Glesoconomorphus ekaterinae sp. nov. (Coleoptera, Mycteridae), representing the first ever fossil species of Coleoptera from the Volyn Region of Ukraine and the first mycterid from late Eocene Rovno amber, is described and illustrated. A key to species of the fossil mycterid genus Glesoconomorphus Alekseev, Pollock & Bukejs, 2019 is presented. The systematic position of Glesoconomorphus within Eurypinae J. Thomson, 1860 is briefly discussed. The oldest finding of phoretic Winterschmidtiidae Oudemans, 1923 mites, found on the type specimen of the new beetle species, is reported.

Eurypinae, identification, morphology, phoresy, Priabonian, Rovno amber, taxonomy

Glesoconomorphus Alekseev, Pollock & Bukejs, 2019 was erected recently to hold the sole species G. nachzehrer Alekseev, Pollock & Bukejs, 2019 (Alekseev et al. 2019) from Eocene Baltic amber (Aleksandrova and Zaporozhets 2008; Iakovleva 2017; Iakovleva et al. 2021). The genus was attributed to Eurypinae J. Thomson, 1860 of Mycteridae Oken, 1843. Eurypinae is a well-defined subfamily within Mycteridae, with the following external features (Pollock 2010; Ivie and Pollock 2012): body slightly convex dorsally, head not produced to form a rostrum, compound eyes comparatively large, labrum exposed dorsally, insertions of antennae not concealed by lateral extension of frons, terminal maxillary palpomere subsecuriform, penultimate antennomere short, dorsal outline of pronotum subquadrate, pronotum laterally carinate, with paired postmedian impression, anterior margin of pronotum without transverse setal pad, scutellar shield flattened dorsally above level of elytra, elytra setose, irregularly punctate, procoxal cavities closed internally and open externally, procoxae contiguous, mesocoxal cavities closed internally and externally, penultimate tarsomere bilobate, tarsal claws swollen basally or with a distinct basal tooth (Alekseev et al. 2019). The male genital organs were not studied for Glesoconomorphus nachzehrer by Alekseev et al. (2019), and therefore their shape and structure remain unknown.

As discussed by Alekseev et al. (2019), Glesoconomorphus differs from other extant eurypine genera by the following combination of external features: ocular groove distinct, head without frontal furrows, compound eyes entire (non-emarginate) and strongly protruding from lateral outline of head, intrafacetal setae not present, pronotum not laterally carinate (this feature differs in the second species discussed below), frontoclypeal suture not indicated, dorsum evenly punctate and setose.

Glesoconomorphus appears close to the extant Conomorphus Champion, 1889 and Stilpnonotus Gray, 1832 due to the presence of a distinct ocular groove narrowly separated from the eyes (Pollock 2016; Alekseev et al. 2019). Among the fossil Eurypinae, Glesoconomorphus was reported to be different from Bertinotus Kirejtshuk & Nel, 2009 from Ypresian Oise amber due to the presence of paramedian depressions at the pronotal base, and a distinctly punctate head (Alekseev et al. 2019), and from Europoeurypus Alekseev, Bukejs & Pollock, 2020 in the absence of ocular grooves, the generally larger body (body length exceeding 10 mm), and the comparatively shorter antenna (Alekseev et al. 2020) (the length of the antenna should not be considered an important genus-rank feature in mycterids according to our expertise).

Rovno amber is considered the southern coeval of Baltic amber (Sokoloff et al. 2018), with extinct tropical elements supposedly represented better than in Baltic amber (Perkovsky 2013, 2016, 2017a, 2018; Colombo et al. 2021a; Radchenko and Perkovsky 2021). More than 300 arthropod species have been formally described from Rovno amber (authors’ data). The share of Baltic amber species from large arthropod orders and suborder reported from Rovno amber varies from less than 13% for Coleoptera species (Legalov et al. 2021a; Kupryjanowicz et al. 2021; Lyubarsky and Perkovsky 2021; Tshernyshev and Perkovsky 2021 and references therein) and 24% for Nematocera (Giłka et al. 2021) to less than 47% for Hymenoptera (Simutnik et al. 2020 and references therein; Colombo et al. 2021b; authors’ data). The new beetle discussed in the present paper is the fourth named fossil arthropod from amber from the Volyn Region of Ukraine. The first one was a new genus and species of cicadellid from Kovel (Dietrich and Perkovsky 2020), the second was a blattid from Manevichi (Anisyutkin and Perkovsky 2021), and the third was a new damselfly from Kovel (Martynov et al. in press).

The aims of the present paper are to describe and illustrate Glesoconomorphus ekaterinae sp. nov., the first known Coleoptera species from Priabonian amber from the Volyn Region of Ukraine, to supplement the definition of the genus, and to provide a key to Glesoconomorphus species. The presence of an abdominal setal patch in Glesoconomorphus ekaterinae sp. nov. confirms placement of the genus in the subfamily Eurypinae. The closure of the procoxal cavities and the presence of an apicoventral binding patch on each elytron, two other common features of Eurypinae (Pollock 2010), remain unknown in Glesoconomorphus since studying them was not possible in the available specimens.

Lisove is a new amber mine in the Volyn Region of NW Ukraine, 9 km east of Manevichi (the former Manevichi district, now Kamen-Kashirsky district).

Paired morphological structures are generally treated as singular in the text.

The specimen was studied and digital images were made using a Leica Z16 APO stereomicroscope equipped with Leica DFC450 Digital Camera at the I. I. Schmalhausen Institute of Zoology of the National Academy of Sciences of Ukraine (Kiev), and subsequently processed with the LAS Core 3.8 and Adobe Photoshop CS5 software.

The holotype is deposited at the Schmalhausen Institute of Zoology of the National Academy of Sciences of Ukraine, Kiev (SIZK).

The composition of fossil Mycteridae was discussed recently in Alekseev et al. (2019, 2020) and is therefore not repeated here. The fact that Conomorphus Champion, 1889 and Stilpnonotus Gray, 1832, the two thermophilic mycterid genera nearest to Glesoconomorphus, are nowadays restricted to the Neotropics (Pollock 2016) indicates that Glesoconomorphus possibly was more common in Rovno amber forest than in Baltic amber forest (Mänd et al. 2018).

The presence of a sex patch on abdominal ventrite II in male Glesoconomorphus ekaterinae sp. nov. and the presence of distinct frontal furrows provide additional support for the placement of Glesoconomorphus in the subfamily Eurypinae of Mycteridae. The structure of the procoxal cavities and the presence or absence of an apicoventral binding patch on each elytron remain unknown in this genus.

Nearly all studied Rovno amber inclusions from the Rovno Region (reported inclusions from Zhitomir Region listed in Melnitsky et al. 2021a) were collected from Klesov and from the Horyn’ River Basin (Perkovsky et al. 2010; Perkovsky 2017b; Mitov et al. 2021); however, new material has been collected from the Varash district (the former districts of Vladimirets and Zarechnoye) of the Rovno Region and from the former Manevichi district of the Volyn Region (basins of the Styr, Veselukha, and Stokhod rivers). These new collections (mostly from Kuchotskaya Volya, Voronki, and Velyki Telkovichi) have revealed many new taxa of Dictyoptera (including Isoptera), Coleoptera, Hemiptera, Hymenoptera, Neuroptera, Raphidioptera, and Trichoptera, as listed in Tshernyshev and Perkovsky (2021), with additions in Legalov et al. (2019, 2021b), Matalin et al. (2021), Giłka et al. (2021), Melnitsky et al. (2021b), Jałoszyński and Perkovsky (2021), and Golub et al. (2021). The new locality (Lisove) and the locality Manevichi belong to the Styr River Basin and could be the source of important new findings, e.g., the hitherto oldest published record of Winterschmidtiidae was known from Miocene Mexican amber (Klimov et al. 2021).

The type species of Glesoconomorphus from Baltic amber is named after “Nachzehrer”, a mystical vampire from the folklore of Germany and Poland that, according to the legend, first persecutes and then murders its natural relatives (Alekseev et al. 2019). We can only speculate that individuals of the type species could not cross the ancient sea and reach the Volyn area (Ivanov et al. 2016, fig.1), where Glesoconomorphus ekaterinae sp. nov., the first of the Rovno amber mycterids, dwelled.

Kirill V. Makarov (Moscow State Pedagogical University, Russia) is thanked for pointing our attention to this peculiar syninclusion. We also are grateful to Nikolai R. Khomich (Rovno, Ukraine) for his help in obtaining the specimen, to Anatoly P. Vlaskin (SIZK) for cutting and polishing the amber piece and to Sergei A. Simutnik (SIZK) for help with photos. Many thanks to Pavel B. Klimov (University of Michigan, Research Museums Center, Ann Arbor, USA) for determination of the mites. We are also indebted to Hiroyuki Yoshitomi (Ehime University Museum, Matsuyama, Japan) for the discussion of the systematic placement of the described beetle specimen.

This research was supported by the Grant-in-Aid for JSPS (Japan Society for the Promotion of Science, Tokyo, Japan) Fellows (20J00159) given to S.Y. We thank the reviewer Darren A. Pollock (Eastern New Mexico University, Portales, USA) and the editor for improving the paper.