Coimedon, Assing, 2015

Assing, Volker, 2015, Two new genera of Medonina from China and Japan (Coleoptera: Staphylinidae: Paederinae), Linzer biologische Beiträge 47 (1), pp. 191-206: 201-204

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Coimedon   nov.gen.

Type species: Lithocharis dissimilis SHARP, 1874  

E t y m o l o g y: The name is composed of the first three letters of the Latin verb coire (to join, to unite) (alluding to the contiguous gular sutures) and the generic name Medon. The gender is masculine.

D e s c r i p t i o n: Species of relatively small size (approximately 4 mm); habitus somewhat intermediate between that of Orsunius   and Acanthoglossa.

Head ( Fig. 31 View Figs 30-38 ) transverse and relatively large in relation to body size, with marked posterior angles, and with somewhat granulosely umbilicate punctation. Antenna ( Fig. 34 View Figs 30-38 ) relatively short and not distinctly incrassate apically; antennomeres VI-X as broad as long or weakly transverse. Ventral aspect ( Fig. 32 View Figs 30-38 ) with moderately dense umbilicate punctation; gular sutures contiguous in posterior half. Labrum ( Fig. 35 View Figs 30-38 ) transverse; general outline of anterior margin convex; middle of anterior margin with U-shaped incision, on either side of this incision with several projecting pale setae, insertions of these setae shaped like small denticles (giving the impression of a denticulate anterior margin). Both mandibles with two molar teeth ( Figs 31-32 View Figs 30-38 ). Maxillary palpus ( Fig. 39 View Figs 39-42 ) four-jointed, palpomeres moderately II and III slender; apical palpomere minute and needle-shaped. Labial palpus three-jointed, shaped as in Fig. 40 View Figs 39-42 . Ligula ( Figs 40-41 View Figs 39-42 ) with two short and widely separated membranous lobes, each of them basally with two minute, barely visible sensillae.

Pronotum ( Fig. 31 View Figs 30-38 ) rather small in relation to head, strongly transverse, with sharply marked anterior and weakly marked posterior angles; punctation distinctly and rather coarsely granulose ( Fig. 36 View Figs 30-38 ); midline without distinct impunctate band. Prosternum with long median keel ( Fig. 32 View Figs 30-38 ).

Elytra with dense punctation. Process of mesoventrite with median keel, apically acute, and reaching half-way between mesocoxae. Protarsomeres I-IV unmodified, longer than broad. Metatarsomere I longer than II, but shorter than combined length of II and III.

Abdomen with moderately fine and moderately dense punctation; microsculpture very shallow (visible only at high magnifications) and composed of scale-shaped meshes; tergites III-VI and sternites III-VI with distinct basal impressions.

3: sternite VII without pronounced modifications; sternite VIII oblong and unmodified ( Fig. 42 View Figs 39-42 ); aedeagus ( Figs 37-38 View Figs 30-38 ) weakly sclerotized, dorso-ventrally more or less distinctly compressed, with apically acute ventral process, and with strongly sclerotized internal structures.

C o m p a r a t i v e n o t e s: Coimedon   somewhat resembles Orsunius   , Granimedon, Acanthoglossa, and Hypomedon   in size and habitus, but differs from all of them by the contiguous gular sutures, the shape and chaetotaxy of the labrum, and the aedeagal morphology. The generally similar shape of the mandibles, the shape of the antennae, and the morphology of the labium suggest that Coimedon   is more closely allied to Acanthoglossa and Hypomedon than to Orsunius   and Granimedon   . It is additionally distinguished from these genera as follows:

from Acanthoglossa by the filiform antennae (Acanthoglossa: preapical antennomeres distinctly transverse), the granulose punctation of the head, the longer molar teeth of the mandibles and the absence of additional minute teeth (Acanthoglossa: each mandible usually with two larger and an additional smaller tooth), the more slender maxillary and labial palpi, the undilated protarsomeres I-IV, the much more slender meso- and metatarsomeres I-IV, the different shape and different punctation of the pronotum (Acanthoglossa: pronotum less transverse, distinctly narrowed posteriad, and with completely rounded posterior angles; punctation granulose; at least with a rudiment of an impunctate median band), the distinct anterior impression on the abdominal tergite VI, and the strongly convex posterior margin of the male sternite VII;

from Hypomedon, with which it shares the presence of two molar teeth on both mandibles, by a more robust body with a larger head, the shape of the antennae (Hypomedon: preapical antennomeres distinctly transverse), the absence of microsculpture on the forebody (Hypomedon: head and pronotum with pronounced microsculpture), the much denser, coarser, and granulose punctation of the head and pronotum, the much more transverse pronotum, the more slender protarsomeres I-IV (Hypomedon: protarsomeres I- IV not distinctly dilated, but noticeably transverse), the much deeper anterior impressions of the abdominal tergites III-VI, and the strongly convex posterior margin of the male sternite VIII;

from Orsunius   by the antennal morphology ( Orsunius   : antennae longer), the different morphology of the mandibles ( Orsunius   : left mandible with three, right mandible with three, rarely four, molar teeth), the shape and chaetotaxy of the ligula ( Orsunius   : with longer lobes and numerous stout sensillae), the more transverse pronotum, the undilated protarsomeres I-IV ( Orsunius   : dilated in most species), the presence of a distinct anterior impression on the abdominal tergite VI, and the shape of the male sternite VIII ( Orsunius   : with posterior excision);

from Granimedon   , with which it shares a male sternite VIII without posterior excision, by the relatively larger head, the much less dense punctation of the forebody, the antennal morphology ( Granimedon   : longer and more slender), the different morphology of the mandibles ( Granimedon   : left mandible with three, right mandible with four pronounced molar teeth), the shape and chaetotaxy of the ligula ( Granimedon   : with longer lobes and numerous stout sensillae), the more transverse pronotum, the presence of a median keel on the mesoventrite, the pronounced anterior impressions on the abdominal tergites IV- VI ( Granimedon   : tergites III-V with very shallow, tergite VI without anterior impression).

For illustrations of Granimedon, Acanthoglossa, Hypomedon   , and Orsunius   see Figs 1- 29 View Figs 1-8 View Figs 9-12 View Figs 13-20 View Figs 21-29 and ASSING (2009, 2011, 2014, 2015), respectively.

D i s t r i b u t i o n: The type locality of Coimedon dissimilis   , at present the sole representative of the genus, is situated in Kyushu, South Japan.


Mykotektet, National Veterinary Institute