Meristogenys stenocephalus

Meristogenys stenocephalus. We recorded calls of four individuals of this species at Melanggong sub-station on 7 March 2023. Calls were emitted sporadically, with several minutes between bouts of calling, and several calls within approximately 10 s during each bout. All males were calling on vegetation within 1.5 m of the ground, and within 3 m of the stream edge, in the stretch of stream immediately visible from the park entrance. Males started calling around dusk, and calling activity seemed to be strongest in the first three hours after dusk. There was no rain during recording hours. Other species active and calling in the same vicinity included Huia cavitympanum, Leptolalax pictus, and Meristogenys orphnocnemis. In the 15 calls we recorded from four individuals, dominant frequencies ranged from 2540–4716 Hz with frequency modulation between 666–6348 Hz (supplementary material). We identified four call types (Table 3; Fig. 3): type A contains one or two harmonics and starts around 6000 to 7300 Hz ending around 2200 to 2500 Hz; type B does not contain harmonics and shows very minimal frequency modulation, starting around 3000 Hz and ending around 2400 Hz; type C is slightly concave, starting between 3000 and 4500 Hz and ending around 2100 to 3100 Hz; type D exhibits a short decline starting above 8200 Hz and ending below 2900 Hz. Like M. stigmachiulus, little has been published about this species beyond its initial description. We noted that while existing records state that this species has “underside of head and body whitish with dark dots on throat and chest” (Inger et al., 2017) (https://www.frogsofborneo.org/frogs/ ranidae/meristogenys/stenocephalus), we found these dots only appear during the day or after preservation, and during normal nocturnal observations the chest and throat are white. Further, males of this species were previously reported as 48–60 mm SVL and females 76–87 mm SVL (Inger et al., 2017), but our observations show males of this species to get up to 64 mm SVL and females to 90 mm SVL (Sheridan et al., 2023). Most notably, no existing descriptions of this species mention the green dorsal colouration with reddishbrown to bright red legs that we commonly observed (Fig. 4). While colouration varies between individuals, and within an individual from day to night, we found this colouration to be quite common and distinctive during nocturnal surveys, and helpful in distinguishing it from other members of this genus. Further, this species is described as having ‘centre of tympanum dark without light spot’ (https://www.frogsofborneo.org/frogs/ranidae/meristogenys/ stenocephalus), but we found the centre of the tympanum to match the colouration on the side of the head, which was often beige or pale, not dark.