Chimerothalassius Shamshev & Grootaert, 2003

Brooks, Scott E. & Cumming, Jeffrey M., 2018, New species of Chimerothalassius Shamshev & Grootaert (Diptera: Dolichopodidae: Parathalassiinae) from the West Indies and Costa Rica, Zootaxa 4387 (3), pp. 511-523 : 512-513

Genus Chimerothalassius Shamshev & Grootaert

Chimerothalassius Shamshev & Grootaert, 2002: 131 . Type-species: Chimerothalassius ismayi Shamshev & Grootaert , by original designation.

Diagnosis. Chimerothalassius is distinguished from other parathalassiine genera by the following characters: head with gena scarcely projected below eye, pair of fronto-orbital bristles close to base of antennae, mouthparts directed ventrally with fleshy labellum, palpus elongate and narrow with long ventral bristles or broadly subtriangular and lacking ventral bristles; thorax with prosternum fused to proepisternum forming precoxal bridge, scutellum with 1 pair of strong dorsally directed bristles near apex; legs with fore coxa usually bearing prominent basal bristle or several long setae, lacking field of short stout spinose setae on anterior surface, tarsomere 5 of each leg with medial apical projection; wing with costa bearing double row of short spine-like setae along anterior margin, R1 short reaching costa before middle of wing, crossvein bm-m complete or incomplete, cell dm absent without veins M2 and dm-m, CuA rounded, cell cua convex apically, CuA+CuP absent or vestigial, anal lobe not developed; male terminalia with hypopygium small, right and left epandrial lamellae apparently fused with hypandrium, left epandrial lamella with non-articulated ventral process, postgonites cradling base of phallus with left and right lobes protruding out from between dorsal and ventral surstylar lobes, cerci short and symmetrical or nearly so; female abdomen with apical segments retracted into segment 5, terminalia with tergite 10 bearing acanthophorite setae, cercus narrowly rounded apically with prominent apical or preapical seta.

Distribution and habitat. Chimerothalassius is now known from coastal localities on the Caribbean islands of Dominica and Montserrat ( Chimerothalassius runyoni sp. nov.), the western coast of Costa Rica ( Chimerothalassius sp.) ( Fig. 19 ), and South Island, New Zealand ( C. ismayi Shamshev & Grootaert ) ( Brooks & Cumming 2011, fig. 12A). The genus appears to be restricted to rocky or stony habitats of coastal beaches ( Fig. 1 ).

Remarks. Shamshev & Grootaert (2002) noted great sexual dimorphism in the chaetotaxy of the palpus and foreleg of the type species, C. ismayi , which is not seen in the newly described species, Chimerothalassius runyoni sp. nov. (see Description and Remarks for this species below). We have examined specimens of two additional undescribed species from South Island, New Zealand (1 male, UGIC; 1 female, USNM) and comparision with a male of C. ismayi from Port Levy (UGIC), suggests that the type series of C. ismayi (8 males and 14 females) may be comprised of two different species, one for each sex. Even though the type specimens of C. ismayi were all collected from a single stony beach on the same day, we suspect that the holotype and remaining male paratypes belong to C. ismayi , whereas the female paratypes belong to one of the additional undescribed species.

Recognition of the two new species from New Zealand, and the new species from Costa Rica brings the total number of known species of Chimerothalassius to five; however, formal description of these species must await the collection of additional specimens.

Figures

FIGURE 19. Known distribution of New World Chimerothalassius species.

FIGURES 1–2. Type locality habitat photograph and female habitus of Chimerothalassius runyoni sp. nov. 1. Rocky coastal type locality at Woodlands Beach, Montserrat (photo by Justin Runyon). 2. Female specimen from Layou River mouth, Dominica collected by W.W.Wirth, January 9 th, 1965.