A new species of Berothidae, Jersiberotha musivum sp. nov., is described and illustrated from mid-Cretaceous (lowest Cenomanian) Myanmar amber. It is easily distinguished from other species of Berothidae by the configuration of the wing venation including: forewing with distinct areas of infuscation surrounding cross-veins and vein forks, all cross-veins simple prior to ScP-RA fusion, presence of two cross-veins ra-rp; absence of inner or outer graduate series of cross-veins; RP with three branches; and absence of ma-mp cross-veins and cua-cup cross-veins; while hind wing has cross-vein 1r-m absent. The previous diagnoses of Iceloberotha Grimaldi, 2000 and Jersiberotha Grimaldi, 2000 are quite unclear because some characters occur mosaically in both genera. In order to solve this problem and distinguish J. musivum from other species in the family, a new key to species of Berothidae from Myanmar amber has been provided and the diagnoses of Iceloberotha and Jersiberotha have been revised.

fossil, lower Cenomanian, Mantispoidea, Neuropterida, taxonomy

The family Berothidae, commonly known as beaded lacewings, together with Mantispidae and Rhachiberothidae, belongs to the superfamily Mantispoidea, which represents one of the major lineages of the crown group of Neuroptera (Wang et al. 2016; Engel et al. 2018; Winterton et al. 2018). The extant Berothidae are distributed in all zoogeographical regions and currently comprise less than 130 described species of 28 genera worldwide (Oswald 2019). The genus Jersiberotha was firstly erected by Grimaldi from the New Jersey amber for sharing the wing characters: two adjacent ra-rp cross-veins in the forewing, only one ma- mp cross-vein (Grimaldi 2000). Engel and Grimaldi (2008) described two other species (J. myanmarensis and J. tauberorum) and a related genus Iceloberotha from Myanmar amber.

Molecular evidence suggested the Berothidae might have diverged during the Late Triassic (Wang et al. 2016). Winterton et al. (2018) and Vasilikopoulos et al. (2020) estimated the divergence between Beorthidae and Mantispidae was in the Early Jurassic, although the oldest definite fossil of Berothidae was reported from the Middle Jurassic (Makarkin et al. 2011). So far, there are about 27 genera and 41 species of fossil berothids described from the Middle Jurassic to late Eocene (Yang et al. 2019; Fuente et al. 2021). The amber from Myanmar is one of the most intensively studied objects amongst Cretaceous fossiliferous resins and contains a remarkably diverse flora and fauna (Grimaldi et al. 2002). It is remarkable that the palaeodiversity of Berothidae is extraordinarily rich from the mid-Cretaceous of Myanmar, being one of the major Neuropteran lineages in this deposit (Ross 2019), with 13 genera and 19 species described, based on the Myanmar amber specimens (Engel and Grimaldi 2008; Yuan et al. 2016; Huang et al. 2018; Makarkin 2018; Yang et al. 2019; Yang et al. 2020). These Myanmar amber berothids show diverse morphological characters and are probably the members, or as the stem-groups of different subfamilies (Huang et al. 2018).

Herein, a new species of Jersiberotha Grimaldi, 2000 is described, based on a well-preserved female specimen from the mid-Cretaceous (ca. 98.8 Ma) of Myanmar. In addition, a revised key to the species of Berothidae from Myanmar amber has been provided. The diagnoses of Iceloberotha and Jersiberotha also have been revised.

This study is based on a single, female specimen preserved in a piece of clear, yellowish Myanmar amber, which was collected from an amber mine, located in the Hukawng Valley of Kachin Province, Myanmar (Chen et al. 2019). The age of Myanmar amber in this investigation is radiometrically dated at 98.79 ± 0.62 Ma, based on U-Pb zircon dating of the volcanoclastic matrix (Shi et al. 2012). However, it is important to highlight that the Zircon date only gives the age of the top bed and a minimum age for the amber, so the geologic age of Myanmar amber may be slightly older than the Zircon date.

The amber piece that contains the inclusions was cut and polished with different grain sizes of sandpaper and finally buffed with polishing powder. The specimen is housed in the Institute of Paleontology and Stratigraphy, School of Earth Sciences, Lanzhou University, Gansu Province, China. Examinations of the specimen were accomplished using a Leica S8APO stereomicroscope, equipped with a Leica DFC295 camera. Images were digitally stacked as photomicrographic composites of approximately 20 individual focal planes obtained using the software Helicon Focus 6 for better visualisation of the 3D structures. Drawings for the analysis were based on the specimen and photographs. Figures were prepared with CorelDraw X4 and Adobe Photoshop CS6.

General terminology of wing venation follows Kukalová-Peck and Lawrence (2004) as interpreted by Yang et al. (2012) and Yang et al. (2014). Terminology of the wing spaces and details of venation (e.g. spaces, veinlets) follows Oswald (1993) and the cross-veins designation follows Makarkin (2015). Terminology of genitalia follows Aspöck and Aspöck (2008). Cross-veins are designated after the longitudinal veins which they connect and are numbered in sequence from the base to the apex of the wing, for example, 1sc-r, first (proximal-most) cross-vein connecting Sc and R; 2m-icu, second cross-vein between M/MP and Cu/CuA.

Abbreviations are as follows: wing venation: ScA, subcosta anterior, ScP, subcosta posterior, RA, anterior radius, RP, posterior sector, RP1, proximal-most branch, MA and MP, anterior and posterior branches of media, CuA, anterior cubitus, CuP, posterior cubitus, AA1-AA3, first to third anterior anal vein; head and antennal structures: La, labrum, MP, maxillary palp, Pe, pedicel, Sp, scape; abdominal and genital structures: T: Tergite; S: sternite; phc: pseudohypocaudae; e: ectoproct; gcx, gonocoxites.

The identification key to the Berothidae species from Myanmar amber was modified from that provided by Yuan et al. (2016), based on the characters of the new species.

Jersiberotha musivum sp. nov. was described, based on a single, female from mid-Cretaceous Myanmar amber. The previous diagnosis between Iceloberotha and Jersiberotha was quite indistinct because some characters occurred mosaically in both genera. A new identification key to the Berothidae species from Myanmar amber was provided to distinguish the new species from others in the Berothidae and the revised diagnoses of Iceloberotha and Jersiberotha were also updated.

We appreciate the valuable comments and useful suggestions on our manuscript from the associate editor (Dr. Atilano Contreras-Ramos), the reviewers (Dr. Vladimir Makarkin, Dr. David Bowles and Dr. Caleb Califre Martins) and another anonymous reviewer. We thank Ms Dan Zuo (Changsha, Hunan, China) and Mr. Dong Han (Henan, China) for donating the type specimen to us for study. This work is supported by the Second Tibetan Plateau Scientific Expedition and Research Program (STEP, No. 2019QZKK0704); Science and Technology Program of Gansu Province (No. 20JR5RA236) and National Natural Science Foundation of China (No. 41972008).