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

description: Cyclosomus acutangulus Kavanaugh and Cueva-Dabkoski, sp. nov.
Figures 5A, 7, 8, 13A, 14A, 15A, 16A, 17A, 21, and 23.
Type material. HOLOTYPE, a male, deposited in IOZ, labeled: “ CASENT 1015370 ”/ “ CHINA, Yunnan Province, Tengchong Co., Wuhe Township, Longjiang Bridge on Longchuanjiang, 1215 m,”/ “ N24.89889° / E098.66667° 30 October 2003, on beach, Liang H.-B. & Shi X.-C. collectors, LHB03-42”/ “HOLOTYPE Cyclosomus acutangulus sp. n. D.H. Kavanaugh & M. Cueva-Dabkoski 2022” [red label]. A total of 28 paratypes: five males and six females, in CAS, same label data as holotype, except first label [unique identifier label] different (“ CASENT 1012641” to “ CASENT 1012646 ” and “ CASENT 1015371 ” to “ CASENT 1015375 ”, respectively); six males and seven females, in IOZ. labeled: “ China, Yunnan, Tengchong, Wuhe, on beach of Longchuan river, N24.8941, E98.6750,” / “ 1215 m, 2015.3.22 N, Liu Y., Shi H.L. collectors”; one male and one female, in CAS and IOZ, labeled: “ China, Yunnan Prov., Tengchong, Wuhe, Longjiangqiao, beach, 24.89176°N / 98.67551°E / 1230 m, 2006.6.3, Kavanaugh D., Brett R. ”; one male and one female, both in NHMUK, labeled: “NE India, ASSAM, Bhalukpong, 26.v.-3.vi.2006. 27° 02’N 92° 35’E, 150m, P. Pacholátko leg.”/ “ L. Dembicky & P. Pacholátko BMNH {E} 2006- 48” Each paratype also bears the following label: “PARATYPE Cyclosomus acutangulus sp. n. D.H. Kavanaugh & M. Cueva-Dabkoski 2022” [yellow label].
Type locality. China, Yunnan, Tengchong County, Wuhe Township, Longchuan River at Longjiang Bridge.
Etymology. The species epithet, acutangulus, is a combination of the Latin adjective, acutus, meaning sharp or pointed, and the Latin noun, angulus, meaning corner or angle, here used as a noun in apposition. It refers to the apical angles of the pronotum, which are exceptionally narrow and pointed in members of this species.
Diagnosis. Adults of C. acutangulus can be distinguished from those of all other Cyclosomus species in Asia by the following combination of character states: Dorsal habitus as in Fig. 7A; pronotum (Fig. 13A) with anterior angles acute, narrow, lateral margins slightly to distinctly sinuate near anterior angles, lateral pale bands very narrow. Members of this species can be distinguished from those of other cyclosomines in the study area by the following combination of character states: Size larger, BL = more than 6.8 mm; pronotum (Fig. 13A) very broad, trapezoidal, almost as wide as elytra at humeral angles, distinctly widest at base; elytra broadly rounded apically, elytral color pattern as in Fig. 7A; front tarsomeres 1 to 3 markedly expanded laterally (Figs. 14A, 15A) in both males and females.
Description. (Fig. 7A). Size. Medium for genus, BL males = 7.1 to 8.2 mm, females = 6.8 to 8.2 mm.
Color. Head piceous except clypeus, labrum, and venter rufous or rufopiceous; antennae, mandibles, maxillae, and maxillary and labial palpi pale yellow-tan. Pronotum piceous with very narrow pale (yellow-tan or rufous) lateral band). Elytra mainly yellow-tan, with black to piceous markings; basal dark band extended laterally to humerus on base anterior to basal margination but only to interval 5 posterior to basal margination; interval 1 piceous to apex or nearly so, middle transverse dark band moderately thick, irregular, extended from intervals 2 to 6, 7, or slightly onto interval 8 in some specimens, portion on intervals 2 to 4 located at about three-fourths of elytral length and with spot on interval 3 offset anteriorly relative to those on intervals 2 and 4, portion on interval 5 to 7 or 8 near midlength of elytra and formed more or less in a transverse row; preapical dark spot present or absent, if present then small. Venter piceous laterally, rufo-piceous medially, elytral epipleurae and apical portion of last abdominal sternite pale yellow-tan. Legs pale yellow-tan.
Reflection, luster, and microsculpture. Dorsum and venter without metallic reflection. Head and pronotum dull, with microsculpture moderately impressed and comprised of isodiametric meshes; elytra slightly shiny with isodiametric meshes slightly less deeply impressed; venter with isodiametric to slightly transverse meshes shallowly impressed.
Head. Eyes large, hemispheric; antennae slightly short, extended only to basal one-fifth of elytra; clypeus bisetose; labrum with three pairs of setae in most individuals, four pairs in a few; mentum asetose, with a broad, apically emarginate medial tooth; submentum anteriorly with a single pair of setae.
Prothorax. Pronotum (Fig. 13A) broad but slightly narrow for genus (ratio PWM/PL = 2.12 to 2.43), trapezoidal, almost as wide as elytra at humeral angles, with anterior angles acute, narrow; apical margin markedly concave between anterior angles; lateral margins slightly to distinctly sinuate near anterior angles, otherwise smoothly curved or nearly straight; basal margin markedly bisinuate, lobate medially; anterior and lateral margination absent or extremely faintly impressed, basal margination distinct laterally, obsolete medially; midlateral setae inserted slightly anterior to mid-length, basolateral setae inserted on lateral edge of pronotum and just anterior to posterior angles. Prosternal intercoxal process moderately long, lanceolate, with complete margination.
Elytra. Broadly ovate, not or only slightly longer than wide (ratio EL/EW = 1.00 to 1.02), broadly rounded apically, humeri obtusely angulate; elytral striae deeply impressed throughout, elytral intervals slightly convex, smooth; parascutellar setiferous pore present at base of interval 1 near junction of striae 1 and 2; two discal setiferous pores present on interval three adjacent to stria 2, one near elytral mid-length and the other near apical one-third; apical seta present, inserted near apex of interval 3; umbilicate series comprised of 11 to 13 setae.
Legs. Tarsal claws, smooth, edentate. Males (Fig. 14A) and females with front tarsi similar in shape and width, but males with tarsomeres 1 to 3 with two rows of adhesive squamosetae (Stork 1980) ventrally (Fig. 15A), females without such setae; middle tarsi with tarsomeres 1 to 3 distinctly broader in males (Fig. 16A) than in females and with two rows of adhesive squamosetae ventrally (Fig. 17A), absent from females.
Male genitalia. Median lobe (Fig. 8) stout, smoothly arcuate, and with apical lamella tapered to a rounded point apically in lateral view, slightly sinusoidal and with apical lamella broadly rounded in dorsal view. Internal sac without evident spines.
Geographical variation. The two specimens from India lack a preapical dark spot found in specimens from the study area, but otherwise are similar.
Habitat distribution. Specimens of this species were collected mainly at night, with the aid of headlamps, on the upper edges of open sandy beaches along the Longchuan River (Fig. 21) at an elevation of 1215 m, where they were found active on the surface of dry or only slightly damp sandy substrate with no or only widely scattered and low vegetation. Members of this genus are known to burrow quickly into dry sand to hide when disturbed during the daytime (Nietner 1857).
Geographical distribution within the Gaoligong Shan. Fig. 7B. We examined a total of 29 specimens (13 males and 16 females) from the study area (see list of type specimens above).
Members of this species were collected only in the southwestern part of the study area (Core Area 6).
Overall geographical distribution. Fig. 23. At present, this species is known only from single areas in western Yunnan Province, China and northcentral Assam, India. These two areas 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 northeasternmost India, at low elevations (below 1500 m) along rivers draining the western and southern slopes of the Himalayan ranges in these areas, respectively.
Geographical relationships with other Cyclosomus species. No other species of Cyclosomus has been recorded from the Gaoligong Shan region, but members of C. acutangulus were found syntopic with C. flexuosus members at the locality in Assam [NHMUK], which is the easternmost known locality for the latter species and the westernmost for C. acutangulus. Other cyclosomine species found syntopic with C. acutangulus at the type locality along the Longchuan River include Tetragonoderus elegans and T. punctatus.
description: Published as part of Kavanaugh, David H., Cueva-Dabkoski, Mollie & Liang, Hongbin, 2023, Inventory of the Carabid Beetle Fauna of the Gaoligong Mountains, western Yunnan Province, China: Species of the Tribe Cyclosomini Laporte, 1934 (Coleoptera: Carabidae), with Descriptions of Two New Species., pp. 451-491 in Proceedings of the California Academy of Sciences 67 (20) on pages 459-462, DOI: 10.5281/zenodo.11067293