Batriscenellus Jeannel, 1958

Yin, Zi-Wei, Li, Li-Zhen & Zhao, Mei-Jun, 2011, Batriscenellus Jeannel (Coleoptera, Staphylinidae, Pselaphinae) redefined, with notes on the Chinese species, Zootaxa 3016, pp. 37-50 : 38-39

Batriscenellus Jeannel, 1958

Type species. Batrisus fragilis Sharp, 1883 (by original designation)

Diagnosis. Head lacking frontal rostrum, lacking semicircular sulcus connecting vertexal foveae, median longitudinal carina distinct to absent, when present separated from frons by transverse sulcus that may vary in depth; antennomere I with subconical trichome at anterolateral margin. Pronotum with distinct median and lateral longitudinal sulci, transverse antebasal sulcus continuous or interrupted near base of median longitudinal sulcus, lacking antebasal spines. Elytra each with two basal foveae, subhumeral foveae present, discal stria extending beyond midpoint of elytral length. Visible tergite I longer than remaining tergites combined.

Redescription. Body yellowish brown to reddish brown, length 1.70–2.34. Head rectangular, slightly wider than long to slightly elongate, antennal tubercles prominent; vertexal foveae nude, located posterior to point level with anterior margin of eyes; with 11 antennomeres, clubs formed by apical three antennomeres; ocular-mandibular carinae present; eyes round and prominent; maxillary palpi with palpomere I minute, II elongate and pedunculate, III short, nearly triangular, IV large, fusiform; with gular carina and single gular fovea.

Pronotum about as long as wide, with four sulci, one pair of lateral antebasal foveae and two pairs of basolateral foveae; lacking spines; paranotal carinae present; with lateral procoxal foveae and subcoxal foveae.

Elytra usually wider than long, narrowed at base; sutural and marginal striae and lateroapical cleft present.

Thorax with median mesoventral foveae widely forked, lateral mesoventral foveae straightly inserted; lateral mesocoxal foveae present; lateral metaventral foveae small, metaventral apex slightly notched. Legs slender, fore and mid tarsomeres II and III subequal in length, hind tarsomeres II slightly longer than III.

Abdomen with lateral margins subparallel to broadly rounded, apex narrowed and rounded; tergite IV largest, with mediobasal impression between mediobasal foveae, basolateral foveae with wide openings, discal carinae present; tergites V–VII successively narrower, V–VI about subequal in length, VII about as long as V and VI combined; sternite IV about as long as V–VII combined, with mediobasal and large basolateral foveae.

Males with sexual characters present on mesotibiae, metafemora, tergites IV–VI, and on sternite IV. Aedeagus strongly asymmetric, median lobe with large basal capsule; parameres fused and strongly reduced, attached on ventral side of capsule, membranous; ventral lobe broad at base, narrowed towards apex; dorsal apophysis inserted at dorsal side of basal capsule, on right side, usually strongly curved leftward, basal foramen large.

Females with eyes smaller, lacking modifications; genitalia basically provided with sternite IX and genital plate, sternite IX divided into two lobes, one usually paired and attached to another larger transverse one, genital plate narrower than sternite IX, with paired lateral arms narrowed apically.

Comparative notes. Batriscenellus is allied to a number of genera (three Asian, two African) centered on Batrisiella Raffray. Current definitions of several group members are insufficient and problematical. Some of them are heavily relied upon the position of male sexual characters. Batriscenellus was defined by the male sexual modifications present on tergites VI–VII ( Jeannel, 1958: 60), and was redefined by Nomura (1991: 299) to include presence of a subconical trichome on the anterolateral margin of the first antennomere. Batrisiella was defined by the male sexual modifications being usually present on tergite IV, and antennomere I lacking modified setae ( Löbl, 2001: 671). However, the definitions of the two genera were confused when specimens of Batrisiella aurita Löbl , Batrisiella satoi Nomura , Batrisiella subalpicola Nomura , and some undescribed species became available for this study. Males of these Batrisiella species and two undescribed species have a sexual patch on tergite IV, while they also have antennomere I bearing subconical setae, and one undescribed species has strongly thickened metafemora in the male. We found it hard to apply the current generic definitions to place these species either in Batriscenellus or Batrisiella . As the male secondary sexual characters of Batrisini may be highly variable within a single genus, and their use as group characters are usually unreliable ( Löbl, 2001: 566), we therefore choose the presence/ absence of a trichome on antennomere I to serve as the only criterion of value in separating the two genera, and the form and position of the male sexual characters are considered useless at the generic level. We are relieved that pictures of the first antennomere of the type species of both genera, Batriscenellus fragilis (Sharp) and Batrisiella caviventris (Raffray) , were available for our use, thanks to the collaboration of Shûhei Nomura. As a result, Batrisiella aurita Löbl , Batrisiella satoi Nomura and Batrisiella subalpicola Nomura are moved to Batriscenellus . New combinations.

Nomura (1995) described the monotypic genus Babascenellus Nomura from Honshu and the Ryukyu Islands of Japan (three identified specimens examined in the present study). As stated, it is separated from Batriscenellus , Batrisiella , and two African genera, Arthromelus Jeannel and Seydelites Jeannel , by the strongly protruding anterolateral margin of antennomeres I in both sexes, and by the dorsal apophysis of the aedeagus not curving at the base. Since the dorsal apophyses of at least several Batrisiella species seem have a straight base ( Löbl, 2001: 683, 688), the character of the curved base of the dorsal apophysis could hardly be considered as a synapomorphy of Batrisiella + Batriscenellus + Arthromelus + Seydelites . For now we accept the placement of Babascenellus as a genus on the basis of its peculiar antennal structure.

We are not familiar with the two African genera Arthromelus and Seydelites . Batrisiella and Arthromelus are separated only by geographical ranges, and were suggested as probable synonyms by Nomura (2003: 166). As to Seydelites , we have only seen a picture of S. franzi Jeannel (Nomura, pers. com.). Males of this species have the lateral margins of tergite IV strongly expanded laterally, but based on the picture we failed to find any consistent character that could serve as a criterion for separating it from Arthromelus or Batrisiella . Accurate placement of the two genera must require further examination of the type species. To determine either the justification or the inappropriateness of the generic status of these related taxa, a phylogenetic analysis based on a wide range of Batrisini genera is probably needed.

Remarks. Within Batriscenellus , four subgenera are currently recognized. Characters used to separate subgenera rely mostly upon the presence/absence and position of male sexual characters on the abdominal tergites. However, the subgeneric concepts were formed largely based on geographically restricted material. Most described species of Batriscenellus are from Japan, and only a few (e.g. B. orientalis , B. vicarius ) are known from the adjacent Russian Far East, the Korean peninsula, and Northeast China (except for one record of B. orientalis in Taiwan). The subgeneric system does not apply well to material from outside this region. Species that have male sexual characters located on different parts of the body cannot be placed in any current subgenus of Batriscenellus as they are defined. We do not believe there is any justification for describing a number of additional subgenera as substitutes for species groups, and here we synonymize Scaioscenellus Jeannel , Nipponoscenellus Nomura , and Batriscenellinus Nomura with Batriscenellus . New synonyms. The genus is divided to six newly proposed species groups which are defined below.