From Abundance to Extinction: Evolutionary History of European Aedemonini (Curculionidae) with a Description of the First Representative from Rovno Amber

: Fossil weevils of the subfamily Molytinae are currently represented by 103 species in 42 genera from 14 tribes. Fossil records of the tribe Aedemonini are known from the Eocene of Europe. This tribe makes up 22% of the London Clay weevil specimens identiﬁed to the genus level and 16% of the Curculionidae genera. At present, the distribution of this tribe is mainly paleotropical, but it was very prominent in the paratropical biota of the London Clay in the early Eocene, and it was still represented in the biota of the amber forests of Europe that retained some tropical elements in the Priabonian. A new species, Electrorhinus vlaskini n. sp., from the tribe Aedemonini of the subfamily Molytinae, is described from Rovno amber. It differs from E . friedhelmi in the smaller body size, ﬁnely faceted eyes, a coarser rugose pronotum, and sparser scales on the body. A list of the fossil Molytinae is compiled. This is the ﬁrst record of a weevil of the subfamily Molytinae in Rovno amber, and the second ﬁnding of a representative of the genus Electrorhinus in the late Eocene and the third record of a species of Aedemonini preserved as a fossil. A key to European species of Molytinae with a rostral channel from Europe is given.


Introduction
Some weevils of the subfamily Molytinae were previously considered the subfamily Cryptorhynchinae [1]. This subfamily included species from the tribe Cryptorhynchini along with representatives of the subtribes Cryptorhynchina, Mecistostylina, and Tylodina, tribes Aedemonini, Camptorhinini, Gasterocercini, Psepholacini, Sophrorhinini, and Torneumatini [1], or it was considered in an even wider sense with the inclusion of the tribes Cleogonini and Ithyporini [2]. Currently, a number of these tribes are included in the subfamily Molytinae [3][4][5].
The first finding of the tribe Aedemonini was in the London Clay (the early Eocene of England) [1,6], and the second from late Eocene Baltic amber [7].

Systematic
Material examined. Holotype: SIZK K-31315, Klesov, Rovno amber, late Eocene. Derivation of name. The species is named in honor of paleoentomologist A.P. Vlaskin (Rovno). Diagnosis. The new species differs from Electrorhinus friedhelmi in the smaller body sizes, finely faceted eyes, coarser rugose pronotum, and sparser scales on the body.

Remarks.
The geniculate antennae and uncinate tibiae support the placement of this species in the family Curculionidae. Placement in the subfamily Molytinae is based on the quite large tibial uncus. The prosternum with rostral channel bounded by carinae in the precoxal and postcoxal portions of the prosternum (Figures 4 and 5) suggest placement in the tribe Aedemonini. The new species belongs to the genus Electrorhinus based on the femora weakly sulcate beneath and the metafemora reaching ventrite 3.  9. Vertex is densely punctured and covered with wide scales. Elytra wider than base of pronotum. Odd-numbered elytral interstices are non-raised. Elytra is 1. 8  Genus Korystina Britton, 1960 Remarks. The genus Korystina was described in the tribe Sophrorhinini [6]. Alonso-Zarazaga and Lyal [1] placed it in the tribe Cryptorhynchini. Legalov [11] transferred this genus in the tribe Camptorhinini. A re-examination of the description and illustrations show that Korystina has the rostral channel of the postcoxal portion of the prosternum bounded by carinae, which characterize the tribe Aedemonini [5], but it is not clear whether it is present on the prothorax or is also located on the mesoventrite. To finally establish the systematic position of Korystina, a re-examination of the type is required. K

Discussion
Fossil weevils of the subfamily Molytinae are currently represented by 103 species in 42 genera from 14 tribes. The oldest forms were described from the Maastrichtian of Canada and Chile [54,55]. The most diverse Molytinae fauna is known from Miocene Dominican amber [17,50,51,53].
The tribe Aedemonini includes 33-35 extant genera [1,3] distributed in sub-Saharan Africa (excluding the desert regions of South Africa), Madagascar, Oriental Region (north to southern Sakhalin, Japan, and South Korea), Australia (except for desert areas), Micronesia, Melanesia, and Polynesia ( Figure 6). Representatives of this group are absent in the New World, Western and Central Palaearctic. Fossil findings are known from the Eocene of Europe [6,7,18]. It is noted that extant species of the tribe avoid dry and cold areas. Almost all species do not cross the line of +15 • C of the mean annual temperature. Several species have adapted to colder conditions in South Korea, Japan, and southern Sakhalin. Perhaps this is due to the monsoon climate. The fossil records are all from the Eocene when the climate of Europe was warm and humid. Aedemonini make up 22% of the London Clay weevil specimens identified to the genus level, and 16% (or even a third if Korystina belongs to the tribe) of the Curculionidae genera. The representation of the tribe was not so significant in any other extant or extinct fauna. Even in the Afrotropical region, where at least 40% of the species and 56% of the genera of Aedemonini are distributed, they make up less than 7% of the species and less than 2.5% of the genera of Curculionidae [60]. It is highly meaningful that hyperdiverse Cryptorhynchini appear to be largely absent from the Afrotropics, where they seem to be replaced by Aedemonini [61], our data. It is interesting to combine the abundance of Aedemonini and Molytinae in general in London Clay with the extreme rarity of bark beetles (represented by a single specimen of ? Blastophagus Eichhoff, 1864 (=Tomicus Latreille, 1802)), while xylophagous insects dominate in this locality [6]. Their mineralization, at least in part, could occur in a specific microtaphotope inside pyritized wood [62]. Moreover, Tailorius is the second most abundant genus of the family Curculionidae (together with Lutago, they account for 62.5% of all weevils determined to be in the genus), and the third most abundant genus in all biotas, and accounts for 16% of all beetles identified to the genus from London Clay. Of course, an extraordinary abundance of Aedemonini in the early Eocene of Europe was not ubiquitous. For example, the species of the tribe are unknown from Oise amber, in which numerous bark beetles were found, as well as a representative of Cryptorhynchini (Oisecalles latosquamosus Legalov, Kirejtshuk et Nel, 2019) [8].
The abundance of Aedemonini in the London Clay may have been due to the rich and diverse tropical vegetation [63,64]. The age of the London Clay Formation is early and middle Ypresian [65]. Bognor remains the principal international source of pyritized insects [66] (p. 93). Rundle and Cooper [67] asserted that insects from the London Clay drifted out to sea with wood from the more westerly, near-shore location of the Hampshire Basin [68]. This is further supported by the presence of numerous flightless larvae [66], together with beetles with their elytra in the resting position [68]. The London Clay Formation contains one of the most important fruit and seed assemblages from the Paleogene [69]. Given its unparalleled diversity [68], more than 350 described species, and superb preservation as well as uncompressed, three-dimensionally preserved morphology [63,70], the flora offers a unique insight into the vegetation present in Europe during the hyperthermals of the early Eocene [71,72]. Numerous clades that are now largely confined to tropical latitudes, e.g., Annonaceae, Arecaceae, Burseraceae, Icacinaceae, and Menispermaceae, are well documented in the flora [63,70]. As was indicated by Collinson and Cleal [68] "in early Eocene times, a zone of lush vegetation had developed in Britain, strongly reminiscent of today's tropical rain forests, dominated by evergreen trees of the sumac, custard apple, dillenia, dogbane, frankincense, flacourtia, icacina, laurel, palm, sabia, soap berry and tea families, and mastic trees of the dogwood family", with abundant lianas of the icacina, grape vine, and moonseed families and numerous mangrove palms and rare, true mangroves in coastal areas [73][74][75][76]. The vegetation, with some reservations, has been compared with the modern paratropical rain forests of lowland Asia [68], and references therein.
Since the late Eocene, there are no fossil records of these Aedemonini beetles [18]. They may have disappeared from Europe during the Oligocene, when the European climate became colder, seasonal, and drier. The new record shows the connection of the European Priabonian fauna with the extant Paleotropical fauna. The weaver ant genus Oecophylla Smith, 1860, is characterized by a similar geological and geographical distribution [77,78], except for a single early Eocene finding in Okanagan [79].
The climate of the Rovno amber forest was warmer than the Baltic one [80,81], so the thermophilic beetles are much better represented there [27,[82][83][84][85][86][87][88][89], resulting in only 15% of known Rovno beetles having anything in common with Baltic amber [87,90]. The genus Electrorhinus could be a new addition to the list of Rovno thermophilic taxa that are much rarer in Baltic amber.