Description of Bryantinus gen. n. from Sarawak, and New Distributional Records for Cerochusa cilioceps in Thailand (Coleoptera: Staphylinidae: Pselaphinae)

A new genus and species of the subtribe Batrisina from western Sarawak, Bryantinus matangus gen. et sp. n., is described, illustrated, and compared with related taxa. In addition, examination of a small series of batrisine material from Thailand revealed a new country record for Cerochusa cilioceps Yin & Nomura, which was previously known only from the island of Hainan in southern China.


Introduction
The ant-loving beetles, or the subfamily Pselaphinae Latreille, is one of the megadiverse groups of the rove beetle family Staphylinidae Latreille. A total of 9,801 species placed in 1,252 genera (including 19 extinct genera and 41 extinct species) [A. F. Newton, unpublished database, 1st October, 2014], grouped in six or seven supertribes [1,2], are known worldwide. Members can be found in all major zoogeographic regions, but are most diverse in tropics [1,3]. The Palaearctic fauna is relatively well-studied at both the generic and species levels, and a catalog has been published [4]. The genera of North America and Mexico are largely known [5,6,7], those of the Neotropical region were treated in Park's works [8,9,10], and temperate South America was covered by Jeannel [11]. In the Oriental region, the pselaphine fauna is still poorly studied in most areas, and many biodiversity hotspots have never been thoroughly sampled. Recently, Nomura and his collaborators published a series of species checklists covering China (Yunnan), Malaysia, Singapore, Borneo, Thailand, and Vietnam, as the first step toward modern taxonomic studies of the pselaphine fauna in these areas [12,13,14,15,16,17]. As to Batrisitae, only a small number of genera, e.g. Mnia Raffray, Cratna Raffray, Sathytes Westwood, etc. were revised by recent workers [18,19,20], while many others still await such treatments. One case indicating the chaotic taxonomic status of Asian pselaphines is that Nomura & Idris listed 109 batrisine species from Malaysia and Singapore [13], among these, many have been placed in the genus Batrisodes since Raffray's time [21,22]. It is possible that none of these species truly belongs to the largely Holarctic genus Batrisodes, and may be moved to other genera in the future, or represent undescribed genera, as partially illustrated by Kurbatov [23].
Our recent studies on the Southeast Asian Batrisitae have documented a number of new taxa [24,25,26], but the gap of the knowledge of the existing richness of this diverse group remains large. In the course of our on-going study of Asian Pselaphinae currently, we are focusing on descriptions of the large loan of material from the Muséum d'histoire naturelle de la Ville de Genève. From this several undescribed genera and numerous undescribed species were noticed. In this paper, we describe a new genus and species of the tribe Batrisini from western Sarawak that is placed near Cerochusa Yin & Nomura and Ceroderma Raffray, and provide new distributional data for the previously described Cerochusa cilioceps Yin & Nomura known from Hainan Island of South China.

Materials and Methods
The material treated in this study is housed in the Muséum d'histoire naturelle, Geneva (MHNG) and the Insect Collection of the Shanghai Normal University, Shanghai (SNUC).
The collection data of the material are quoted verbatim. A slash (/) is used to separate different labels. Depository of type material of respective species is indicated by their type label.
The following abbreviations are applied: AL-length of the abdomen along the midline; AW-maximum width of the abdomen; EL-length of the elytra along the sutural line; EWmaximum width of the elytra; HL-length of the head from the anterior clypeal margin to the occipital constriction; HW-width of the head across eyes; PL-length of the pronotum along the midline; PW-maximum width of the pronotum. Length of the body is a combination of HL+PL+EL+AL.

Nomenclatural acts
The electronic edition of this article conforms to the requirements of the amended International Code of Zoological Nomenclature, and hence the new names contained herein are available under that Code from the electronic edition of this article. 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:6BD08956-763D-4033-9399-184C5933C87F. The electronic edition of this work was published in a journal with an ISSN, and has been archived and is available from the following digital repositories: PubMed Central, LOCKSS.
Abdomen (Figs. 2G-I) with tergite IV (first visible tergite) longer than tergite V; lateral margins of tergite IV-VII edged by thin marginal carinae, which extend entire tergal length; tergite IV with broad basal impression and one pair of lateral foveae; lacking discal carinae; tergites V-VII lacking basal impression, each with one pair of small lateral foveae. Sternite IV with small median and  Male with vertex slightly modified, transverse sulcus slightly broader and deeper than that in female. Aedeagus with paramere fused to median lobe to form elongate ventral lobe; with semisclerotized dorsal lobe.
Comparative notes. The new genus is placed near Cerochusa and Ceroderma, and may be a sister taxon of the former. All of these taxa share a flat body form, a triangular head, a transverse pronotum, and placement of the male features on the head dorsum. Bryantinus shares with Cerochusa many character states and a similar foveal pattern, but the lateral pronotal longitudinal sulci and basal elytral foveae are lacking, while Cerochusa possesses a pair of lateral sulci on the pronotum, and has two basal foveae on each elytron. Bryantinus shares with Ceroderma the lack of discal carinae on tergite IV, but can be separated by the presence of basomedian and basolateral foveae on sternite IV; in contrast Ceroderma has three basal elytral foveae, and the basomedian and basolateral foveae of sternite IV are lacking.
Etymology. The new genus is named after Gilbert E. Bryant  (1878-1965), who collected the material used in this work. The gender is masculine. The specific epithet refers to the type locality of the new species.
Female (Fig. 1B). Similar to male in general appearance, only distinguishable by presence of very thin, shallow transverse sulcus on frons, versus broader, slightly deeper one in male. Measurements: BL 2. Comparative notes. Bryantinus matangus can be readily separated from all other batrisines by the diagnostic features for the genus, combined with the male feature on the frons, which is probably a species-specific characteristic.
Comments. The form of the modifications on the head dorsum and the aedeagus (Figs. 3A-C) leave no doubt that the population from Thailand is conspecific with that from the type locality [24].