Crossing the Tethys on "biotic ferries": new mayfly genera of Gondwanan origin in Mesozoic and Cenozoic deposits of Myanmar and India (Insecta: Ephemeroptera: Teloganodidae).

backgoundMesozoic and Cenozoic fossils from Myanmar and the Indian subcontinent provide a crucial source of information on the global distribution of biota after the breakup of East Gondwana and the subsequent northward drift of these land masses towards Asia. While the mayfly fauna of Burmese amber is relatively well studied, data on extinct Ephemeroptera from India remain scarce.

resultsHere, we describe for the first time a fossil adult mayfly reliably assigned to the family Teloganodidae. Based on a single male imago discovered in mid-Cretaceous Burmese amber, we establish a new species and genus, Chibiphemera cretalota gen. & sp. nov. based on the following combination of characters: (i) small body and forewing size; (ii) distinctive forewing venation, including the positions of RS and MP forks; (iii) strongly reduced hind wings, with a distally positioned costal process and markedly diminished venation; (iv) presence of pad-like pretarsal claws on the forelegs together with pointed claws on the middle and hind legs; and (v) unique shape of genitalia characterized by deeply separated, stick-like penis lobes and a markedly elongated gonostyli segment I. Adult morphological characters show affinities between the fossil Chibiphemera gen. nov. and extant South African and Malagasy genera of Teloganodidae. Plesiomorphies in the forewings and genitalia of Chibiphemera gen. nov. suggest an early diverged position within the family. Additionally, we re-examine the holotype of the Cenozoic species Teloganella gurhaensis Agnihotri et al., 2020, originally described from a single larva from the late Palaeocene–early Eocene Palana Formation (India), and redescribe it. It is defined by larval characters such as (i) a broad pronotum protruding anterolaterally, (ii) strongly expanded femora that are widest centrally, (iii) tibiae moderately widened distally, (iv) robust, hooked pretarsal claws, (v) a small, styliform gill I attached to abdominal segment I near its outer margin medially, and (vi) the presence of three caudal filaments. We establish a monotypic genus Bharataganodes gen. nov. for Bharataganodes gurhaensis (Agnihotri et al., 2020) comb. nov., and discuss its systematic position within Teloganodidae and its relationships with other genera.

conclusionsTogether, these fossils support a Gondwanan origin for Teloganodidae and highlight the importance of the Burma Terrane and the Indian Plate as key dispersal routes for aquatic insects across the Tethys to Asia during the Mesozoic–Cenozoic transition.