Discovery of Lebambromyia in Myanmar Cretaceous Amber: Phylogenetic and Biogeographic Implications (Insecta, Diptera, Phoroidea)

SIMPLE SUMMARY: Phoroid flies are an ancient lineage of Diptera, which includes megadiverse, widespread groups like the scuttle flies, as well as species-poor, sometimes relict, groups like flat-footed and ironic flies. The earliest fossils of phoroid flies are from Early Cretaceous. In this paper we describe a second species of the enigmatic phoroid fly genus Lebambromyia. The genus was erected to accommodate an extinct species, L. acrai Grimaldi and Cumming, from Lebanese amber deposit, dated at ca. 120 Mya. A new species, L. sacculifera sp. nov., is described here based on a single female specimen embedded in Myanmar “mid-Cretaceous” amber, which is over 20 Ma younger than the Lebanese outcrop, implying that this genus had a wide geographic and temporal distribution. The state of preservation of the new specimen and its study with phase contrast X-ray microtomography show that this ancient fly was characterized by a mix of ancient and modern features, such as specialized sensory areas in the antenna. Phylogenetic analyses support that Lebambromyia was related to flat-footed and ironic flies, but a clear phylogenetic position remains elusive. ABSTRACT: Lebambromyia sacculifera sp. nov. is described from Late Cretaceous amber from Myanmar, integrating traditional observation techniques and X-ray phase contrast microtomography. Lebambromyia sacculifera is the second species of Lebambromyia after L. acrai Grimaldi and Cumming, described from Lebanese amber (Early Cretaceous), and the first record of this taxon from Myanmar amber, considerably extending the temporal and geographic range of this genus. The new specimen bears a previously undetected set of phylogenetically relevant characters such as a postpedicel sacculus and a prominent clypeus, which are shared with Ironomyiidae and Eumuscomorpha. Our cladistic analyses confirmed that Lebambromyia represented a distinct monophyletic lineage related to Platypezidae and Ironomyiidae, though its affinities are strongly influenced by the interpretation and coding of the enigmatic set of features characterizing these fossil flies.