Mark 4

From May 2010 to October 2014, photo-identification (photo-ID) surveys were conducted using an 8-m boat powered by one 140HP 4-stroke outboard engine. The surveys were undertaken year-round, weather permitting, with sea state ≤ 3 in Beaufort scale, following similar procedures as described by Karczmarski et al [65 ] and whenever possible (weather permitting) they covered the entire study area. Once a dolphin or group of dolphins was sighted, the animals were approached at low speeds (< 6 km/h) and group size, age-class composition and behavioural state were recorded. Subsequently, the dolphins were photographed by at least two researchers, aiming at close-ups of their dorsal fins and upper bodies, using digital cameras Canon EOS 1D Mark III and/or Mark IV equipped with 100-400mm f/4.5–5.6 zoom lenses, with a conscious effort to capture both left and right body sides of all group members regardless of distinctiveness, age-class or behaviour of the individuals.

The specimens were collected in northwestern China from July to August 2016–2017 using sweep netting, light trapping, and Malaise trapping. The specimens were studied and illustrated with a ZEISS Stemi 2000-c stereomicroscope; the photo illustrations were taken under a Canon Mark IV with Canon MP-E 65 mm lens. The descriptions were based on specimens preserved in 95% alcohol. Genitalic preparations of males were made by macerating the apical abdomen in cold 10% NaOH for 12–15 hours. After examination, preparations were transferred to fresh glycerin for preservation and stored in a microvial pinned below the specimen. The morphological terminology mainly follows McAlpine (1981) . Type specimens are deposited in the Entomological Museum of China Agricultural University (CAU), Beijing, China.