Rhyparus platypygus Skelley and Smith 2024, new species
Creators: name: Smith, Paul E. Skelley Andrew B. T.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Scarabaeidae
Rhyparus
Rhyparus platypygus

description: Rhyparus platypygus Skelley and Smith, new species
Figures 18–28, 41
Diagnosis. A member of Rhyparus, distinguished from all other Western Hemisphere species by the following combination of characters: small size; pronotal intercostal surfaces not densely punctate; juxtasutural elytral costa interrupted by caudal bulb; pygidial juncture with abdominal ventrite 5 not perpendicular to body (45° angle in male, Fig. 28; much less in female, Fig. 27; compare with typically perpendicular juncture in Fig. 29); male and female pygidia convex or flattened (not concave), with medial carina broad; and distribution in Guatemala (Izabal) and Honduras (Cortés) (Fig. 41).
Description. Holotype female (Fig. 18–20). Body length 3.63 mm, width 1.19 mm. Elongate, parallel-sided, flattened, dark brownish black; dorsal costae weakly alutaceous, somewhat glossy; costal intervals strongly alutaceous, dull; partly clothed with indistinct, fine, very short setae on head and all longitudinal costae on pronotum and elytra.
Head. Surface dull, alutaceous, transversely subhexagonal (Fig. 21). Clypeus trapezoidal, anteriorly truncate in anterior view, concave between teeth in dorsal view; anterior margin narrowly upturned with sharp obtuse tooth on each side of medial third, lateral thirds concave to rounded obtuse tooth anterior of clypeo-genal junction. Gena moderately lobed laterally, distinctly excavate anterior of eyes. Clypeal disc convex with two indistinct longitudinal costae weakly evident in anterior view and dorsal profile; peridiscal impression strong basally, anteriorly a coarsely punctured, weak groove. Frons with four small, distinct frontodiscal costae, lateral costae longer than medial costae. Head with evenly scattered punctures; coarser punctures at base of head, smaller punctures on clypeal disc; punctures with a short, pale yellow seta.
Pronotum. Surface alutaceous, dull; costae weakly alutaceous, glossy, widest in middle; with paramedian, discolateral, and submarginal costae distinct, all with anterior portions convex. Paramedian costae incomplete, prominent at anterior margin, obsolete at constriction near anterior third, distinct straight but diverging towards posterior margin. Discolateral costa nearly straight, distinctly interrupted by fovea on anterior third, present at anterior margin. Submarginal costa complete, sinuate; posterior lobe reduced, flattened. Median interval at constriction of paramedian costae with few small punctures. Other costal intervals impunctate except for four large pores at anterior margin and at basal third on each side of paramedian costae. Interval between discolateral and submarginal costae with posterior half convex medially, subcostate, ends at the posterior angle of the pronotum. Lateral margin deeply notched, with prominent anterior and intermediate lobes; anterior lobe slightly smaller than intermediate lobe, both angulate laterally; posterior lobe lacking. Posterior marginal groove broad, deep, and crenated by pronotal costae.
Scutellum. Scutellar shield minute, narrow, apex acute.
Elytra. Surface of intervals alutaceous, dull; costae weakly alutaceous, glossy, widest in middle; flattened intervals with coarse, distinctly separated punctures (Fig. 18, 22). Juxtasutural costa interrupted caudally by bulb, not attaining apex; weakly convex. Discomedian costa straight from base to apex; weakly more prominent anteriorly, medially convex as discolateral costa; gradually swelling at apex to small postdiscal bulb; trichome of costa small, hidden in groove. Discolateral costa prominent, straight medially, weakly curving at caudal ends. Posthumeral costa distinct, complete to apex, narrower than discolateral costa. Submarginal costa narrow entire length; turning upward weakly and abruptly inward to caudal bulb, forming a small, tubercular angulation. Costal interval 1 (between juxtasutural and discomedian costae) flattened, with 18 coarse punctures in outer row. Costal interval 2 (between discomedian and discolateral costae) with two rows of coarse, rounded, distinctly separated punctures. Costal interval 3 (between discolateral and posthumeral costae) with three rows of coarse, rounded, distinctly separated punctures; punctures in median row smaller than outer rows. Costal interval 4 (between posthumeral and submarginal costae) with punctures somewhat transverse, not connected to adjacent row medially; rugose-washboard surface medially, decreasing basally. Caudal trichomes at end of costae small, hidden; trichome of caudal bulb narrowed, transversely elongate. Caudal bulbs moderately large, transverse; in dorsal view, weakly prominent laterally, curving inward and caudally to interrupt juxtasutural costa; anterior margin projecting, broadly rounded, dividing trichome opposite of discomedian costa; in caudal view, somewhat broadly rounded dorsally and laterally. Dorsal surface of caudal bulb weakly alutaceous, weakly glossy, apparently impunctate, with scattered minute setae; surface between bulb and caudal margin of elytra dull, concave with several foveate punctures.
Ventral thorax. Surface alutaceous, dull, punctures bearing a short seta. Metaventrite flattened; median longitudinal groove on posterior two-thirds of ventrite, width slightly less than mesotarsi, equally widened at ends; disc on either side of groove with minutely punctate area bounded laterally by short series of coarse punctures; punctures on remainder of disc fine, evenly scattered.
Abdomen. Abdominal ventrites 2–4 with narrow, transverse, anterior groove fluted; posterior margin with row of small, shallow punctures; ventrites laterally with indistinct, shallow, triangular depression with coarse punctures, depression more distinct on posterior ventrites; rest of surface with scattered, fine punctures bearing a short seta. Abdominal ventrite 5 (last) as long as preceding two ventrites medially; surface evenly coarsely punctate, punctures separated by one puncture diameter; medially with cluster of punctures forming small fovea each side of midline; laterally with transversely elongate, triangular fovea; anterior margin with narrow, punctate groove extending to lateral margin. Pygidium greatly depressed against abdominal ventrite 5 (Fig. 26–27), surface parallel with surface of ventrites; median carina broadly flattened, widening to a weakly bilobed projection that encroaches upon the two medial fossae on ventrite 5.
Legs. All femora weakly glossy, with moderately deep, distinct punctures; all punctures bearing a very short seta. Profemoral punctures enlarged and prominent, mesofemoral and metafemoral punctures moderate in size and less distinct. Mesofemur robust medially; posterior margin weakly sinuate, with weakly convex swelling at middle and apical third. Metafemur narrow, moderately widened medially. Protibia with bidentate apex; inner tooth minute; medial margin weakly concave in apical third. Mesotibia and metatibia with apex truncate; lacking inner apical spine and concave inner margin. Mesotarsomere 1 as long as mesotarsomeres 2–4; ventral setae fine, glossy surface visible. Metatarsomere 1 as long as metatarsomeres 2–5 combined.
Allotype male. Body length 3.80 mm, width 1.20 mm. Similar to female in most characters. Pronotum with paramedian costae weakly curving inward while diverging to posterior margin. Mesotibia with apex truncate; large, medially projecting spine on inner apical angle; inner margin concave in apical quarter. Metatibia weakly widened to truncate apex; large, medially projecting spine on inner apical angle; inner margin weaky concave in apical third.
Apical half of pygidium with central carina basally split, Y-shaped; top of Y prominent, not tuberculate; median carina broad, flattened (Fig. 19, 23), surface convex, lacking concavity in lateral view (compare Fig. 22, 28 with Fig. 29); each side of median carinae with alutaceous, triangular depression. Genitalia (Fig. 24–25) with phallobase arched, tubular; parameres short, less than one-quarter length of phallobase; parameres straight in lateral view, gradually narrowing to rounded apex in caudal view.
Variation. Length 3.50–4.06 mm, width 1.13–1.31 mm. Elytra with discolateral costal anterior and posterior ends weakly curved inward, appearing straight in some, curving more distinctly in others, slightly sinuate medially in a few specimens. Paramedian pronotal costae are posteriorly straight or weakly curving, and the degree of divergence posteriorly is somewhat sexually dimorphic. However, some specimens vary enough that gender cannot be confidently determined based on this character.
Material examined. Holotype female and allotype male deposited in FSCA: “ GUATEMALA: Dept. Izabal, / E of Morales, 7-VI-2002, R.E. Woodruff, dung traps // [red paper] HOLOTYPE ♀ / Rhyparus / platypygus / des. 2024 / Skelley & Smith”. Allotype with similar label except blue, stating “ ALLOTYPE ♂ ”.
Paratypes (13): same data as holotype (allotype + 2 FSCA, 1 CMNC); GUATEMALA: Department Izabal; E. of Morales, Sierra del Merendon, Finca Firmeza, 1km W of Honduras, 1250 m elev., 27-28-V-2003, at light, cloud forest R Woodruff, J. Monzon (3 FSCA); SE of Morales, Finca Firmesa 2, 15°21’51’’N, 88°41’28’’W, 3880 ft., 21–22-VI-2001, W.B. Warner, J. Monzón-Sierra, & R. Cunningham, ultraviolet, mercury vapor, & mercury halogen light (2 WBWC); near Cerro Negro Norte, 1 km W Honduras, 1150 m, 6–7-VI-2002, mercury vapor light, J. & C. Monzon, S. Davis, R.E. Woodruff (2 FSCA). HONDURAS: Department Cortés; P.N. Cusuco, 18.7 km N Cofradía, 5.4 km W Buenos Aires, Cerro Jilinco, 1960 m, 26-VIII-1994, R. Anderson, pine/cloud forest litter, Berlese (1 CMNC); Department Ocotepeque; R.B. Güisayote, 21-V-1995, R. Turnbow, mercury vapor & blacklight (1 RHTC).
Etymology. Named “ platypygus ” for the highly modified pygidium of the females, which is also flattened in males when compared to other species. Derived from the Greek “ platys ” meaning broad or flat, combined with “ pyge ” meaning rump or buttocks.
Comments. The modified and depressed female pygidium of R. platypygus is presently unique for the Western Hemisphere members of Rhyparus. However, this form of pygidium occurs in a group of species related to Rhyparus stebnickae Minkina, Anichtchenko, Vasiljeva and Skelley found widely in Indonesia and oceanic countries to its east (e.g., Minkina et al. 2022, 2023, 2024; Minkina and Jákl 2024). All of these Eastern Hemisphere species differ from R. platypygus in several characters, most notably by being at least two times larger in body size and having densely punctate surfaces between the pronotal costae.
description: Published as part of Smith, Paul E. Skelley Andrew B. T., 2024, Five unusual new species of Rhyparus Westwood, 1845 from Mexico and Central America (Coleoptera: Scarabaeidae: Aphodiinae: Rhyparini), pp. 1-19 in Insecta Mundi 2024 (91) on pages 11-14, DOI: 10.5281/zenodo.14662346