Pselaphaulax Reitter 1909

Owens, Brittany E. & Carlton, Christopher E., 2022, Revision of the New Zealand species of the Genus Pselaphaulax Reitter (Staphylinidae: Pselaphinae: Pselaphitae: Pselaphini), Zootaxa 5155 (2), pp. 221-244 : 223

Pselaphaulax Reitter 1909

Pselaphaulax Reitter (1909: 218)

Type species: Pselaphus dresdensis Herbst, 1792 (monot.)

Redescription (based on Owens et al. 2019). Males. Head: eyes rounded, composed of 15–20 facets. Vertex convex; shallow sulcus beginning at base of vertex, extending to level of vertexal foveae; vertexal foveae large, set into margins of vertexal depression parallel to middle of eyes; vertexal depression widest between eyes, confluent with sulcus extending to apex of rostrum. Rostral sulcus bounded by lateral, flattened ridges extending to antennal acetabula. Frontal margin of rostrum in dorsal view typically straight to slightly emarginate, with sparse, suberect setae. Antennal segment one as long as antennomeres 2-4, antennae otherwise unmodified. Gular mound modified, hemispherical, about as long a wide or narrowed and longer than wide, glabrous; area of head posterior to gular mound flattened, slightly concave, sometimes bearing flattened modified scales; gular foveae present, paired. Maxillary palpomere I elongate, 1/2 as long as palpomere II; palpomere II narrow, enlarged distally, shorter than head; maxillary palpomere III quadrate; maxillary palpomere IV as long as head, widened in distal 1/3-1/2, apical area smooth to roughened, v-shaped sensory patch present, margined by carina. Thorax: Pronotum widest at 1/2 length, narrowed anteriorly and posteriorly; basal sulcus present, delimited by lateral antebasal foveae, median antebasal fovea reduced to depression, margined by two short carinae. Prosternum in front of coxae slightly convex, anteriorly with modified flattened setae; lateral procoxal foveae present. Mesoventrite with median shield; lateral mesoventral foveae present in large cavities filled with dense setae, meeting internally; lateral mesocoxal foveae absent; median mesoventral foveae present, paired, meeting internally; mesocoxae separated by extension of meso- and metaventrite. Metaventrite afoveate, variously modified; metacoxae separated by extension of ventrite I. Elytra with three basal foveae, single sutural fovea; single discal stria, sutural striae present; apical fringe of setae present.

Abdomen: Tergites of usual form for tribe, unmodified; tergite 2 without obvious basal foveae, lateral basal sulcus extending along width of ventrite, obscured by dense band of setae along posterior edge. Ventrite I covered in dense, shining setae; ventrite II variously modified with median depressions, sulci, or projections; ventrites otherwise unmodified.

Females: similar to males except eyes may be smaller, composed of fewer facets; secondary sexual modifications of the legs and second ventrite absent.

Comments. NZ species in this genus are primarily united by the presence of an antebasal sulcus on the pronotum margined by lateral antebasal foveae, the median antebasal foveae present and sometimes delimited by two small carinae (may be reduced to a median pit), maxillary palpi IV widened in the distal 1/3 to1/2 with a v-shaped sensory patch margined by a carina, and the gular swelling prominent, about as long as wide or narrower and slightly longer than wide. While several groups in NZ likely representing undescribed genera may superficially resemble Pselaphaulax , no other groups possess a combination of these character states. Pselaphaulax is most similar to Pselaphotumulus and Pselaphogenius , but can quickly be distinguished, most noticeably, by the rounded to slightly emarginate apical margin of the rostrum (pointed in Pselaphotumulus and some Pselaphogenius ), the gular process rounded or ovate-rounded (greatly expanded to cover the entire gular area of the head in Pselaphotumulus ), and the presence of an antebasal sulcus on the pronotum (absent in Pselaphogenius ).

Superficially, NZ specimens in the genus can be divided into two “species groups” which can consistently be distinguished by several characters, including: shape of gular mound (ovate, narrowed apically and posteriorly in group 1, rounded, widened apically and rounded or narrowed posteriorly in group 2); modifications of the area behind gular mound (nude in group 1, covered in flattened modified scales in group 2); the degree of reduction of the median antebasal fovea (present and margined by carinae in group 1, reduced and pit-like in group 2); and modifications of the mesoventral shield (bearing a single, setose fovea in group 1, lacking setose fovea in group 2). All species described in the previous Chatham Islands manuscript ( Owens et al. 2019) are members of group 2. Pselaphaulax intermedius possesses a mixture of characters (gular mound rounded posteriorly as in group 2, area behind gular mound nude as in group 1, median antebasal fovea present as in group 1, and mesoventral shield bearing a setose fovea as in group 2). Further investigation and comparison with Asian fauna may eventually warrant the designation of subgeneric status to these species groups within NZ Pselaphaulax , but under the current system they should be considered informal designations encompassing morphological variation within the genus.