With the discovery of Maigus sontagae gen. nov., sp. nov. in Baltic amber, all the literature of the fossil family Berendtimiridae Winkler, 1987 is revised. The family is now polytypic, with the subfamilies Berendtimirinae Winkler, 1987 (nominotypical) and Retromalisinae subfam. nov. This new subfamily is established to include Retromalisus Kazantsev, 2020 and Maigus gen. nov. In addition, Jantarokrama utilis Kirejtshuk & Kovalev, 2015 is transferred from Elateridae: Omalisinae to Berendtimiridae: Berendtimirinae, joining Berendtimirus Winkler, 1987.
1. Introduction
Until now, the fossil family Berendtimiridae Winkler, 1987 consisted of two monotypic genera, both species found in Baltic amber: Berendtimirus progenitor Winkler, 1987 and Retromalisus damzeni Kazantsev, 2020 (Winkler 1987; Weitschat & Wichard 2010; Bouchard et al. 2011; ŚlipiŃski et al. 2011; Alekseev 2017b; Kazantsev 2020; Ding et al. 2022). A careful study of diagnostic characters allows us to add to this family another species, Jantarokrama utilis Kirejtshuk & Kovalev, 2015, originally attributed to the family Omalisidae (Kirejtshuk & Kovalev 2015; Alekseev 2017a, 2022; Kundrata et al. 2020a, 2020b, 2021; PaČkovÁ 2021). The original attribution of this species to Omalisidae (currently, Elateridae: Omalisinae; Kusy et al. 2018) had been controversial (e.g., Bocek et al. 2018). With the discovery of the new genus described here, this extinct family from Baltic amber can now be considered polytypic, with two subfamilies. Our analysis is designed to help clarify the taxonomic position of the family Berendtimiridae by highlighting its variability.
2. Material and methods
The holotype is embedded in a clear yellow piece of Baltic amber measuring approximately 17 x 5.5 x 4 mm, and preserved at the Museum of Amber Inclusions in Gdańsk, Poland. The specimen, found in the Kaliningrad region in Russia, was examined using a Carton stereomicroscope 0.8–40x. Photographs were taken with a Canon EOS 70D camera equipped with a Canon MP-E 65 mm macro lens and processed with PhotoImpact Viewer SE.
3. Systematic palaeoentomology
Family Berendtimiridae Winkler, 1987
Subfamily Berendtimirinae Winkler, 1987
Type genus: Berendtimirus Winkler, 1987.
Genera included: Berendtimirus Winkler, 1987; Jantarokrama Kirejtshuk & Kovalev, 2015.
Diagnosis: The subfamily is characterized by six ventrites exposed. The sixth ventrite is considerably retracted in the genus Jantarokrama.
Distribution: Known only from Baltic amber.
Remarks: Another specimen that closely resembles Jantarokrama utilis is present in the Kaliningrad Regional Amber Museum in Kaliningrad, Russia (Alekseev 2022), while the holotype of Jantarokrama utilis is preserved in the National Museum of Natural History of Paris (MNHN), France (Kirejtshuk & Kovalev 2015; Kundrata et al. 2021; PaČkovÁ 2021).
Subfamily Retromalisinae nov.
urn:lsid:zoobank.org:act:F3A68794-D2CB-4D0A-BCC5-A51DC5C25371
Type genus: Retromalisus Kazantsev, 2020.
Genera included: Retromalisus Kazantsev, 2020; Maigus nov.
Diagnosis: The subfamily is characterized by eight ventrites exposed.
Distribution: Known only from Baltic amber.
Genus Maigus nov.
urn:lsid:zoobank.org:act:C9C6E409-E477- 42D8-95DC-908733BDD1AD
Type species: Maigus sontagae gen. nov., sp. nov., by monotypy.
Etymology: Named in honour of the Museum of Amber Inclusions, Gdańsk (MAIG), Poland, where the amber piece is deposited. The gender is masculine.
Differential diagnosis: Very similar to the genus Retromalisus, the new genus differs by having more elongated and extruded posterior corners, elytral epipleura that do not fully reach the elytral apexes (fully sclerotised epipleura extending to the elytral apices in Retromalisus) and a pronotum without ribs and carinae, while in Retromalisus the disk medially has an obscure longitudinal rib, and laterally transverse carinae reaching the lateral margins (Kazantsev 2020).
Description: Small size. Head transverse, rounded. Last maxillary palpomere globular and apically pointed. Antennae 11-segmented, filiform, antennomere II about 1.5 times shorter than scape. Pronotum transverse, trapezoidal, without rib and carinae, with posterior corners very extruded. Elytra elongated with 10 regular longitudinal rows of impressed punctuation, epipleura almost completely developed. Prosternum short. Abdomen with eight ventrites, the first medially completely interrupted by metacoxae, the last largely invaginated. Tarsal formula 5-5-5 with the penultimate tarsomere bilobed, claws simple.
Distribution: Currently known only from Eocene Baltic amber found in the Kaliningrad region in Russia.
Maigus sontagae sp. nov.
Figs. 1, 2
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Etymology: Named in honour of ELźBIETA SONTAG (Museum of Amber Inclusions, Gdańsk), founder and long-term curator of the museum.
Type: Holotype: Likely male, Baltic amber, housed at the Museum of Amber Inclusions, Gdańsk, Poland, with the code MAIG 7001 (ex coll. JONAS DAMZEN: JDC11137).
Type locality: Amber mine in the Yantarny settlement, Sambian Peninsula, Kaliningrad region, Russia.
Type horizon: Middle Eocene (Lutetian) (47.8–41.2 Ma) to late Eocene (Priabonian) (37.8–33.9 Ma).
Description: Adult, winged, elongate, rather robust, probably male. Body length: about 2.5 mm (the specimen is slightly bent). Body entirely dark brown. Head moderately large, transverse, slightly narrowed posteriorly, almost completely exposed, pubescent. Eyes large, spherical, inserted in lateral-upper part of the head, interocular dorsal distance ca. 1.4 times greater than eye diameter. Palps small, slender; ultimate palpomeres very elongated, narrowed and pointed apically. Antennae long, reaching the apex of elytra, 11-segmented, filiform, strongly pubescent; antennomere I elongated, robust, slightly club-shaped; antennomere II about 1.5 times shorter than scape; antennomere III approximately as long as second and only very slightly longer; antennomeres IV–VIII longer than previous one, subequal with antennomeres VII–VIII only very slightly shorter; antennomeres IX–X shorter than previous ones; antennomere XI elongated with pointed apex. Pronotum transverse, narrower than head, trapezoidal; anterior margin rather straight with rounded corners; posterior margin straight, protruded backward in the middle; posterior corners acute and long; sides straight, slightly wider at posterior part, shallowly incised before posterior angles; disk pubescent and sparsely punctate, flat, without longitudinal rib and transverse carinae; margins bordered. Scutellum short, elongated, pointed at apex. Elytra elongated, almost parallel-sided, wider than pronotum, with 10 regular longitudinal rows of impressed punctuation with the distance between punctures subequal to their diameter and a short humeral carina along interspace 6; epipleura sclerotized not fully reaching elytral apices; pubescence short, apex rounded. Metathoracic wings fully developed, as long as elytra or slightly longer. Prosternum short, wide at base, with impressed punctuation. Abdomen with eight transverse, pubescent ventrites; penultimate ventrite semi-circularly incised; ultimate ventrite largely invaginated. Legs relatively long and slender; coxae elongated, very robust; trochanters elongated, rounded at apex, apically overlaying bases of femora; femora straight, cylindrical, enlarged from middle to apex; tibiae cylindrical, shorter than femora, tibial spurs absent; tarsi 5-segmented, tarsomeres I–III narrow without plantar pad, tarsomere II about 1.5 times shorter than first, tarsomere III about 1.4–1.5 times shorter than second, tarsomere IV incised to the base and conspicuously widened; claws simple.
Syninclusions: Air bubbles, stellate hairs, botanical remains.
4. Discussion
A small subfamily of beetles distributed in the western Palearctic region, the Omalisinae are classified in the superfamily Elateroidea, with obscure phylogenetic relationships that have been traditionally placed in the cantharoid clade (BocÁk & Brlik 2008). Omalisinae were once classified as a family (Omalisidae), but recent genomic and phylogenetic analyses indicate the terminal positions of the beetles are within the broadly defined well-sclerotized and fully metamorphosed Elateridae, and therefore they are now considered a subfamily of Elateridae (Omalisinae) (Kusy et al. 2018). Interestingly, molecular phylogenies have demonstrated the morphological similarity with other soft-bodied beetles is a case of parallel evolution, homoplasy rather than apomorphy.
The typical characters that distinguish the Berendtimiridae family from its closest taxa are the second and third antennomeres similar in size and vestiture, and the cranium that resembles a raised flat shield-like structure (Winkler 1987; Poinar & Fanti 2016). Retromalisus differs from species in Cantharidae and Omalisinae in possessing complete sclerotised elytral epipleura, a short prosternum with a short intercoxal process and wide and deeply incised penultimate tarsomeres (Kazantsev 2020).
Kirejtshuk & Kovalev (2015) described Jantarokrama as a member of the family Omalisidae, though remarking about its close resemblance to Berendtimirus. In fact, Jantarokrama shows some small characters in common with the Omalisinae, including the short antennomere II (only slightly longer in Berendtimiridae) and narrowly separated antennal insertions (widely separated in Berendtimiridae). In contrast, Jantarokrama differs from all representatives of Omalisinae in having a particularly long scape, somewhat longer antennomeres, more narrowly separated antennal bases, much shorter elytra with broadly arcuate sides, a different shape of the prosternum and no elytral costae. Jantarokrama appears more like Berendtimirus, showing similar elytral sculpture and pronotal shape, with the same number of ventrites (six) and a short prosternal process. Based on BBocÁk & Brlik (2008), genera of Omalisidae such as Omalisus, Thilmanus and Phaeopterus have seven ventrites visible. Therefore, we assign Jantarokrama to Berendtimiridae Berendtimirinae.
Fig. 1.
Maigus sontagae gen. et sp. nov. in Baltic amber (code MAIG 7001). A – Holotype, dorsal view; B – ventral view.
Fig. 2.
Maigus sontagae gen. et sp. nov. in Baltic amber (code MAIG 7001). A, B – Holotype, lateral views.
With the discovery of the new genus and our analysis of Jantarokrama and Berendtimiridae, it is clear that important morphological characters can vary widely in the family, which is why we establish a new subfamily here. For example, the number of ventrites – an important trait in distinguishing among the various families of soft-bodied beetles (Crowson 1972) – differs between Berendtimirinae and Retromalisinae.
It is important to note that the phylogenetic relationship of Berendtimiridae to other taxa remains obscure (Jeng 2008; Tihelka et al. 2019). As part of the Elateroidea, this family could be related to Elateridae Omalisinae but also to Lycidae or Cantharidae. Discoveries of additional specimens will help clarify the relationships among these intriguing beetles.
Key to Berendtimiridae subfamilies:
1. Six ventrites exposed (sixth considerably retracted in Jantarokrama) Berendtimirinae
-. Eight ventrites exposed, last largely invaginated Retromalisinae
Acknowledgements
We are extremely grateful to JONAS and ALEKSEJ DAMZEN (Vilnius, Lithuania) for the generous donation of the inclusion to the MAIG, and for the excellent photographs. We also thank the two reviewers for their helpful suggestions for improving our manuscript.
