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Five specimens of primary larvae of Ripiphoridae (Insecta: Coleoptera) are reported from one piece of Cretaceous Kachin amber. They represent two morphotypes: one conicocephalate and one belonging to the tribe Ripidiini (represented by four specimens). The conicocephalate morphotype is compared with similar larvae known from Kachin, Taimyr and Manitoba Cretaceous amber, and the larvae of Ripidiini are compared with their Cretaceous, Eocene and extant relatives. Phylogenetic analyses were performed to establish a working hypothesis about possible relationships of both lineages. The results, which conform with a recent molecular phylogeny, indicate that the larvae described here belong to Ripidiini or are closely related, respectively. To allow taxonomic and systematic work with conicocephalate larvae from Kachin amber, a collective group name †“Ripilarva” nov. is proposed here to accommodate these immature stages. Both species of †“Ripilarva” nov. from Kachin amber are described: †“R.” parabolica sp. nov. and †“R.” kachinensis sp. nov. Syninclusion of †“Ripilarva” kachinensis sp. nov. and four larvae of a species of Ripidiini indicate that females of both ripiphorids chose the same time and microhabitat for oviposition in the Kachin Cretaceous forest. The results are further verified by the use of UV-photography, as the different larval morphotypes occurred in the same resin flow. The presence of larvae of Ripidiini in clusters contrary to the solitary occurrence of †“Ripilarva” nov. in Cretaceous amber of Russia, Canada, USA, and Myanmar is interpreted as a possible result of different oviposition strategies, with different numbers of eggs deposited at one spot. Graphical abstract

As the only direct records of the history of evolution, it is critical to determine the geological source of biota-bearing fossils. Through the application of synchrotron-radiation micro-computed tomography (SR-µ-CT), Fourier-transformed infrared-spectroscopy (FT-IR), visual evaluation of ultraviolet fluorescence (UV-VS), radiocarbon dating (14C quantification), and historical sleuthing, we were able to identify and sort 161 (83 Baltic amber, 71 Copal and 7 Kauri gum pieces) individually numbered and largely mislabeled pieces of East African Defaunation resin (~145 years old) and copal (~390 years old), as well as Baltic amber (~35 million years old) from the Phyletisches Museum collection. Based on this collection, we define two new species: ‡Amphientomum knorrei Weingardt, Bock & Boudinot, sp. nov. (Psocodea: Amphientomidae, copal) and †Baltistena nigrispinata Batelka, Tröger & Bock, sp. nov. (Coleoptera: Mordellidae, Baltic amber). For selected taxa, we provide systematic reviews of the fossil record, including: Amphientomidae, for which we provide a key to all species of Amphientomum, extant and extinct, and recognize the junior synonymy of Am. ectostriolatum Li, 2002 (an unjustified emendation) under Am. ectostriolate Li, 1999 (syn. nov.); the fossil ant genus †Yantaromyrmex and the clades Dorylinae, Plagiolepidini, Camponotus, Crematogaster, and Pheidole (Formicidae); the Nevrorthidae (Neuroptera); and Doliopygus (Coleoptera: Curculionidae: Platypodinae). We synonymize Palaeoseopsis Enderlein, 1925 with Amphientomum Pictet, 1854, syn. nov. and transfer one species from Amphientomum, forming Lithoseopsis indentatum (Turner, 1975), comb. nov. To prevent the uncritical usage of unidentifiable fossils attributed to Camponotus for macroevolutionary analysis, we transfer 29 species to the form genus †Camponotites Steinbach, 1967, which we consider to be most useful as incertae sedis in the Formicinae. We treat †Ctt. ullrichi (Bachmayer, 1960), comb. nov. as unidentifiable hence invalid stat. nov. We also transfer †Ca. mengei Mayr, 1868 and its junior synonym †Ca. igneus Mayr, 1868 to a new genus, †Eocamponotus Boudinot, gen. nov., which is incertae sedis in the Camponotini. Concluding our revision of Camponotus fossils, we transfer †Ca. palaeopterus (Zhang, 1989) to Liometopum (Dolichoderinae), resulting in †L. palaeopterum comb. nov. and the junior synonymy of †Shanwangella Zhang, 1989, syn. nov. under Liometopum Mayr, 1861. Because the type specimens of the genera †Palaeosminthurus Pierce & Gibron, 1962, stat. rev. and †Pseudocamponotus Carpenter, 1930 are unidentifiable due to poor preservation, we consider these taxa unidentifiable hence invalid stat. nov. To avoid unsupported use of the available fossils names attributed to Crematogaster for divergence dating calibration points, we transfer three species to a new collective taxon that is incertae sedis in Myrmicinae, †Incertogaster Boudinot, gen. nov., forming †In. aurora (LaPolla & Greenwalt, 2015), †In. praecursor (Emery, 1891), comb. nov., and †In. primitiva (Radchenko & Dlussky, 2019), comb. nov. Finally, we transfer †Ph. cordata (Holl, 1829) back to Pheidole, and designate a neotype from our copal collection based on all available evidence. All new species plus the neotype of ‡Ph. cordata are depicted with 3D cybertypes from our µ-CT scan data. We introduce the convention of a double dagger symbol (‡) to indicate fossils in copal or Defaunation resin, as these may yet be extant. To further contextualize our results, we provide a discussion of amber history and classification, as well as the Kleinkuhren locality, to which multiple specimens were attributed. We conclude with conspecti on key biological problems and increasing potential of µ-CT for phylogenetic paleontology.

Abstract Background During the Mesozoic, there were many insects in several holometabolous orders (Neuroptera, Mecoptera and Diptera) with elongated mouthparts adapted for feeding on nectar. The evolutionary history of the megadiverse order Coleptera, which has a great diversity of mouthparts and feeding strategies, is well documented since early Permian with a significant peak in diversity in the Triassic. Currently, however, there is no evidence that in the Mesozoic these beetles fed on nectar despite the recorded specializations for pollination of flowering plants in several families since the mid-Cretaceous. Results Here we describe a new wedge-shaped beetle Melanosiagon serraticornis gen. et sp. nov. from mid-Cretaceous Burmese amber attributed to Macrosiagonini (Ripiphoridae: Ripiphorinae), which has elongated galea comparable to that in the extant parasitoid genus Macrosiagon, and a well known example of adaptation for nectar feeding in Coleoptera. Furthermore, Salignacicola gen. nov. is established for Macrosiagon ebboi Perrichot, Nel et Néraudeau, 2004, based on the holotype found in mid-Cretaceous amber from France. Systematic positions of both newly established genera are discussed. A list of potential wasp and bee hosts of Ripiphorinae from the Mesozoic is provided. Conclusions This study presents evidence of the earliest occurrence of specialized nectar feeding mouthparts in Coleoptera. Melanosiagon serraticornis is closely related to extant Macrosiagonini. In all genera belonging to subfamily Ripiphorinae the primary larvae are adapted for parasitism on aculeate Hymenoptera (bees and wasps) and adults are associated with blossoms of flowering plants, in terms of their specialized morphology. Adults of Macrosiagon visit blossoms of flowering plants to obtain nectar and lay eggs from which the hatching larvae attack visiting wasps and bees. An association with flowers of some tropical trees is already corroborated in some extant species. Interestingly the larvae of Ripiphorinae are also found in Burmese amber. Thus, both life stages of the mid-Cretaceous Ripiphorinae indicate a close association of this lineage with flowering trees.