Behaviors are challenging to reconstruct for extinct species, particularly the nature and origins of acoustic communication. Here we unravel the song of Archaboilus musicus Gu, Engel and Ren sp. nov., a 165 million year old stridulating katydid. From the exceptionally preserved morphology of its stridulatory apparatus in the forewings and phylogenetic comparison with extant species, we reveal that A. musicus radiated pure-tone (musical) songs using a resonant mechanism tuned at a frequency of 6.4 kHz. Contrary to previous scenarios, musical songs were an early innovation, preceding the broad-bandwidth songs of extant katydids. Providing an accurate insight into paleoacoustic ecology, the low-frequency musical song of A. musicus was well-adapted to communication in the lightly cluttered environment of the mid-Jurassic forest produced by coniferous trees and giant ferns, suggesting that reptilian, amphibian, and mammalian insectivores could have also heard A. musicus' song.call evolution | Tettigoniidae | bushcricket | biomechanics | biological asymmetry K atydids produce species-specific calling songs that form part of the acoustic ecology of tropical forests (1, 2). The rubbing of a toothed vein on one wing against a plectrum on the other wing results in sound production by stridulation, exploiting resonant (musical) (3, 4) or nonresonant (broadband) (4, 5) biophysical mechanisms, depending on the species. Which of these two mechanisms represents ancestral sound production remains a key question in the evolution of insect acoustic communication (6)(7)(8). Here, we reconstruct the song of a katydid fossil with exceptionally well-preserved stridulatory structures, and find that musical singing at low frequencies was already established by the middle Jurassic (165 Ma). We describe this specimen as Archaboilus musicus, from the extinct family Haglidae (Orthoptera), a group basal to all extant katydids (9, 10). These findings imply that A. musicus was nocturnal, and that its call was adapted for long-range communication in an environment with light clutter (11). A recent paleobotanical reconstruction of the geometry, vegetation density, and biomass of the Jurassic Forest from northwest China (12) reveals an environment populated by coniferous trees (e.g., Araucaria) with nearest neighbor distances ranging from 1.5 to 20.3 m, and giant ferns (e.g., Angiopteris, Osmunda, and Caniopteris) occupying the lower layers of the understory forest. This forest architecture indicates a sparse vegetation density that is acoustically compatible with the proposition that the song frequency of A. musicus was well adapted to long-distance communication close to the ground. Such a forested environment would also enable long-range acoustic signaling and communication by other animals (e.g., amphibians, reptilians) as well as a variety of arthropod species (13).
Systematic PaleontologyInsecta Linnaeus, 1758; Orthoptera Olivier, 1789; Haglidae Handlirsch, 1906; Cyrtophyllitinae Zeuner, 1935; Archaboilus Martynov, 1937.Archaboilus musicu...