Tmesiphodimerus Coulon and Yin

Yin, Zi-Wei, Coulon, Georges & Li, Li-Zhen, 2013, Description of two new species of the genus Tmesiphodimerus gen. n. (Coleoptera: Staphylinidae: Pselaphinae) from South Asia, Zootaxa 3694 (4), pp. 336-342 : 337-339

Tmesiphodimerus Coulon and Yin , new genus

( Figs 1–4 )

Type species: Tmesiphodimerus sinensis Yin and Coulon , new species (here designated).

Diagnosis. Head with small vertexal foveae, lacking frontal fovea; lateral branches of U-shaped cephalic sulci interrupted by an ocular plate (here termed) starting from the inner margin of the eyes. Maxillary palpomeres II and III each bearing an apicolateral tuft of short setae. Pronotum with small median and lateral antebasal foveae. Abdomen with tergite V longest.

Description. Head transverse ( Figs 1 A, B), frontal rostrum short and wide, slightly prominent antennal tubercles separated by wide, shallow median sulcus; with nude, punctiform vertexal foveae, lacking frontal fovea ( Fig. 2 A); lacking postantennal notches at lateral margins; lateral postantennal pits developed into wide setose Ushaped sulci ventral to antennal insertions ( Fig. 2 B), sulci interrupted by broad, smooth ocular plates ( Figs 2 D, 4B); lacking ocular-mandibular carinae; postgenae rounded laterally, with tufts of dense, thick setae; gula ( Fig. 2 C) slightly swollen, gular foveae in small transverse impression, lacking gular carina or sulcus. Antennae with 11 antennomeres, clubs formed by apical four antennomeres. Maxillary palpi ( Figs 3 B, 4C) moderately large, palpomeres I minute, II elongate, pedunculate in basal halves, slightly to strongly prolonged apicolaterally with apical tuft of short setae, lateral margins of palpomeres III strongly lobed laterally, with tuft of short setae; IV broadly rounded laterally; palpal cone fused.

Pronotum ( Figs 2 E–G) with small, nude lateral and median antebasal foveae; disc with broadly rounded hump. Prosternite lacking paranotal carinae; with deep lateral procoxal foveae.

Each elytron ( Fig. 2 H) with two large basal foveae and small subbasal fovea; shallow, broad discal stria extending posteriorly to nearly two-thirds elytral length; sutural stria complete; lacking subhumeral fovea and marginal stria; lateroapical cleft widely notched.

Mesoventrite ( Fig. 2 I) with prepectal foveae widely separated, median mesoventral foveae merged into wide opening, widely forked and deeply inserted internally, lateral mesoventral foveae broad, reaching to lateral branches of median mesoventral foveae; lateral mesocoxal foveae present; metaventrite lacking foveae, apex with looped notch.

Legs simple, lacking spines; profemora thickened, setose ventrally; protibiae thickened to middle, slightly arcuate at apical third; third tarsomeres longest, second tarsomeres two-thirds length of third ones; tarsal claws subequal.

Abdomen ( Figs 2 J–L) with tergite V (second visible tergite) longest; tergite IV with deep, setose basal sulcus forming large pockets at lateral endings, lacking mediobasal fovea, basolateral foveae in sockets, with median and discal carinae extending through tergal length; tergite V with basal sulcus shallower and thinner, basolateral foveae present, with short lateral carinae and complete median carina; tergites VI–VII with basolateral foveae. Sternite V (third visible sternite) longest, IV–V with deep, setose basal sulci, basolateral foveae developed as cuticular pockets; sternite IV with lateral carinae complete, V with carinae extending to two-thirds sternal length; IV–VII with basolateral foveae.

Males with enlarged antennal clubs, modified or simple. Aedeagus with median lobe nearly symmetric; parameres symmetric; dorsal diaphragm oval.

Comparative notes. Tmesiphodimerus belongs to a group of genera centered on Tmesiphorus LeConte, 1849 , characterized by the maxillary palpomeres II and III each bearing a lateral projection with a small apical tuft of setae. In Tmesiphorus, Tmesiphomimus Löbl, 1964 and Dacnotillus Raffray, 1908 , these lateral penicillate appendages are long and thin while they are much shorter and conical in Tmesiphodimerus . In Ctenotillus Raffray, 1897 , the pubescence is made of small, scale-like setae, the elytra bear longitudinal ridges and the first two visible tergites are equal in length.

The most important feature that separates Tmesiphodimerus from all other tmesiphorine genera is the presence of a smooth, shiny ocular plate extending from the inner margin of the eyes towards the antennal insertions, and therefore dividing the subantennal sulcus into two separate branches.

Etymology. The generic name is a combination of ‘Tmesiph’, a common stem used in the tribe Tmesiphorini , and the Greek word ‘dimer’, meaning ‘divided to two parts’, referring to the unique shape of the subantennal sulci. Gender is masculine.

Figures

FIGURE 1. Dorsal habitus of Tmesiphodimerus sinensis (A) and T. malaysianus (B). Scales (mm): 0.5.

FIGURE 2. Diagnostic features of Tmesiphodimerus. A. Head, in dorsal view. B. Same, in lateral view. C. Same, in ventral view. D. Subantennal sulcus. E. Pronotum, in dorsal view. F. Same, in lateral view. G. Same, in ventral view. H. Left elytron. I. Meso- and metaventrite. J. Abdomen, in dorsal view. K. Same, in lateral view. L. Same, in ventral view. Scales (mm): J – L = 0.5; A – C, E – I = 0.2; D = 0.1.

FIGURE 3. Diagnostic features of Tmesiphodimerus sinensis. A. Antenna. B. Maxillary palpus. C. Sternite IX. D. Aedeagus, in dorsal view. E. Same, in lateral view. F. Same, in ventral view. G. Parameres, in lateral view. H. Same, in ventral view. Scales (mm): A, D – F = 0.2; B, G, H = 0.1; C = 0.05.

FIGURE 4. Diagnostic features of Tmesiphodimerus malaysianus. A. Antenna. B Subantennal sulcus. C. Maxillary palpus. D. Sternite IX. E. Aedeagus, in dorsal view. F. Same, in lateral view. G. Same, in ventral view. H. Parameres, in lateral view. I. Same, in ventral view. Scales (mm): A = 0.2; B, C, E – G = 0.1 mm; D, H, I = 0.05 mm.