101urn:lsid:arphahub.com:pub:DF2AD546-A4F0-51AC-B38C-88216742E553urn:lsid:zoobank.org:pub:9B96196F-9505-457E-8F01-0E12D644C289ZittelianaZITT2512-53382747-8106Pensoft Publishers10.3897/zitteliana.100.187338187338Research ArticleAnimaliaArthropodaHexapodaInsectaInvertebrataLepidopteraMicropterigidaeMicropterigoideaPalaeontologyPalaeozoologyCenozoicPaleogeneCentral EuropeEuropeAmber Lepidoptera: First confirmable record of Micropterix Hübner, 1825 from Eocene Baltic Amber (Insecta, Micropterigidae)KurzMichael A.https://orcid.org/0009-0004-6757-919X1Writing - original draftFischerThilo C.thilo.c.fischer@gmx.dehttps://orcid.org/0000-0001-7371-40532Writing - original draftNaturkundliche Gesellschaft, Josef-Waach-Str. 13/1, A-5023 Salzburg, AustriaNaturkundliche GesellschaftSalzburgAustriaBavarian State Collection of Zoology, Münchhausenstraße 21, D-81247 Munich, GermanyBavarian State Collection of ZoologyMunichGermanyhttps://ror.org/04rekk491
Corresponding author: Thilo C. Fischer (thilo.c.fischer@gmx.de)
Academic editor: Mike Reich
202606082026100163169F7D5BB4B-ECF9-595C-80BC-5EEEA38ED958CD5A0626-BCDD-4836-9F41-99FF2327933B0202202612072026Michael A. Kurz, Thilo C. FischerThis is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.https://zoobank.org/CD5A0626-BCDD-4836-9F41-99FF2327933B
Lepidoptera from succinite ambers are studied systematically. Here, one male of a new species of Micropterix Hübner, 1825, i.e. Micropterixeocenicasp. nov. is described, being the first confirmable record of this genus from Eocene Baltic amber. It is compared with Micropterixgertraudae Kurz & Kurz, 2010, known until now only from a single female, although probably not belonging to this genus, and also to recently described genera related to Micropterix from Bitterfeld amber. Phylogenetic and paleobiogeographical implications are discussed. The male genitalia of a fossil Micropterix are figured for the first time. A minimal geological age of 33.9 to 37.8 million years (Priabonian) for the genus Micropterix is provided by this report, further confirming a European origin of Micropterix s.str.
Micropterigidae (“jaw moths”) are the most primitive lineage of extant Lepidoptera, still possessing mandibles, used for consuming pollen, liverworts or, exceptionally, fern spores (Kristensen and Skalski 1999; Scoble 2002; Imada et al. 2011; Gibbs 2014; Han et al. 2024).
Fossil Micropterigidae have been described from sediments as well as ambers; finds older than Cretaceous are restricted to sediment fossils (Sohn et al. 2012). As a most basal family they are of special interest in elucidation of Lepidoptera evolution. Fossils of Micropterigidae are extremely rare. In Baltic amber, Lepidoptera occur in 1 out of 200 inclusions; among these, Micropterigidae occur in 1 out of 50 Lepidopteran inclusions (own observations, in the studied collection of author TF, there are 32 Micropterigidae of some 1500 Lepidoptera). Yet among Micropterigidae, only this one specimen of the genus Micropterix has been identified. Unique systematic position and extreme rarity underscore the relevance of reporting and identifying such finds.
The present paper is the first in a planned series, dealing with new findings of fossil Lepidoptera. The series will start with the most basal Lepidoptera from the authors’ collections and in conjunction with previously published material.
Material and methods
Amber inclusions were purchased by the authors from trusted amber dealers known by long-term business relationship so that authenticity is assured. Authenticity is also checked by material characteristics and presence of typical trichomes, when present. Amber pieces are kept in sealing plastic zip bags inside metal boxes at a constant temperature.
The inclusions were studied under incident and transmitted light with different types of microscopes and stereo magnifiers.
The stacking image was produced by the amber dealer and purchased with the specimen. Line drawings were made by hand and subsequently improved by ChatGPT and GIMP 2.10.26, checking against the original.
Holotype • ♂: Russia, Kaliningrad area, Priabonian, ID-no. nkis.info, TF00226-5202, coll. Fischer #5202, to be deposited at SNSB (Staatliche Naturwissenschaftliche Sammlungen Bayerns) with publication under #SNSB-BSPG 2026 I 8.
Line drawing of genital apparatus of the holotype Micropterixeocenica.
https://binary.pensoft.net/fig/1738243Etymology.
The species name eocenica refers to the fossil state and geological age of the new species.
Diagnosis.
Small sized, non glossatan moth with homoneurous wing venation and jugate wing coupling, spurs only at hind legs (0-0-4), wing venation Micropterix-type.
Description.
1 ♂ (Fig. 1). Forewing length: 2.55 mm, hindwing length: 2.05 mm. Head with erect, hair-like scales; eyes semiglobular, about 220 µm in diameter, not enlarged; presence of ocelli not detectable; maxillary palpi long, in total about 0.88 mm, with 5 segments (appr. 73, 73, 330, 360, and 43 µm in length); labial palpi and other mouthparts not visible; antennae about 4/5 of forewing length, moniliform, not thickened, with 36 flagellomeres; scapus and pedicellus swollen, pedicellus, however, only slightly; flagellomeres slightly longer than broad, somewhat rounded, with ascoid sensillae; thorax and tegulae shining golden; spur formula of legs 0-0-4, epiphysis present; midtibia short, without spurs, with fine bristles at distal end; hind tibia with a pair of spurs each at about 2/3 of tibial length and at distal end; abdomen partly covered by a wax-like emulsion and hidden by the right wings.
Venation (Fig. 2, mirror image of left wings): Forewing: Jugum present. Humeral vein present; Sc forked at about midlength, the branches reaching costa at about 0.35 and 0.54 of forewing length; R unforked, reaching costa at about 0.68 of forewing length; crossvein Sc-R present; Rs1+Rs2 on common stem; cell probably closed (not clearly visible); Rs3 from cell, originating very close to Rs4; Rs4 distinctly preapical; M1 from crossvein R-M (indistinct); M2+M3 forked just beyond midlength on common M-stem; crossvein M-Cu probably present (not clearly visible); CuA forked at about 3/4 of its length, on a short basal stem with M and R; CuP weakly developed; A1+A2 fused near basis, basal loop not recognizable; Hindwing: Sc and R separate, but close together, reaching costa at 0.51 and 0.64 of hindwing length; crossvein Sc-R not detectable; R emerging at appr. 1/6 of hindwing length from R-stem; Rs1+ Rs2 on common stem; cell closed; RS3 from one point with Rs4 from cell; Rs4 slightly preapical; M1 from crossvein R-M; M2+M3 forked just beyond midlength; CuA forked at about 4/5 of its length; CuP present; A1+A2 present, but not clearly visible.
Genitalia (Fig. 3, mirror image of left side): Complex of uncus, tegumen and accessory claspers not clearly visible, but distinctly separated from the complex of vinculum and valvae; uncus very short, rounded; tegumen bulbous, its posterior margin slightly emarginated with 6–7 moderately long, stout, unmodified setae (“accessory claspers”); vinculum inflated, but not clearly visible; valvae long and slender, continuously curved, apically somewhat broadened, medially slightly constricted, setose and with a group of 3–5 moderately short, stout and thickened setae at distal end.
Material.
Piece of Baltic amber, irregular, ca. 14 mm × 11.5 mm × 2 mm, ID-no. nkis.info, TF00226-5202, ex coll. Fischer #5202, deposited at SNSB under # SNSB-BSPG 2026 I 8.
Micropterixeocenica resembles extant Micropterix-species in most aspects, except for the weakly developed accessory claspers and the absence of a Y- or T-like modification of the setae on them (although the latter character is known also from extant members of the genus). The valvae, however, are Micropterix-like and the probably inflated vinculum also strongly supports this thesis. Furthermore, the venation completely falls within the variability of the genus, the preapical position of Rs4 in both fore- and hindwing being very indicative for Micropterix.
From Micropterixgertraudae Kurz & Kurz, 2010 the new species differs mainly in the presence of crossvein Sc-R and the origin of Rs3 and Rs4 from one point in the forewing, the probable absence of crossvein M-Cu in the hindwing, and especially, however, in the preapical position of Rs4 in both fore- and hindwing (apical in M.gertraudae). M.gertraudae is therefore doubted as belonging to the genus Micropterix.
Similar long and slender valvae like in M.eocenica seem to be present also in Saxomicropterixschumanni Mey, 2019 and in Wichardiusfossiliphilus Mey, 2019 from Bitterfeld amber, but in both species the accessory claspers are absent. In Saxomicropterixschumanni, this is true at least for the ventral part of the valvae (“horizontally cleft” according to Mey 2019). Both species also have a much longer uncus (slender in S.schumanni, broadly rounded in W.fossiliphilus). Furthermore, S.schumanni also has distinctly elongated flagellomeres.
DiscussionPhylogeny
Micropterigidae is the most archaic family of extant Lepidoptera. The imagines have fully developed mouthparts with functional mandibles, with which they feed on pollen, liverworts or fern spores. The fossil record of Micropterigidae probably dates back to the Toarcian in Germany (near Dobbertin and Grimmen, i.e. appr. 180 Ma, Ansorge 2002, 2003), being only 10 Ma younger than the oldest fossil attributable to Lepidoptera at all, Archaeolepismane Whalley, 1985 from the Sinemurian in Dorset, England.
Several apomorphies have been recognized, distinguishing Micropterigidae from other archaic Lepidopteran families (according to Kristensen and Skalski 1999; Kristensen in litt.). Of them, the following are clearly traceable in the fossil: (1) Presence of “ascoid” sensillae (branched basiconic sensillae) on each flagellormer, (2) swollen pedicel, (3) labial palpi greatly shortened, and (4) spur formula 0-0-4, i.e. absence of mesotibial spurs.
Based on gene sequences (ribosomal 16S RNA), five lineages have been recognized by Gibbs et al. (2004), with their basal nodes dating back into the Jurassic:
- Sabatinca s.str.: Presently only known from Oceania (New Zealand and New Caledonia, Gibbs 2014); fossil records are also acknowledged in Burmese amber (Cockerell 1919; Zhang et al. 2017, Ngô-Muller et al. 2020) and, probably, the Toarcian in Germany (Ansorge 2002, 2003).
- Australian lineage: This lineage is assumed to be the basalmost of all Micropterigidae (Gibbs et al. 2004). It is presently restricted to Australia, Tasmania, New Zealand, New Caledonia (Gibbs 2010) and, with a single known species, also from Vietnam (Mey et al. 2021).
- Southern Sabatincoid lineage: This poorly supported “Gondwana”-lineage is presently distributed in Australia, South Africa, Madagascar, Central and South America. Fossils attributed to the southern Sabatincoid lineage are the Cretaceous genus Terncladus (Han et al. 2024) and Eocenic Baltimartyria (Mey 2011).
- Northern Hemisphere genera: This group of genera occurs in North America (Epimartyria) and, species-rich, in the eastern Palearctic region (especially in Japan), stretching into south-eastern Asia (China, Taiwan, Northern Vietnam). However, Northern Hemisphere genera are also present in Baltic amber with two described species in the genus Electrocrania (Kurz 2015).
- Micropterix-lineage: The most species-rich lineage in extant Micropterigidae, comprising nearly half of all described species is restricted in distribution mainly to the Mediterranean, but stretches far into Northern Europe and, with few species, even to the eastern Palearctic region. Based on the tree-building method, it is either supposed to be the second basal-most lineage, having diverged from the Australian lineage as early as in the Jurassic, or the sister group of Sabatinca and the other Northern Hemisphere genera with a division point in the Cretaceous (Gibbs et al. 2004; Imada et al. 2011). The monophyly of Micropterix is not only strongly supported by molecular data, but also by the overall morphology. Fossils definitely belonging to the Micropterix-lineage are currently only known from the Eocene - Priabonian period (Baltic amber) (Kurz and Kurz 2010) and from Bitterfeld amber (Mey 2019). Nevertheless, a forewing from the Toarcian of Grimmen (Germany) may also belong to this lineage (Ansorge 2003). The genus Auliepterix Kozlov, 1989 dating back to the Upper Jurassic, given that it is a Micropterigid at all, may also be an early ancestor of Micropterix. Undoubtedly the genus Micropterix s.str. is a young member of the family. This is supported not only by the fossil record mentioned above, which does not date back earlier than the Priabonian, but also by the limited distribution of this most species-rich clade within the family. It is counterintuitive that the name-giving genus of this primitive and old family would be phylogenetically young, but can be understood given that early Lepidopterology took place in Europe, which is the centre of distribution of Micropterix s.str.
The morphology of the male genitalia of Micropterixeocenica is typical for true Micropterix, i.e. the presence of “accessory claspers” with a row of stout setae on the posterior margin of the tegumen (although only weakly developed) and the long and slender valvae, also with stout and thickened setae at the apex. These characters are recognized as apomorphies of Micropterix s.str., as is the preapical position of Rs4 in both fore- and hindwings (see also Zeller-Lukashort et al. 2007: 240).
The report of the genus Micropterix from Eocene Baltic amber gives a minimal geological age of 33.9 to 37.8 million years (Priabonian) for it (Kosmowska-Ceranowicz et al. 1997; Sadowski et al. 2020). This also provides another valuable calibration point for an extant genus within Micropterigidae, for which DNA analysis is possible.
Paleobiogeographical implications
Micropterigidae comprise about 200 described extant and fossil species with several dozens still undescribed (Whalley 1978; Kristensen 1984; Gibbs and Lees 2014; Kurz and Kurz 2025). This family has a worldwide distribution with biodiversity hotspots in Oceania, Southern Africa and Madagascar (Gibbs et al. 2004; Lees in litt.) and especially in the Mediterranean (Heath 1986, 1987; Zeller-Lukashort et al. 2007; Kurz and Kurz 2025).
Of the nearly 80 species of genus Micropterix described, only two have reached Eastern Asia (Micropterixaureatella and M.sikhotealinensis) and a further two “miocenic” relatives are known from the Indian Himalayas (Lees et al. 2010), whereas the majority of them are scattered around the Mediterranean basin.
Although Micropterixgertraudae has been described from Baltic amber by Kurz and Kurz in 2010 already, its placement in Micropterix is questionable, due to its lack of clearly attributable apomorphies (Kurz and Kurz 2010). Putative members of the Micropterix lineage have been recently described from Bitterfeld amber (Mey 2019), but a true fossil Micropterix has still been missing. Therefore, the described male is the first representative of Micropterix s.str., based on the given apomorphies. This strongly supports the thesis, that Micropterix s.str. is one of the youngest members of Micropterigidae, that developed not long before the Eocene in the amber forests of Europe.
The climate of the Baltic amber forests was reconstructed as thermophilic (Alekseev and Alekseev 2016) or warm temperate (Sadowski et al. 2020). These forests from the Eocene Eridanus River region (nowadays Scandinavia and Baltic Sea region) consisted of manifold conifers (Sadowski et al. 2017) and Fagaceae, especially Quercus species (Sadowski et al. 2020), and a rich flora with extant relatives in Southeast Asia, Europe and North America (Spahr 1993) (Fig. 4). The presence of numerous heliophilous Lepidoptera, like Adelidae and also Micropterigidae indicates not only a more or less open plant growth, but also a somewhat constant soil humidity throughout the year, which is known to be essential for the development of Micropterigidae larvae (Zeller-Lukashort et al. 2007; Gibbs 2014).
Artistic illustration of a Baltic amber forest (Marion Kurz).
https://binary.pensoft.net/fig/1738244Conclusion
The discovery of a true Micropterix member from Baltic amber, besides its assumed relatives and precursors of Northern hemisphere genera, strongly supports a European evolvement of that genus. Until now, this thesis has been based only on the recent distribution of extant Micropterix. No relative of the Micropterix lineage, neither extant nor fossil, is known from outside the Palearctic region.
Acknowledgements
Georg Gerhardt-Rhodes and Robert Massey are acknowledged for editing the manuscript as native speakers. Anastasiia A. Tarasova is gratefully acknowledged for reviewing and improving the manuscript. The authors have no support to report.
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The authors have declared that no competing interests exist.
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