Cretaceous Research 100 (2019) 126e133 Contents lists available at ScienceDirect Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes Short communication yCretohlezkus gen. nov. from Upper Cretaceous Burmese amber demonstrates ancient origins of suctorial mouthparts in Eucinetidae (Coleoptera: Scirtoidea) Paweł Jałoszynski Museum of Natural History, University of Wrocław, Sienkiewicza 21, 50-335 Wrocław, Poland article info abstract Article history: Eucinetidae is a small beetle family comprising only ten extant genera. Five of them have unusually Received 14 January 2019 modified mouthparts with a strongly transformed labium, which shows features interpreted as adap- Received in revised form tations to suctorial feeding. Among the hyperdiverse Coleoptera, similar feeding adaptations are known 21 February 2019 only in several genera of Cerylonidae and Leiodidae. Fossils attributed to Eucinetidae or representing taxa Accepted in revised form 18 March 2019 presumably closely related to eucinetids are known from Lower Cretaceous of China and Upper Jurassic Available online 23 March 2019 of Mongolia, but none of them shows modified mouthparts. The first fossil of a ‘suctorial eucinetid’, yCretohlezkus alleni gen. et sp. nov., is reported in the present paper, based on a well-preserved specimen Keywords: y Fossil in Cenomanian Burmese amber. A preliminary phylogenetic analysis placed Cretohlezkus near base of ‘ ’ Beetle the monophyletic suctorial eucinetid lineage, but branch support was too low to present a robust Myanmar evolutionary hypothesis. The prementum of yCretohlezkus is modified as strongly as that of extant Cenomanian members of this group, demonstrating early origins of still only speculative feeding habits of the ‘suc- torial eucinetids’, which presumably use Myxomycetes or Basidiomycetes as the source of food. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction The scirtoid family Eucinetidae is a small group that comprises less than 50 extant species classified in the extant genera Bisaya The huge order of Coleoptera or beetles is characterized by Reitter, 1884, Eucilodes Vít, 1985, Eucinetella Nikitsky, 1996, Euci- biting mouthparts, and exceptions from the groundplan are not netus Germar, 1818, Euscaphurus Casey, 1885, Jentozkus Vít, 1977, very common. However, some highly specialized modifications are Noteucinetus Bullians & Leschen, 2004, Nycteus Latreille, 1829, known, most notably a suctorial feeding apparatus, which has Proeuzkus Vít, 2000, and Tohlezkus Vít, 1977 (Leschen, 2016, and independently evolved in phylogenetically distant groups, as Myr- later additions). They can be readily distinguished by a fusiform micholeva Lea, 1910 (Staphylinoidea: Leiodidae), several genera of body form and large metacoxal plates that cover most of the met- Cerylonidae (Cucujoidea), e.g., Cautomus Sharp, 1885 and Rostror- aventrite (Leschen, 2016). Eucinetids are cryptic beetles, usually ylon Slipinski, 1991 (Cerylonidae), and several genera of scirtoid collected by sifting leaf litter, under bark of trees or in rotten wood; Eucinetidae (Leschen, 2016). Interestingly, even though these some species have been found in association with Myxomycetes or modifications are unusual and highly interesting, their morphology Basidiomycetes, on which the adults and larvae supposedly feed remains exceptionally poorly characterized, and almost nothing is (Leschen, 2016). Adults of some species can also be collected by known about actual function of structures that form the piercing- pitfall traps in sandy and relatively dry xerothermous habitats sucking apparatus. Even the source of food for these beetles has (Jałoszynski, pers. obs.). not been confirmed yet (e.g., Newton, 2016), and the question when The most unusual feature of eucinetid beetles is a high pro- such adaptations have originated remains open. portion of taxa with strongly modified adult mouthparts, with the anterior portion of the labium (i.e., the prementum) strongly elongate, subtriangular, and presumably functioning as a piercing device. Leiodidae with ~380 genera (Newton, 2016) have only one Abbreviations: cPJ, collection of Paweł Jałoszynski, Wrocław, Poland; MNHW, genus with piercing-sucking mouthparts, and among 52 genera of Museum of Natural History, University of Wrocław, Wrocław, Poland. Cerylonidae there are only six genera with a strongly elongate, E-mail address: [email protected]. https://doi.org/10.1016/j.cretres.2019.03.016 0195-6671/© 2019 Elsevier Ltd. All rights reserved. P. Jałoszynski / Cretaceous Research 100 (2019) 126e133 127 clearly suctorial labium (Slipinski, 1991). The development of suc- Tohlezkus rufus (Sakai, 1980) (Japan; cPJ), and Eucinetus haemor- torial mouthparts seems to have been much more important for the rhoidalis (Germar, 1818) (Poland; cPJ) were studied by scanning radiation of Eucinetidae, which include five, out of the total number electron microscopy; morphological structures of all remaining of ten extant genera, with the prementum modified to a various extant Eucinetidae were extracted from descriptions and illustra- extent. In Bisaya and possibly also in one species of Proeuzkus, the tions given by Bullians & Leschen (2004), Nikitsky (1996), and Vít prementum is intermediary between the unmodified and the (1977, 1985, 1995, 2000). Acalyptomerus sp. was selected to root suctorial form, and these mouthparts can be regarded as semi- the analysis. suctorial, although their function is not known. It is also un- Phylogenetic analysis was based on 22 non-additive and unor- known whether the taxa with modified mouthparts form a dered adult morphological characters; inapplicable entries were monophyletic group within Eucinetidae, as phylogenetic re- assigned a gap value (“e”) and treated equivalent to missing data constructions for this family have not been obtained so far. Some (“?”). Character states coded as 0 do not indicate plesiomorphies. The compression fossils were attributed to Eucinetidae, or to a new data matrix was assembled in Nexus Data Editor for Windows v. 0.5.0 family yMesocinetidae Kirejtshuk & Ponomarenko, 2010, presum- (Page, 2001); characters are numbered starting from zero (as ably closely related to Eucinetidae; they come from the Lower required by TNT); parsimony analyses were conducted in TNT Cretaceous of China (136.4e130.0 Ma), and Upper Jurassic of (Goloboff et al., 2008) in two variants: under equal weights and with Mongolia (150.8e145.5 Ma), respectively (Hong, 1995; Kirejtshuk & implied weighting (at the weighting function K ranging from 3.0 to Ponomarenko, 2010). Actual relationships of these taxa within 9.0) using the implicit enumeration method. The symmetric resam- Scirtoidea need to be clarified, but none of these extinct beetles has pling (P ¼ 33; 100 replicates) was also conducted in TNT. Character modified, suctorial mouthparts. mapping was made in WinClada v. 1.00.08 (Nixon, 1999); trees were In the present study the first definite Upper Cretaceous member annotated in Corel 9.397. The characters and character states are of Eucinetidae is reported, and as its mouthparts represent the given in Appendix A; the data matrix is presented in Appendix B. suctorial form, an attempt to place the new taxon within the taxonomic context is also made. 4. Systematic palaeontology 2. Geographic and geological context Suborder: Polyphaga Emery, 1886 Superfamily: Scirtoidea Fleming, 1821 The studied specimen comes from the Hukawng Valley, Kachin Family: Eucinetidae Lacordaire, 1857 State of northern Myanmar. The only amber mine which is a subject of a commercial extraction is located in the Noije Bum Hill Genus yCretohlezkus Jałoszynski gen. nov. (26150N; 96340E) (e.g., Jałoszynski et al., 2017a, b: fig. 1), which urn:lsid:zoobank.org:act:D8D9421F-832C-4AC0-8B72- consists of folded Cretaceous and Paleogene deposits (Cruickshank 8B5C76126692 & Ko, 2003). Amber is associated with a narrow horizon in fine- Fig. 1 grained facies and it was dated as of the earliest Cenomanian age (98.79 ± 0.62 Ma) by Cruickshank & Ko (2003) and Shi et al. (2012). Derivation of name. The name is based on a stem derived from the Marine fossils such as ammonites and foraminifers, abundance of extant genus name Tohlezkus, combined with the prefix Cre-, which amber, coalified plant materials and common coal laminations in is short for Creto- and refers to the age of the fossil. Gender the fine clastic facies suggest that depositional environment must masculine. have been nearshore (Cruickshank & Ko, 2003). Type species. yCretohlezkus alleni Jałoszynski (here designated). Diagnosis. Prementum suctorial, strongly elongate and sub- 3. Material and methods triangular; frontoclypeal suture present; labial palps much longer than prementum; labial palpomere 1 extremely elongate, much 3.1. Specimen handling and imaging longer than 2. Description. Body (Fig. 1AeF) fusiform and slender, moderately The fossil specimen here described is deposited at MNHW, with convex dorsally and flattened ventrally, not constricted between the collection number 1331. The inclusion was observed (as dry pronotum and elytra. Vestiture of setae dense, short, suberect to specimen and submerged in cedar oil for better visibility) under erect. Head (Fig. 1C, E, F) strongly tilted ventrad so that entire frons Nikon SMZ1500 (Nikon, Tokyo, Japan) and Leica M205C (Leica and a part of vertex are visible in ventral view; surface of frons and Microsystems, Wetzlar, Germany) stereomicroscopes. Photographs vertex partly collapsed; posterior margin of vertex broadly were