Trouble in Myanmar: The worrying case of Burmese Amber.

Cretaceous ‘Burmese Amber’ has been extensively worked at several sites across northern Myanmar (though mostly in Kachin State) in the last 20 years. The amber is fairly clear, and often found in large chunks, providing an exceptional window into the Middle Cretaceous Insect fauna, as well as preserved examples of small Vertebrates, feathers from Birds and other Dinosaurs, and even the only known Ammonite preserved in amber. However, the trade in amber from Myanmar has raised deep concerns, as has the wider nature trade in gemstones from the country, due to the deteriorating Human rights situation in the country, and the highly exploitative working conditions at many mines there. Most noatably, in 2017 the Myanmar military seized direct control of the region, forcing many local residents (who were accused of being supporters of the Kachin Independence Army) to flee, and bringing in new workers from other parts of the country.

In April 2020 Emily Rayfield, Jessica Theodor, and David Polly of the Society of Vertebrate Paleontology sent a letter to the editors of over 250 scientific journals, raising concern about the trade in amber from Myanmar, Human rights abuses within the country, the ongoing conflict situation in the region, and the blurring of the distinction between public and private collections that had occurred in some journals with regard to material from the region (in order for a study to be published in a journal, the material involved should be held in a collection that has a predetermined policy on the making of material available to other researchers, such as a museum or university collection, rather than in private ownership).

 

Flowers preserved in amber from Kachin State, Myanmar. Myanmar Amber Museum.

This was followed in May 2020 by an editorial published in the Journal of Systematic Palaeontology in which editors Paul Barrett and Zerina Johanson, stated that that journal would no longer be publishing articles based wholly or in part upon amber from Myanmar, whether newly collected or from historic collections, citing concerns about working conditions at mines in Myanmar, the use of money obtained from the sale of amber and other gemstones to by arms and fund conflicts in the region, and the widespread illegal removal of amber from the country.

The issue has been addressed again in the June 2021 issue of the journal Nature Ecology and Evolution, with an editorial and a series of articles by scientists with views on the topic.

In the first of these papers, a group of scientists led by Chao Shi of the College of Marine Science and Biological Engineering at Qingdao University of Science and Technology and the Key Laboratory for Plant Diversity and Biogeography of East Asia at the Kunming Institute of Botany, argue that while the Human rights situation in Myanmar is now severe enough to justify a ban on the use of new specimens from the country in published scientific studies, a great deal of this material is already present in musuem and university collections around the world, and that it would be unreasonable to exclude this material from future studies.

 

A mining camp in a forest in Kachin State in 2010. Blood Amber/Kachin Development Networking Group.

In the second paper, Zin-Maung-Maung-Thein of the Department of Geology at the University of Mandalay, and Khin Zaw of the Centre of Ore Deposits and Earth Sciences at the University of Tasmania, raise concerns about Burmese Amber as a focus for 'parachute science', a term which refers to the practice of scientists from wealthy countries 'parachuting' into less well-off nations, collecting data or materials, then returning to their home nations to work on this material, without any benefit to the host nation, and often with scientists from that nation henceforth hampered from accessing the data or materials, due to their new location, and the high cost of accessing published information in many journals and other publications (ironically, this article is itself paywalled, and cannot be accessed without a subscription to Nature Ecology and Evolution, unless a fee is paid (US8.99 for the one-page article). In the case of Myanmar, amber is typically extracted then sold overseas, where it may be worked on by local scientists who are acting in good faith, but who in so doing are excluding scientists in Myanmar from accessing the same material. A study by Emma Dunne of the University of Birmingham and Nussaïbah Raja-Schoob of Friedrich-Alexander-Universität Erlangen-Nürnberg, and presented by Emma Dunne at a meeting of the Palaeontological Association in 2020, found that not a single publication on Burmese Amber in the English language published in the last 30 years included a local collaborator, whereas articles on Cainozoic Primates from Myanmar often did (suggesting that there is a local interest in palaeontology, and scientists in Myanmar who would be willing to work with with outside scientists). Dunne and Raja suggest that this difference may be because of the difference in status between amber and other fossils in Myanmar; in theory fossils are treated as antiquities in Myanmar, and a special permit is needed to export them, but amber is a 'gemstone' and may be exported without a permit (the export of gemstones, such as jade, rubies, and amber is a major earner of hard currencies for Myanmar). Zin-Maung-Maung-Thein and Khin Zaw suggest that scientists outside Myanmar wishing to work on this material should contact the government of Myanmar for permission, as well as museums and universities in the country to seek local collaborators.

In the final paper, Paul Barrett, Zerina Johanson and Sarah Long of the Natural History Museum again visit the dual legal nature of fossils in Burmese Amber, pointing out that the current situation is a 'legal quagmire' which researchers should contemplate very carefully before entering.

Finally, the editorial piece, having considered these issues, lays out the current policy for the publication of studies based upon material from Myanmar (or other troubled or contentious areas), across all Nature journals; to whit that the export of material must be in line with both local and international law, and that any material used in such studies should be deposited in a recognised museum, collection or accessible repository. 

 

The tip of the wing of a fledgeling Cretaceous Bird, trapped in Burmese Amber. Ming Bai/Chinese Academy of Sciences.

Whilst this editorial policy would seem to go some way towards addressing the problems of Burmese Amber, it by no means resolves all the issues raised within the articles. Notably, the number of publications featuring material from Burmese Amber has been rising sharply since 2010, and in particular since 2017, when the Myanmar military is reported to have taken over the amber-producing mines, and news of Human rights abuses associated with the mines began to emerge. Thus, one of the major concerns about Burmese Amber is behaviour of the ruling military junta, which is accused of both abusing the rights of miners, and of using money from the sale of amber to buy arms and fund conflicts against minority groups within Myanmar. This cannot be addressed by complying with Myanmar's export laws, since those laws are drawn up by, and serve the interests of, those accused of committing Human rights abuses. 

Neither can the problem of parachute science be resolved simply by making sure that specimens are in collections where they are (in theory) available to scientists from their home country. No matter how good the intentions of such countries, the cost of travelling to them in order to study material is often prohibitively expensive, particularly if more than one country needs to be visited to see scattered specimens. This is compounded by an increasing tendency by governments in Europe and North America to refuse to allow researchers from other parts of the world to enter their countries at all, something which plays well with sections of the western media that have taken to scapegoating immigrants at every opportunity, but which compounds the injustice of having material removed from countries to be studied in other parts of the world.

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Astreptolabis laevis: A new species of Earwig from Cretaceous Burmese Amber.

Earwigs, Dermaptera, are one of the smaller orders of Insects and consist of approximately 2000 modern species segregated into 12 families. These are distinctive Insects, with their generally flattened appearances, often leathery integument, tegminized forewings, broad fan-shaped hind wings, and, most distinctive of all, the terminal forceps formed of their modified cerci. Within the Dermaptera, the modern fauna falls entirely within the suborder Neodermaptera, with the earliest definitive Neodermaptera are found in the Lower Cretaceous. There have been 22 Neodermapteran Earwigs described from Cretaceous amber. Of these, six are classified in the extant family Pygidicranidae, including four adults and two nymphs. Although the record of Earwigs preserved in Cretaceous and Cenozoic amber has grown rapidly, well-preserved specimens of adult earwigs are still rather uncommon and it remains a difficulty to associate nymphs with adults when not found as syninclusions. Moreover, the precise phylogenetic placement of many fossil Earwigs continues to be poorly understood.

It a paper published in the journal ZooKeys on 12 February 2020, Yue Mao of the College of Life Sciences and Academy for Multidisciplinary Studies at Capital Normal University, Michael Engel of the Division of Entomology at the Natural History Museum, and Department of Ecology & Evolutionary Biology at the University of Kansas, and the Division of Invertebrate Zoology at the American Museum of Natural History, and Dong Ren and Taiping Gao, also of the College of Life Sciences and Academy for Multidisciplinary Studies at Capital Normal University, describe a new species of Pygidicranid Earwig from Middle Cretaceous Burmese Amber.

Cretaceous ‘Burmese Amber’ has been extensively worked at several sites across northern Myanmar (though mostly in Kachin State) in the last 20 years. The amber is fairly clear, and often found in large chunks, providing an exceptional window into the Middle Cretaceous Insect fauna. This amber is thought to have started out as the resin of a Coniferous Tree, possibly a Cypress or an Araucaria, growing in a moist tropical forest. This amber has been dated to between 105 and 95 million years old, based upon pollen inclusions, and to about 98.8 million years by uranium/lead dating of ash inclusions in the amber.

The new species is placed in the genus Astreptolabis, which currently contains one other species, Astreptolabis ethirosomatia, also from Burmese Amber, and given the specific name laevis, meaning, 'polished' or  'smooth', in reference the integumental surface (skin) of the species. Astreptolabis laevis is described from three specimens, two females and a male with its genitalia partly exerted (the male genetalia is considered important in the classification of Insects, but is seldom preserved in fossils.The specimens were collected from mines in the Hukawng Valley of Kachin; the amber mines are located at the north end of Noije Bum village, approximately  18 km southwest of Tanai.

 Astreptolabis laevis, holotype, CNU-DER-MA2018001, female. (A) Photo, (B) line drawing. Scale bars are 0.5 mm. Mao et al. (2020).

The genus Astreptolabis is placed on its own within a separate, extinct, subfamily of the Pygidicranidae, the Astreptolabidinae, which is distinguished by its small size, 3.50–5.30 mm in length, and straight and tubular cerci which, would have been of little use as grasping foreceps. Astreptolabis laevis can be distinguished from Astreptolabis ethirosomatia by the lower number of setae (hairs) on itshead, thorax and tegmina (modified forewings which form a wing case into which the hind wings are folded), and the larger compound eyes, which encompass the entire lateral surface of the head from the antennal articulations to the posterior border.

Astreptolabis laevis, holotype, CNU-DER-MA2018001, female. (A) Photo of pronotum, (B) line drawing of hind wing, (C) photo of legs, (D) photo of vavula. Scale bars: 0.2 mm (A), (C), 0.5 mm (B), 0.1 mm (D). Mao et al. (2020).

The larger of the two female specimens has a total length of 3.61 mm,, the male 5.30 mm. The hind wing of the holotype of Astreptolabis laevis is well preserved, and one is unfolded and extended. The base of the hind wing is obscured because of the position of the specimen, but most of the preserved structures are similar to those of extant Earwigs. The female paratype CNU-DER-MA2018002 shares the same characters with the holotype, but the integument of this paratype is somewhat roughened and the pronotum seems broader than the holotype; however, these differences may be the result of taphonomy. The male paratype CNU-DER-MA2018003 shares the same characters with the holotype except for a larger body size, which seems to be a sexual difference. Otherwise, differences in body size are mainly reflected in tegmen length and abdominal length which are longer than the female, but otherwise proportional.

Astreptolabis laevis, paratype, CNU-DER-MA2018002, female. (A) Photo, (B) line drawing, (C) photo of legs, (D) photo of cerci. Scale bars: 0.5 mm (A), (B), 0.2 mm (C), 0.1 mm (D). Mao et al. (2020).

Up to now, many than 1000 species of insects have been reported from Burmese Amber, including Termites, Stick Insects, Scorpionflies, lots of Wasps, Beetles, Lacewings, etc.; however, Earwigs are still quite rare compared to most of the other groups. Astreptolabis spp. are the smallest Earwigs within Pygidicranidae so far, females being as small as about 3.5 mm in length including cerci. Antenna has at least 14 antennomeres, which is an unusually small number for basal Neodermaptera and likely autapomorphic for the subfamily. Although the known representatives are quite peculiar among living and fossil Earwigs, particularly in the straight, tapering, tubular cerci which clearly would have had little force as a grasping structure (contrary to virtually all other Neodermaptera), it has the usual traits typical of the suborder such as the absence of ocelli, the trimerous tarsi, unsegmented cerci, and absence of venation in the tegmina. The straight and tubular cerci which likely did not function for grasping could imply that Astreptolabidines used other strategies for predation, or were scavengers or detritivores and therefore did not hunt. The new species is typical in nearly all traits with the type species, aside from minor differences in largely setation, and proportions of structures. Nonetheless, the new species helps to refine our understanding of the circumscription for the genus and subfamily, and gives us some initial knowledge as to variations that may occur within the lineage. Unfortunately, while it would be revealing to learn more about the structure of the ventral cervical sclerites and thoracic sterna, these cannot be discerned in any of the new specimens and await future discoveries to provide such insights. Nonetheless, the discovery of the male for the group is important, and the uniqueness of the Astreptolabidinae is reinforced by the peculiar features of the male genitalia. Like other Pygidicranidae, the male has two virgae, rather than four terminal virgal sections present in Diplatyidae. However, unlike most other Pygidicranidae the parameres are broader and lack terminal teeth or incisions, and are instead comparatively simple, tapering to an acute apex. These are either specializations apomorphic for the subfamily, or could also suggest that including Astreptolabidinae within Pygidicranidae renders the family paraphyletic. If the latter, then there may be need to elevate the subfamily to family rank, but such a formal decision must await further character data such as the form of the thoracic sterna which could provide evidence of affinity to one or more subfamilies within Pygidicranidae as currently defined. However, the female valvulae slightly extending beyond the subgenital plate is a trait known only among the Pygidicranidae, and this feature in Astreptolabis laevis tends to corroborate its inclusion among pygidicranids. For the time being, the male of Astreptolabis laevis emphasizes the distinctiveness of the lineage and highlights the need to obtain further character data for this group of peculiar, ancient Neodermaptera. If the subfamily were to fall outside of Pygidicranidae it remains uncertain whether it would be basal to the family or more closely related to Epidermaptera, and perhaps information on sternal forms would aid such a determination. The presence of complex, heavily sclerotized accessory structures ventral to the paired distal lobes is at least reminiscent of the accessory structures sometimes found among Diplatyids, although the size and form of those in Astreptolabis are drastically different. If these were homologous, then it might suggest that Astreptolabidinae are intermediate in phylogenetic position between the basal families Diplatyidae, Haplodiplatyidae, and Karschiellidae relative to Pygidicranidae.

Astreptolabis laevis, paratype, CNU-DER-MA2018003, male. (A) Dorsal view, (B) ventral view,
(C) photo of pronotum and legs, (D) photo of male genitalia, (E) enlarged view of male genitalia. Scale bars: 1 mm (A, B), 0.5 mm (C), 0.2 mm (D), 0.1 mm (E). Mao et al. (2020).

Interestingly, the wing morphology of the hind wings of Astreptolabis laevis is quite similar to extant Earwigs. Though the broad attachment and the base of the hind wing is covered by the tegmina, the anal area is relatively clear, and the same areas of folding can be discerned as is found across all Neodermaptera, emphasizing the consistency of this specialization within the order. In addition, the shortened tegmina is known to allow for flexibility in the abdomen and its role in folding the hind wings when not in use and this behavioral repertoire is likely also conserved.

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Angimordella burmitina: A pollen-associated Tumbling Flower Beetle from Cretaceous Burmese Amber.

Angiosperms, Flowering Plants, are the most diverse group of Land Plants. The earliest unequivocal pollen and macrofossils of Angiosperms are generally thought to date from the early Hauterivian (about 130 million years ago) and early Aptian (about 125 million years ago), respectively, despite claims based on other fossils and molecular analyses. The apparently rapid and tremendous evolutionary diversification of Angiosperms during the Cretaceous was the great 'abominable mystery' mentioned by Darwin and continues to be an active and sometimes a controversial area of research. Insect pollination (entomophily) is generally considered to be a key contributor to the Cretaceous radiation of Angiosperms. It is generally thought to be the dominant pollination mode of Angiosperms during the early mid-Cretaceous with specialisation increasing during the angiosperm radiation, supported by basal flower morphology, palynological data, and phylogenetic inferences. Some Cretaceous Insects are palynivores of Angiosperms based on their pollen- or nectar-feeding mouthparts, gut contents, or coprolites. However, a palynivore is not equivalent to a pollinator. Only direct evidence (pollen-carrying behaviour and pollen-feeding mouthparts) can provide unambiguous demonstration of ancient Insect pollination. Until now, direct evidence of Cretaceous Insect pollination supports Insect-Gymnosperm pollination, such as that involving Thrips, True Flies, Beetles, and Scorpionflies. Although both Insects and Angiosperms were common during the mid-Cretaceous, direct evidence for Cretaceous Insect-Angiosperm pollination mode has been absent.

In a paper published in the Proceedings of the National Accademy of Sciences of the USA on 11 November 2019, Tong Bao of the State Key Laboratory of Palaeobiology and Stratigraphy at the Nanjing Institute of Geology and Palaeontology, the Center for Excellence in Life and Paleoenvironment of the Chinese Academy of Sciences, and the Institut für Geowissenschaften at Universität Bonn, Bo Wang, also of the State Key Laboratory of Palaeobiology and Stratigraphy at the Nanjing Institute of Geology and Palaeontology, the Center for Excellence in Life and Paleoenvironment of the Chinese Academy of Sciences, and of the Key Laboratory of Zoological Systematics and Evolution at the Institute of Zoology of the Chinese Academy of Sciences, Jianguo Li, again of the State Key Laboratory of Palaeobiology and Stratigraphy at the Nanjing Institute of Geology and Palaeontology, the Center for Excellence in Life and Paleoenvironment of the Chinese Academy of Sciences, and David Dilcher of the Department of Geology and Atmospheric Science at Indiana University, describe a new species of Tumbling Flower Beetle, Mordellidae, from a pieces of Burmese Amber, with associated Angiosperm pollen, which they argue provides the first direct evidence of Insect pollination of Angiosperms in the Cretaceous.

Beetles constitute almost a quarter of all Animal species on Earth, and are among the most prominent pollinators of Angiosperms. More than 77 000 beetle species are estimated to visit flowers. Among these flower-visiting Beetles, Tumbling Flower Beetles are one of the most species-rich families, and adults are easily recognised by their humpbacked body, deflexed head, pointed abdomen, and stout hind legs. The majority of extant adult Mordellids feed on Angiosperm pollen Cretaceous Mordellids have been hypothesised to be Angiosperm pollinators, but direct evidence of this has been lacking.

Cretaceous ‘Burmese Amber’ has been extensively worked at several sites across northern Myanmar (though mostly in Kachin State) in the last 20 years. The amber is fairly clear, and often found in large chunks, providing an exceptional window into the Middle Cretaceous Insect fauna. This amber is thought to have started out as the resin of a Coniferous Tree, possibly a Cypress or an Araucaria, growing in a moist tropical forest. This amber has been dated to between 105 and 95 million years old, based upon pollen inclusions, and to about 98.8 million years by uranium/lead dating of ash inclusions in the amber.

The new species is named  Angimordella burmitina, where 'Angimordella' is a combination of Angiosperm, for Flowering Plant, and Mordella, the genus name from which Mordellidae is derived, and 'burmitina' is a mineralogical name used for Burmese Amber. The species is described from a single specimen, a complete Beetle with left side visible but its right side covered by abundant microbubbles. A Thrips is near the maxillary palpi of the Beetle on the left side. This Beetle is small, about 4.25 mm in length, with serrated antennae, abundant wrinkles and folds on the protonum (backplate covering the abdomen) and elytra (wingcases), but not the legs.

Cretaceous Tumbling Flower beetle Angimordella burmitina. (A) Habitus. (B) Drawing. (C) Prothorax and pronotum highlighted by red dashed lines. (D) Microtomographic reconstruction of the head. Maxillary palpi highlighted in yellow. (E) Abdomen, I−IV represent first to fifth abdominal ventrites. (F) Hind leg, I−IV represent first to fourth metatarsomeres. an, antennae; cl, claw; mp, maxillary palp; py, pygidium; sp, spines on metatibiae and metatarsi; tr, trochanter. Bao et al. (2019).

The body of Angimordella burmitina is strongly convex, wedge-shaped, and widest near base of prothorax, becoming slightly narrowed anteriorly and posteriorly. The head is strongly declined, with mouthparts directly posteriorly, and compound eyes which are finely faceted and glabrous. The occipital regionis wide, and has a a surface covered with wrinkles and hairs, matching perfectly with anterior edge of the pronotum. The antennae are comparatively short, with 7 visible antennomeres, and obviously serrate, all features considered diagnostic of a Tumbling Flower Beetle

There are at least 62 pollen grains (from only the visible left side of the Beetle) in the amber in total, of which 24 pollen grains aggregate into two small clusters near the abdominal end of the Insect. Pollen grains in the amber are retitricolpate and highly uniform in morphology. The shape of the grains is approximately oblate spheroidal, and they  measure 30.95−22.08 μm × 20.68−13.93 μm in equatorial view, based on measurement of the 27 best preserved pollen grains. The pollen clump shape is irregular, and the pollen grains are well preserved, indicating that they are natural floral remains rather than coprolites. These pollen grains can be confidently attributed to the Eudicot monophyletic group (true Dicotyledons), members of which are distinguished from all other Angiosperms by their tricolpate pollen structure. Bao et al. do not assign the pollen to a taxon given the nature of this microscopic method conducted within amber.

Angimordella burmitina and tricolpate pollen grains. (A) Habitus. Pollen grains attached to the body are indicated by red dots, unattached are indicated by yellow dots, clumped pollen are indicated by blue squares. (B)−(H) Locations are highlighted in (A). (B) and (C) Pollen grains near the body. Yellow arrows point to colpi. (D) and (E) Pollen grains on the body. (F)−(H) Clumped pollen grains. (G) and (H) Locations are highlighted in (F) and (G), respectively. Blue arrows point to colpi. Bao et al. (2019).

Angimordella burmitina exhibits a series of specialized body structures related to its flower-visiting behavior, similar to its modern counterparts, which feed on various angiosperm pollen. It has the Mordella-type apical maxillary palpomere (part of the mouth), which is enlarged and securiform (axe-shaped). This maxillary palpomere is blocked by a Thrips, but the palpomere shape was revealed by micro-tomography. This specialised modification of the maxillary palpomere has been known to aid collecting and most likely transporting pollen grains. Angimordella burmitina has a curved and laterally compressed body with a strongly declined head, allowing for flexibility when feeding inside the flower. Its hind legs are well developed, with enlarged metacoxa and metafemora and spiny metatibiae and metatarsi, which make it easier to move on the corolla and from one flower to another. Moreover, Angimordella burmitina has fine hairs; the spacing and height of these hairs influence the ability of the hairs to carry pollen grains. Accordingly, the hairs on the Beetle’s thorax and abdominal sternites are distinctly longer than 30 μm, and the spacing between the hairs is consistent with the width of the coexistent pollen grains (about 20 μm) and is well-adapted for holding and transporting pollen grains. 

Angimordella burmitina is covered by abundant tricolpate pollen grains that are mainly distributed on the thorax and abdomen. Tricolpate pollen is both the defining and most important character of the Eudicots, a group which comprises about 75% of extant Angiosperm species. The earliest fossil record of tricolpate pollen is about 125 million years old, slightly older than the earliest Eudicot macrofossil. By 99 million years ago (i.e. Burmese Amber age), tricolpate pollen had become widespread worldwide and Eudicot macrofossils are reported from Burmese Amber. Many Cretaceous plants with tricolpate pollen are animal-pollinated and characterised by their ornamentation, size (10−300 μm), and clumping characteristics. Small Angiosperm pollen grains in amber, especially those buried under Insect body hairs, are often not visible under optical microscopy and, thus, could be easily overlooked. In Bao et al's study, the pollen grains between body hairs were detected by confocal laser scanning microscopy, which takes advantage of pollen fluorescence, which contrasts with the surrounding dark Insect cuticle. The tricolpate pollen grains found in Burmese amber exhibit remarkable zoophilous pollination features including their reticulate surface and presence of pollen clumping, thus providing more evidence to support beetle-mediated pollination. Interestingly, only one type of pollen was found on this Beetle. This could reflect that there were not very many different types of flowers during the mid-Cretaceous or that the Insect visited only one type of flower before it was trapped in the amber.

Ecological reconstruction of Angimordella burmitina. These Tumbling Flower Beetles are feeding on Eudicot flowers. The colour and morphology of flowers are artistic only. Bao et al. (2019).

The Mordellidae, comprising about 1500 extant species worldwide, are among the most basal group of Tenebrionoidea based on morphological analysis and molecular data. Although Mordellid-like beetles are reported from the Middle-Late Jurassic of China and Kazakhstan, the earliest true Mordellids (i.e. members of the extant subfamily) are known from the mid-Cretaceous Spanish and Burmese amber. Angimordella burmitina is among the earliest true Mordellids and indicates that Mordellid-Angiosperm pollination mutualisms have been present since at least 99 million years ago. These mutualisms may be an important driver for the radiation of true Mordellids.

Bao et al. believe this provides direct evidence of Cretaceous Insect pollination of Angiosperms, which is strongly supported by the flower-visiting body shape, specialised pollen-feeding mouthparts, and zoophilous pollen grains attached to the body. The prior earliest direct evidence of Insect pollination of Angiosperms was reported from several pollen-collecting Bees from the Middle Eocene of Eckfeld and Messel (48 and 45 million years old, respectively) in Germany. Their findings thereby extend the known geological range of direct evidence of Insect pollination of Angiosperms by at least 50 million years.

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Promyrmister kistneri: A new species of myrmecophile Clown Beetle from Cretaceous Burmese Amber.

Clown (of Hister) Beetles, Histeridae, are a diverse group of carnivorous Beetles found across the globe. They are easy to distinguish, the elytra (wing cases) that do not cover the ends of their abdomens and club-like tips to their antennae. They occupy a wide range of ecological niches, with most species feeding on other Arthropods and small invertebrates, though other specialise in the carrion of larger animals (and in some cases are used by forensic entomologists to help determine how long bodies have been dead). The group contains many myrmecophile species; Beetles that have evolved the ability to live within the colonies of Ants, largely by using chemical and behavioural mimicry to fool the Ants generally highly aggressive defence responses. This trait appears to have evolved several times within the Histeridae, with one subfamily, the Haeteriinae, being entirely made up of myrmecophile Beetles  highly specialised for this lifestyle.

In a paper published in the journal eLife on 16 April 2019, Yu-Lingzi Zhou of the Key Laboratory of Zoological Systematics and Evolution at the Institute of Zoology of the Chinese Academy of Sciences, and the Australian National Insect Collection, Adam Ślipiński, also of the Australian National Insect Collection, Dong Ren of the College of Life Sciences at Capital Normal University, and Joseph Parker of the Division of Biology and Biological Engineering at the California Institute of Technology, describe a new species of myrmecophile Clown Beetle from Cretaceous Burmese Amber.

Cretaceous ‘Burmese Amber’ has been extensively worked at several sites across northern Myanmar (though mostly in Kachin State) in the last 20 years. The amber is fairly clear, and often found in large chunks, providing an exceptional window into the Middle Cretaceous Insect fauna. This amber is thought to have started out as the resin of a Coniferous Tree, possibly a Cypress or an Araucaria, growing in a moist tropical forest. This amber has been dated to between 105 and 95 million years old, based upon pollen inclusions, and to about 98.8 million years by uranium/lead dating of ash inclusions in the amber. 

The oldest fossil Ants appear in this amber, and the roughly contemporary Charentese Amber of France, though they are all considered to be 'stem group' Ants (members of the Ant lineage, more closely related to living Ants than to other Hymenopterans, but not descended from the most recent common ancestor of all living Ants) rather than 'crown group' Ants (Ants which are descended from the most recent common ancestor of all living Ants).

The new species is named Promyrmister kistneri, where 'Promyrmister' means 'early-Ant-Clown Beetle', and 'kistneri' honiurs David Kistner, for his expertese on Social Insect symbionts. It is described from a single specimen, which is 3.2 mm long and 2.3 mm wide, roughly oval in shape, black or dark brown in colour, and has visible hairs on its dorsal surface.

Promyrmister kistneri  (A) Dorsal habitus of holotype CNU-008021 with origin of exudate globule (black arrow) and elytral striae (white arrows) indicated; the three lateral striae are complete (top three arrows), the three medial striae appear incomplete. (B) Right lateral habitus with flight wing indicated. (C) Ventral habitus, boxed region expanded in panel H. (D) Head, dorsal and (inset) frontal views, with antennal scapes and frontoclypeal carina (FC) indicated. (E) Right foreleg, laterally expanded femur and tibia indicated. (F) Proventral mesoventral boundary showing proventral keel with posterior incision. (G) Left pronotal margin, lateral view, showing possible origin of putative glandular exudate; arrow in G corresponds to that in panel A. (H) Ventrite one showing proximal leg segments (Trc: trochanter) and postcoxal gland openings (white arrows), with globule of putative exudate emanating from left postcoxal gland opening. Zhou et al. (2019).

The specimen shows a number of traits that lead Zhou et al. to colclude that it is both a myrmecophile and a member of the Haeteriinae. These include broad expansions of the tibiae with spines on the outer margin, short tarsi received on the outer face of each tibia, a triangular antennal scape, pronounced antennal cavities on the prothoracic hypomeron, and a broad proventral lobe to fully embrace the retracted head, all of which are thought to be protective modifications that enable myrmecophile beetles to withstand handling by ant mandibles.

Reconstruction of Promyrmister with stem-group host ant and larva (ant based on Gerontoformica). Zhou et al. (2019).

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