Chasmogenus sinnamarensis, 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 sinnamarensis sp. nov. Figures 15F , 17

Type material.

Holotype (male): "French Guyana:/ Road Petit Saut,/ Crique Eau Claire/ xii.2002-1.2003./ M. Balke leg.", "DNA VOUCHER/ Extraction #/ SLE-77" (SEMC). Paratypes (3): same data as holotype (3 exs., SEMC including DNA Voucher SLE517).

Differential diagnosis.

Chasmogenus sinnamarensis is similar in morphology and size to C. berbicensis , but can be differentiated from that species by the form of the mentum, which possesses an elevated ridge posterior to the anteromedial notch. This mentum character is also shared with the Andean species C. bariorum , C. cuspifer , and C. lineatus , however these species either have a distinctly toothed mesoventrite (not toothed in C. sinnamarensis ) or clypeus without an anteromedial emargination (emarginated in C. sinnamarensis ).

Description.

Size and color. Total body length 4.9-5.0 mm. Body form elongate oval with slightly curved lateral margins. Dorsum of head dark brown. Pronotum dark brown with slightly paler lateral margins, elytra uniformly dark brown. Head. Ground punctation on head fine. Clypeus with anteromedial emargination, which exposes broadly rounded shaped gap between clypeus and labrum. Mentum moderately depressed in anterior half with rounded anteromedial notch followed by rounded elevated ridge just posterior of the notch. Maxillary palps long, longer than width of head immediately posterior to eyes. Thorax. Ground punctation on pronotum fine. Prosternum mildly tectiform. Mesoventrite with very weak elevation forming a posteromedial longitudinal carina. Metafemora densely and uniformly pubescent in basal nine-tenths. Aedeagus. Aedeagus (Fig. 15F ) with median lobe widest at base, nearly parallel sided in basal three-quarters, then narrowing abruptly to form an acute triangular apex which is even with or slightly extends beyond the apex of the parameres. Sclerite of the median lobe not expanded. Gonopore situated less than half of one gonopore width below the apex of the median lobe. Parameres symmetrical, with outer margins straight, with apex very slightly inwardly curved and bluntly rounded. Basal piece long, ca. as long as the length of the parameres.

Etymology.

Named after the Sinnamary River, close to where it was collected. To be treated as a noun in apposition.

Distribution.

Only known from the type locality in French Guiana (Fig. 17 ).

Biology.

This species was collected from a clear water creek.

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 17. Distribution of Chasmogenus spp.