Lendatus, a new genus of Xanthopygina (Coleoptera: Staphylinidae: Staphylininae) with description of three new species

A new genus of Xanthopygina rove beetles is described here as Lendatus gen. nov. The new genus includes three new species: L. bolivianus sp. nov., described from Bolivia, L. philothalpiformis sp. nov. described from Costa Rica and Panama, and L. platys sp. nov. described from Bolivia, Colombia, Ecuador and Peru. Lendatus belongs to the Isanopus group of genera of Xanthopygina and can distinguished from all the genera based on the unique punctation on the pronotum and the long apical setae of the paramere. A key to the three species of Lendatus along with photographs and illustrations is provided for the identification of species.


INTRODUCTION
Xanthopygina is a diverse group of mostly neotropical rove beetles that includes (before the publication of this paper) 29 genera. In the latest phylogenetic analyses of the subtribe, Chatzimanolis & Brunke (2019) were able to examine all genera of Xanthopygina and identified the major lineages of the subtribe, One of them was the Isanopus group of genera, which included four genera: Zackfalinus Chatzimanolis (Chatzimanolis, 2012) as the sister group of Peripus Chatzimanolis & Hightower (Chatzimanolis & Hightower, 2019); identified in the phylogeny paper as genus 5), and Isanopus Sharp (Chatzimanolis, 2008) as the sister group of genus 2. That genus 2 is described in this paper as the new genus Lendatus Chatzimanolis and includes three new species.
The sister group relationship between Isanopus and Lendatus was first identified by Chatzimanolis (2014) in the first molecular phylogeny of the subtribe, where Lendatus was presented in that phylogeny as 'undescribed genus'. Delimiting new taxa, especially above the species level is not straightforward and ideally one should have multiple lines of evidence before proposing formal taxonomic names. While I had strong molecular evidence that Lendatus is indeed a new genus for quite some time, I did not feel comfortable describing Lendatus as new taxon until the completion of the morphological analysis of the subtribe that included all described genera and a number of undescribed ones.
Please note that several of the specimens currently deposited in SEMC will be transferred to MUSM per previous institutional/collecting agreements.
The electronic version of this article in Portable Document Format (PDF) will represent a published work according to the International Commission on Zoological Nomenclature (ICZN), and hence the new names contained in the electronic version are effectively published under that Code from the electronic edition alone. This published work and the nomenclatural acts it contains have been registered in ZooBank, the online registration system for the ICZN. The ZooBank LSIDs (Life Science Identifiers) can be resolved and the associated information viewed through any standard web browser by appending the LSID to the prefix http://zoobank.org/. The LSID for this publication is urn:lsid:zoobank.org:pub:0612FF19-38E8-4072-AF74-0EB16165841. The online version of this work is archived and available from the following digital repositories: PeerJ, PubMed Central and CLOCKSS.  & Brunke, 2019 for characters differentiating all genera in the Isanopus group) based on the following morphological characteristics: basal transverse carina on sternum 3 acutely pointed medially; lack of dense meshed microsculpture on sterna 5-7 (Fig. 4C); antennomeres 8-10 quadrate or elongate (Fig. 3E); and mesocoxae moderately to strongly separated (Fig. 4B). Lendatus was recovered as the sister group to Isanopus (Chatzimanolis, 2014;Chatzimanolis & Brunke, 2019) and the sister group relationship is supported by the following morphological characteristics (besides the molecular data supporting that relationship): coarse punctures impressed in flange at posterior angle of pronotum (Fig. 2); and lateral area of basal transverse carina on sternum 3 sinuate. Synapomorphies for Lendatus include: apical setae on paramere long, produced over the median lobe (Figs. 5-7), longer than any other Xanthopygina genus; and distribution of punctures on disc of pronotum split into anterior and posterior parts by diagonal longitudinal line, a unique character state in Xanthopygina. Additional characteristics that can distinguish Lendatus from Isanopus include: paramere not extremely reduced (as in Isanopus) and tarsomeres of middle and hind legs not enlarged and lobed (as in Isanopus).

Taxonomy
Some species of Oligotergus Bierig may look superficially similar to Lendatus, but species in that genus typically lack the characteristics of the Isanopus group. Additionally, L. philothalpiformis has the same color pattern with some Philothalpus Kraatz species but Philothalpus can be easily distinguished by the presence of a pair of accessory ridges on the anterior basal transverse carina of tergum 3 (see Chani-Posse et al., 2018). Description. Habitus as in Fig. 1. Body medium-sized, forebody 4.6-5.8 mm long; without long bristle-like setae. Coloration of head and pronotum dark brown to black with metallic overtones or bright reddish-orange; elytra dark metallic green, blue or purple; abdomen dark brown or reddish brown to dark brown. Head ( Fig. 2) shape rectangular; head length in comparison to pronotum shorter to subequal. Eye size relative to length of head large, more than 3/4 length of head. Postclypeus in comparison to frons not deflexed, anterior margin more or less straight. Middle of epicranium impunctate but with microsculpture. Postmandibular ridge laterally; with deep punctures demarcating raised postmandibular ridge dorsolaterally present. Gular sutures not joined before neck extended close to each other at base of head capsule. Nuchal ridge present. Neck disc punctures sparse. Antennae (Fig. 3E), antennomere 1 same width or slightly wider than 2. Antennomere 3 elongate, three times as long as wide; antennomere 4 with tomentose pubescence; antennomere 6 with curved, distinctly longer and thicker subapical setae than other macrosetae, forming circlet; antennomeres 1-11, cylindrical, longer than wide; antennomeres 8-10 symmetrical; antennomeres 5-10 without club; antennomere 11 in males subequal to 10.
Mouthparts with labrum having broad U-shaped emargination, lobes strongly separated. Mandibles (Figs. 3A-3B) relative length typical (i.e., closed mandible not extending beyond margin lateral margin of head); without asymmetrical torsion. Mandibles in dorsal view curved from apical half; in lateral view straight; left and right mandibles each with one tooth. Maxilla ( Fig. 3D) with galea much shorter than palpus; maxillary palpus with P 3 distinctly shorter than P 2 ; P 4 distinctly longer than P 3 ; P 4 not dilated. Hypopharynx and labial palpi as in Fig. 3C; labial palpus P 3 widest before apex, without long dense setae on entire lateral sides. Ligula small, entire. Mentum with alpha setae present; hypostomal cavity present, moderately delimited. Pronotum (Fig. 2) shape of lateral margins in dorsal view posteriad of midpoint straight to sinuate (except L. platys convex); anterior angles in dorsal view not strongly acuminate and produced laterad. Pronotum near anterolateral angles without raised impunctate spots; anterolateral corners with punctation; disc of pronotum with punctation split into anterior and posterior parts by diagonal longitudinal line of punctures; with coarse punctures impressed in flange at posterior angle of pronotum; with microsculpture. Pronotum subquadrate; narrower than head at widest points. Hypomeron ( Fig. 4A) with superior marginal line continuous to anterior margin; superior marginal line without deflection under anterior angles in ventral view; inferior marginal line continued as a separate entity beyond anterior pronotal angles and curving around them. Postcoxal process absent. Basisternum slightly longer than furcasternum; basisternum with pair of macrosetae situated far from anterior margin of prosternum.
Abdomen (Figs. 4C-4D) with protergal glands having well-developed acetabula. Anterior basal transverse carina on terga 3-5 without pair of accessory ridges; tergum 3 without posterior basal transverse carina and without curved carina (arch-like) on disc; center of tergum 5 with punctation; posterior half of tergum 5 in lateral view not appearing bulging. Sternum 3 with acutely pointed basal transverse carina medially; laterally basal transverse carina sinuate; basal transverse carina absent on sternum 4; sternum 5 without dense, meshed microsculpture anterolaterally; sternum 7 with sparse punctation laterally. Males with secondary sexual structures (emargination medially on sterna 7 and 8); without porose structure. Females without obvious secondary sexual structures. Diagnosis. Lendatus bolivianus and L. platys can be distinguished from L. philothalpiformis by the coloration of head and pronotum (dark brown to black in L. bolivianus and L. platys; bright reddish-orange in L. philothalpiformis). Lendatus bolivianus can be distinguished from L. platys by the shape of the pronotum (becoming narrower (concave) posteriorly ( Fig. 2A) in L. bolivianus; becoming wide (convex) posteriorly (Fig. 2C) in L. platys); the shape of the paramere (paramere wider, converging to apex in dorsal view (Fig. 5B) in L. bolivianus; paramere narrower, parallel-sided from base to apex in dorsal view (Fig. 7B) in L. platys); and the length comparison between the anterior portion of the paramere and median lobe (median lobe slightly longer than paramere (Figs. 5A-5B) in L. bolivianus; median lobe much longer than paramere (Figs. 7A-7B) in L. platys). Description. Forebody length 4.9-5.5 mm. Coloration of head, pronotum and ventral side of body dark brown to black; mouthparts and antennae dark orange; elytra metallic purple with green overtones; legs dark brown except tarsi dark orange; abdomen dark brown to black except segment 7 (posterior 1/4 orange) and segment 8 (orange).
Aedeagus as in Fig. 5; paramere in dorsal view gradually converging to rounded apex; in lateral view paramere slightly convex, converging to broadly rounded apex; paramere with peg setae as in Fig. 5C; paramere narrower but slightly longer than median lobe; median lobe in dorsal view converging to apex; in lateral view median lobe becoming narrower from middle to apex; with small dorsal subapical tooth. Distribution. Known from the province of La Paz in Bolivia. Habitat. All specimens were collected in the Yungas forest along eastern slope of the Andes Mountains in Bolivia (at elevations of 2,000 m or above) by shifting litter or flight intercept traps. Etymology. The specific epithet refers to the country of Bolivia. (Figs. 1B,2B,3,4,6,9) urn:lsid:zoobank.org:act:7AFD3EE5-49B1-495D-A289-2C390B06BF61  Diagnosis. Lendatus philothalpiformis can be easily recognized among the existing species in the genus due to the bright reddish-orange coloration of the head and pronotum. Additionally, it is the only species known with a Central American distribution. Description. Forebody length 4.6-5.8 mm. Coloration of head, pronotum and prosternum bright reddish-orange (in few specimens brown); mouthparts, antennae and legs reddishorange to brown; elytra metallic green or blue; meso-and metaventrite brown; abdomen reddish-orange to brown (frequently with segment 6 dark brown) except segment 7 dark brown with posterior 1/3 orange and segment 8 orange.

Lendatus philothalpiformis Chatzimanolis, new species
Head with 1-2 irregular rows of large punctures on each side of central impunctate area (except anteriorly); with additional 3-4 large punctures on epicranium; with microsculpture and micropunctures. Head width/length ratio = 1.5. Pronotum width/length ratio = 0.92; pronotum widest anteriorly, becoming strongly narrower (concave) posteriad; diagonal longitudinal line of punctures on disc of pronotum with 3-4 large punctures; anterolateral to that line pronotum with less than 5 large punctures; posterolateral to that line pronotum impunctate; pronotum with microsculpture and micropunctures; pronotum/elytra length ration = 0.92. Males with broad, shallow margination on sternum 7 (Fig. 4C); sternum 8 with shallow V-shaped emargination. Aedeagus as in Fig. 6; paramere in dorsal view almost parallel-sided but apex wider; in lateral view paramere slightly convex, converging to narrow rounded apex; paramere with peg setae as in Fig. 6C; paramere narrower than median lobe except just before apex; paramere longer than median lobe; median lobe in dorsal view converging to apex; in lateral view median lobe becoming narrower from middle to narrowly elongate apex; with large dorsal subapical tooth. Distribution. Known from many provinces in Costa Rica and the provinces of Bocas del Toro and Chiriqui in Panama. Habitat. Specimens were collected with malaise, pitfall and flight intercept traps and by shifting leaf litter in wet tropical lowland forests or tropical cloud forests at elevations of 5-1,950 m). Etymology. The specific epithet is derived from the words Philothalpus and formis and refers to the superficial resemblance of this species to species in the genus Philothalpus.