A new fossil species of Attagenus Latreille (Coleoptera: Dermestidae) in Rovno and Baltic ambers, with a brief review of known fossil beetles from the Rovno amber Lagerstätte

Based on two specimens originating from Eocene Rovno and Baltic ambers, Attagenus (Aethriostoma) gedanicissimus sp. nov. is described, illustrated and compared with the related fossil Mesozoic species A. (Aethriostoma) turonianensis Peris et Háva, 2016. The common beetle species for Baltic and Rovno ambers suggests the exceptional temporal and geographical closeness of palaeoecosystems that produced both amber deposits. An updated checklist of Coleoptera known from Rovno amber (57 species belonging to 20 families) is compiled and provided with a bibliography of the original descriptions. The registered Rovno amber beetle assemblage contains only eight species that also occur in Baltic amber (14 %), while the similarity at the generic level is 56 % at the moment. The relationship between the Rovno and Baltic amber deposits and subjectiveness of present-day results of the beetle assemblage research are briefly discussed (urn:lsid:zoobank.org:pub:289B5A43C57A-4B75-8A15-6E61F4AFCD81).


Introduction
The problem of mutual affinity in the triad of the main European Palaeogene fossil resins (Baltic amber, Bitterfeld amber and Rovno amber) is still under discussion in the 20th century (Hoffeins and Hoffeins, 2003;Perkovsky et al., 2007;Weitschat, 2008;Szwedo and Sontag, 2009;Sontag and Szadziewski, 2011;Wolfe et al., 2016;Dunlop et al., 2018;Mänd et al., 2018;Kypke and Solodovnikov, 2018). All these fossil resins are succinites, and all originate from geographically proximate localities of central and eastern Europe (from the southern Baltic area, eastern Germany, and southern Belarus and northern Ukraine) (Perkovsky et al., 2010a;Weitschat and Wichard, 2010;Rappsilber, 2016;Bogri et al., 2018). All these fossil resins are rich in bioinclusions (Spahr, 1981;Poinar, 1992;Perkovsky et al., 2003Perkovsky et al., , 2010bPerkovsky et al., , 2012Weitschat and Wichard, 2002;Perkovsky, 2016a;Alekseev, 2017;Rappsilber and Wendel, 2019;etc.). Unfortunately, the biodiversity of these ambers is unevenly studied: the known beetle assemblage of Baltic amber is more than 8 times larger than the known beetle assemblage of Rovno amber and more as than 30 times larger than the known beetle assemblage of Bitterfeld amber (Alekseev, 2013(Alekseev, , 2017Bukejs et al., 2016). Differences in volume of knowledge make data statistically incorrect and unreliable and also cannot provide any arguments concerning the discussion about the age of these ambers.
The Dermestidae (Coleoptera) contains about 1680 valid taxa worldwide (Háva, 2015) and fossil representatives of this family are relatively frequent in ambers. Taxonomic and morphological diversity of Cretaceous Dermestidae suggests an ancient origin of this group with some lineages showing remarkable evolutionary stasis for almost 100 million years (Deng et al., 2017). In total, nine extinct species of the genus Attagenus Latreille, 1802 from fossil resin are documented to date. Five species belonging to the nominative subgenus have 96 A. Bukejs et al.: A new fossil species of Attagenus Latreille (Coleoptera: Dermestidae) been described previously from the Eocene Baltic amber: A. hoffeinsorum Háva, Prokop et Hermann, 2006;A. balticus Háva, Prokop et Hermann, 2008;A. obesus Háva, Prokop et Hermann, 2008;A. yantarnyi Háva et Bukejs, 2012;and A. gorskii Háva, 2014. Three species of nominative subgenus have been described from the Cenomanian Burmese amber: A. burmiticus Cai, Hava et Huang, 2017;A. lundi Háva et Damgaard, 2017;and A. secundus Deng,Ślipiński, Ren et Pang, 2017. One species of the subgenus Aethriostoma Motschulsky, 1858 is known from the Turonian New Jersey amber: A. turonianensis Peris et Háva, 2016. In the current paper, the second extinct species of the subgenus Aethriostoma is described and illustrated from early Cenozoic amber (Rovno and Baltic). Data about the Coleoptera described from Rovno amber are summarized and briefly discussed.

Material and methods
The material examined is deposited in the following collections: the Museum of Amber Inclusions, University of Gdańsk (Poland, MAIG); the private collection of Anders Damgaard (Holstebro, Denmark, ADC), subsequently deposited in the Zoological Museum, University of Copenhagen, Denmark.
The amber pieces were polished by hand, allowing improved views of the included specimens, and they were not subjected to any supplemental fixation.
Observations of the specimens were made using a Nikon SMZ ® 745T stereomicroscope. The photographs were taken using a Canon 70D ® camera with a macro lens (Canon MP-E 65 mm). Extended depth of field at high magnifications was achieved by combining multiple images from a range of focal planes using Helicon Focus ® v. 6.0.18 software. Measurements were taken using an ocular micrometer (expressed in millimetres).

Remarks
The studied amber beetles show the combination of characters unequivocally corresponding to Attagenini within Attageninae: prosternum not forming "collar", mouthparts free, antennal club with three compact antennomeres, abdomen with five visible ventrites and elytra not shortened.
The specimens considered here were assigned to the subgenus Aethriostoma within Attagenus based on the combination of the following characters: (1) disc of metaventrite nearly twice as wide as long and (2) body strongly convex and widely oval (in Attagenus s. str. disc of metaventrite nearly twice as long as wide, and body less convex and more narrowly obovate).

Type material
Holotype: 6278 (ex. coll. Jonas Damzen JDC 8531) (MAIG); Rovno amber; adult, sex unknown. Complete beetle is included in subtriangular, transparent amber piece, with dimensions of 25 mm × 19 mm × 16 mm and maximum thickness of 6 mm. Syninclusions consist of one specimen of Nematocera (Diptera) and numerous small to minute organic particles.
Paratype: "AlDlo 558" (ADC); Baltic amber; adult, sex unknown. Complete beetle is included in transparent amber piece, with dimensions of 23 mm × 21 mm and maximum thickness of 5 mm. Syninclusion consists of one specimen of Nematocera (Diptera).

Etymology
The epithet of the new species is the Latin adjective gedanicus in the superlative and is formed from Gedanum, the Latin name of Gdańsk where the specimen is deposited.

Differential diagnosis
Attagenus (Aethriostoma) gedanicissimus sp. nov. differs from the single known fossil representative of the subgenus, Attagenus (Aethriostoma) turonianensis Peris et Háva, 2016 (USA; Late Cretaceous: Turonian; New Jersey amber) in the following characters: antennomere 11 shorter than antennomeres 9-10 combined; pronotum strongly transverse, 3× as wide as long; abdominal sutures almost straight; and larger body size; while in A. turonianensis antennomere 11 as long as antennomeres 9-10 combined; pronotum transverse, 2.1× as wide as long; abdominal sutures concave; and distinctly smaller body size (1.81 mm). The new Eocene species A. (Aethriostoma) gedanicissimus sp. nov. differs from extant representatives of the subgenus in the unicolour blackish body and appendages (in contrast to the rufous palpi and basis of antennae in A. philippinensis Háva, 2016 and the entirely rufous appendages in A. sparsutus (Reitter, 1881)) and uniform, dark and comparatively sparse setation of dorsum (in contrast to the golden setation of A. philippinensis Háva, 2016 distinctly denser on pronotal base). Dorsal setation does not form any lightcoloured patterns: fasciae or maculae (in contrast to A. undulatus (Motschulsky, 1858) and A. irroratus (Blackburn, 1903)). Additionally, in new fossil species the antennomere 11 is slightly tapered beyond the midpoint.
Pronotum strongly transverse, about 3× as wide as long, base of pronotum nearly as wide as elytral base; lateral margins of pronotum widely rounded, posterior margin bisinuated, narrowly bordered. Hypomeron with deep antennal cavity. Prosternum not forming "collar", covered with strong microreticulation.

Rovno amber as a geographical variety of Baltic amber
Amber that is chemically similar to Baltic amber is widespread in the Dnieper River basin in Belarus and Ukraine (Savkevich, 1970), in the Kiev (upper Eocene) and Kharkov (lower Oligocene) formations, and in the Quaternary deposits (Zherikhin and Eskov, 1999). The most important amber deposits were discovered near Klesov and near Dubrovitsa in the Rovno region (Ukraine), where the amber has been mined since the 1980s. Some authors believe that this Rovno amber was transported to the Dnieper area from the north across the sea and thus originates from the same region as Baltic amber (e.g. Katinas, 1987). Others suggest a local origin from the Ukrainian shield (e.g. Perkovsky et al., 2007;Mänd et al., 2018). A comparison of inclusions may offer a clue to this problem (Zherikhin and Eskov, 1999), but in the current state of knowledge, the distribution of the different groups of insects gives equivocal results. "The faunas of Ceratopogonidae enclosed in amber from Rovno, Bitterfeld and the Baltic are very similar, showing that they inhabited similar palaeoenvironments in the same palaeogeographic region" (Sontag and Szadziewski, 2011, p. 781), whereas the data obtained from comparison of the Hymenoptera assemblages "provide evidence supporting the previously proposed suggestion on the different origin of four main European sources of succinite" (Perkovsky, 2018, p. 353). On the basis of comprehensive research on one systematic group of Rovno beetles, the Scydmaeninae, it is con- cluded that subtropical and tropical taxa were present in the region where Rovno amber formed, whereas the Baltic amber beetle assemblage was more hygrophilous and adapted to a colder climate in general (Jałoszyński and Perkovsky, 2016). Taking into account the existence of many small Eocene amber outcrops in Poland, Ukraine and Belarus (and possible slight variability in their bioinclusions), the naming "Baltic amber sensu lato" for all these local types of succinites including Belarus amber, Rovno amber, etc., could be used. However, we follow the traditional view and use the name "Rovno amber" as separate from "amber type".

Checklist of Coleoptera known from Rovno amber
As an additional part of the study, a checklist of all known Coleoptera from Rovno amber is compiled and presented below. Synonymy for two taxa is provided according to Gimmel et al. (2019) and Reike et al. (2017).  Perkovsky, 2008 The known assemblage of the Rovno amber Coleoptera composes 57 species belonging to 50 genera and 20 families. A total of 49 species are known only from this Lagerstätte, and eight species (Anaspis horaki, Attagenus gedanicissimus sp. nov., Baltostigus horribilis, Dysanabatium kechrimparense, Latridius alexeevi, Mimoplatycis notha, Neolitochropus bedovoyi, Orchesia rasnitzyni) are also known or are primarily described from Baltic amber (i.e. are common for these two ambers). From the listed beetle genera with described species, 28 genera (56 %) are common with Baltic amber, i.e. have described analogues; 13 genera are palaeoendemic for Rovno amber (26 %); and 9 genera (18 %) are recent but have no described species in Baltic amber.
The study of Rovno amber was focused first of all on new descriptions and on the search for new taxa, while studies on the similarities and differences with the assemblage of Baltic amber species were mainly beyond the scope of the current palaeontological papers. The ratio of 49 palaeoendemic species to eight species common with Baltic amber is a subjective present-day stage of research, but not an objective and real ratio of common and "endemic" Coleoptera in these ambers. The species list of the Rovno amber beetles does not contain any data on many species-rich beetle families in Baltic amber (Aderidae, Carabidae, Cerambycidae, Cleridae, Elateridae, and Scirtidae) at all: although these families are known in Rovno amber, the representatives are still without generic or specific attribution. We suppose that the lack of such information is a very important part of the general scarcity of reliable data for analysis at the moment.
Data availability. No data sets were used in this article.
Author contributions. AB and VIA conceived of the presented idea and wrote the manuscript with input from JH. AB designed the study and prepared the description of the new species, JH supervised the differential diagnosis of the new species, VIA performed the list of Rovno fossil beetles. All authors provided critical feedback and helped to shape the research, analysis and manuscript.
Competing interests. The authors declare that they have no conflict of interest.
Acknowledgements. The authors are sincerely grateful to Elżbieta Sontag (Museum of Amber Inclusions, University of Gdańsk, Poland) and Anders Damgaard (Holstebro, Denmark) for the loan and to Jonas Damzen (Vilnius, Lithuania) for informing us about the interesting specimen, assistance during our amber research and permission to use photographs of the holotype. The authors are grateful to Andreas Herrmann (Stade, Germany) and the one anonymous reviewer for their helpful comments and corrections on an earlier version of this paper. The study of VIA was done with the support of the state assignment of IO RAS (theme no. 0149-2019-0013).
Financial support. This research has been supported by the IO RAS (grant no. 0149-2019-0013).

102
A. Bukejs et al.: A new fossil species of Attagenus Latreille (Coleoptera: Dermestidae) Review statement. This paper was edited by Florian Witzmann and reviewed by Andreas Herrmann and one anonymous referee.