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| Baltosidis damgaardi Szawaryn, 2021 |
Abstract
Molecular studies on the evolution of ladybird beetles date their origin somewhere in the Cretaceous, but no fossils are known from that period. The oldest representatives come from the Eocene, with the richest diversity found in Baltic amber. Until now, representatives of only three tribes (from around 40 known) have been recognized. Recent investigation of Baltic amber have revealed representatives of the fourth tribe (Microweiseini), which are described here as Baltosidis gen. nov. with three new species: B. damgaardi sp. nov., B. damzeni sp. nov. and B. szadziewskii sp. nov. In order to test the systematic placement of this extinct genus, a phylogenetic analysis of Microweiseinae was conducted. The results place Baltosidis in a cluster with four modern genera of Microweiseini distributed exclusively in the New World. Such a distribution pattern is surprising because no close relatives of the newly described fossil genus are known from Europe or even from the Palaearctic region. Analysis of the distribution of Microweiseini genera leads to the conclusion of a possible Gondwanan origin of the tribe. Further comparison of the diversity of the ladybird beetles from modern ecosystems with those known from Baltic amber suggests substantial differences between these communities and a recent radiation of modern fauna.
Keywords: Baltic amber, biogeography, Coccinelloidea, Eocene, evolution, new genus, palaeontology
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| Baltosidis damgaardi. A, habitus ventral. B, habitus dorsal. C, details of tarsus. D, details of setation on elytra. E, tip of elytra with sutural lines. F, meso- and metaventrite. G, head, prosternum, mesoventrite. H, postcoxal lines on ventrite 1. I, details of an eye and antenna. J, tip of abdomen and female genitalia. Holotype, GPIH 5030 (A–D, F–I); paratype, ALD Co80 (E); paratype, GPIH 5031 (J). |
Systematic palaeontology
Order Coleoptera Linnaeus, 1758
Suborder Polyphaga Emery, 1886
Superfamily Coccinelloidea Latreille, 1807
Family Coccinellidae Latreille, 1807
Subfamily Microweiseinae Leng, 1920
Tribe Microweiseini Leng, 1920
Genus †Baltosidis gen. nov.
Type species: †Baltosidis damzeni.
Diagnosis: Baltosidis is most similar to the genus Parasidis, having ten antennomere antenna with three-antennomere club, ventrite 1 with complete or almost complete v-shape abdominal postcoxal lines and four tarsomeres. However, it can be distinguished by a presence of distinct sutural carinae placed in the apical half of elytra. From similar-looking Coccidophilus Brèthes, 1905 and Stictospilus Brèthes, 1924, it can be separated by four-segmented tarsi (three segmented in both genera) and an antennal club consisting of three antennomeres (in Coccidophilus it consists of two antennomeres).
Etymology: First part of the name is derived from the Baltic Sea, the second refers to the genus Parasidis to which it is related.
Baltosidis damgaardi sp. nov.
Diagnosis: Baltosidis damgaardi can be distinguished from congeners by pronotum and elytra covered with two types of setae: long, stiff bristles intermixed with short hairs. Moreover, its abdominal postcoxal lines are widely separated from accessory lines. Ventral surface setose.
Etymology: The specific epithet is dedicated to Anders L. Damgaard (Copenhagen, Denmark), collector of one of the paratypes, who allowed me to examine his collection of coccinellid beetles.
Locality and horizon: Eocene, Baltic amber, Gulf of Gdańsk area (secondary deposit).
Baltosidis damzeni sp. nov.
Diagnosis: Baltosidis damzeni can be distinguished from other Baltosidis species by glabrous pronotum and elytra, abdominal postcoxal lines almost fused with accessory lines, but not forming distinctly closed v-shape. Ventral surface glabrous.
Etymology: The specific epithet is dedicated to my friend Jonas Damzen (Vilnius, Lithuania) collector and donator of the type specimens to the MAIG.
Locality and horizon: Eocene, Baltic amber, Gulf of Gdańsk area (secondary deposit).
Baltosidis szadziewskii sp. nov.
Diagnosis: Baltosidis szadziewskii is characterized by fine, short setae on pronotum and elytra, abdominal postcoxal lines fused with accessory lines apically forming v-shape. Ventral surface setose.
Etymology: The specific epithet is dedicated to Prof. Ryszard Szadziewski (University of Gdańsk, Poland), entomologist and expert on recent and fossil Ceratopogonidae (Diptera), who encouraged me to investigate Baltic amber coleopterans.
Locality and horizon: Eocene, Baltic amber, Gulf of Gdańsk area (secondary deposit).
Karol Szawaryn. 2021. The First Fossil Microweiseini (Coleoptera: Coccinellidae) from the Eocene of Europe and Its Significance for the Reconstruction of the Evolution of Ladybird Beetles. Zoological Journal of the Linnean Society. zlaa180. DOI: 10.1093/zoolinnean/zlaa180