Dahl.

Paratype: SAMA R71700 (FN SJR15396), juvenile, same details as holotype except collected on 23 May 2017.

Referred specimens.

SAMA R71748 (FN SJR[JCUNQ]5097), Summit ridge of Mt Sisa, Hela Province, Papua New Guinea (6.1343°S, 142.7536°E; 2450 m a.s.l.) collected on 29 October 1999 by S. Richards; SAMA R71749 (FN SJR8645), Summit of Mount Elimbari, Chimbu Province, Papua New Guinea (6.1899°S, 145.1486°E; 2566 m a.s.l.) collected on 01 December 2004 by S. Richards and C. Dahl.

Diagnosis.

With a snout-urostyle length of 44.4 mm in an adult male the new species is among the largest species of the genus; in New Guinea only Cophixalus riparius reaches a similar size. It is distinguished from C. riparius and all other congeners by the following unique combination of characters: body robust, head short (HL/SUL 0.31); legs moderately short (TL/SUL 0.42), third toe longer than fifth; fingers and toes with greatly expanded triangular terminal discs, all with circum-marginal grooves; discs of fingers much larger than those of toes (T4D/F3D 0.76); dorsal surfaces including rear of tarsus with scattered low tubercles, ventral surfaces smooth; most of dorsal surfaces brown-olive (RAL 8008) with irregular beige (most similar to RAL 1001) flecking; ventral surfaces whitish overlain with moderately dense reddish-brown pigmentation; advertisement call a loud explosive ‘bark’ produced singly or in groups of up to eight, each containing 13-19 pulses lasting 60-80 ms, dominant frequency 1.5 kHz.

Description of the holotype

(Fig. 1a-d View Figure 1 ). An adult male with vocal slits, calling when collected. For measurements see Table 1 View Table 1 . Head slightly broader than long (HL/HW 0.89), canthus rostralis rounded; loreal region steep, slightly concave; snout protruding in profile, slightly pointed in dorsal view; nostrils directed dorsolaterally, closer to tip of snout than to eyes; horizontal eye diameter much greater than eye-naris distance (ED/END 1.48); tympanum relatively small (TyD/ED 0.37), not well-demarcated; supratympanic skin fold narrow but well defined in life and preservative; internarial distance greater than distance between eye and naris (END/IND 0.83); tongue large, pear-shaped, posterior margin rounded and free; two prepharyngeal ridges, anterior ridge with 10 tiny lobes, posterior one with 14 denticles; vocal slits moderately long, located on both sides of tongue. Legs relatively short (TL/SUL 0.42); webbing between fingers and toes absent; discs of fingers triangular, wider than triangular discs of toes (T4D/F3D 0.76); all finger and toe discs with circum-marginal grooves; relative length of fingers 3>4>2>1 (Fig. 1c View Figure 1 ). Third toe slightly longer than fifth; relative length of toes 4>3>5>2>1 (Fig. 1d View Figure 1 ); most subarticular, metatarsal and metacarpal tubercles indicated by light colour but structurally only scarcely developed. In life dorsal surfaces and posterior of tarsus with scattered low tubercles; all ventral surfaces smooth.

Dorsal surfaces in life predominantly clay-brown (RAL 8003) (Fig. 1a View Figure 1 ), paler on flanks than mid-dorsum; mid-dorsum, upper flanks and incomplete lumbar spots with several irregular beige flecks; upper arms including elbows, and tarsi including tibio-tarsal joints, also with beige flecking; ventral surfaces whitish with more (on extremities) or less (on abdomen, chest and throat) dense reddish-brown pigmentation (Fig. 1b View Figure 1 ); rear of thighs monochromatic pale brown (RAL 8025). Iris whitish with sparse network of dark brown reticulations.

In preservative dorsal and lateral surfaces darker brown, beige flecks less obvious prior to staining with alcian blue. After staining, dorsal surfaces uniformly slate gray (RAL 7015) with pale brown (RAL 8025) areas detectable through the gray; dorsal surfaces of hands beige brown (RAL 8024); throat pale brown with soft blue tinge; chest and abdomen with pronounced blue tinge; ventral surfaces of extremities predominantly pale brown.

Description of the paratype

(Fig. 2a-c View Figure 2 ). A juvenile (SUL 15.4 mm) of undetermined sex. For measurements see Table 1 View Table 1 . General body and head shape, and presence of low tubercles on dorsum and tarsi similar to holotype but colour pattern in life strikingly different. Head and nape in dorsolalateral and dorsal views with large light ivory (RAL 1015) blotch (Fig. 2a, b View Figure 2 ). This blotch continues anteriorly to nostrils where it is interrupted at tip of snout by triangular brown-grey (RAL 7013) spot; and posteriorly to urostyle. Light ivory area framed dorsolaterally by two irregularly shaped gray-brown (RAL 8019) stripes extending from behind eyes to well-defined lumbar spots. Additional light ivory areas on dorsal surfaces of upper arms, around tibio-tarsal articulations, on dorsal surfaces of tarsi and on upper flanks. Snout partially beige-red (RAL 3012) dorsally and laterally. Dorsal surfaces of thighs and shanks, lower flanks, anterior forearm and subocular region olive grey (RAL 7002). Throat, chest, abdomen and lower surface of thighs rather uniform olive grey with few irregular whitish spots (Fig. 2c View Figure 2 ). Iris pebble grey (RAL 7032) with dark brown reticulations (Fig. 2a View Figure 2 ). Several morphological ratios of the juvenile paratype deviate substantially from those of the adult paratype (Table 1 View Table 1 ). Further material is required to determine whether these differences represent ontogenetic change.

Vocalisation.

The advertisement call of Cophixalus gigiraensis is a short, harsh barking note uttered singly or in series containing 2-8 notes (Fig. 3a-c View Figure 3 ). Eight calls (two single calls and three sets of couplets) of the holotype were of sufficient quality for analysis. Intervals between these note=call series were 28-37 s but many other frogs were heard calling at longer intervals of up to several minutes (S. Richards, personal observations). The number of pulses and length of calls is difficult to assess exactly, due to an echo possibly associated with their calling position inside small holes in tree trunks, but these eight notes=calls contain 8-17 pulses (mean 14.6 ± 3.2), some incompletely divided, lasting approximately 68-106 ms (mean 78.5 ± 12.4 ms). Intervals between calls produced in couplets are 812-910 ms (n = 3); dominant frequency is at 1.5 kHz and there is a weak fundamental frequency band at 0.6 kHz (Fig. 3b, c View Figure 3 ). An unvouchered specimen uttered three call series in a row consisting of 5, 8 and 7 calls. These calls were much shorter than those produced by the holotype (50-77 ms, mean 64.7 ± 6.4 ms, n=20) and intercall intervals were also shorter (240-349 ms, mean 266.9 ± 29.0 ms, n=17) than in the calls from the holotype.

Distribution.

Cophixalus gigiraensis is known with certainty only from Gigira (Hides) Ridge at the northern edge of the Kikori River basin in Hela Province, Papua New Guinea (Fig. 4 View Figure 4 ). It may also occur on nearby Mount Sisa ( Richards and Armstrong 2018; this location falls within the yellow square indicating the type locality in Fig. 4 View Figure 4 ), and on Mount Elimbari about 270 km east of the type locality ( Richards et al. 2021) but resolution of the status of those populations will require collection of additional material. If the Mount Elimbari population is confirmed to belong to C. gigiraensis then this will represent a large range extension and demonstrate that this species occurs in close proximity to its close relative C. riparius . Cophixalus gigiraensis was not found at lower altitudes elsewhere in the Kikori River basin, despite intensive surveys on the Agogo Range at altitudes between 1,000 and 1,700 m a.s.l. over many years.

Habitat and habits.

Cophixalus gigiraensis is an arboreal species that calls at night from ~15-30 m high in Nothofagus trees in mid-montane rainforest on karst terrain (Fig. 5 View Figure 5 ). It is not possible to safely climb these large trees so, although the species appears to be moderately abundant because numerous specimens were heard calling in the vicinity of the type locality in 2005 and again between 2015 and 2019, only one adult male and one juvenile have been captured. The adult male was calling from a height of about six metres at the entrance to a small hole in the vertical trunk of a large Nothofagus tree, while the juvenile was on low foliage in the forest understorey at night. The new species occurs in sympatry with six other microhylid frog species: Choerophryne brevicrus ( Günther & Richards, 2012), two undescribed Choerophryne species, Hylophorbus richardsi Günther, 2001, Oreophryne anamiatoi Kraus & Allison, 2009 and O. notata Zweifel, 2003, the limnodynastid Platyplectrum aganoposis (Zweifel, 1972) and the pelodryadids Litoria iris (Tyler, 1962) and L. vivissimmia Oliver, Richards & Donnellan, 2019.

Etymology.

The specific epithet Cophixalus gigiraensis refers to the type locality of this species, Gigira Ridge, otherwise known as Hides Ridge. Gigira is the local Huli Community’s name for this mountain.

Comparison with other species.

Only one other species of Cophixalus on New Guinea, C. riparius (Fig. 6 View Figure 6 ), reaches the size of C. gigiraensis . Cophixalus riparius was described by Zweifel in 1962 on the basis of a large series (224 specimens including the holotype) from the east slope of Mt Wilhelm in Western Highlands Province.

The holotype of C. gigiraensis differs biometrically from five randomly selected adult males and five adult females from the Porol Cophixalus riparius -series in having a longer head (HL/SUL 0.31 vs. 0.26-0.30), a higher HL/HW ratio (0.89 vs. 0.72-0.88), and a broader disc on the first toe (T1D/SUL 0.050 vs. 0.040-0.049; T1D/F1D 0.88 vs. 0.63-0.77). Males from the Porol Range are somewhat smaller than females (14 adult males measured 37.8-41.1 mm SUL and 10 adult females 41.2-47.1 mm SUL). Sexual size dimorphism is common among many anuran species but has rarely been recorded for species in the genus Cophixalus . This also suggests that C. gigiraensis may be slightly larger than C. riparius , but additional material of the new species is required to confirm this.

The advertisement calls of C. riparius and the new species are different (compare Figs 3 View Figure 3 , 7 View Figure 7 ). A series of four calls produced by a C. riparius (SAMA R71660) near the type locality on Mt Wilhelm are long, guttural croaks lasting 751-1031 ms (mean 927 ms) and contain 34-35 pulses. Calls in the series are separated by intervals of 4.5-5.4 s. A conspicuous feature of these calls is that pulse rate is much faster at the beginning of the call than at the end (Fig. 7a, b View Figure 7 ). Dominant frequency is at 1.55 kHz (Fig. 7c View Figure 7 ). A second call series produced by a C. riparius (SAMA R71701) on Mt Michael, about 70 km SSW of the type locality, is of poorer quality but in all pertinent respects agrees with calls produced by the near-topotypic animal. It also contains four long, rasping calls, and pulse rate declines markedly during each call. In contrast, the short, barking calls of C. gigiraensis last just 50-106 ms, contain 8-17 pulses, and pulse rate does not change during the call; call intervals within series last 0.24-0.90 s.

There also appear to be some ecological differences between the two species. The large series of C. riparius collected at the type locality by Hobart Van Deusen (> 200 specimens "amid grass, low shrubs, or boulders") and by Fred Parker in the Porol Range suggests that not only was the species abundant at those locations but that they were commonly encountered on or near the forest floor. In contrast, C. gigiraensis appears to be restricted to the mid and upper canopy of Nothofagus trees (Fig. 5 View Figure 5 ). The only animal encountered near the ground during 1.5 months of survey effort in the vicinity of the type locality, spread over several years (2015-2019), was the juvenile paratype. It was perched on a leaf approximately 2 m above the ground in the forest understorey. The adult holotype was the lowest-calling individual heard during numerous surveys, being only ~6 m above the forest floor. It was collected by binding several long saplings together to dislodge it from its arboreal calling perch.

Procoracoids in the genus Cophixalus

According to Parker (1934), Zweifel and Parker (1989), Burton and Zweifel (1995), Kraus and Allison (2000, 2009a), Kraus (2012) and Richards and Günther (2019) one of the key features defining the genus Cophixalus is the lack of procoracoids. During investigation of the ventral elements of the pectoral girdle to determine generic allocation of the new species, we discovered that the holotype of C. gigiraensis and several randomly chosen specimens of C. riparius from the Porol Range all have cartilaginous procoracoids. Their structure is similar to that of Oreophryne species wherein the procoracoids do not reach the scapulae. Lateral processes of procoracoids in a preserved and partly dissected specimen of C. riparius stained with alcian blue (ZMB 42612, Fig. 8a View Figure 8 ) and in two cleared and double stained specimens (ZMB 42593 and ZMB 42625) of this species are longer (reaching roughly to middle of the coracoid bone) and narrower than in the holotype of C. Cophixalus gigiraensis , and the shape of the proximal part is flat in C. riparius from the Porol Range but high (triangular) in C. gigiraensis (compare Fig. 8a, b View Figure 8 ). Based on the existing preparations it is not possible to determine whether the procoracoids are connected directly with the sternum or whether an omosternum is a component of the structure of proximal parts of the procoracoids.

It is possible that Zweifel (1962) did not detect these small and fragile elements in C. riparius because most specimens examined internally were done so via dissection, and only the absence of a clavicle was confirmed in two cleared and stained specimens ( Zweifel 1962). It is also possible that the Porol Range material does not represent C. riparius , but the large series from that location examined by us is indistinguishable from topotypic C. riparius . We do not speculate further on this discrepancy other than to note that further investigations of these structures in topotypic C. riparius are required. Studies of additional material are also required to determine whether the observed differences in the shape of the procoracoids between three C. riparius from the Porol Range and one C. gigiraensis are species specific.