Key to males of eastern Palearctic Ceratophyus species

Species distribution after Hillert & Král (2013), Nikolajev et al. (2016) and this paper.

1 Apical tooth of protibia simple; aedeagus as in Figs. 7–9; body length 18.0– 23.5 mm; China (Hebei, Heilongjiang, Inner Mongolia), Mongolia (Dornod, Hentiy, Sükhbaatar), Russia (Buryatiya, Zabaykalskiy Kray)..................................................................................................... Ceratophyus dauricus (Jekel, 1866)

- Apical tooth of protibia bifid. …......................................................................... 2

2 Elytral striae finely impressed, becoming finer to absent posteriorly, elytral intervals flat; aedeagus as in Figs. 10–12; body length 19.5–21.0 mm; China (Sichuan). ….................................... Ceratophyus kabaki Nikolajev, 2007

- Elytral striae distinctly impressed, visible to apex, elytral intervals convex (Fig. 1).................................. 3

3 Base of pronotal horn and areas laterally of it rugose; aedeagus as in Figs. 16–18; body length 18.0– 27.5 mm; China (Beijing, Gansu, Hebei, Inner Mongolia, Ningxia, Shaanxi, Shanxi, Qinghai and Xinjiang), Mongolia (Dornogovi)......................................................................................... Ceratophyus sinicus Zunino, 1973

- Base of pronotal horn and areas laterally of it simply punctate.................................................. 4

4 Setation of lateral margin of head, pronotum and ventral surface reddish brown; areas laterally of pronotal horn smooth (without punctures), elytral stria 5 usually reaching elytral base; aedeagus as in Figs. 13–15; body length 18.0– 27.5 mm; China (Xinjiang), Kazakhstan, Kyrgyzstan ............................... Ceratophyus mesasiaticus Medvedev & Nikolajev, 1974

- Setation of lateral margin of head, pronotum and ventral surface blackish (Figs 1–3); whole surface of pronotal disc distinctly, densely punctate (Fig. 1), elytral stria 5 usually not reaching base (Fig. 1); aedeagus as in Figs. 4–6; body length 18.5–22.0 mm; China (Gansu, Qinghai)........................................... Ceratophyus amdoensis Král & Jákl, new species