Scydmaenus (Choleropsis) geniculatus
Creators: name: Jałoszyński, Paweł
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Scydmaenus
Scydmaenus geniculatus

description: Scydmaenus (Choleropsis) geniculatus (King)
Heterognathus geniculatus King, 1864: 98.
Scydmaenus (Cholerus) geniculatus (King); Csiki, 1919: 72.
Scydmaenus princeps sensu Franz, 1975: 288 (misidentified).
Scydmaenus gracilis sensu Franz, 1975: 292 (misidentified).
(Figs 20–29, 53, 60–61, 71, 191)
Type material studied. Lectotype (here designated) (AUSTRALIA): ♂ mounted on card with “ ♂ ” and “LECTOTYPE” written in pencil (Fig. 20), with labels illustrated in Fig. 191: “K23218” [brownish, handwritten], “ SYNTYPE / Heterognathus / geniculatus / King, 1863 {sic!}” [yellow, printed and handwritten], “K 197785” [white, printed] (AMS). Paralectotypes (3 exx.). ♀, on separate mounting card pinned below lectotype, with same labels (but identity of female uncertain!) (AMS); ♂, “K23218” [brownish, handwritten], “ SYNTYPE / Heterognathus / geniculatus / King, 1863 {sic!}” [yellow, printed and handwritten], “K 197784” [white, printed] (AMS); ♂, “K29219” [brownish, handwritten], “K 197787” [white, printed], “ SYNTYPE ” [yellow, printed] (AMS).
Additional material studied (7 exx.). NEW SOUTH WALES: 2 ♂♂, Illawarra (correctly identified, presumably by Lea) (ANIC, on permanent loan from Macleay Museum, University of Sydney); 2 ♂♂, New South Wales, Sydney (ANIC, on permanent loan from Macleay Museum, University of Sydney, cPJ); 2 ♂♂, New South Wales, Ropes Creek (ANIC, on permanent loan from Macleay Museum, University of Sydney); 1 ♂, misidentified as Heterognathus princeps by Lea, Glenn Innes, leg. Lea (SAMA).
Specimens studied as high-quality photographs. Doubtful syntype, ♂ (Figs 28–29), “Heterocerus {sic!} / princeps / Type RLK / Paramatta” [brownish, handwritten], “princeps / King / N- {unclear}” [brownish, handwritten], “C. Schaufuss 1930” [white, printed], “ Scydmaenus / (Cholerus) / princeps King / det.H.Franz” [white, handwritten and printed], “ Heterognathus / princeps King ” [white, handwritten], “DEI Müncheberg / Col - 03300” [greenish, printed], “SDEI Coleoptera / # 303734” [white, printed], “ Syntypus ” [red, printed] (misidentified as H. princeps and used by Franz (1975) to redescribe Scydmaenus princeps; if this specimen is a syntype of Heterognathus princeps, then it must be removed from the type series because of misidentification; the handwriting and style of historical labels suggest that none of them is an original King’s label, so very likely this specimen is not a syntype) (SDEI).
Revised diagnosis (based on male). Antennomeres 9 and 10 subequal in width, 9 much shorter than 10 and strongly transverse (Figs 60–61); antennomere 10 strongly elongate and with broad and deep lateral impression (Fig. 60); aedeagus in dorsal view (Figs 24, 27) with apical margin straight and as wide as about half of total width of median lobe, lateral subapical lobes narrowly subtriangular, each distinctly longer than broad and projecting strongly laterally and weakly proximally, in lateral view (Figs 25, 27) distal region of median lobe weakly broadened, with dorsal margin rounded in proximal half and concave in distal half; metaventrite (Fig. 71) with deep median impression about as broad as half width of metaventrite and filled with short setae, but impression flanked by much longer setae.
Redescription. Body of male (Figs 21, 23) slightly flattened, elongate and slender, BL 11.71– 1.98 mm; pigmentation uniformly light to moderately dark brown, appendages indistinctly lighter (difference best visible in darkest specimens); cuticle moderately glossy, covered with vestiture of yellowish setae.
Head (Figs 21–23, 28–29) in dorsal view transversely subrectangular, broadest at eyes, HL 0.31–0.38 mm, HW 0.33–0.40 mm; vertex and frons confluent and weakly convex, posterior margin of vertex distinctly concave, arcuate; tempora slightly more than twice as long as length of eye in dorsal view; supraantennal tubercles indistinct; frons over antennal fossae broadly subtrapezoidal and with straight anterior margin. Eyes small, nearly semicircular in shape, indistinctly emarginate posteriorly and oblique in relation to long axis of head. Punctures on frons and vertex fine, inconspicuous; setae short, sparse, suberect, those on tempora as sparse as those on head dorsum. Genae as sparsely setose as frons and vertex.Antennae (Figs 22, 29, 53, 60–61) long and slender, AnL 1.05–1.08 mm; three terminal antennomeres forming sharply delimited club; scape about 3 times as long as broad, distinctly broadening distally; pedicel twice as long as broad; antennomeres 3–4 each slightly elongate, 5 twice as long as broad, 6 nearly symmetrical and about as long as broad, 7 and 8 each distinctly transverse and strongly asymmetrical, 9 strongly asymmetrical, strongly transverse, with oblique lamina on distomesal margin demarcated by deep notch (best visible in Fig. 29), 10 nearly twice as long as 9 and subequal in width, strongly asymmetrical, with broad lateral impression; 11 only as long as 10, nearly twice as long as broad, slightly asymmetrical.
Pronotum in dorsal view (Fig. 23) elongate, broadest near anterior third, PL 0.50–0.58 mm, PW 0.43–0.48 mm; anterior and lateral margins confluent and rounded; posterior corners obtuse-angled and blunt; posterior margin nearly straight; base with narrow but distinct posterior marginal carina and with two pairs of small, distinct, sharply marked and relatively deep antebasal pits, each slightly to distinctly transverse. Pronotal disc covered with fine and inconspicuous punctures; setae similar to those on frons and vertex, short, moderately dense, suberect. Ventrally prothorax with nearly asetose and impunctate hypomera; basisternal region sparsely covered with short recumbent setae.
Elytra (Fig. 23) oval, broadest slightly in front of middle, EL 0.90–1.03 mm, EW 0.63–0.70 mm, EI 1.44–1.56. Humeral calli weakly elevated; basal impression on each elytron barely marked; basal elytral foveae lacking; apices separately rounded. Punctures fine and inconspicuous; setae similar to those on pronotum. Hind wings not studied.
Metaventrite (Fig. 71) with large and deep longitudinal median impression about as broad as half width of ventrite, with diffuse lateral margins, filled with short setae and flanked by conspicuously long setae.
Legs (Fig. 23) long and slender; unmodified, except for distal penicillus on mesotibiae and weakly broadened protarsomere 1 and ventral tenent setae distributed on protarsomeres 1–3; protarsi short, tarsomeres 1–4 each about 1.5 × as long as broad, tarsomere 5 3.5 × as long as broad and slightly shorter than tarsomeres 2–4 combined; mesotarsi long, tarsomere 1 nearly 5 × as long as broad and subequal in length to tarsomeres 2–4 combined, tarsomeres 2–4 each about 1.5 × as long as broad, tarsomere 5 nearly 3.5 × as long as broad, subequal in length to tarsomeres 3–4 combined; metatarsi as long as mesotarsi, tarsomere 1 about 3.5 × as long as broad, tarsomeres 2–4 each elongate but decreasing in length distally, tarsomere 5 3.5 × as long as broad, subequal in length to tarsomeres 3–4 combined.
Aedeagus (Figs 24–27) elongate but not very slender, AeL 0.35 mm, in dorsal view median lobe broadest at middle and indistinctly constricted in sub-basal and subapical regions; apical region subtrapezoidal, strongly tapering and with straight apical margin as wide as about half of total width of median lobe; lateral subapical lobes prominent and sharply demarcated from median lobe, each subtriangular, distinctly longer than wide, strongly projecting laterally and only slightly proximally; ostium situated in subapical third of median lobe, flagellum with abruptly broadened and asymmetrical vesicular structure; median lobe in lateral view with distal portion delimited by deep submedian constriction, its dorsal surface convex in proximal half and concave in distal half.
Female. Unknown.
Distribution. SE Australia: CE and NE Queensland (most specimens from vicinity of Sydney).
Remarks. The name geniculatus appears in Franz (1975) on p. 274, in a list of King’s species names originally combined with Heterognathus. Interestingly, Franz (1975) did not redescribe this species under its own name, even though he redescribed it twice: on p. 288 misidentified as S. princeps, and on p. 292 misidentified as S. gracilis. The ‘redescription’ of S. princeps sensu Franz was based on a single ‘syntype’ preserved in coll. Schaufuss (SDEI), which is a male (Figs 28–29) that almost certainly was not a part of the type series (judging from labels). The antennal modification of this male does not agree with the description and illustration given by King (1864: pl. VII 2) for Heterognathus princeps, which shows a deep lateral cavity in the antennomere 9, and the antennomere 10 about as long as broad with only a shallow longitudinal impression. The specimen from SDEI does not have such a cavity in the antennomere 9, and its antennomere 10 is distinctly elongate and has a deep lateral impression (Fig. 29). It is S. geniculatus, with identical antennal modifications as those in syntypes of Heterognathus geniculatus preserved at AMS (Fig. 22). Scydmaenus geniculatus was also misidentified as S. princeps by Lea (1 ♂ from SAMA). It was certainly possible to confuse species of Scydmaenus with modified antennal clubs in times when a stereomicroscope was not invented yet (King), or was still a rare instrument in hands of zoologists (Lea).
Scydmaenus geniculatus clearly differs from all remaining species of Choleropsis in the antennomere 9 strongly transverse, only half as long as antennomere 10, the antennomere 10 massive, strongly elongate, and with a deep and broad lateral impression. In all remaining species the antennomere 9 is at most as broad as long, only slightly shorter than 10, and the antennomere 10 is only slightly elongate. Only in S. kurandae the antennomere 10 has a lateral impression, but it is much narrower than that in S. geniculatus. The aedeagus of S. geniculatus is unique: no other species in this subgenus has the median lobe in dorsal view broadened at middle, and the subapical lateral lobes elongate subtriangular and directed laterally and proximally.
description: Published as part of Jałoszyński, Paweł, 2023, Scydmaenus Latreille of Australia: Revision of species in subgenera Choleropsis Franz, Kingius Franz, Mascarensia Franz, Parallomicrus Franz, Scottiscydmaenus Franz, and description of Ascydmaenus subgen. n. (Coleoptera, Staphylinidae, Scydmaeninae), pp. 1-75 in Zootaxa 5371 (1) on pages 16-19, DOI: 10.11646/zootaxa.5371.1.1, http://zenodo.org/record/10144644