On the rare Neotropical genus Ophionthus Bernhauer (Coleoptera: Staphylinidae: Staphylininae): redescription of the type species and description of a new species

Two female specimens of the Neotropical genus Ophionthus Bernhauer were found during museum collection surveys, representing different species of the genus. These species are Ophionthus serpentinus Bernhauer, 1908 and O. asenjoi sp. nov. The genus Ophionthus was monotypic until the present study and only known from a single male specimen from Central Peru. The genus is redescribed with the inclusion of female characters from both the type species and the new species here proposed. Additionally, the systematic position of Ophionthus within the Neotropical lineage of Philonthina and its geographical distribution in Peru are reassessed. Descriptions, diagnoses, illustrations, pictures, a cladogram, and a distribution map are provided.


Introduction
Philonthina Kirby, 1837 is the most speciose subtribe inside the mega-diverse rove beetle tribe Staphylinini Latreille, 1802 (Chani-Posse et al. 2018a), accounting for more than 2800 species classifi ed in 75 genera worldwide. Thirty-fi ve of these occur in Central and South America (CASA) (including Mexico and all other countries of Central and South America) and 24 are endemic to CASA (Chani-Posse et al. 2018b;Asenjo et al. 2019;Chani-Posse & Ramírez-Salamanca 2020a, 2020bRamírez-Salamanca et al. 2020).
One of these genera that is endemic to CASA is Ophionthus, that was described by Bernhauer (1908) to accommodate the species Ophionthus serpentinus Bernhauer, 1908 which was fi xed as the type species by subsequent monotypy (Blackwelder 1952). Since then, references to this genus in the literature have been scarce and mostly limited to citations in catalogues and checklists (e.g., Blackwelder 1944;Herman 2001), until recent studies placed it within the Neotropical lineage of Philonthina and nested within the so-called Paederomimus-complex (e.g., Chani-Posse 2013;Chani-Posse et al. 2018a, 2018bChani-Posse & Ramírez-Salamanca 2020a, 2020b. However, the most recent results (Chani-Posse & Ramírez-Salamanca 2020a) cast doubt on its current status due to its placement within a group of species closely related to Musicoderus Sharp, 1885 and the presence of protarsomeres with discal setae on their ventral surface, also found in other Neotropical genera (Chani-Posse & Ramírez-Salamanca 2020b; Ramírez-Salamanca et al. 2020). Therefore, a reassessment of its morphological characters as well as further insights into its biogeographical affi nities are needed to clarify its generic limits and phylogenetic relationships within the Neotropical Philonthina lineage (Chani-Posse & Ramírez-Salamanca 2020a, 2020b).
As part of our on-going studies on the Neotropical Philonthina and the examination of type and non-type material from European as well as North and South American museum collections, we have recently found two female specimens that belong to Ophionthus as defi ned by Chani-Posse (2014a). One of them, which was identifi ed by us as O. serpentinus, is deposited in the Entomological Collection of the Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, Lima, Peru (MUSM) and was collected by Hans-Wilhelm Koepcke (1914Koepcke ( -2000 and Maria Koepcke (1924Koepcke ( -1971, German zoologists who lived in Peru between 1950and 1974(Aguilar 2009). The second specimen is deposited in the Instituto Fundación Miguel Lillo, Tucumán, Argentina (IFML) and was collected by Wolfgang Karl Weyrauch (1907-1970, another German zoologist who lived in Peru from 1939 to 1961 and moved to Argentina -together with his private collection -in 1962 where he stayed until his death (Willink 1999).
The objectives of this paper are to redescribe Ophionthus and its type species, O. serpentinus, using characters from both external morphology and male and female genitalia, and to describe a new species, O. asenjoi sp. nov., based on female characters. Also, we provide the fi rst specifi c collection locality for O. serpentinus and discuss the type locality, increasing the morphological and distributional data available for this genus. Finally, the systematic placement of Ophionthus within the Neotropical lineage of Philonthina is reassessed based on a phylogenetic analysis of morphology.

Examination of specimens and terminology
Rove beetles were examined as pinned dry specimens, relaxed in warm soapy water for fi ve minutes, rinsed, then the last abdominal segments were dissected and cleared in 10% KOH solution, washed in distilled water, and examined as wet preparations in glycerin. Dissections and observations were made using Nikon SMZ745 and Leica S6 D microscopes. The dissected segments were placed in polyethylene microvials with glycerin and pinned under the respective specimens. For detailed examination of the protarsomeres, the right foreleg of a female specimen was dissected from the body and prepared as follows: fi rst, it was cleaned using an ultrasonic bath for three minutes, then the leg was dried, and lastly mounted on a metal stub using a Z-Axis electrically conductive tape and sputter-coated with gold. Micrographs were obtained using a JEOL JSM-6610LV scanning electron microscope. Photographs were taken using a Leica EC3 digital camera attached to the Leica S6 D microscope.
All measurements are in mm. The following measurement abbreviations are used: A1, A2, A3 = length of fi rst, second or third antennomere BL = overall body length (from the apex of the labrum to the apex of the abdomen) EL = elytron length at side (straight line from humerus to apex; seen from above) EW = elytron maximum width HL = length of head capsule (from anterior margin of frontoclypeus to neck constriction, along midline) HW = head capsule maximum width (measured at widest point, including eyes) PL = pronotum length along midline PW = pronotum maximum width S1 = length of metatarsomere 1 S5 = length of metatarsomere 5 (last) TL = temple length (from the posterior margin of the eye to the nuchal groove) YL = eye length (seen from above) Terminology mainly follows Smetana (1995) and Chani-Posse (2014b). For the type material, information on the labels was written verbatim, quotation marks " " separate different labels, and a slash / separates different lines within a label. The text within square brackets [ ] is explanatory and/or inferred information and is not included on the original labels. Handwriting on labels of type specimens was compared to the respective author's handwriting using Horn et al. (1990).

Depositories
The type and non-type material studied here were borrowed from the following collections (collection managers and/or curators in parenthesis):

Georeferencing of the type locality
With the aim of tracing and georeferencing the type locality of O. serpentinus as well as that of our new species, O. asenjoi sp. nov., we used the Ornithological Gazetteers of Peru (Vaurie 1972;Stephens & Traylor 1983), the Gazetteer of Peruvian entomological stations (Lamas 1976), documentation of Jelski's fi eldwork and material collected in Peru (Taczanowski 1874(Taczanowski , 1875(Taczanowski , 1884Mlíkovský 2009), as well as the catalogue of Weyrauch's type localities georeferenced (Breure 2012) and personal comments given by Dr Gerardo Lamas. Altitude, if it was not given by the original author, was extracted from Google Earth Pro (2020). We made a list of potential places that match with the type localities "Peruvia centralis" and "N-Peru: Bambamarca" in order to know the distribution of these species, summarized in the Supp. fi le 1. As for the female specimen of O. serpentinus, whose locality data is associated with the fi eld collection code "Coll. Koepcke #665" on its label, we referred to the catalogue of sampling sites of Koepcke (1982) which provides information about collecting places and fi eld observations for more than 2000 sites in Peru. Maps were elaborated using QGIS (2020).

Phylogenetic analysis
In order to validate the taxonomic status of Ophionthus as a distinct genus of Philonthina and to confi rm its monophyly and systematic placement within the Neotropical lineage, we included our new data (female characters for O. serpentinus) and the new species (O. asenjoi sp. nov.) into the original dataset by Chani-Posse & Ramírez-Salamanca (2020a). From a total of 132 characters and 79 taxa, we found three coding errors in the original matrix (i.e., characters 6, 77 and 82) for O. serpentinus. Rectifi cations for this species are as follows: 6(1), antennomere 1 as long as or longer than antennomeres 2 and 3 combined; 77(0), protarsomeres 2 and 3 each as long as to longer than wide, and 82(0), discal setae without terminal plate. The resulting data matrix (see Supp. fi le 2) was analysed by means of maximum parsimony (MP) under the same previous conditions (Chani-Posse & Ramírez-Salamanca 2020a).

Diagnosis
The genus Ophionthus can be differentiated from other genera of Neotropical Philonthina by the combination of the following characters: head and pronotum broadened anteriad, antennomere 1 at least twice as long as 2 and almost as long as antennomeres 2 and 3 combined, labial palpomere 2 cylindrical, protarsomeres 2-3 with discal setae on ventral surface and without marginal setae, prosternum with sternacostal ridge joining superior line of hypomeron, metatarsomere 1 almost twice as long as 5.
HEAD. Subhexagonal and slightly transverse (male) to subquadrate (female) in shape, slightly broadened anteriad, narrower in female (Figs 2A, 3A) than male (Fig. 1A); nuchal ridge present; postmandibular ridge absent; postgenal ridge present; ventral basal ridge present, extending more or less parallel to ventral portion of postoccipital suture; infraorbital ridge present or absent; dorsal and ventral surface of head with scarce setation, microsculpture dense and undulate. Eyes large, moderately convex, occupying apical half of lateral margin of head, shorter than temples seen from above. Gular sutures joined before neck. Frontoclypeus with a short longitudinal groove. Antennae inserted closer to anterior margin of frontoclypeus than to eyes, moderately long, not reaching base of pronotum, increasing gradually in width toward apex; antennomere 1 without apical spine-like seta, distinctly longer than antennomere 2 and almost as long as antennomeres 2 and 3 combined; antennomere 3 slightly longer than antennomere 2; pubescence starting on antennomere 4 to 11. Clypeus entire and fused with frons. Labrum rectangular, distinctly emarginate, sclerotized except apical margin, with several setae and macrosetae at apical margin. Mandible prominent, 1.4× length of head, with setose prostheca well-developed, with a groove on dorso-lateral margin. Maxilla with lacinia elongate and densely setose along internal apical half margin, with galea prominent and densely setose at apex; maxillary palpus long, palpomeres 1 to 4 glabrous with scarce setae at apices; palpomere 1 small; palpomere 2 slightly curved, longest, shorter than 3 and 4 combined; palpomere 4 cylindrical, longer than segment 3. Mentum transverse, with anterior margin slightly emarginate, one seta at each latero-lateral corner. Labial palpus moderately long; palpomere 1 shorter than 2; palpomere 2 shorter than 3; palpomere 3 cylindrical, shorter than 1 and 2 combined.
PRONOTUM. Distinctly longer than wide, slightly broadened anteriad, front margin subtruncate, hind margin slightly arcuate, anterior and posterior angles rounded (Figs 1A, 2A, 3A); disk with two dorsal rows of punctures sub-parallel to each other; lateral puncture of pronotum bearing long macroseta separated from superior line of pronotal hypomeron by a distance more than three times as large as diameter of puncture; surface with fi ne and dense microsculpture. Prosternum without distinct midlongitudinal carina; basisternum longer than furcasternum, with transverse carina variable (either complete or rudimentary). Mesoventrite somewhat elongate, with sternopleural suture distinctly oblique; mesoventral intercoxal process rounded, forming an obtuse angle.
ABDOMEN. Tergum I with paired prototergal glands manifested by invaginated capsules with small openings. Terga III-V with anterior basal transverse carina distinct, posterior basal transverse carina always distinct on tergum III, distinct to not distinct on terga IV-V; area between anterior and posterior carinae deeply and sparsely punctate; surface with fi ne and dense microsculpture of transverse and oblique waves.

Immature stages
Unknown.

Geographical distribution
The genus Ophionthus, with two species known at present, has been recorded from the departments of Cajamarca, La Libertad, and Junín in Peru. Based on the information of the specimen labels (locality and habitat), Ophionthus is distributed mainly in the ecoregion of Peruvian Yungas (Olson et al. 2001). However, according to Morrone´s regionalization (2014) those localities belong to the biogeographical province of Puna (Figs 4-5, Supp. fi le 1).

Bionomics
The species of Ophionthus are considered general predators as are the other genera of Philonthina. One specimen of O. serpentinus was collected in a clearing in montane forest and riverside shrubbery. Bernhauer, 1908 Figs Bernhauer (1908) stated that Skalitzky gave him a unique specimen of O. serpentinus; the specimen mentioned above agrees with the original description and is considered to be the holotype, fi xed by monotypy. COLOURATION. Head, thorax, and abdomen shiny black, except apical half of tergum VII, apical third of sternum VII, and segments VIII and IX yellow; mandibles, maxillary and labial palps, elytra, and legs dark brown; antennomeres 1-9 dark brown to black and 10-11 yellowish (Figs 1A, 2A-B).
ABDOMEN. Abdominal terga III-V each with posterior basal transverse carina distinct. MALE SEXUAL CHARACTERS. Tergum VIII with hind margin projected, forming an obtuse angle (Fig. 1C). Sternum VIII slightly emarginate apically at middle, with numerous long setae on apical area and small setae on basal area (Fig. 1D). Sternum IX symmetrical, narrowed in the middle of its lateral margins, deeply emarginate apically, with several fi ne and short setae at each side of emargination (Fig. 1E). Tergum X with apex rounded, with numerous setae at apex (Fig. 1F). Aedeagus with median lobe distinctly broadened at middle and gradually narrowed towards a rather truncate apex seen from above, paramere triangular with base concave (Fig. 1G-H), internal sclerites as in Fig. 1G-H. FEMALE SEXUAL CHARACTERS. As described for the genus.

Geographical distribution and bionomics
The male holotype of O. serpentinus was collected in 1873 by Jelski in "Peruvia centralis" (Fig. 1B). Jelski travelled and collected in the central Andes of Peru during that year (Solsky 1875;Taczanowski 1875;Mlíkovský 2009) and the localities he visited are summarized in the Supp. fi le 1 and Figs 4-5. Based on these analyses, the type locality "Peruvia centralis" is located in the department of Junín, but we do not have more information (e.g., day and/or month of collection) to improve the accuracy of this type locality (Fig. 1B). Additionally, the new locality provided by the female specimen from Hacienda Llaguén, ca 7°40′ S, 78°40′ W, 1800 m [m a.s.l.] (Koepcke 1982) is located in the department of La Libertad and close to the Forest of Llaguén (7°42′ S, 78°44′ W, 2642 m [m a.s.l.]), which is described as a dry cloud forest, with high human disturbance and used for grazing cattle and as a source of fuel (Valencia 1990). Hacienda Llaguén is placed in the ecoregion of Peruvian Yungas (Olson et al. 2001) or in the Puna province (Morrone 2014) (Fig. 4) and nowadays it is placed in the ecosystem of Andean shrublands (MINAM 2019). According to label information, the female specimen was collected in an open area within a montane forest and riverside shrubbery. COLOURATION. Head, thorax, and abdomen piceous, except apical half of tergum VII, apical third of sternum VII, and segments VIII and IX yellow; mandibles, maxillary and labial palps, elytra and legs dark brown; antennomeres 1-8 dark brown to black and 9-11 yellowish (Fig. 3A).

Geographical distribution and bionomics
Ophionthus asenjoi sp. nov. is only known at present from its type locality in Bambamarca, department of Cajamarca, Northern Peru at 3000 m [m a.s.l.] (Fig. 4). In addition, it is known that on the same collection day as that of the holotype of O. asenjoi sp. nov. (i.e., 28 Jun. 1956), Weyrauch collected two specimens of Cajamarca triseriata Roewer, 1957 (Arachnida: Opiliones) in "Nord-Peru: Cerro Macheipungo, 4 km NW Bambamarca" (Roewer 1957: 75), which is georeferenced as 06°41′ S, 78°32′ W (Breure 2012: 5). Therefore, it is highly probable that this locality is the same or close to where the holotype of O. asenjoi sp. nov. was collected. Bambamarca belongs to the ecoregion of Peruvian Yungas (Olson et al. 2001) or Puna province (Morrone 2014) and is nowadays agricultural land, surrounded by an urban zone and Andean shrubland ecosystem (MINAM 2019). Bernhauer, 1908 and O. asenjoi sp. nov.

Discussion
After reviewing most of the available type and non-type material of Philonthina from the main collections in Europe, North and South America, we found only three specimens of Ophionthus, one of them being the male holotype of the type species, O. serpentinus. The two additional specimens are a female of O. serpentinus (MUSM) and another female of O. asenjoi sp. nov. (IFML), both collected in Peru in 1952 and 1956, respectively. The holotype of O. serpentinus was also collected in Peru, in 1873, and represents the oldest known collected specimen of Ophionthus. Based on this evidence, we confi rm that the two species of Ophionthus are collected very rarely and in small numbers. The rarity could be due to low population densities, lack of collecting effort and/or a diffi cult-to-sample microhabitat (i.e., fl owers or vegetation), changes in anthropic land use (the collecting site of O. asenjoi sp. nov. now consists of agricultural and urban lands), or a combination of these causes.
The previous systematic assessment by Chani-Posse & Ramírez-Salamanca (2020a) placed Ophionthus into the so-called Paederomimus complex of the Neotropical lineage of Philonthina. Although not related to any of the clades that contain the type species of the most diverse but not monophyletic genera of Philonthina in CASA (i.e., Belonuchus Nordmann, 1837, Paederomimus Sharp, 1885, Philonthus Stephens, 1829), Ophionthus appeared not far from the Musicoderus clade in that study, i.e., in a wellsupported sister group relationship with Belonuchus barbicornis Bernhauer, 1916, a species only known from the Andes of Colombia. Our new assessment herein does not only confi rm Ophionthus as a member of the Neotropical lineage and the Paederomimus complex, but it also validates its status as a distinct genus (Fig. 6). Furthermore, its former close relationships to B. barbicornis and other previously allied taxa are not supported here, and their phylogenetic relationships within the Paederomimus complex remain unclear. Thus, Ophionthus is revealed as a morphologically distinct genus within the Neotropical lineage.