Cyclosomus acutangulus Kavanaugh & Cueva-Dabkoski
Creators: name: Kavanaugh, David H.
name: Cueva-Dabkoski, Mollie
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Carabidae
Cyclosomus
Cyclosomus acutangulus

description: Cyclosomus acutangulus Kavanaugh & Cueva-Dabkoski
Figures 2, 4, 14A, 15A, 16A, 17A, 18A, 20
Cyclosomus acutangulus Kavanaugh & Cueva-Dabkoski, 2023: 459. HOLOTYPE, a male, deposited in IOZ. Type locality: China, Yunnan, Tengchong County, Wuhe Township, Longchuan River at Longjiang Bridge.
Diagnosis. Adults of C. acutangulus can be distinguished from those of all other Cyclosomus species in Asia by the following combination of character states: Body size medium for genus, males = 7.1 to 8.2 mm, females = 6.8 to 8.2 mm; pronotum (Fig. 14A) with anterior angles narrow, distinctly acute, lateral margins slightly to distinctly sinuate near anterior angles, disk dark piceous to black, with lateral pale bands well-defined and very narrow; free apex of prosternal intercoxal process long (as in Fig. 15C); elytra with preapical dark spot present or absent; elytral epipleura with long setae only in humeral and subhumeral areas, setae in apical two-thirds distinctly shorter; median lobe of male genitalia with shaft evenly arcuate and tapered subapically, with apical lamella thick, slightly deflected ventrally in lateral aspect (Fig. 16A), shaft slightly broadened for most of its length, then tapered to base of short, narrow, smoothly rounded apical lamella in dorsal aspect (Fig. 17A).
Members of C. acutangulus are most similar to those of C. suturalis but differ from the latter in having the pronotum with anterior angles narrow and markedly acute, lateral margins slightly to distinctly sinuate near the anterior angles, and the lateral pale bands well-defined and very narrow. Males of the two species also differ in the curvature of the median lobe in lateral aspect (compare Fig. 16A with Fig. 16G) and in shape of the apical lamella in dorsal aspect (compare Fig. 17A with Fig. 17G).
Habitat distribution. In Yunnan, specimens of this species were collected only at night, with the aid of headlamps. They were found active on the surface of dry or only slightly damp sandy substrate, with no or only widely scattered and low vegetation, on the upper edges of open sandy beaches along the Longchuan River (Fig. 18A) and Nanwanhe at elevations of 1215 and 931 m, respectively.
Geographical distribution. We examined a total of 30 specimens (14 males and 16 females) from the following localities: CHINA: Yunnan: Longchuan County, Zhangfeng (Nanwanhe, 24.1959°/97.7844°, 931 m, 25 March 2015, Y. Liu and H.L. Shi collectors [one female; IOZ]); Tengchong County, Wuhe Township (Longjiang Bridge on Longchuanjiang, 24.89889°/98.66667°, 1215 m, 30 October 2003, H.B. Liang and X.C. Shi X collectors [six males and six females]), (beach of Longchuan River, 24.8941 / 98.6750 °, 1215 m, 22 March 2015, Y. Liu and H.L. Shi collectors [six males and seven females; CAS and IOZ]), (Longjiangqiao, 24.89176°/98.67551°, 1230 m, 3 June 2006, D.H. Kavanaugh and R.L. Brett collectors [one male and one female]). INDIA: Arunachal Pradesh: Bhalukpong (27.0333°/92.5833°, 150 m, 26 May-3 June 2006, P. Pacholátko collector [one male and one female; NHMUK]).
At present, this species is known only from one locality in northeastern India and two localities in western Yunnan Province, China (Fig. 20). The localities in India and Yunnan are about 650 km apart, and it is likely that this species occurs also in suitable habitats in the intervening region, including northern Myanmar (Kachin State), and northeastern India (Arunachal Pradesh and Nagaland states), at low elevations (below 1500 m) along rivers draining the western and southern slopes of the Himalayan ranges in these areas, respectively.
Geographical variation. The specimens from the locality in northeastern India lack the preapical dark spot found in specimens from the localities in Yunnan, but otherwise are similar.
Geographical relationships with other Cyclosomus species. Members of C. acutangulus have been found syntopic with those of C. flexuosus at Bhalukpong, Arunachal Pradesh, India [NHMUK] but nowhere with any other species. The geographical ranges of C. acutangulus and C. suturalis may overlap slightly in westernmost Yunnan. In fact, both species have been found on sandy beaches along the Longchuan River (Longchuanjiang) but at different localities more than 150 km apart along the river course and at different elevations (the former above 1200 m and the latter at 734 m). Otherwise, the range of C. acutangulus is not known to overlap with that of any other Cyclosomus species.
description: Published as part of Kavanaugh, David H. & Cueva-Dabkoski, Mollie, 2023, A Review of Genus Cyclosomus Latreille (Coleoptera: Carabidae: Lebiinae: Cyclosomini) in Asia., pp. 493-537 in Proceedings of the California Academy of Sciences 67 (21) on pages 501-503, DOI: 10.5281/zenodo.11512952