Chasmogenus tafelbergensis, Smith & Short, 2020

Smith, Rachel R. & Short, Andrew Edward Z., 2020, Review of the genus Chasmogenus Sharp, 1882 of northeastern South America with an emphasis on Venezuela, Suriname, and Guyana (Coleoptera, Hydrophilidae, Acidocerinae), ZooKeys 934, pp. 25-79 : 25

Chasmogenus tafelbergensis sp. nov. Figures 16A-D , 17 , 21C

Type material.

Holotype (male). "Suriname: Sipaliwini District/ 3°55.600'N 56°11.300'W, 600m/ CSNR: Tafelberg Summit, nr/ Augustus Creek Camp, pools &/ creeks on trail into Arrowhead/ basin; leg. Short & Bloom. 17.viii.2013; SR13-0817-01A", "HOLOTYPE/ CHASMOGENUS/ tafelbergensis sp. n./ des. Smith & Short", "DNA VOUCHER/ Extraction #/ SLE-1825". (NZCS).

Differential diagnosis.

The strongly asymmetrical parameres, highly reduced basal piece, and extraordinary depth of the aedeagus (Fig. 16A-D ) will easily separate this species from all others except C. ignotus , from which it may be differentiated by its narrower aedeagal profile. Examination of the aedeagus is the only way to definitively identify this species. Unassociated females may not be determined with certainty.

Description.

Size and color. Total body length 3.3 mm. Body form elongate oval with slightly curved lateral margins. Dorsum of head bicolored, frons dark red-brown, clypeus and labrum dark orange-brown. Pronotum and elytra uniformly dark brown. Head. Ground punctation on head moderately coarse. Clypeus with anteromedial emargination, which exposes angulate gap between clypeus and labrum. Mentum moderately depressed in anterior half with anteromedial subtriangular notch. Maxillary palps long, longer than width of head immediately posterior to eyes. Thorax. Ground punctation on pronotum moderately coarse. Prosternum mildly tectiform. Mesoventrite with very weak elevation forming a posteromedial longitudinal carina. Metafemora densely pubescent in basal six-sevenths. Aedeagus. Aedeagus (Fig. 16A-D ) with median lobe highly modified, appearing as a narrow subparallel-sided strap and partly rotated laterally, with apex extending to the apex of the parameres. Sclerite of the median lobe extremely well developed and appearing as a thin curved strut that extends the full length of the genitalia. Gonopore oriented laterally (Fig. 15B ); situated twice gonopore width below the apex of the median lobe. Parameres asymmetrical, with left paramere wider than right paramere; outer margins of parameres strongly sclerotized, with the sclerotized region on the right paramere thicker than the left. Aedeagus, especially the parameres, thickened, such that it takes on a highly three-dimensional appearance (Fig. 16B, C ); in lateral view widest in basal half, with dorsal surface strongly convex, with ventral surface nearly flat. Basal piece short, less than half the length of the parameres; partly obscured by the strongly sclerotized and enlarged base of the median lobe and parameres.

Etymology.

Named after Tafelberg, a low elevation sandstone tepui in central Suriname. To be treated as a noun in apposition.

Distribution.

This species only known from the summit of Tafelberg Tepui in Suriname (Fig. 17 ).

Biology.

The single specimen of this species was collected from forested pools which contained extremely dense layers of leaf litter detritus (Fig. 21C ).

Figures

Figure 15. Aedeagi of Chasmogenus spp. A-D C. pandus A dorsal view (Suriname) B side view (Suriname) C specimen from French Guiana D specimen from Brazil E C. ligulatus F C. sinnamarensis G C. undulatus H, I C. acuminatus H specimen from Suriname I specimen from Guyana. Scale bars: 0.25 mm.

Figure 16. Aedeagi of Chasmogenus spp. A-D C. tafelbergensis A dorsal view B side view C side view D ventral view E-H C. ignotus E dorsal view F side view G side view H ventral view. Scale bar: 0.25 mm.

Figure 17. Distribution of Chasmogenus spp.

Figure 21. Habitat of Chasmogenus spp in Suriname. A Type locality and habitat for C. brownsbergensis, Brownsberg Nature Park (collecting event SR 12 - 0804 - 03 A) B type locality and habitat for C. ligulatus, near Mt. Kasikasima (collecting event SR 12 - 0320 - 02 A) C type locality and habitat for C. tafelbergensis, summit of Tafelberg tepui (collecting event SR 13 - 0817 - 01 A) D type locality and habitat for C. schmits, S of Kwamala along the Kutari River (collecting event SR 10 - 0316 - 01 B) E habitat for C. acuminatus, Central Suriname Nature Reserve, Raleighvallen (collecting event SR 16 - 0316 - 01 B) F habitat for C. guianensis, upper Palumeu River, (collecting event SR 12 - 0311 - 01 A).