Oryssoma politum, Irmler, 2015

Irmler, Ulrich, 2015, New Neotropical genera and species of the tribe Osoriini (Coleoptera: Staphylinidae: Osoriinae), Beiträge Zur Entomologie = Contributions to Entomology 65 (1), pp. 173-196 : 181-182

Oryssoma politum spec. nov.

( Figs 4A–D , 15C )

Type material: Holotype male: Ecuador, Napo Prov., Jatun Sacha Biol. Stat., 21 km E. Puerto Napo (77°37.42W, 1°03.57S), 400 m elevation, lowland rain forest, collected by flight intercept trap, 21.07.1994, leg. F. Génier ( KNHM).

Paratypes: Ecuador, Napo Prov., 1 female with same data as holotype ( KNHM); Sacha Lodge (76°27.32'W, 0°28.15'S), 250 m elevation, collected by flight intercept trap, female, 26.– 28.10.2004, leg. G. de Rougemont ( UIC) .

Etymology: The specific name derived from the same Latin name meaning polished and refers to the polished surface.

Description: Length: 3.0 mm. Colouration: Black, pronotum slightly lighter, dark brown, legs and antennae light brown; labrum and small area at base of antennae light reddish; abdomen reddish.

Head: 0.36 mm long, 0.52 mm wide; eyes distinctly prominent; semi-circular, temples half as long as eyes; sides in front of eyes shortly parallel; then abruptly narrowed in sinuate curve to anterior angles of clypeus; anterior edge of clypeus produced in semi-circular curve; labrum semicircular, too; punctation weak and sparse; one setiferous puncture in front of eyes and another setiferous punctures on vertex close to eyes; supraocular puncture distinctly impressed; without microsculpture; surface polished and shiny.

Antennae as long as head and half of pronotum combined; second antennomere elongate, oval; as long as two following antennomeres; following antennomeres increasing in width; third and fourth antennomeres narrower than second antennomere and approximately quadrate; fifth and sixth antennomeres distinctly wider than long; sixth antennomere twice as wide as long; following antennomeres distinctly thicker than preceding antennomeres and approximately 1.5 times wider than long.

Pronotum: 0.45 mm long, 0.53 mm wide; widest shortly behind anterior angles; slightly narrowed to posterior angles; shortly in front of posterior angles emarginate; lateral margin fine; in dorsal aspect, visible in its total length; continued to posterior edge; punctation sparse and irregular in size; with moderately fine punctures and micro-punctures; along lateral margin and anterior edge with several setiferous punctures; pair of setiferous punctures on posterior disc close to posterior margin; without microsculpture; surface polished and shiny.

Elytra: 0.65 mm long, 0.58 mm wide; sides parallel; shoulders distinct, but rounded; punctation weak and sparse; punctation nearly invisible in deep coriaceous groundsculpture; row of four setiferous punctures along lateral margin; further setiferous punctures along posterior edge and on disc; surface shiny.

Abdomen finely and sparsely punctate; each segment with transverse row of setiferous punctures; segments seven and eight with two rows of setiferous punctures; without micro-sculpture; surface polished and shiny.

Protibia: 0.39 mm long, 0.10 mm wide; eight spines on outer edge; apical spines inserted on short digits; on posterior face with second row of four spines and with several long yellow setae; three tarsomeres; first elongate; nearly twice as long as second; inner emargination with comb visible in its total length.

Aedeagus with long basal lobe and much shorter apical lobe; apical lobe forming short hook ending in acute apex; paramera short, but slightly longer than apex of apical lobe; endophallus creased and spiralled.

Diagnosis: Among the three species of Oryssoma , O. politum can be easily identified by the thick prominent eyes. In O. exalatus and O. schwarzi the eyes are not prominent and smaller. The penultimate antennomeres are wider in O. politum than in the two other species. The pronotum of O. politum is slightly emarginate in front of the posterior angles and with impressions, whereas it is without emargination and impressions in O. exalatus and O. schwarzi .

Oryssoma exalatum ( BLACKWELDER, 1943) new comb. ( Figs 3A–C , 15D )

Osorius exalatus BLACKWELDER, 1943: 200

Type material examined: Holotype male: Trinidad, Cave in Aripo Valley , 600 m elevation, 18.04.1935, leg. N.A. Weber ( MCZ).

Description: Length: 2.3 mm. Colouration: light brown, legs and antennae yellow.

Head: 0.42 mm long, 0.50 mm wide; eyes not prominent, temples nearly twice as long as eyes; in front of eyes, fore-head slightly narrowed to base of antennae, then emarginate and strongly narrowed; clypeus produced in semi-circular curve; labrum semi-circular, too; punctation moderately deep and dense; on average, interstices between punctures twice as wide as diameter of punctures; on posterior vertex slightly denser than on fore-head; netlike microsculpture weak; surface shiny.

Antennae slightly longer than head; second antennomere thick and elongate, twice as long as wide and nearly two times longer than conical third antennomere; following antennomeres increasing in width; third and fourth antennomeres narrowed than second; fifth approximately as thick as second; fourth to tenth antennomere approximately quadrate, only fifth slightly wider than long.

Pronotum: 0.46 mm long, 0.56 mm wide; widest at anterior angles; narrowed posteriad in smooth and even curve; without forming posterior angles; lateral margin fine; in dorsal aspect visible in total length; posterior edge margined; punctation irregular in size; moderately dense; on average, interstices between punctures at least as wide as diameter of punctures; netlike microsculpture weak; surface shiny.

Elytra: 0.43 mm long, 0.54 mm wide; widest close to posterior angles; evenly narrowed to shoulders; shoulders obtuse; three setiferous puncture close to lateral margin; one setiferous puncture on anterior disc on each side of suture; punctation indistinct; with coriaceous groundsculpture; surface shiny.

Abdomen with dense transverse netlike microsculpture and moderately deep and dense punctation; each segment with transverse row of setiferous punctures.

Protibia slender; with seven spines on outer edge; apex with two very long spines; posterior face with six spines and several setae; first tarsomere with two long and thick setae at apex.

Aedaegus slender; basal lobe thick and long; apical lobe shorter and curved like short hook ending in acute apex; paramera not longer than apex of apical lobe.

Diagnosis: The species is only known from the single type male found in a cave in Trinidad. Concerning the trimere tarsae, the shape of the labrum and the structure of the aedeagus the species has to be placed to the genus Oryssoma together with O. schwarzi and O. politum . It can be easily differentiated from these two species by the short elytra and the nearly semi-circular shape of the pronotum. It is not clear, if the light brown colouration can be referred to the life in a cave or the immature status of the specimen.

Key to species of the genus Oryssoma fore, a thorough comparison between the two species was impossible. I found no further difference between the species as did BLACKWELDER (1943). Thus, it is likely that O. microptera is the female of O. exalatum . But synonymisation has to wait until more material of the two species is available.

Figures

Fig. 1–4: Ouloglene barberi (1), Oryssoma schwarzi (2), O. exalatum (3), O. politum (4); antenna (A), protibia in posterior aspect (B), aedeagus (C), last sternite (D); scale bar: 0.1 mm.

Fig. 15: Head, pronotum, and elytra of Ouloglene barberi (A), Oryssma schwarzi (B), O. politum (C), O. exalatum (D), Tumboecus verhaaghi (E), and T. struyvei (F); scale bar: 0.5 mm.