Onomeris Cook, 1896

Wesener, Thomas, 2010, Revision of the American Pill Millipedes I: Onomeris and Trichomeris (Diplopoda, Glomerida, Glomeridae), Zootaxa 2725, pp. 28-40 : 31-32

publication ID	https://doi.org/ 10.5281/zenodo.199966
DOI	https://doi.org/10.5281/zenodo.6206525
persistent identifier	https://treatment.plazi.org/id/920FBB59-1965-BF12-FF6F-7754FDB0F94C
treatment provided by	Plazi
scientific name	Onomeris Cook, 1896
status

Treatment

Genus Onomeris Cook, 1896 View in CoL

Onomeris Cook, 1896: 43 View in CoL . Type species O. underwoodi View in CoL

– Chamberlin & Hoffman 1958: 12; Jeekel 1971: 16; Mauriès 1971: 434; Hoffman 1980: 68; Hoffman 1999: 17; Mauriès 2005: 243 (list genus name).

Trichomeris Loomis, 1943: 374 View in CoL . New synonymy Type species: T. sinuata – Chamberlin & Hoffman 1958: 13; Jeekel 1971: 18; Hoffman 1980: 68; Hoffman 1999: 18 (list genus name).

The redescription of the genus is presented here in more detail in order to focus the following redescriptions of the species on the unique characters of each species.

Type species: Onomeris underwoodi Cook, 1896

Other species included: Onomeris australora Hoffman, 1950 ; Onomeris sinuata ( Loomis, 1943) new comb.

Genus diagnosis: Shares the general shape of telopods, with a prefemoral and a femoral trichostele, a prefemoral process, and especially the presence of a differentiated process on the femur ( Fig. 5 View FIGURE 5 B), only with species of the Asia genus Hyleoglomeris . Tarsus and tibial process of telopod generally of slender appearance ( Fig. 5 View FIGURE 5 A). Differs from Hyleoglomeris and most other genera of Glomeridae (but not the European Tectosphaera Mauriès, 2005 ) in presence of a strongly modified head, which bears a conspicuous Y-shaped ledge on frontal side, and laterally of crest above organ of Tömösváry large grooves for antennae ( Fig. 1 View FIGURE 1 A). Thoracic shield with a large hyposchism field bearing numerous transverse striae whose caudal edge is drawn behind tergal contour, a clear impression present before hypochism ( Fig. 1 View FIGURE 1 B). Like in Hyleoglomeris but unlike Glomeris male leg 17 greatly reduced in size, with a high outer coxal lobe and a 3-segmented, vestigial telopodite with an apical spine ( Fig. 2 View FIGURE 2 B).

Redescription: Length of non-stretched but unrolled specimens of both sexes ca 4–5 mm, width 2.2–2.8 mm, respectively.

General coloration clearly visible in the type series of O. sinuata and O. australora , faded in the type series of O. underwoodi , but relatively well conserved in more recently collected material of O. underwoodi and O. sinuata . Dark brown with laterally lighter grey markings. In the field, specimens are of a shiny appearance resembling micro-gastropods. Tergites 2–11 laterally on metazona with oval greyish-white area, which does not reach margins of tergite. Center of collum light grey; center of head light, margins of head as well as lateral grooves dark brown. Antenna and legs dark brown.

Head with a setose labrum ( Fig. 1 View FIGURE 1 A). Head centrally with Y-shaped crest rising between antennae and expanding to posterior margin. Laterally of crest, from posteriorly of antennae and organ of Tőmősváry to ocelli with deep antennal grooves ( Fig. 1 View FIGURE 1 A).

Ocellaria black, ocelli 5+1 ( O. underwoodi ) or 6+1; lenses convex ( Fig. 1 View FIGURE 1 A).

Antennae with four large apical cones, antennomere 6 ca 2.1 ( O. underwoodi ) – 2.5 times as long as broad. Antennomere 3 as long as 1 and 2 combined ( Fig. 1 View FIGURE 1 A).

Organ of T ő m ő sváry elongate, ca 2.4–2.5 times as long as broad ( Fig. 1 View FIGURE 1 F).

Gnathochilarium lateral palps more slender and with fewer sensory cones than inner palps ( Fig. 1 View FIGURE 1 D). Central pads and endochilarium on inner side centrally with circa 15 sensory cones in a circular arrangement; more laterally with another area of circa 10 cones ( Fig. 1 View FIGURE 1 E).

Mandible: external tooth with a small notch on dorsal side. Inner tooth 4-combed; four rows of pectinate lamellae; condylus a barely detectable 'bump', weakly developed ( Fig. 2 View FIGURE 2 A).

Collum with two transverse striae ( Fig. 1 View FIGURE 1 C).

Thoracic shield with a large hyposchism field whose caudal edge is drawn behind tergal contour ( Fig. 1 View FIGURE 1 B). Clear impression present in front of schism. Shield with numerous transverse striae, of which three or four cross the dorsum ( Fig. 1 View FIGURE 1 B). Striae 1 or 2 striae lie above, 5 or 6 level to, and further 4 or 5 posterior to the schism ( Fig. 1 View FIGURE 1 B). Thoracic shield like other tergites sparsely covered with numerous minute pits ( Fig. 1 View FIGURE 1 B), a short setae rising at each pit.

Following tergites 3–11 covered with numerous short setae ( Fig. 4 View FIGURE 4 A), usually inserting in a pit ( Fig. 4 View FIGURE 4 B). Dorsal ozopore without any conspicuous ridges. Anterior margin of tergites with wavy ridge projecting posteriorly in a tooth-like pattern ( Fig. 4 View FIGURE 4 A). Tergites laterally without discernable striae, lateral edges not projecting posteriorly.

Male anal shield at least faintly ( O. sinuata ), more often strongly concave medially at caudal edge ( Fig. 5 View FIGURE 5 E).

Male leg 17 ( Fig. 2 View FIGURE 2 B) particularly strongly reduced, with a low, broad, rounded coxal lobe and a 3-segmented vestigial telopodite.

Male leg 18 ( Fig. 3 View FIGURE 3 A) less strongly reduced, with a syncoxial notch and a 4-segmented telopodite. Second joint of telopodite flattened, last telopodite with strongly developed spine ( Fig. 3 View FIGURE 3 A)

Telopod ( Figs 3 View FIGURE 3 B, 5A–C) strongly robust, with a high, roundly subtrapeziform ( Fig. 3 View FIGURE 3 B) to bilobed ( Fig. 6 View FIGURE 6 C) syncoxital lobe flanked by setose, apically simple horns. Prefemur with strongly developed trichostele. Femur with trichostele of circa half the length of the prefemur one, posteriorly with very large, triangular process. Femur with strongly sclerotized, distal finger on posterior side, as well as a field of sclerotized teeth located centrally on the posterior face of finger ( Fig. 5 View FIGURE 5 B). Tibia and tarsus, as well as tarsus and femoral process forming a chela ( Fig. 5 View FIGURE 5 A). Tibia with long, strongly sclerotized, but slender distal finger caudolaterally; finger with a small field of sclerotized teeth at its base ( Fig. 3 View FIGURE 3 B). Tarsus slender, basally curved 45–65 degrees towards syncoxite, otherwise straight ( Fig. 3 View FIGURE 3 B), inner margin towards femoral process with sclerotized teeth ( Fig. 3 View FIGURE 3 B). Apex of tarsus well-rounded, posteriorly with curved spine ( Fig. 3 View FIGURE 3 B).

Synonymization of Trichomeris Loomis, 1943 under Onomeris Cook, 1896 . The synonymization of Trichomeris und Onomeris was suggested previously ( Hoffman 1999, p. 18: "This monotypic genus is probably not separable from Onomeris "). Re-study of the type specimen of T. sinuata , the only described Trichomeris species, shows that this species indeed belongs into Onomeris . The telopod differences between T. sinuata and Onomeris species, which even prompted the different systematic placement of both by Mauriès (1972, 2005), were based on erroneous drawings by the first describer.

Position of the genus Onomeris within the Glomerida . Currently, authors agree that Onomeris should be placed in the pill millipede family Glomeridae (Hoffman 1980, Mauriès 2005), based on the presence of setae and an outgrowth on the mesal side of the telopod ( Fig. 5 View FIGURE 5 A). On the tribe level, the position of Onomeris needs to be fixed through a phylogenetic analysis, which is beyond the scope of this study. In the most recent system ( Mauriès 2005), Onomeris is placed in the tribe Glomerini together with the mainly West European genera Glomeris , Sicilomeris and Loboglomeris , while Trichomeris is not mentioned. However, according to the character descriptions ( Mauriès 2005), the presence of a differentiated process on the femur, which is clearly present in Onomeris ( Fig. 5 View FIGURE 5 A), would place this genus in the large tribe Dooderiini, and there particularly close to the Asian genus Hyleoglomeris (see Golovatch et al. 2006, 2010).