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A new species of small-eyed Quedius (Coleoptera: Staphylinidae: Staphylininae) from the Early Cretaceous of China
Cretaceous Research 44 (2013) 54e57
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A new species of small-eyed Quedius (Coleoptera: Staphylinidae: Staphylininae) from the Early Cretaceous of China Chenyang Cai, Diying Huang* State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, Jiangsu Province 210008, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 29 August 2012 Accepted in revised form 24 March 2013 Available online 21 April 2013
Quedius cretaceus sp. nov., belonging to the Recent widespread staphylinine genus Quedius, is described and figured based on an exquisitely preserved specimen from the Lower Cretaceous Yixian Formation at Huangbanjigou, Liaoning Province, Northeast China. The new species, bearing relatively small and anteriorly-located eyes, displays remarkable resemblances to some members of the extant subgenus Microsaurus. However, it can be readily recognized from its rest of congeners by the combination of moderately separated gular sutures, relatively small procoxae, short metacoxae, and pronotal hypomeron with relatively large postcoxal process. This new find from the Early Cretaceous (ca. 125 Ma) represents the oldest fossil record for Quedius. It also suggests that the worldwide-distributed genus has already originated at least in the Early Cretaceous. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Staphylininae Quedius Early Cretaceous Yixian Formation
1. Introduction With more than 7700 described species and 340 genera, the rove beetle subfamily Staphylininae is one of the most diverse groups of the Staphylinine group of subfamilies (Grebennikov and Newton, 2009; Thayer, 2005). The earliest fossil staphylinines are reported from the Lower Cretaceous Laiyang Formation (Laostaphylinus Zhang, 1988, see Herman, 2001; Solodovnikov et al., 2012) and Yixian Formation (Cretoprosopus Solodovnikov et al., 2012, Durothorax Solodovnikov et al., 2012, Paleothius Solodovnikov et al., 2012, Paleowinus Solodovnikov et al., 2012, Thayeralinus Solodovnikov et al., 2012 and Megolisthaerus, see Cai and Huang, 2013; Yue et al., 2010) of China. An unnamed species (Species A) of tribe Xantholinini is known from the Late Cretaceous amber of France (Schlüter, 1978). In addition, another originally monotypic genus Cretoquedius, belonging to the extant tribe Staphylinini, was discovered from the Late Cretaceous of Russia (Ryvkin, 1988) and recently reported from the Early Cretaceous of northeastern China (Solodovnikov et al., 2012). Even though Cretoquedius is morphologically very close to the extant common genus Quedius of Staphylinini, no definite Mesozoic fossils of this genus have been found to date. The genus Quedius Stephens, 1829, including almost 800 species found in Neotropical, Nearctic, Palaearctic, Oriental and Australian Regions, is one of the most species-rich groups in the world
(Herman, 2001). However, there is strong evidence that the genus is not monophyletic and that at least some of the lineages from regions excluding the Holarctic belong to separate genera (Solodovnikov, 2006). The fossil records of Quedius are all confined to the Cenozoic era (e.g., Oustalet, 1874; Scudder, 1890; Wickham, 1912). Recently, we have recognized a well-preserved rove beetle from the Lower Cretaceous Yixian Formation (ca. 125 Ma) near Huangbanjigou village, which is morphologically similar to some representatives of the subgenus Microsaurus of Quedius. 2. Material and methods The specimen described here was collected from the yellowish tuff of the Yixian Formation. The holotype is dorso-ventrally compressed, with structures on the ventral side more visible than those on the dorsal side. The type specimen is housed in the Nanjing Institute of Geology and Palaeontology, CAS, Nanjing, China. It was examined both dry and moistened with 75% alcohol. Observations were made using an Olympus SZX7 microscope. Photographs were taken using a Zeiss Discovery V20 microscope with a digital camera attached. The line drawing was made with aid of a drawing tube attached to an Olympus SZX7 microscope. All measurements are in mm. 3. Systematic paleontology
* Corresponding author. E-mail address: [email protected] (D. Huang). 0195-6671/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.cretres.2013.03.004
Order Coleoptera Linnaeus, 1758 Family Staphylinidae Latreille, 1802
C. Cai, D. Huang / Cretaceous Research 44 (2013) 54e57
Subfamily Staphylininae Latreille, 1802 Tribe Staphylinini Latreille, 1802 Subtribe Quediina Kraatz, 1857 Genus Quedius Stephens, 1829 Quedius cretaceus sp. nov. Figs. 1 and 2 Diagnosis. The new species can be separated from other members of Quedius by having the following combination of characters: small procoxae, short metacoxae and pronotal hypomeron with large postcoxal process. Derivation of name. Derived from the Latinized “cretaceus”, meaning the new species is of the Cretaceous age. Holotype. NIGP156220; only one piece of impression fossil included, without counterpart. Horizon and locality. Lower Cretaceous Yixian Formation, Huangbanjigou, Beipiao City, Liaoning Province, northeastern China. Description. Body length (from mandibles to apex of tergite IX) 9.80. Head capsule rounded, widest across the hind margins of eyes, 1.72
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in length (including mandibles), 1.26 wide, about 0.85 times as wide as pronotum; temple slightly longer than eye. Eye relatively small, occupying anterior half of side of head. Infraorbital ridges below eyes distinct and complete. Gular sutures moderately separated, closest nearly at posterior third, diverging anteriorly and posteriorly. Antenna 11-segmented, not geniculate, without a club, extending to half of pronotal length; antennomere 1 very long, gradually thickened apically, about two times as long as the second; antennomere 2 narrower than 1, thickened to apex; antennomeres 3 slightly longer than 2, about the same width as 2; antennomeres 4 and 5 slightly longer than wide, shorter than 3; 6e10 subquadrate; 11 relatively large, nearly oval-shaped. Antennal insertions seemingly located at anterior margin of head capsule, with distance between antennal insertions longer than distance from antennal insertion to eye. Mandible large and elongate, narrowed apically, base broad and apex sharply pointed; left mandible apparently with two preapical teeth, right with one single tooth on the inner margin. Maxillary palpus partly preserved, apparently long. Neck constriction present, broad, about 0.7 times as wide as head. Pronotum narrowed anteriorly, widest at posterior third, width 1.49, length 1.45. Anterolateral angle developed, nearly rectangular. Lateral and posterior margins well-rounded. Disc of pronotum not visible. Pronotal hypomera strongly inflected. Pronotal postcoxal processes relatively large, subtriangular, located nearly at middle of
Fig. 1. Quedius cretaceus sp. nov., NIGP156220. A, general habitus, photographed under low-angled light. B, same, moistened with 75% alcohol. C, line drawings of the holotype. Scale bars represent 2 mm.
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C. Cai, D. Huang / Cretaceous Research 44 (2013) 54e57
Fig. 2. Q. cretaceus sp. nov. A, enlargement of head. B, enlargement of prothorax. C, enlargement of meso- and metaventrites. D, enlargement of abdominal sternites III and IV, with V-shaped anterior margin of sternite III indicated. E, enlargement of left antenna. All moistened with 75% alcohol. Scale bars represent 500 mm. a, antennomere; am, anterior margin; c, carina; e, eye; gs, gular suture; ior, infraorbital ridge; map, metaventral anterior process; mpp, mesoventral posterior process; mtt, metatrochanter; pc, procoxa; pcp, postcoxal process.
pronotum. Scutellum not preserved. Prosternum transverse, with median longitudinal carina. Prosternal process present, obtuseangled. Elytra about 1.2 times as long as pronotum, 1.71 long, combined width 1.89. Surface apparently without striae; anterolateral corners rounded. Mesoventrite without medial carina, with short, sharp mesosternal intercoxal process. Metaventrite large and longer than mesoventrite. Metaventral process protruding anteriorly, but obtuse. Hind wings developed, partly preserved. Legs moderately long; anterior legs slightly shorter than the other two; middle legs slightly shorter than the posterior ones. Procoxae relatively small, contiguous. Mesocoxae large, suboval, slightly oblique, sub-contiguous. Metacoxae relatively small, subtriangular, with anterior margin curved, about 0.84 times as long as wide. All femora robust, elongate. Tibiae gradually widened apically. Protarsi 5-segmented, basal four tarsomeres bilobed and wide, 5 elongate. Meso- and metatarsi elongate. Abdomen relatively long, more or less parallel-sided along most of length, narrowing anteriorly, tapered from abdominal segment VII to apex. Segments IIIeVI each apparently with two pairs of paratergites. Anterior margin of sternite III concave, slightly V-shaped. Lateral tergal sclerites relatively broad. The structures
interpreted as paired gonocoxites suggest that this specimen is a female. 4. Discussion This new specimen, bearing a remarkable Quediina-like habitus, can be easily placed in the extant subfamily Staphylininae, which is well supported by its relatively large body size, very elongate basal antennomere, broad neck constriction, typical metacoxae with anterior margin well curved, 5-segmented protarsi, and abdominal tergites each with two pairs of paratergites (Newton et al., 2000). It can be attributed to the extant tribe Staphylinini as evidenced by the distance between antennal insertions longer than distance from antennal insertion to eye, antennae not geniculate, neck distinct and broad, and anterior margin of prosternum without antesternal sclerite (Newton et al., 2000). Moreover, this specimen can be referred to the subtribe Quediina by its general habitus, including the presence of complete infraorbital ridge and anterior angles of pronotum produced beyond anterior margin of prosternum (Newton et al., 2000; Smetana and Davies, 2000; Solodovnikov, 2006). Even though the genus Quedius is currently proved to be not monophyletic (Solodovnikov, 2006), the new species can be
C. Cai, D. Huang / Cretaceous Research 44 (2013) 54e57
placed in Quedius based on the combination of characters: 1) pronotal hypomeron with well-developed postcoxal process; 2) prosternum with median longitudinal carina; and 3) mesosternum with sharp intercoxal process (e.g., Smetana, 1995). Other key features delimiting Quedius are pronotum with dorsal rows of one to numerous punctures on disk and aedeagus with parameres fused into a single lamella (e.g., Smetana, 1995). Because of the ventral preservation, it is impossible to determine whether punctures on pronotal disk are present, and no information on the characteristic aedeagus is available (only female described herein). Even though the new species shares a number of features with extant Quedius, especially the subgenus Microsaurus by having relatively small eyes (Smetana, 1971), it retains relatively small procoxae, pronotal hypomeron with large postcoxal process, and relatively short metacoxae. It is noteworthy that the extant genus Quedius, and even most members of the subfamily Staphylininae, is usually characterized by having the pronotal hypomeron with a small basal postcoxal process. The well-developed and relatively large postcoxal process is typically confined to the allied subfamily Paederinae (Newton et al., 2000). The find of Q. cretaceus from the Early Cretaceous, about 125 million years ago, is the earliest definitive record for this worldwide-distributed genus, supporting its antiquity and that this group has already originated at least in the Early Cretaceous. Even though no definitive staphylinine rove beetles have been reported from the Jurassic period to date, an increasing number of fossil staphylinines have been known from a number of Cretaceous deposits in the world. Many of them are given as figures, but without detailed description or taxonomic discussion, including an unnamed specimen from the Early Cretaceous Santana Formation of Brazil (figure 10.28 in Grimaldi and Engel, 2005; figure 2D in Grimaldi and Maisey, 1990), an unnamed species from the Early Cretaceous Koonwarra bed of Victoria, Australia (figure 35B in Jell and Duncan, 1986), and a well-preserved one from the Early Cretaceous Jordanian amber (Kaddumi, 2007). In addition, an enigmatic genus Megolisthaerus (Yue et al., 2010) from the Early Cretaceous Yixian Formation of China has been recently reinterpreted as a member of Staphylininae, rather than the Tachyporine group of subfamilies (Cai and Huang, 2013). Therefore, there is more convincing evidence suggesting that the subfamily Staphylininae was more diverse in Early Cretaceous than previously thought. Compared to other Mesozoic staphylinines, the new species can be readily separated from Laostaphylinus, Mesostaphylinus, Megolisthaerus, and the species from the Jordanian amber by its rounded head capsule and distinctly broad neck; from the species from the French amber by having broad neck and large robust mandibles. Of all the Mesozoic fossils, the new species displays the most similarities with Cretoquedius from the Late Cretaceous of Russia and the Early Cretaceous of China, including the body shape, antennal shape and length, and subparallel abdomen. However, it differs from the latter in possessing larger body size, smaller eyes (not occupying most of lateral side of head) and shorter elytra. Acknowledgements We are grateful to two anonymous reviewers for providing useful criticism and constructive suggestions. This research was supported by Chinese Academy of Sciences (KZCX2-YW-QN104), Outstanding Youth Foundation of Jiangsu Province (BK 2012049), National Basic Research Program of China (2012CB821903), and the National Natural Science Foundation of China (91114201 and J1210006).
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References Cai, C.-Y., Huang, D.-Y., 2013. Megolisthaerus, interpreted as staphylinine rove beetle (Coleoptera: Staphylinidae) based on new Early Cretaceous material from China. Cretaceous Research 40, 207e211. Grebennikov, V.V., Newton, A.F., 2009. Good-bye Scydmaenidae, or why the ant-like stone beetles should become megadiverse Staphylinidae sensu latissimo (Coleoptera). European Journal of Entomology 106, 275e301. Grimaldi, D.A., Maisey, J.G., 1990. Introduction. Insects from the Santana Formation, Lower Cretaceous, of Brazil. In: Grimaldi, D.A. (Ed.), 1990. Bulletin of the American Museum of Natural History, vol. 195. American Museum of Natural History, New York, pp. 5e14. Grimaldi, D., Engel, M.S., 2005. Evolution of the Insects. Cambridge University Press, Cambridge, UK, 755 p. Herman, L.H., 2001. Catalog of the Staphylinidae (Insecta: Coleoptera). 1758 to the end of the second millennium, Parts I-VII. Bulletin of the American Museum of Natural History 265, 1e4218 (in 7 vols.). Jell, P.A., Duncan, P.M., 1986. Invertebrates, mainly insects, from the freshwater Koonwarra Fossil Bed (Korumburra Group) S. Gippsland, Victoria. Memoir Association of Australian Palaeontologists 3, 111e205. Kaddumi, H.F., 2007. Amber of Jordan e the oldest prehistoric Insects in fossilized resin, Third ed. Publications of the Eternal River Museum of Natural History, Amman (Jordan), 298 p. Kraatz, G., 1857. Naturgeschichte der Insecten Deutschlands. Abt. 1. Coleoptera, Zweiter Band. Nicolai, Berlin, pp. 377e1080. Latreille, P.A., 1802. Histoire naturelle, générale et particulière, des crustacés et des insectes, vol. 3. F. Dufart, Paris, 467 p. Newton, A.F., Thayer, M.K., Ashe, J.S., Chandler, D.S., 2000. Staphylinidae Latreille, 1802. In: Arnett Jr., R.H. (Ed.). In: Thomas, M.C. (Ed.), American Beetles. the United States of America, vol. 1. CRC Press, Boca Raton, Florida, pp. 321e322. Oustalet, E., 1874. Recherches sur les insectes fossiles des terrains tertiaires de la France, Deuxieme partie. Insectes fossiles d’Aix en Provence. Annales des sciences geologiques, Paris 5, 1e347. Ryvkin, A.B., 1988. Novye melovye Staphylinidae (Insecta) s dal’nego vostoka. Paleontologicheskii Zhurnal 4, 103e106. Schlüter, T., 1978. Zur Systematik und Palökologie harzkonservierter Arthropoda einer Taphozönose aus dem Cenomanium von NW-Frankreich. Berliner Geowissenschaftliche Abhandlungen. A: Geologie und Paläontologie 9, 1e150. Scudder, S.H., 1890. The Tertiary insects of North America. Report of the United States Geological Survey of the Territories, 13, 1e734. Smetana, A., 1971. Revision of the tribe Quediini of America north of Mexico (Coleoptera: Staphylinidae). Memoirs of the Entomological Society of Canada 79. vi þ 1e303. Smetana, A., 1995. Revision of the tribes Quediini and Tanygnathinini. Part III. Taiwan (Coleoptera: Staphylinidae). Special Publication Number 6. National Museum of Natural Science, Taichung, Taiwan, Republic of China, 145 p. Smetana, A., Davies, A., 2000. Reclassification of the north temporate taxa associated with Staphylinus sensu lato, including comments on relevant subtribes of Staphylinini (Coleoptera: Staphylinidae). American Museum Novitates 3287, 1e88. Solodovnikov, A., 2006. Revision and phylogenetic assessment of Afroquedius gen. nov from South Africa: Toward new concepts of the genus Quedius, subtribe Quediina and reclassification of the tribe Staphylinini (Coleoptera: Staphylinidae: Staphylininae). Annals of the Entomological Society of America 99, 1064e1084. Solodovnikov, A., Yue, Y.-L., Tarasov, S., Ren, D., 2012. Extinct and extant rove beetles meet in the matrix: Early Cretaceous fossils shed light on the evolution of a hyperdiverse insect lineage (Coleoptera: Staphylinidae: Staphylininae). Cladistics, 44 p. http://dx.doi.org/10.1111/j.1096-0031.2012.00433.x. Stephens, J.F., 1829. A systematic catalogue of British insects: being an attempt to arrange all the hitherto discovered indigenous insects in accordance with their natural affinities, containing also the references to every English writer on entomology, and to the principal foreign authors, with all the published British genera to the present time. Part 1. Insecta Mandibulata. Baldwin and Cradock, London. xxxiv þ 416 pp. Thayer, M.K., 2005. Staphylinidae Latreille, 1802. In: Beutel, R.G., Leschen, R.A.B. (Eds.), Coleoptera, Beetles. vol. 1, Morphology and Systematics (Archostemata, Adephaga, Myxophaga, Polyphaga Partim), Handbuch der Zoologie/Handbook of Zoology. Band/vol. IV: Arthropoda: Insecta (Kristensen, N.P, Beutel, R.G., Eds.). Teilband/Part 38. Walter de Gruyter, Berlin and New York, pp. 296e344. Wickham, H.F., 1912. A report on some recent collections of fossil Coleoptera from the Miocene shales of Florissant. Bulletin from the Laboratories of Natural History of the State University of Iowa 6, 3e38. Yue, Yanli, Ren, Dong, Solodovnikov, A., 2010. Megolisthaerus chinensis gen. et sp. n. (Coleoptera: Staphylinidae incertae sedis): an enigmatic rove beetle lineage from the Early Cretaceous. Insect Systematics & Evolution 41, 317e327. Zhang, Junfeng, 1988. The late Jurassic fossil Staphylinidae (Coleoptera) of China. Acta Entomologica Sinica 31, 79e84. pl. 1 (in Chinese and English).
Contents lists available at SciVerse ScienceDirect
Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes
A new species of small-eyed Quedius (Coleoptera: Staphylinidae: Staphylininae) from the Early Cretaceous of China Chenyang Cai, Diying Huang* State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, Jiangsu Province 210008, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 29 August 2012 Accepted in revised form 24 March 2013 Available online 21 April 2013
Quedius cretaceus sp. nov., belonging to the Recent widespread staphylinine genus Quedius, is described and figured based on an exquisitely preserved specimen from the Lower Cretaceous Yixian Formation at Huangbanjigou, Liaoning Province, Northeast China. The new species, bearing relatively small and anteriorly-located eyes, displays remarkable resemblances to some members of the extant subgenus Microsaurus. However, it can be readily recognized from its rest of congeners by the combination of moderately separated gular sutures, relatively small procoxae, short metacoxae, and pronotal hypomeron with relatively large postcoxal process. This new find from the Early Cretaceous (ca. 125 Ma) represents the oldest fossil record for Quedius. It also suggests that the worldwide-distributed genus has already originated at least in the Early Cretaceous. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Staphylininae Quedius Early Cretaceous Yixian Formation
1. Introduction With more than 7700 described species and 340 genera, the rove beetle subfamily Staphylininae is one of the most diverse groups of the Staphylinine group of subfamilies (Grebennikov and Newton, 2009; Thayer, 2005). The earliest fossil staphylinines are reported from the Lower Cretaceous Laiyang Formation (Laostaphylinus Zhang, 1988, see Herman, 2001; Solodovnikov et al., 2012) and Yixian Formation (Cretoprosopus Solodovnikov et al., 2012, Durothorax Solodovnikov et al., 2012, Paleothius Solodovnikov et al., 2012, Paleowinus Solodovnikov et al., 2012, Thayeralinus Solodovnikov et al., 2012 and Megolisthaerus, see Cai and Huang, 2013; Yue et al., 2010) of China. An unnamed species (Species A) of tribe Xantholinini is known from the Late Cretaceous amber of France (Schlüter, 1978). In addition, another originally monotypic genus Cretoquedius, belonging to the extant tribe Staphylinini, was discovered from the Late Cretaceous of Russia (Ryvkin, 1988) and recently reported from the Early Cretaceous of northeastern China (Solodovnikov et al., 2012). Even though Cretoquedius is morphologically very close to the extant common genus Quedius of Staphylinini, no definite Mesozoic fossils of this genus have been found to date. The genus Quedius Stephens, 1829, including almost 800 species found in Neotropical, Nearctic, Palaearctic, Oriental and Australian Regions, is one of the most species-rich groups in the world
(Herman, 2001). However, there is strong evidence that the genus is not monophyletic and that at least some of the lineages from regions excluding the Holarctic belong to separate genera (Solodovnikov, 2006). The fossil records of Quedius are all confined to the Cenozoic era (e.g., Oustalet, 1874; Scudder, 1890; Wickham, 1912). Recently, we have recognized a well-preserved rove beetle from the Lower Cretaceous Yixian Formation (ca. 125 Ma) near Huangbanjigou village, which is morphologically similar to some representatives of the subgenus Microsaurus of Quedius. 2. Material and methods The specimen described here was collected from the yellowish tuff of the Yixian Formation. The holotype is dorso-ventrally compressed, with structures on the ventral side more visible than those on the dorsal side. The type specimen is housed in the Nanjing Institute of Geology and Palaeontology, CAS, Nanjing, China. It was examined both dry and moistened with 75% alcohol. Observations were made using an Olympus SZX7 microscope. Photographs were taken using a Zeiss Discovery V20 microscope with a digital camera attached. The line drawing was made with aid of a drawing tube attached to an Olympus SZX7 microscope. All measurements are in mm. 3. Systematic paleontology
* Corresponding author. E-mail address: [email protected] (D. Huang). 0195-6671/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.cretres.2013.03.004
Order Coleoptera Linnaeus, 1758 Family Staphylinidae Latreille, 1802
C. Cai, D. Huang / Cretaceous Research 44 (2013) 54e57
Subfamily Staphylininae Latreille, 1802 Tribe Staphylinini Latreille, 1802 Subtribe Quediina Kraatz, 1857 Genus Quedius Stephens, 1829 Quedius cretaceus sp. nov. Figs. 1 and 2 Diagnosis. The new species can be separated from other members of Quedius by having the following combination of characters: small procoxae, short metacoxae and pronotal hypomeron with large postcoxal process. Derivation of name. Derived from the Latinized “cretaceus”, meaning the new species is of the Cretaceous age. Holotype. NIGP156220; only one piece of impression fossil included, without counterpart. Horizon and locality. Lower Cretaceous Yixian Formation, Huangbanjigou, Beipiao City, Liaoning Province, northeastern China. Description. Body length (from mandibles to apex of tergite IX) 9.80. Head capsule rounded, widest across the hind margins of eyes, 1.72
55
in length (including mandibles), 1.26 wide, about 0.85 times as wide as pronotum; temple slightly longer than eye. Eye relatively small, occupying anterior half of side of head. Infraorbital ridges below eyes distinct and complete. Gular sutures moderately separated, closest nearly at posterior third, diverging anteriorly and posteriorly. Antenna 11-segmented, not geniculate, without a club, extending to half of pronotal length; antennomere 1 very long, gradually thickened apically, about two times as long as the second; antennomere 2 narrower than 1, thickened to apex; antennomeres 3 slightly longer than 2, about the same width as 2; antennomeres 4 and 5 slightly longer than wide, shorter than 3; 6e10 subquadrate; 11 relatively large, nearly oval-shaped. Antennal insertions seemingly located at anterior margin of head capsule, with distance between antennal insertions longer than distance from antennal insertion to eye. Mandible large and elongate, narrowed apically, base broad and apex sharply pointed; left mandible apparently with two preapical teeth, right with one single tooth on the inner margin. Maxillary palpus partly preserved, apparently long. Neck constriction present, broad, about 0.7 times as wide as head. Pronotum narrowed anteriorly, widest at posterior third, width 1.49, length 1.45. Anterolateral angle developed, nearly rectangular. Lateral and posterior margins well-rounded. Disc of pronotum not visible. Pronotal hypomera strongly inflected. Pronotal postcoxal processes relatively large, subtriangular, located nearly at middle of
Fig. 1. Quedius cretaceus sp. nov., NIGP156220. A, general habitus, photographed under low-angled light. B, same, moistened with 75% alcohol. C, line drawings of the holotype. Scale bars represent 2 mm.
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C. Cai, D. Huang / Cretaceous Research 44 (2013) 54e57
Fig. 2. Q. cretaceus sp. nov. A, enlargement of head. B, enlargement of prothorax. C, enlargement of meso- and metaventrites. D, enlargement of abdominal sternites III and IV, with V-shaped anterior margin of sternite III indicated. E, enlargement of left antenna. All moistened with 75% alcohol. Scale bars represent 500 mm. a, antennomere; am, anterior margin; c, carina; e, eye; gs, gular suture; ior, infraorbital ridge; map, metaventral anterior process; mpp, mesoventral posterior process; mtt, metatrochanter; pc, procoxa; pcp, postcoxal process.
pronotum. Scutellum not preserved. Prosternum transverse, with median longitudinal carina. Prosternal process present, obtuseangled. Elytra about 1.2 times as long as pronotum, 1.71 long, combined width 1.89. Surface apparently without striae; anterolateral corners rounded. Mesoventrite without medial carina, with short, sharp mesosternal intercoxal process. Metaventrite large and longer than mesoventrite. Metaventral process protruding anteriorly, but obtuse. Hind wings developed, partly preserved. Legs moderately long; anterior legs slightly shorter than the other two; middle legs slightly shorter than the posterior ones. Procoxae relatively small, contiguous. Mesocoxae large, suboval, slightly oblique, sub-contiguous. Metacoxae relatively small, subtriangular, with anterior margin curved, about 0.84 times as long as wide. All femora robust, elongate. Tibiae gradually widened apically. Protarsi 5-segmented, basal four tarsomeres bilobed and wide, 5 elongate. Meso- and metatarsi elongate. Abdomen relatively long, more or less parallel-sided along most of length, narrowing anteriorly, tapered from abdominal segment VII to apex. Segments IIIeVI each apparently with two pairs of paratergites. Anterior margin of sternite III concave, slightly V-shaped. Lateral tergal sclerites relatively broad. The structures
interpreted as paired gonocoxites suggest that this specimen is a female. 4. Discussion This new specimen, bearing a remarkable Quediina-like habitus, can be easily placed in the extant subfamily Staphylininae, which is well supported by its relatively large body size, very elongate basal antennomere, broad neck constriction, typical metacoxae with anterior margin well curved, 5-segmented protarsi, and abdominal tergites each with two pairs of paratergites (Newton et al., 2000). It can be attributed to the extant tribe Staphylinini as evidenced by the distance between antennal insertions longer than distance from antennal insertion to eye, antennae not geniculate, neck distinct and broad, and anterior margin of prosternum without antesternal sclerite (Newton et al., 2000). Moreover, this specimen can be referred to the subtribe Quediina by its general habitus, including the presence of complete infraorbital ridge and anterior angles of pronotum produced beyond anterior margin of prosternum (Newton et al., 2000; Smetana and Davies, 2000; Solodovnikov, 2006). Even though the genus Quedius is currently proved to be not monophyletic (Solodovnikov, 2006), the new species can be
C. Cai, D. Huang / Cretaceous Research 44 (2013) 54e57
placed in Quedius based on the combination of characters: 1) pronotal hypomeron with well-developed postcoxal process; 2) prosternum with median longitudinal carina; and 3) mesosternum with sharp intercoxal process (e.g., Smetana, 1995). Other key features delimiting Quedius are pronotum with dorsal rows of one to numerous punctures on disk and aedeagus with parameres fused into a single lamella (e.g., Smetana, 1995). Because of the ventral preservation, it is impossible to determine whether punctures on pronotal disk are present, and no information on the characteristic aedeagus is available (only female described herein). Even though the new species shares a number of features with extant Quedius, especially the subgenus Microsaurus by having relatively small eyes (Smetana, 1971), it retains relatively small procoxae, pronotal hypomeron with large postcoxal process, and relatively short metacoxae. It is noteworthy that the extant genus Quedius, and even most members of the subfamily Staphylininae, is usually characterized by having the pronotal hypomeron with a small basal postcoxal process. The well-developed and relatively large postcoxal process is typically confined to the allied subfamily Paederinae (Newton et al., 2000). The find of Q. cretaceus from the Early Cretaceous, about 125 million years ago, is the earliest definitive record for this worldwide-distributed genus, supporting its antiquity and that this group has already originated at least in the Early Cretaceous. Even though no definitive staphylinine rove beetles have been reported from the Jurassic period to date, an increasing number of fossil staphylinines have been known from a number of Cretaceous deposits in the world. Many of them are given as figures, but without detailed description or taxonomic discussion, including an unnamed specimen from the Early Cretaceous Santana Formation of Brazil (figure 10.28 in Grimaldi and Engel, 2005; figure 2D in Grimaldi and Maisey, 1990), an unnamed species from the Early Cretaceous Koonwarra bed of Victoria, Australia (figure 35B in Jell and Duncan, 1986), and a well-preserved one from the Early Cretaceous Jordanian amber (Kaddumi, 2007). In addition, an enigmatic genus Megolisthaerus (Yue et al., 2010) from the Early Cretaceous Yixian Formation of China has been recently reinterpreted as a member of Staphylininae, rather than the Tachyporine group of subfamilies (Cai and Huang, 2013). Therefore, there is more convincing evidence suggesting that the subfamily Staphylininae was more diverse in Early Cretaceous than previously thought. Compared to other Mesozoic staphylinines, the new species can be readily separated from Laostaphylinus, Mesostaphylinus, Megolisthaerus, and the species from the Jordanian amber by its rounded head capsule and distinctly broad neck; from the species from the French amber by having broad neck and large robust mandibles. Of all the Mesozoic fossils, the new species displays the most similarities with Cretoquedius from the Late Cretaceous of Russia and the Early Cretaceous of China, including the body shape, antennal shape and length, and subparallel abdomen. However, it differs from the latter in possessing larger body size, smaller eyes (not occupying most of lateral side of head) and shorter elytra. Acknowledgements We are grateful to two anonymous reviewers for providing useful criticism and constructive suggestions. This research was supported by Chinese Academy of Sciences (KZCX2-YW-QN104), Outstanding Youth Foundation of Jiangsu Province (BK 2012049), National Basic Research Program of China (2012CB821903), and the National Natural Science Foundation of China (91114201 and J1210006).
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