Dtsch. Entomol. Z. 67 (1) 2020, 35-49 | DOI 10.3897/dez.67.50078 Gee re BERLIN A review of Himalcercyon stat. nov., with description of a new species from the Chinese Himalaya and an updated key to Asian genera of Megasternini (Coleoptera, Hydrophilidae) Fenglong Jia!, Zulong Liang’, Martin Fikaéek*? 1 Institute of Entomology, Life Science School, Sun Yat-sen University, Guangzhou, 510275, Guangdong, China 2 Department of Entomology, National Museum, Cirkusova 1740, CZ-193 00 Praha 9, Czech Republic 3 Department of Zoology, Faculty of Science, Charles University, Vinicéna 7, CZ-128 44 Praha 2, Czech Republic http://zoobank.org/56BB973D-BE4E-47AE-BC98-C1F1151C41C4 Corresponding author: Martin Fikaéek (mfikacek@gmail.com) Academic editor: James Liebherr # Received 12 January 2020 # Accepted 11 March 2020 Published 11 May 2020 Abstract Himalcercyon Hebauer, 2002 stat. nov. is elevated to genus rank based on the unique form of its mesoventral elevation. The genus is reviewed, redescribed, and illustrated in detail. Two species are recognized: Himalcercyon mirus (Hebauer, 2002) comb. nov. from Nepal and H. franzi sp. nov. from Chinese Himalaya (Xizang Autonomous Region). Both species are illustrated and diag- nosed. An updated key to the Asian genera of the tribe Megasternini (Coleoptera, Hydrophilidae, Sphaeridiinae) is provided, along with the SEM micrographs of ventral morphology of these genera. New replacement name Oreosternum nom. nov. is proposed for Oreocyon Hebauer, 2002 which is preoccupied by Oreocyon Marsh, 1872 (Mammalia, Oxyenidae) and Oreocyon Krumbiegel, 1949 (Mammalia, Canidae). Key Words Asia, morphology, new replacement name, new species, new status, Oriental Region, Sphaeridiinae, taxonomy, Xizang, China Introduction Megasternini is the largest clade of terrestrial water scavenger beetles, containing approximately 580 de- scribed species currently classified in 52 genera (Jia et al. 2011, 2019; Ryndevich 2011; Short and Fikaéek 2011; Fikaéek et al. 2012a, 2013, 2015b; Fikaéek and Rocchi 2013; Makhan 2013; Deler-Hernandez et al. 2014; Arria- ga-Varela et al. 2017, 2018a, b; Ryndevich and Prokin 2017; Ryndevich et al. 2017; Shatrovskty 2017; Szcze- panski et al. 2018). Since the 1980s, 20 new genera of Megasternini have been described from the A frotropical, Australian, Oriental, and Neotropical regions by Hansen (1989, 1990, 1999a), Hebauer (2002a, 2003), Fikaéek et al. (2013), and Arriaga- Varela et al. (2018a). Nearly half of the described megasternine species are classified 1n the genus Cercyon. This led d’Orchymont (1942), Smetana (1978), and Hebauer (2002a, 2003) to divide Cercyon into numerous subgenera, 11 of which are currently con- sidered valid (Hansen 1999b; Short and Hebauer 2006). However, most of these only contain one to a few species, and the majority of Cercyon species are still members of the nominotypical subgenus Cercyon s. str. A phyloge- ny of the Hydrophilidae based on molecular data from six genes (Short and Fika¢éek 2013), which included only four Cercyon species, indicated that Cercyon is very like- ly a polyphyletic genus. Moreover, preliminary studies have revealed that even some of the small subgenera are not monophyletic (e.g., Arriaga-Varela et al. 2018a). Additional studies are therefore necessary to establish a natural classification of the group and allow for reliable identification of genera and species. Copyright Fenglong Jia et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 36 Fenglong Jia et al.: A review of Himalcercyon and key to Asian Megasternini genera The mountains on the southern margin of the Qing- hai-Xizang (Tibetan) Plateau are known for their highly diverse and endemic faunas (e.g., Huang et al. 2007; Deng et al. 2020), of which terrestrial Hydrophilidae are a component. More than 80 species of terrestrial hydrophilid beetles have been reported from Nepal and Bhutan (Hansen 1999b; Hebauer 2002a, b), most of which are until now only known from the Himala- yas. Recently, some of the species originally described from the Himalayas have also been recorded from the mountains in the Chinese provinces of Yunnan and Si- chuan (e.g., Cercyon divisius Hebauer, 2002: Ryndev- ich et al. 2017), indicating that the mountain systems on southern and south-eastern margin of Qinghai-Xi- zang are interconnected, thus forming the so-called Si- no-Himalayan subregion (for details see Proches and Ramdhani 2012). Other species originally known from the Himalayas are widespread at high elevations on the Qinghai-Xizang Plateau (C. berlovi Shatrovskiy, 1999: Jia et al. 2011) and seem to be plateau endemics that reach lower altitudes at the margins of their range, which seems uncommon for endemics of the plateau (see, e.g., Angus et al. 2016). Recently, we received a small sample of terrestrial hydrophilids from Motuo County, Xizang Autonomous Region, China, a region in the Himalayas at the south- ern margin of the Qinghai-Xizang Plateau. In contrast to the more northern regions of the Xizang Autonomous Region, Motuo County includes middle to low eleva- tions and is affected by monsoon rains; it is, therefore, warmer and more humid than the main plateau areas. The material contained a species of the Megasternini which is unique in the morphology of its mesoventral plate. We originally considered it to be an undescribed genus, but a detailed survey of megasternine taxa de- scribed from the Himalaya region revealed that Cercyon mirus Hebauer, 2002 from Nepal, which was assigned to the monotypic subgenus Himalcercyon Hebauer, 2002 in the original description (Hebauer 2002a), shares the unusual mesoventral morphology with our specimens. Hence, we here redescribe Himalcercyon and elevate this subgenus to the rank of genus based on its unique ventral morphology; we (re)describe and illustrate both species. We also provide an updated key to the Asian genera of the Megasternini. Material and methods We examined the type series of Cercyon mirus and the small series (10 specimens) of the new species from Motuo County. Male genitalia of the holotypes of both species were examined and photographed in the original position (i.e. with the median lobe inserted in the teg- men). Due to the very limited material available, separa- tion of the median lobe is not always easy and sometimes results in partial damage of some parts of the aedeagus. dez.pensoft.net Genitalia were photographed in glycerol. The aedeagus of the holotype of C. mirus was subsequently embedded in a drop of alcohol-soluble Euparal resin on a piece of glass glued to a small piece of cardboard attached below the respective specimen. Habitus photographs were taken using a Canon D-550 digital camera with attached Canon MP-E65mm f/2.8 1—5 macro lens. Genitalia were pho- tographed using a Canon D1100 digital camera attached to an Olympus BX41 compound microscope (C. mirus) or using an Olympus SZX7 stereomicroscope (new spe- cies); combined, focus-stacked images were made with Helicon Focus (Helicon Soft Ltd, Ukraine) software. Scanning electron micrographs of C. mirus and of the Asian genera of the Megasternini were taken using a Hitachi S-3700N environmental electron microscope at the Department of Paleontology, National Museum in Prague; SEMs of the new species were taken using a Phenom Prox scanning electron microscope in the Bio- logical Museum of the Sun Yat-sen University. Images were combined into figures using Adobe Photoshop CS6. All original images, including additional views not pre- sented in this paper, are included in the dataset submitted to the Zenodo archive (https://zenodo.org/ under https:// doi.org/10.5281/zenodo.3693743. SEMs of the megas- ternine genera for the identification key are mostly based on specimens deposited in NMPC, except for rare genera (Kahanga, Gillisius) for which holotypes were examined. Examined specimens are deposited in the following collections: NMPC National Museum, Praha, Czech Republic (M. Fikacek); Staatliches Museum fur Naturkunde, Stuttgart, Germany (W. Schawaller); SMNS SYSU Biological Museum, Sun Yat-sen University, China (F.-L. Jia). Taxonomy Himalcercyon Hebauer, 2002, stat. nov. Figures 1-4 Cercyon (Himalcercyon) Hebauer, 2002: 39. Type species. Cercyon (Himalcercyon) mirus Hebau- er, 2002: Diagnosis. Dorsal surface pubescent; anterior margin of clypeus rounded; frontoclypeal suture not forming transverse ridge between eyes; eyes small, separated 5—6~ the width of one eye; prosternum strongly carinate medially, without ridge demarcating median portion from lateral portions (Figs 2D, 3B); antennal grooves distinct, well demarcated laterally, not reaching lateral margins of prothorax (Figs 2D, 3B); mesoventrite bear- ing hydrofuge pubescence; mesoventral elevation ar- rowhead-shaped, widely attaching metaventral process Dtsch. Entomol. Z. 67 (1) 2020, 35-49 SF Figure 1. Habitus and genital morphology of Himalcercyon species. A—D. H. mirus (A, B. Paratypes; C, D. Holotype). E-H. H. franzi sp. nov. (E, F. Paratypes; G, H. Holotype). A, E. Dorsal view; B, F. Lateral view; C, G. Aedeagus in dorsal view; D, H. Sternite [X in dorsal view. (Figs 2F, 3C), cavities for reception of procoxae ending far anterior to mesocoxae (Figs 2F, 3C); metaventrite with a pentagonal posteromedian glabrous area weak- ly projecting anteriorly between mesocoxae; femoral lines absent; anterolateral transverse arcuate ridge ab- sent (Fig. 2E); each elytron with 10 striae (Figs 1A, B, E, F, 3H); first abdominal ventrite carinate throughout (Fig. 2A); last abdominal ventrite with a glabrous apical area (Fig. 2A); median lobe deeply inserted into phallo- base (Fig. 1C, G); median portion of sternite [X tongue- shaped (Fig. 1D, H). Redescription. Body broadly oval and moderately convex; body outline not interrupted between pronotum and elytra. dez.pensoft.net 38 Fenglong Jia et al.: A review of Himalcercyon and key to Asian Megasternini genera mY Figure 2. Morphology of Himalcercyon mirus (Hebauer, 2002). A. Complete ventral view. B. Mentum. C. Prosternal carina in ventrolateral view. D. Prosternum and hypomeron. E. Meso- and metaventrite. F. Details of mesoventral plate. Head. Excised in front of eyes laterally, antennal base exposed. Labrum concealed under clypeus, not exposed dorsally. Clypeus not deflexed, truncate ante- riorly, without anterolateral extensions; anterior margin narrowly beaded. Frontoclypeal suture obsolete, only visible as impunctate bar. Frons with even surface. Eyes rather small, rounded, projected laterally; interocular dez.pensoft.net distance ca 5—6x the width of one eye in dorsal view. Dorsal punctation of head consisting of punctures each bearing a long seta. Maxillary palpus slightly longer than half of width of head, with ventral sucking disc in male; palpomere 2 strongly swollen, longer than pal- pomere 3; palpomere 4 symmetrical, slightly shorter than palpomere 2, but longer than palpomere 3. Men- Dtsch. Entomol. Z. 67 (1) 2020, 35-49 ~ |__| G 200 um 39 J 300 pm Figure 3. Morphology of Himalcercyon franzi sp. nov. A. Mentum. B. Prosternum and hypomeron. C. Mesoventral elevation. D. Antenna. E. Mesotarsus, ventral view. F. Median portion of metaventrite. G. Elytral punctation. H. Elytral apex. tum ca 2.1—2.4= as wide as long, trapezoidal, anterior margin not emarginate medially (Figs 2B, 3A). Labial palpomere 3 slightly longer and as broad as palpomere 2, symmetrical. Gula well developed throughout, wide posteriorly, moderately narrowed anteriorly. Antennae with nine antennomeres, ca 0.7 width of head; scape a little longer than antennomeres 2—6 combined; club compact, pubescent, ca 2x as long as wide (Fig. 3D), slightly longer than scape. Prothorax. Pronotum relatively short and transverse, widest at base; surface smooth, punctation consisting of setiferous punctures, all punctures of the same size and shape; transverse series of punctures along posterior margin absent. Prosternum well developed, slightly tec- dez.pensoft.net 40 Fenglong Jia et al.: A review of Himalcercyon and key to Asian Megasternini genera tiform, strongly carinate medially, without elevated me- dian portion or ridge demarcating median portion from lateral parts (Figs 2D, 3C); antennal grooves distinct, well demarcated, arcuate laterally, not reaching lateral margins of prothorax (Figs 2D, 3B). Prosternal process reaching midpoint of procoxae, not bifurcate apically (Fig. 2D). Mesothorax. Mesoventrite fused to mesepisterna, bearing hydrofuge pubescence; median portion abruptly raised in posterior half to form arrowhead-shaped eleva- tion (Figs 2E, F, 3C), its surface pubescent; cavities for reception of procoxae ended well before mesocoxae (Figs 2E, F, 3C). Each elytron with 10 punctate striae (Figs 1A, B, E, F, 3H), striae sharply impressed. Interval punctation consisting of setiferous punctures (Fig. 3G). Scutellar shield small, triangular. Metathorax. Metaventrite moderately raised medially, forming a bare pentagonal area weakly projected anteri- orly between mesocoxae (Figs 2E, 3F); lateral portions with coarse punctures, bearing fine hydrofuge pubes- cence (Fig. 2E). Anterolateral ridge absent; femoral lines absent (Fig. 2E). Metepisterna subparallel, ca 6.5x as long as wide. Hind wings well developed, ca 2.4~ as long as wide; r-m-crossvein rising from base of radial cell; cu- bital spur rising from apex of M-Cu loop; m-crossvein vestigial; basal cell elongate, wedge cell absent; anal lobe weakly developed. Legs. Coxae partly with hydrofuge pubescence, meso- coxae moderately separated (Fig. 2A). Femora with tibial grooves demarcated by ventral and dorsal ridges; ventral face of pro- and mesofemora glabrous, metafemora with fine microsculpture consisting of transverse lines. Tibiae weakly, gradually widened from base to apices, with fine and sparse lateral spines. Tarsi with five tarsomeres, with dense and short setae ventrally. Meso- and metatarsi with Key to species of Himalcercyon tarsomere | ca 2 as long as tarsomere 2 (Fig. 3E), tar- somere 5 slightly shorter than tarsomere 1; claws small and moderately curved (Fig. 3E). Abdomen with five ventrites covered by fine hydro- fuge pubescence; ventrite 1 2x as long as ventrite 2, strongly carinate throughout (Fig. 2A); posterior margin of ventrite 5 simply rounded, with an apical glabrous area. Aedeagus (Fig. 1C, G) of the Cercyon type, 1.e. with median lobe reaching deeply into phallobase in natural position; parameres ca 2 as long as phallobase, with transversely bent apices; phallobase with asym- metrical basis (manubrium). Median part of sternite IX not reduced, forming a broad tongue-shaped structure (Fig. 1D, H). Discussion. Hebauer (2002a) proposed Himalcercy- on as a Subgenus of Cercyon, mentioning that it corre- sponds to Cercyon in all characters except for the shape of the mesoventral plate. The form of the mesoventral elevation is one of most important generic characters in the Megasternini, and clearly differentiates both Hi- malcercyon species from all other members of the genus Cercyon. Both species of Himalcercyon are very simi- lar to each other in all important characters and in the general form of male genitalia, indicating that they are likely closely related. Moreover, both species occur in the Himalayas. All of this supports Himalcercyon as a monophyletic clade that differs from Cercyon, as well as other megasternine genera, in the character current- ly considered as crucial at the generic level. For this reason, we elevate Himalcercyon to genus rank. See Diagnosis for the characters distinguishing Himalcer- cyon from other megasternine genera, and the identifi- cation key for a comparison of Himalcercyon with other Asian Megasternini. 1 Body broadly oval, elytra combined 1.1x longer than wide (Fig. 1A). Prosternum widely carinate medially (Fig. 2C, D). Antennal groove weakly arcuate laterally (Fig. 2D). Mesoventral elevation wider, ca 1.5x as long as wide (Fig. 2E, F). Apex of the median lobe narrowly rounded, median lobe about as long as parameres and phallobase combined (Fig. 1C) .... iL DARIN AAR: eT oe HE Rf OR NS H. mirus (Hebauer, 2002) - Body moderately oval, elytra 1.3x longer than wide (Fig. 1E). Prosternum narrowly carinate medially (Fig. 3B). Antennal groove angulate laterally (Fig. 3B). Mesoventral elevation narrower, ca 2.0x as long as wide (Fig. 3C). Apex of median lobe pointed, median lobe shorter than parameres and phallobase combined (Fig. 1G).............:.:::06 H. franzi sp. nov. Himalcercyon franzi sp. nov. http://zoobank.org/AFO2DECB-FD93-4COF-BAC8-13498287A831 Figures 1E-—-H, 3, 4 Type locality. China, Xizang Autonomous Region, Mo- tuo County, track from Dayandong to Hanmi, 2200—2400 ma.s.l. [GPS ca 29.4283N, 95.0498E]. Material examined. Holotype: CHINA e 1 3; Xi- zang, Motuo County, Dayandong-Hanmi; 2200-2400 m as.l.; 13 Aug 2005, Tang Liang leg.; SYSU [verba- dez.pensoft.net tim label data: ,,CHINA, Xizang, Motuo Coun., Dayan- dong-Hanmi, alt. 2200—2400 m, 13.viu1.2005, TANG Li- ang leg.”’]. Paratypes: CHINA e 9; same data as for holotype; SYSU e 4; Xizang, Motuo County, Nage-Dayandong; 2900-3300 m a.s.1.; 12 Aug 2005; Tang Liang Igt.; SYSU e 1; Xizang, Motuo County, Nage-Dayandong; 2900- 3300 ma.s.l.; 12 Aug 2005; Tang Liang Igt.; NMPC. Description. Form and color. Body size 2.5—2.8 mm (2.6 mm in holotype), body width 1.5—1.7 mm (1.55 mm Dtsch. Entomol. Z. 67 (1) 2020, 35-49 Figure 4. Known distribution of Himalcercyon: Circles. H. mi- rus (Hebauer); Square. H. franzi sp. nov. Color shading of the map indicated altitude: green = lowest, brown = highest. in holotype), widest at anterior third of elytra, arcuately narrowing posteriad (Fig. 1E). Dorsum dark brown; head of some specimens with paler clypeus; pronotal lateral margins yellow brown; elytral apices and posterior half of lateral elytral margins slightly paler; epipleuron red- dish brown; antenna, maxillary and labial palpi reddish brown; legs reddish brown, with darker femora. Head. Clypeus with moderately dense fine setiferous punctures, smooth between punctures. Frons with punc- tures coarser and somewhat denser than those on clypeus, smooth between punctures. Mentum 2 wider than long, rugose, with dense coarse punctures (Fig. 3A), slightly concave anteriorly. Antenna with pedicel ca 0.2 as long as scape, pedicel ca. as long as antennomeres 3 and 4 combined, cupule small (Fig. 3D). Thorax. Pronotum with punctation similar to that on frons, interstices without microsculpture; lateral margin- al bead shortly overlapping to anterior margin but not to posterior margin, stopping at posterior angle. Scutellar shield smooth, with three to five punctures. Elytral stri- ae sharply impressed (Figs 1E—F), striae 6, 8, and 9 not reaching base; intervals with much finer and sparser punc- tures than on pronotum, each interval puncture bearing a fine short seta (Fig. 3G), interstices between punctures smooth. Epipleuron with bare outer and pubescent inner portion delimited from each other by a fine ridge, inner pubescent part narrower than the outer part, reaching the level of posterior part of metaventrite. Mesoventral eleva- tion arrowhead-shaped, ca 2.0 longer than wide, densely pubescent (Fig. 3C). Metaventrite with large median ele- vation, finely and sparsely punctate (Fig. 3F), interstices without microsculpture; lateral portions microsculptured with sparse coarse punctures and dense pubescence. Legs with trochanters densely pubescent, femora with sparse and moderately coarse punctures, interstice between punctures with fine microsculpture consisting of trans- verse lines. Male genitalia. Middle lobe of abdominal sternite IX wide, shorter than lateral struts (Fig. 1H). Aedeagus (Fig. 1G) with median lobe ca 0.8 as long as tegmen; paramere ca 1.5x as long as phallobase. Paramere gradu- 41 ally narrowed from base to apex, truncate apically, wid- ened inwards to form a process with a few setae. Median lobe broader than paramere, gradually narrowing in api- cal third, apex pointed, gonopore subapical. Etymology. The species is named after Dr Franz He- bauer, a German taxonomist of the Hydrophiloidea who recognized and described Himalcercyon as a subgenus of Cercyon. Distribution. Only known from the type locality in the eastern Himalaya (Motuo county, Xizang Autonomous Region, China) (Fig. 4). Himalcercyon mirus (Hebauer, 2002), stat. nov. Figures 1A—D, 2, 4 Cercyon (Himalcercyon) mirus Hebauer 2002: 39. Type locality. Nepal, Kathmandu district, Sheopuri Mt., 2100-2300 m a.s.l. [GPS ca 27.816672N, 85.400000E]. Material examined. Holotype: NEPAL e | <@; Kath- mandu Distr. Sheopuri Mt.; 2100-2300 m a.s.1.; 25 Jun 1988; W. Schawaller leg.; SMNS. Paratypes: NEPAL e 2 99; same data as for holo- type; SMNS e 1 9; same data as for holotype; NMPC e 1 9; Annapurna, Telbrung Danda; 2600—2800 m a.s.1.; 13 Jun 1997; Schmidt leg.; SMNS. Redescription. Form and color. Body size 3.1- 3.5 mm (3.4 mm in holotype), body width 2.0-2.1 mm (2.0 mm in holotype), widest at anterior third of elytra, weakly narrowing posteriad (Fig. 1A). Dorsum pitchy- brown to black; head with paler clypeus; pronotal mar- gins brown; elytral apices and posterior half of lateral elytral margins brownish; epipleuron pitchy brown lat- erally, reddish mesally; antenna, maxillary and labial palpi brown to reddish brown; legs reddish brown, with darker femora. Head. Clypeus with moderately dense fine setiferous semicircular punctures, smooth between punctures. Frons with punctures of the same size and density as those on clypeus, smooth between punctures. Mentum 1.4 wider than long, rugose, with dense punctures (Fig. 2B), slight- ly concave anteriorly. Antenna with pedicel ca 0.2 as long as scape, pedicel ca. as long as antennomeres 3 and 4 combined, cupule small. Thorax. Pronotum with punctation similar to that on frons, interstices without microsculpture; lateral margin- al bead shortly overlapping to anterior margin but not to posterior margin, stopping at posterior angle. Scute- llar shield smooth, with five to seven punctures. Elytral striae sharply impressed (Fig. 1A), striae 6, 8, and 9 not reaching base; intervals with finer and sparser punctures than on pronotum, each puncture bearing a fine short seta, interstices between punctures smooth. Epipleuron with bare outer and pubescent inner portion delimited from each other by a fine ridge, inner pubescent part nar- rower than the outer part, reaching the level of posterior dez.pensoft.net 42 Fenglong Jia et al.: A review of Himalcercyon and key to Asian Megasternini genera ps Figure 5. Ventral view of thorax of eastern Palaearctic and Oriental genera of the Megasternini. A. Cryptopleurum ferru- gineum. B. Megasternum concinnum. C. Pacrillum manchuricum. D. Pachysternum nigrovittatum. E. Peltocercyon coomani. F. Armostus schenklingi. part of metaventrite (Fig. 1A). Mesoventral elevation arrowhead-shaped, ca 1.5x longer than wide, sparse- ly pubescent (Fig. 2F). Metaventrite with large median elevation, finely and sparsely punctate (Fig. 2E), inter- stices without microsculpture; lateral portions microscu- Iptured, with sparse coarse punctures and dense pubes- cence. Legs with trochanters densely pubescent, femora with sparse and moderately coarse punctures, interstice between punctures with fine microsculpture consisting of transverse lines. dez.pensoft.net Male genitalia. Middle lobe of abdominal sternite [Xx narrow, shorter than lateral struts (Fig. 1D). Aedeagus (Fig. 1C) with median lobe ca as long as tegmen; param- ere ca 1.5x as long as phallobase. Paramere gradually narrowed from base to apex, obliquely truncate apically, widened inwards to form a process with a few setae. Me- dian lobe ca as wide as paramere, gradually narrowing in apical third, apex narrowly rounded, gonopore subapical. Distribution. Known from two localities in central Nepal (Fig. 4). Dtsch. Entomol. Z. 67 (1) 2020, 35-49 43 Figure 6. Ventral view of thorax of eastern Palaearctic and Oriental genera of the Megasternini. A. Morastus gracilipalpis. B. Ooster- num sp. (O. soricoides group). C. Emmidolium excavatum. D. Chimaerocyon shimadai. E. Paroosternum sp. F. Oreosternum frigidum. Key to Eastern Palaearctic and Oriental genera of the Megasternini The following key is mainly based in the ventral characters, namely the form of prosternum and meso- and metaven- trite, which are illustrated in Figures 5—8. The concept of some of the genera will likely be modified in the future; the key reflects the current status. The key includes all genera occurring east of Iran, the Black Sea, and the Ural Mountains. (i.e. it does not cover the Near East and the Arabian Peninsula); eastwards it includes all regions west of New Guinea. See Table 1 for the number of described species and references to the most important keys or taxonomic treatments for each genus. Remarks and numbers of species only refer to those from the Eastern Palaeartic and Oriental Regions. ik Antennal grooves large, reaching to the lateral margin of hypomeron (Fig. 5A, B, D)..........2..::ccececeeeeceeeeeeeeeeeseeeeeeeaeees 2 - Antennal grooves absent or small, not reaching to the lateral margin of the hypomeron (Figs 5E, F, 6, 7, 8A-C).......... 5 dez.pensoft.net 44 * Fenglong Jia et al.: A review of Himalcercyon and key to Asian Megasternini genera Metaventrite with complete femoral lines reaching from posteriomesal portion to anterolateral corner (Fig. 5A, D)..... 3 Metaventrite without complete femoral lines, at most with short vestiges anterolaterally. (Fig. 5B, C)..........:..:::::eeeeeee 4 Mesoventral plate wider than long. Prosternum with wide plate without median carina (Fig. 5A). Mentum with sharply Heliiteg-ariterOlaleral COtierSsGie Sais he aes FORE Sec eg ee RRM A ses hes RB Ok in Bedale Cryptopleurum Mulsant Mesoventral plate approximatley as long as wide. Prosternal plate approximately as long as wide, with more or less distinct median carina (Fig. 5D). Mentum with bluntly rounded anterolateral corners........... Pachysternum Motschulsky Median portion of prosternum roof-like, high (Fig. 5C). Mesoventral plate longer than wide. Metaventrite without any traces of femoral lines (Fig. 5C). Anterior tibia without anterolateral ExCiSiON .............::6s:eeeeeeeee Pacrillum d'Orchymont Median portion of prosternum with flat hexagonal plate, not carinate medially (Fig. 5B). Mesoventral plate slightly wider than long. Metaventrite with vestiges of femoral lines in anterolateral corners (Fig. 5B). Anterior tibia anterolaterally with INVA NALIN as cana tomate h dpaceu gn Sncc apnea tekemucsa yes cate nienwddctehdenuyueat tosnturadecahestanu yess ececqesnddmbdonsswawe tence Megasternum Mulsant Metaventrite with postcoxal ridge widely diverging from posterior margin of coxal cavity and forming an arcuate ridge feachine lateral mareineot ImetaventhiteCEieSaGe) sO Als ES) ass cancun! Orr en madsen mame ore Sanalenass yecammmul eee ideas tenasenl eee’. ae 6 Metaventrite with postcoxal ridge parallel to posterior margin of coxal cavity or nearly so, reaching anterolateral corner ol metaventrite-andnot torming-anyarcuate nidge(Figss6C—h. 7, SAC). .cda recs a5 et ove Peels po otoatteteehes sete paetnaettnaues dt i) Metaventrite with complete femoral lines crossing the arcuate postcoxal ridge and X-shape in form (Fig. 5E). Mesoventral elevation narrowly elongate or narrow but widely contacting metaventrite ..............c:eeeeeeeeee Peltocercyon d'Orchymont Metaventrite without X-shaped structure, femoral lines absent or short, not crossing with arcuate postcoxal ridge CRIBS TR ROP ae) ee Ne arg er Oe RU NS IY are EE Pe Ee ee ee ee eo 7 Mesoventral plate widely contacting metaventrite (Fig. 6A, B). Median portion of prosternum at least weakly delimited TEST aCe heels DOREMOINS F acaa tapos cht rane de ro yen parse 2 2. x: aaron cage oe a dene Aon aarieahg tn emai cag eres nase ne neh ances oman ane 8 Mesoventral plate separated from metaventrite by a wide deep gap (Fig. 5F). Median portion of prosternum simply CAMate “MetCeliMTeCMbOn Mlle halMBOnt LOM ste cc. tA mnt 0, Clee er beten th) ee Sw A Many fel are re oe SIN Peebee: oe RU) maou Armostus Sharp Metaventrite with deep triangular impression along its lateral margin (Fig. 6A).............::::::seeeeeeee Morastus d'Orchymont WetaventateswThownSuchtinPReSSION CS Oye aoe Ss as eee REN Ae ee oe ok ee ete esters ee eae eee eo Oosternum Sharp Median portion of prosternum highly elevated and/or delimited from lateral portions by sharp ridges (Figs 6C-F, 7A-D)...10 Median portion of prosternum finely carinate, not delimited from lateral portions (Figs 7E, F, 8A, B).............:::::e 18 Pronotum with deep longitudinal grooves (Fig. 8E). Bare portion of metaventrite very wide (Fig. 6C). Tiny beetles: length srs | alhe79 OMA lk ee eo Pe ee Se Ae cee 2, Se A ee ee Emmidolium d'Orchymont Surface of pronotum without distinct longitudinal depressions. Bare portion of metaventrite confined to medial part ony Wainy teimoderatelye arse heeles:.cs cunt fa. su ens ate eres ee eR aed rpms Ane Ju ans emac rsh ee 11 Median portion of prosternum in form of very small triangular, very highly elevated projection. Antennal grooves absent (Fig. 6D). Abdomen with apical emargination..............::.:eeeeeeeee ee Chimaerocyon Fikacek, Maruyama, Vondracek & Short Median portion of prosternum never so tiny and not so highly elevated. Antennal grooves present, even though some- times rather small. Abdomen never with apical EMargination ...............cccccecccecceccseceeececeaeetecseeeuseceeecescecsseseeeceregensenses 12 Prosternal: elevation wi tiiateralmmareinsideelyVsexcrseckeRie: GE, yi tas re case eee cet I oo ce BT ile Prosternal elevation with lateral margins or ridges straight (Fig. 7A-D) ........cccccccccceeceecee eee eeseeeeeeeeeeeeeeeeseeeeeeaeeaseegeeees 14 Tiny species, 1.2-1.6 mm. Metaventrite with complete femoral lines (Fig. 6E). Antennal grooves present.............::.:::0: Paroosternum Scott Large species, ca 3.0 mm. Metaventrite without femoral lines (Fig. 6F). Antennal grooves absent ....Oreosternum nom. nov. Elytral series deeply impressed with the impressions contiguous to anterior margin of each elytron (Fig. 8F, G). Mesoven- tralselevationzlonger than wick Thomo locsubeval Cries AAGN Ss ci scccsatcndat ss tte sede cetmenlby stitch Keaceeet tle asd stent dees 15 Elytral series not impressed or impressions of elytral striae series not reaching anterior margin of each elytron. Mesoven- traleclevalion SONS alenOn sass Ot lenaS: WIS: ry tect sit, eters Mee veg rere ctor pe peers ieee Se Seah st 16 Pronotum highly bulged in lateral view, not forming a continuous curve with elytra. Anterior margin of prosternal eleva- tion strongly projecting anteriad (Fig. 7A). Mesoventral elevation SUDPHOMDOIC .......... ec cece eee eee eee eens Bolbonotum Hansen Pronotum not highly bulged in lateral view, forming a continuous curve with elytra. Anterior margin of prosternal eleva- onrstraientchia. 7B)s Meseventral elevation Subovallt Sr: 27ers, eg Sa ee ee Kahanga Hansen Grooves for reception of procoxae ending far before the anterior margin of mesocoxal cavities (Fig. 8C). Mesoventral PALS LON Me oa acest edited Srtewiccdigand Lee beta dupneasinnemephn de tinted dnrtasamatach ae Mrleedt a iomasesietene eet ies Gillisius d'Orchymont (part)* Grooves for reception of proxocae reaching nearly the mesocoxal cavities (Fig. 7C, D). Mesoventral elevation approxi- ARE 1hol havskse (Ane .-wrcbodl fo) yfoale LOL e e aaORNneS 000 Ne REDON Ot 20 Luk Stem Ce, bh ANOLE Le! es Oe 6 1 OL Se ONES 0s Jo Le Mesoventral elevation nearly semi-elliptical (Fig. 7C), with wide marginal rim. Postcoxal ridges on the metaventrite meeting mesally and forming a short median longitudinal ridge. Metatibiae densely pubescent ventrally (Fig. 8H). Large lel selkciwarar eee MoH IPAM cece arrests Res welt nreeet ete nM bap eta crete eet ey «at Meeeeee hte ee es shee eee ht oD Australocyon Hansen Mesoventral elevation more less pentagonal, without any marginal rim (Fig. 7D). Postcoxal ridges mesally bending pos- teriad, remaining separate, forming two short median longitudinal ridges (in one species largely obsolete). Metatibie without dense ventral pubescence. Medium sized to tiny species: 2.0-2.9 MM...........::0:::ceeeeeee tees Nipponocercyon Sato the type species, G. madurensis d’Orchymont, 1925, keys out here. dez.pensoft.net Dtsch. Entomol. Z. 67 (1) 2020, 35-49 45 18 19 20 * Abdominal ventrite 1 without median carina. Mesoventral elevation narrowly laminar (Fig. 7E)..... Cycreon d'Orchymont Abdominal ventrite 1 carinate medially. Mesoventral elevation in form of a lamina or an elongate plate.................. Ks) Ventral face of meso- and metatibiae with dense, long pubescence. Ventral morphology similar to Figure 7F.............0. eae ie Ona pe es ee a ee Ree A Cet eC San PE ee Pilocnema Hansen Ventral face of meso- and metatibiae never densely pubescent, at most with sparse short setae. Ventral morphology Sitanllll cite COs SLOSS Walch Sih esse itt te a I ae. ocean Mee Rete cede cee bie eee enc eet ee eet lS 2 20 Mesoventral elevation laminar or forming an oval elongate plate; posterior part of the plate rounded or acute (as in Mesoventral elevation elongate, but sharply cut off posteriorly, contacting metaventrite more or less in a straight line (as Wal OR ec Oo Mcre ees ol se ete: cee Sa als ooh ile scores os Mel oo aioe Ee ae mies oe cee ye aa lls i eee oe eee teal oh ere ee Oe Cas Median portion of prosternum with a pair of transverse ridges partly delimiting prosternal process (Fig. 8A).............:. ath cae se rs a rae 2 aed Rey RO te 2 col venta Pa een sae oR ect 0 wee a ce Ooh ee Pseudocercyon d'Orchymont Median portion of prosternum without such ridges, only simply carinate (Fig. 8B) .............:ceeeeeeeeeeee sees ees Cercyon Leach Mesoventral elevation arrowhead-shaped, with lateral angulate lobes (Figs 2F, 3C) ...........:.:::0e: Himalcercyon Hebauer Mesoventral elevation elongate oval (as in Fig. 8C); if small lateral lobes are present, they are below the plate.......... Zo lida -conkinentalysoutneastsAstarainch @ initials tebe... aati aa Rant Payee Voorn, LSU RR amr Feat ae Gillisius d'Orchymont (part) ishaaclseot thea alay7Arciiielace nate ets veers |. pememy e080) or dmeme rs 5 seman ECU Seeecuets |S Fame vel Toe eae FP Ae ane et vase Pelosoma Mulsant™ the status of Gillisius and Asian Pelosoma is unclear. Figure 7. Ventral view of thorax of eastern Palaearctic and Oriental Megasternini. A. Bo/bonotum sp. B. Kahanga inconspicua, holotype. C. Australocyon sp. (A. pilocnemoides group). D. Nipponocercyon shibatai. E. Cycreon floricola. F, Pilocnema sp. dez.pensoft.net 46 Fenglong Jia et al . A review of Himalcercyon and key to Asian Megasternini genera Figure 8. Ventral view of thorax and additional diagnostic characters of eastern Palaearctic and Oriental genera of the Megasternini. A-C. Ventral view: A. Pseudocercyon andrewesi. B. Cercyon sp. C. Gillisius madurensis, holotype. D-H. Other characters: D. Cryptopleurum coomani, mentum. E. Emmidolium excavatum, pronotum. F. Bolbonotum sp., base of elytra. G. Kahanga inconspic- ua, holotype, base of elytra. H. Australocyon sp. (A. pilocnemoides group), hind femur. New replacement name Oreosternum nom. nov. = Oreocyon Hebauer 2002a: 35 (not Marsh 1872: 406, not Krumbiegel 1949: 591). Type species. Oreocyon frigidus WHebauer, 2002 (= Oreosternum frigidum comb. nov.) Comments. While preparing the key, we noticed that the genus name Oreocyon is preoccupied by two older names: Oreocyon Marsh, 1872 (a fossil oxyaenid mammal, today a synonym of Patriofelis Leidy, 1872) dez.pensoft.net and Oreocyon Krumbiegel, 1949 (a genus of Canidae described based on fur remains, later renamed to Dasycyon Krumbiegel, 1953 due to homonymy and today considered as a synonym of Canis Linnaeus, 1758). To avoid the homonymy, we are here proposing a new replacement name Oreosternum nom. nov. for Oreocyon Hebauer, 2002. The new name combines the prefix oreo- referring to mountains as used in the original name, and the core sternum, referring to the expected close relationship of this genus to Paroosternum Scott, 1913 exhibited by the prosternal morphology (see the key above). The new name is gender neutral. Dtsch. Entomol. Z. 67 (1) 2020, 35-49 47 Table 1. List of Eastern Palaearctic and Oriental general of the Megasternini, with number of described species and references to the most important keys or taxonomic treatments. Genus Described species Keys or original descriptions Armostus 11 d’Orchymont 1942; Hebauer 2002a; Hoshina and Satd 2006 Australocyon e Hansen 2003; Fikaéek et al. 2012 Bolbonotum 3 Hansen 1999a Cercyon 148 Shatrovskiy 1992; Hansen 1999b; Short and Hebauer 2006; Hoshina 2008; Jia et al. 2011; 2019; Ryndevich et al. 2017; 2019; Ryndevich and Prokin 2017 Chimaerocyon 2 Fikaéek et al. 2013 Cryptopleurum f: d’Orchymont 1926; Jia and Zhang 2017 Cycreon 4+ 1 ssp. Arriaga- Varela et al. 2018b Emmidolium 1 Fikaéek 2007 Gillisius 2 d’Orchymont 1925a; 1926 Himalcercyon 2 this paper Kahanga 1 Hansen 1999a Megasternum 4 Shatrovskiy 1989; Fikacek et al. 2012; Ryndevich 2017 Morastus 1 d’Orchymont; 1926 Nipponocercyon 3 Hoshina and Fikaéek 2010; Fikaéek et al. 2012; 2015a Oosternum 9 Hebauer 2002a; Hoshina and Sat6 2004b; 2005 Oreosternum 1 Hebauer 2002 Pachysternum 1] Fikaéek et al. 2012 Pacrillum 5 Hoshina and Satéd 2004a; Fikatéek and Hebauer 2005; Shatrovskiy 1989 as Agnaeformia Paroosternum 5 Hebauer 2006 Pelosoma 2 d’Orchymont 1925b; 1932 Peltocercyon 4 d’Orchymont 1925a; Hoshina 2016; 2018 Pilocnema 1 Hansen 2003 Pseudocercyon 1 d’Orchymont 1926 Discussion Acknowledgements The genus-level systematics of the tribe Megasternini are currently based on the traditionally understood genera, defined by characters of the prosternum and meso- and metaventrite, i.e. structures which are morphologically very diverse within the clade. Following this approach, it is possible to define small and morphologically rather uniform genera for roughly half of the known species. On the other hand, the remaining half of megasternine species (i.e. ca 270 species) is assigned to the genus Cer- cyon Leach, 1817 as they are rather uniform in ventral characters. Eleven subgenera are defined inside of Cer- cyon to facilitate the identification of species, some of which seem to truly group related species (e.g., Arcocer- cyon Hebauer, 2003, Paracycreon d’Orchymont, 1942), but others very likely grouping unrelated species sharing a single derived character (e.g., Acycreon d’Orchymont, 1942; see Arriaga- Varela et al. 2018b). Preliminary mo- lecular analyses (Short and Fikacéek 2013, Arriaga-Varela unpubl. data) clearly indicate that Cercyon as currently circumscribed is a polyphyletic genus which needs to be reclassified in the future. To facilitate future analyses, it is necessary to reexamine Cercyon species and define groups of morphologically similar and likely closely re- lated species. Selected representatives of these groups should later be included in the phylogenetic analysis. To that end, this paper recognizes Himalcercyon as such a group. The phylogenetic position of this clade needs to be tested in future analyses. We thank Dr Li-zhen Li, Dr Liang Tang, Mr Jia-yao Hu, Mr Xiao-bin Song (all Shanghai Normal University, China) for their kind help during the visit of the senior author and for the donation of type specimens to us. We are obliged to Max Barclay Christine Taylor (Nat- ural History Museum, London, UK) and Pol Limbourg (Institute Royal des Sciences Naturelles, Brussels, Bel- gium) for allowing us to examine holotypes of Kahanga inconspicua and Gillisius madurensis whose SEMs we used in the key. We are indebted to B. Clarkson (Insti- tuto Oswaldo Cruz — Fiocruz, Rio de Janeiro, Brazil), S.K. Ryndevich (Baranovichy State College, Baranovi- chy), A.E.Z. Short (University of Kansas, Lawrence, USA) and J.K. Liebherr (Cornell University, Ithaca, USA) for their comments and corrections of the early draft of this paper. This study was supported by Nation- al Natural Science Foundation of China (31772494) to F-L. Jia and by the Ministry of Culture of the Czech Republic (DKRVO 2019-2023/5.I.b, National Museum, 00023272) to M. Fikaéek. References Angus RB, Jia F-L, Chen Z-N, Zhang Y, Vondratek D, Fikatek M (2016) Taxonomy, larval morphology and cytogenetics of Lihelophorus, the Ti- betan endemic subgenus of Helophorus (Coleoptera: Hydrophiloidea). Acta Entomologica Musei Natioalis Pragae 56 (1): 109-148. dez.pensoft.net 48 Fenglong Jia et al.: A review of Himalcercyon and key to Asian Megasternini genera Arriaga- Varela E, Seidel M, Deler-Hernandez A, Senderov V, Fikaéek M (2017) A review of the Cercyon Leach (Coleoptera, Hydrophil- idae, Sphaeridiinae) of the Greater Antilles. 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