Fossiliferous Cretaceous Amber from Myanmar (Burma): Its Rediscovery, Biotic Diversity, and Paleontological Significance

Amber from Kachin, northern Burma, has been used in China for at least a millennium for carving decorative objects, but the only scientific collection of inclusion fossils, at the Natural History Museum, London (NHML), was made approximately 90 years ago. Age of the material was ambiguous, but probably Cretaceous. Numerous new records and taxa occur in this amber, based on newly excavated material in the American Museum of Natural History (AMNH) containing 3100 organisms. Without having all groups studied, significant new records and taxa thus far include the following (a † refers to extinct taxa): For Plants: An angiosperm flower (only the third in Cretaceous amber), spores and apparent sporangia of an unusual but common fungus, hepatophyte thalli and an archegoniophore of Marchantiaceae, and leafy shoots of Metasequoia (Coniferae). Metasequoia is possibly the source of the amber. For Animals: Mermithidae and other Nematoda; the oldest ixodid tick (a larval Amblyomma); bird feathers; and the only Mesozoic record of the Onychophora (“velvet” worms), described as †Cretoperipatus burmiticus, n. gen., n. sp. (Peripatidae). Poinar's classification of the Onychophora is substantially revised. Still largely unstudied, the fauna of mites (Acari) and spiders (Araneae) appears to be the most diverse ones known for the Mesozoic. For Insecta: Odonata indet. (wing fragment); Plecoptera indet.; new genera of Dermaptera, Embiidina, and Zoraptera (the latter two as the only definitive Mesozoic fossils of their orders). Within Hemiptera, there are primitive new genera in the Aradidae, Hydrometridae, Piesmatidae, Schizopteridae, and Cimicomorpha (Heteroptera), as well as in †Tajmyraphididae (Aphidoidea), and †′otopsyllidiidae. An adult snakefly (Raphidioptera: †Mesoraphidiidae) is the smallest species in the order, and new genera occur in the Neuroptera: Coniopterygidae, Berothidae, and Psychopsidae, as well as larvae of apparent Nevrorthidae. Coleoptera are largely unstudied, but are probably the most diverse assemblage known from the Cretaceous, particularly for Staphylinidae. An adult lymexylid, the most primitive species of Atractocerus, is the first Mesozoic record of the family. In Hymenoptera there are primitive ants (Formicidae: Ponerinae n. gen., and †Sphecomyrma n.sp [Sphecomyrminae]), the oldest record of the Pompilidae, and significant new records of †Serphitidae and †Stigmaphronidae, among others. Diptera are the most diverse and abundant, with the oldest definitive Blephariceridae and mosquito (Culicidae), as well as new genera in the Acroceridae, Bibionidae, Empidoidea; a new genus near the enigmatic genus Valeseguya, and an unusual new genus in the †Archizelmiridae. †Chimeromyia (Diptera: Eremoneura), known previously in ambers from the Lower Cretaceous, is also represented.The stratigraphic distribution of exclusively Mesozoic arthropods in Burmese amber is reviewed, which indicates a probable Turonian-Cenomanian age of this material (90–100 Ma). Paleofaunal differences between the NHML and AMNH collections are discussed, as is the distinct tropical nature of the original biota. Burmese amber probably harbors the most diverse biota in amber from the Cretaceous, and one of the most diverse Mesozoic microbiotas now known.