Nipponocercyon Sato , 1963

Fikacek, Martin, Ryndevich, Sergey & Jia, Fenglong, 2012, An aberrant species of Nipponocercyon from Sichuan, China (Coleoptera, Hydrophilidae, Sphaeridiinae), ZooKeys 214, pp. 13-27 : 15-16

Nipponocercyon Sato, 1963

Adapted differential diagnosis.

The inclusion of Cryptopleurum sichuanicum into Nipponocercyon (see below) requires a modification of the differential diagnosis of the genus as follows:

Head without transverse interantennal ridge; eyes small, separated by 9 × of one eye; mentum weakly bisinuate on anterior margin; antennae with 9 antennomeres; maxilla with or without sucking disc in males; maxillary palpomere 2 strongly widened distally; posterior tentorial pits minute; pronotum evenly convex, lateral margin not deflexed or slightly deflexed; transverse row of larger punctures along posterior margin of pronotum absent (large areas without microsculpture in Nipponocercyon sichuanicus may actually resemble enlarged punctures on the first view, but the punctures are as large as those in disc when examined in detail, see Fig. 8); median portion of prosternum weakly to distinctly separated from lateral portions, bearing coarse setiferous sculpture; median portion of prosternum carinate medially (carina distinct in Nipponocercyon shibatai , partly obliterated by the sculpture but still apparent in Nipponocercyon sichuanicus , compare Figs 12 and 15); prosternal process wide, deeply excised; antennal grooves moderately large to large, not reaching lateral margin of hypomeron (Figs 11, 14); anteroventral margin of prothorax with a small denticle on the contact of prosternum and hypomeron; profemur with elongate ventral depression along anterior margin; elytron with 10 punctural series; elytral intervals flat or highly convex; lateral margins of elytra not denticulate nor serrate; mesoventral cavities for reception of procoxae large, reaching mesocoxae; preepisternal elevation subpentagonal, widely contacting metaventral process, median portion of metaventrite slightly to very distinctly elevated; postcoxal ridge lying parallel to posterior margin of mesocoxal cavity, not overlapping to lateral margin of metaventrite; lateral portions of metaventrite with coarse punctation (smaller punctures may be intermixed or absent); metanepisternum narrow, but distinct throughout; abdominal ventrite 1 carinate medially, with coarser punctation than ventrites 2-5; phallobase asymmetrical, much shorter than parameres; gonopore situated in basal half of median lobe; male sternite 9 with median tongue-like projection; male sternite 8 without median projection.

A few characters listed as diagnostic for Nipponocercyon by Hoshina and Fikáček (2010) have to be excluded as they are only present in Nipponocercyon shibatai but absent from Nipponocercyon sichuanicus : antennomeres 7-8 with groups of peg-like sensilla ventrally; metaventrite with two short mesal ridges anteriorly (but remnants of ridges seem to be retained in some specimens of Nipponocercyon sichuanicus ; see the structure indicated as mtr in Fig. 20).

Recognition.

By the combination of median portion of the prosternum differentiated from lateral portions, subpentagonal preepisternal elevation of the mesothorax widely contacting the metaventrite, large mesothoracic cavities for reception procoxae (reaching to anterior margin of mesoxocal cavity) and metanepisternum well developed both anteriorly and posteriorly, Nipponocercyon is most similar to the genus Australocyon Hansen, 1990. It may be easily distinguished from the Australian and Neotropical species of Australocyon by the male sternite 9 with tongue-like median portion (Fig. 4c), and male sternite 8 without median projection; from Australocyon pilocnemoides group it may be distinguished by the undifferentiated surface of the subpentagonal mesoventral plate (with a semicircular median portion defined by a wide bead in Australocyon pilocnemoides group, see Fig. 6 in Hansen (2003)), unmodified antennal morphology (in contrast to long antennae with prolonged antennal club pointed at apex and antennomere 6 not cup-like in shape in Australocyon pilocnemoides group), and the excavate ventral surface of profemora (without any sculptured depression in Australocyon pilocnemoides group).

When the size of mesoventral cavities for reception of procoxae is not taken into consideration, Nipponocercyon may resemble other megasternine genera with small subpentagonal mesoventral plate, clearly defined prosternal plate and male sternite 9 tongue-like medially (characters distinguishing the respective genus from Nipponocercyon are listed in parentheses: Agna (prosternal plate without deeply excised prosternal process, antennal grooves very small and angular in shape, profemur without sculptured depression); Bolbonotum and Kahanga (elytral grooves deep and wide, reaching total base of elytra, prosternal plate projecting both anteriad and posteriad, profemur without ventral impression, mesoventral plate rhomboid when examined in detail, gonopore apical), Deltostethus (mesoventral plate with wide marginal bead, profemur without ventral depression, gonopore apical), and Pelocyon (metavetrite with complete femoral lines, prosternal plate longer than wide). Nipponocercyon sichuanicus may resemble some species of the genera Cryptopleurum , Pachysternum and Cyrtonion by its large antennal grooves, large grooves for reception of procoxae, reduced epipleura and strongly sculptured body. See below under that species for characters distinguishing it from the mentioned genera.

Composition and distribution.

The genus now includes two species, one distributed in Kyushu, Shikoku and the southern part of the Honshu, the other occuring in high altitudes of the mountain ranges in the Chinese province of Sichuan (Fig. 23).

Key to Nipponocercyon species