Rhyparus hexadentatus 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 hexadentatus

description: Rhyparus hexadentatus Skelley and Smith, new species
Figures 6–12, 41
Diagnosis. A member of Rhyparus readily distinguished from all other Western Hemisphere species by the strongly bilobed caudal bulb. Other important diagnostic characters include the pronotal lateral margin with anterior lobe more prominent than intermediate lobe, elytron with discomedian costa greatly reduced or absent medially, elytral trichome narrowed and partially divided by caudal bulb near discolateral costa; second and third costal intervals of elytron having three rows of equally coarse punctures (rows may be confused medially in third interval, appearing as four rows in some), and with elytron having three distinct lobes apically. Known from Mexico and Guatemala (Fig. 41).
Description. Holotype male (Fig. 6–8). Body length 5.3 mm, width 2.0 mm. Elongate, somewhat parallel-sided, flattened, dark brownish black, surface generally dull, partly clothed with fine, pale yellow setae on head and all longitudinal costae on pronotum and elytra.
Head. Surface subglossy, weakly alutaceous, transversely subhexagonal (Fig. 9). Clypeus trapezoidal, anteriorly weakly concave in anterior view, concave between small teeth in dorsal view; anterior margin weakly upturned with obtuse tooth on each side of medial third, lateral thirds concave to rounded tooth anterior of clypeo-genal junction. Gena moderately prominently lobed laterally, distinctly excavated anterior of eyes. Clypeal disc convex with two costae evident only as small tubercles visible in dorsal view; peridiscal impression strong basally, broadly grooved anteriorly. Frons with four short frontodiscal costae, medial two weakly developed, lateral two distinct. Head with widely scattered fine punctures, slightly larger and denser at base of head, smaller punctures on clypeal disc widely separated; punctures with a short, pale yellow seta.
Pronotum. Surface dull, costae more glossy, widest anteriorly, with paramedian, discolateral, and submarginal costae distinct. Costae on each side with very small punctures bearing a very small seta. Paramedian costae incomplete, most prominent at anterior margin, reduced and obsolete at constriction near anterior third; distinct and diverging to posterior margin. Discomedian costa basally straight, distinctly interrupted by fovea on anterior third, present at anterior margin. Submarginal costa complete to posterior margin, sinuate, with angulation just posterior of middle. Costal intervals between paramedian, discolateral, and submarginal costae anteriorly with four coarse punctures. Interval between paramedian costae coarsely punctate over constriction at anterior third. Basally, paramedian and discolateral costae each with two foveate punctures on each side, at base (heavily encrusted) and posterior quarter. Lateral margin strongly sinuate, reduced posteriorly; anterior lobe prominent, sharply projecting laterally; intermediate lobe reduced, sharp.
Scutellum. Scutellar shield minute, narrow, apex acute.
Elytra. Surface dull, subglossy; each elytron with five elevated costae separated by five flattened intervals; intervals coarsely, rugosely punctate (Fig. 10). Costae (where present) narrow, sharply convex; on each side with a row of very small punctures bearing a short seta. Juxtasutural costa complete from base to apex, depressed to apex. Discomedian costa sinuate, strongly reduced (or absent) medially; gradually swelling at apex to small postdiscal bulb, lacking apical patch of setae. Discolateral costae narrow entire length, sinuate, medially concave and curving inward at apex into trichome. Posthumeral costa less prominent than discolateral costa, weakly sinuate, curving inward to trichome at apex. Submarginal costa narrow entire length, sharply turning inward at apex and with bifid caudal bulb, each elytron appears tridentate apically. Costal intervals flattened, dull, with foveate punctures, slightly separated, surface rugose; second and third costal intervals with three rows of equally large punctures, third costal interval with three rows of equally coarse punctures; all puncture rows complete nearly to apex, where they abruptly end at declivity into trichomes. Caudal trichomes small, narrowed. Caudal bulbs large, divided with medial and lateral lobes in dorsal view; dorsally flattened in caudal view; slightly projecting anteriorly and dividing trichome opposite discolateral costa; bulb coarsely punctured on posterior margin; surface between bulb and apical elytral margin alutaceous with foveate punctures.
Ventral Thorax. Surface weakly dulled, alutaceous. Metaventrite flattened, in the middle with distinct deep longitudinal median impression in posterior three-quarters, impression equally deep and wide along length; disc on either side with punctation large and regularly spaced, separated by one diameter, decreasing in size anteriorly and laterally, all punctures bearing short setae.
Abdomen. Abdominal ventrites 2–4 with narrow, transverse, anterior groove that is smoothly margined, crenate interiorly; ventrites laterally with large, distinct, triangular depression, 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 or less; medially with small carina on anterior half having punctate fovea on either side of midline and a transversely elongate punctate fovea laterally; anterior margin with a narrow, crenated groove extending to lateral margin. Pygidium with central carina strong, split at basal third thus Y-shaped, complete to apex; each side with large, triangular, alutaceous areas occupying most of surface.
Legs. All femora weakly glossy, with moderately deep, distinct punctures; all punctures bearing a very short seta. Mesofemur robust, with posterior margin bearing a single blunt angulation at middle and another indistinct angulation at apical third. Metafemur narrow, weakly widened at apical third. Protibia with bidentate apex; inner tooth greatly reduced; medial margin straight. Mesotibia with apex truncate; large, medially projecting tooth on inner apical angle; inner margin straight in apical third. Metatibia weakly widened to truncate apex; tooth of inner apical angle small, projecting caudally; inner margin straight in apical third. Mesotarsi with basal tarsomere as long as next three tarsomeres. Metatarsomere 1 as long as metatarsomeres 2–5 combined.
Genitalia. Male genitalia (Fig. 11–12) with basal piece long; parameres short, rounded in caudal view, length a quarter basal piece length.
Allotype female. Body length 5.3 mm, width 1.9 mm. Similar to male in most characters. Mesotibia lacking inner apical tooth. Metatibia with inner apical tooth reduced. Abdominal ventrite 5 lacking the punctate fovea on either side of midline. Pygidium similar to males except median carina reduced in apical half, not reaching apex.
Variation. Body length 4.7–5.8 mm, width 1.8–2.2 mm. Discomedian elytral costa varies from distinctly reduced to absent medially. Most specimens from Veracruz, Mexico have the discomedian costa absent, obscured by punctures, but some have it weakly present. In comparison, most from Guatemala have it evident but weak, while some have it reduced and only evident by straight rows of punctures. Although showing some regional variation, these all have other characters defining the species. Another variation is with the second and third costa intervals of the elytron having three rows of equally coarse punctures, occasionally coalescing. Puncture rows of the third costal interval may be confused medially, appearing as four rows in some.
Material examined. Holotype male and allotype female in FSCA: “ MEXICO: Veracruz / Rancho Viejo, ‘ Piedra Blanca’ / 19°30′59.33″N, 97°00′32.90″O / 1639 m, 7-12-VIII-2016, J. Luis / S. Huerta, trampa de luz UV // [red paper] HOLOTYPE ♂ / Rhyparus / hexadentatus / des. 2024 / Skelley & Smith”. Allotype with similar label except blue, stating “ ALLOTYPE ♀ ”.
Paratypes. In addition to the holotype and allotype, 29 paratypes were studied: GUATEMALA: Guatemala: Puerta Parada, 16-X-1999, J. C. Schuster (1 FSCA); Jalapa: Miramundo, Pino Dulce, 14.53388°N 90.15236°W, 2300 m, 18-IX-2008, R.S. Anderson, cloud forest, ex sifted leaf litter, RSA2008-135 (1 CMNC); Quetzaltenango: Fuentes Georginas, 2400–2600 m, 14–16-VI-2015, J. B. Heppner & E. Fuller, (1 FSCA); Zunil, Las Fuentes Georginas, 14°45′0.4″N, 91°28′48.8″W, 2440m, 26-VI-2011, Ratcliffe, Cave, Cano, Moore, cloud forest, MV/BL (2 UNSM); San Marcos: rd. to Bojanal (sic), 23-X-2006, R. Turnbow, mv + bl (2 RHTC); Los Pocitos, 15.16540 −92.11480, 2405m, 10-VI-2015, R. Anderson, cloud forest litter, 2015-134 (1 CMNC); Parque Municipal Refugio del Quetzal, 14.93916 −91.87296, 1818m, 4-VI-2015, R. Anderson, cloud forest litter, 2015-103 (1 CMNC); Suchitepéquez: Refugio El Quetzal, 14.55827 −91.19124, ± 50 m, 2022m, 16-VI-2009, R.S. Anderson, oak forest, ex sifted leaf litter, RSA2009-104 (1 CMNC). MEXICO: Chiapas: Mpio. Angel Albino Corzo, Reserva Biosfera El Triunfo, Campamento El Quetzal, 15°43.239′N, 92°56.405′W, 1800m, 18-VII-2007, R. S. Anderson, mixed hardwood forest litter, 2007-017 (1 CMNC); Oaxaca: 32 km S.W. Valle Nacional, KM85, 1650 m, 26-VII-1992, R. S. Anderson, trans/cloud forest, leaf litter Berlese, 1992-030 (1 CMNC); 15 mi. S. Valle Nacional, 4000ft, 20-V-1971, H. Howden (1 CMNC); Veracruz: same data as holotype (allotype + 10 FSCA; 4 IEXA, 2 NHML).
Etymology. The species epithet reflects the distinct caudal lobe development and dentate apex of the submarginal costa on the elytra appearing as six large caudal teeth.
Comments. Rhyparus hexadentatus shows an interesting mix of characters. The reduced discomedian elytral costa and the caudal bulb sharply angulate anteriorly, splitting trichome close to the discolateral costa (see arrow in Fig. 10, compare with Fig. 1, 13, 18, 30) place it close to R. zayasi Cartwright and Woodruff and R. sculpturatus Cartwright and Woodruff. However, the pronotal shape with enlarged anterior marginal lobes and the 3–4 rows of punctures in the third elytral interval are more similar to R. blantoni Cartwright and Woodruff, R. suspiciosus Cartwright and Woodruff, and R. spilmani Cartwright and Woodruff. Rhyparus hexadentatus differs from all of these by having three distinct puncture rows in the second elytral interval and a bilobed caudal bulb.
Although the variations within the populations of R. hexadentatus appear notable on paper, only with an adequate series of specimens can we see these are only variations, and that they vary regionally. In this species, care was needed when examining development of elytral costae and counts of interval puncture rows. Variable series, such as those available here, illustrate the caution needed when attempting to describe any minorly different aphodiine based on only one or a few specimens.
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 5-8, DOI: 10.5281/zenodo.14662346