Insects such as crickets and grasshoppers rub wing structures – a stridulatory ridge with tiny teeth and a hard edge – against one another to produce sounds. Pitch and rhythm depend on the number and spacing of the teeth on the stridulatory ridge, as well as the shape and movement of the wings. Thorin Jonsson’s Chinese research partners have discovered extremely well-preserved fossils of nine different grasshopper species that lived at the same time in the same region, namely during the Middle Jurassic period in what is now Inner Mongolia. The ‘sound-producing structures’ are so clearly visible on these fossils that the biologists were able to reconstruct the pitches and the fundamental syllables – that is, the smallest ‘musical’ units – of the mating calls through various analyses, simulations and AI-assisted evaluations.
“Our findings reveal a wide variety of call frequencies. Several species produced pure, low-pitched sounds like modern crickets, whilst others produced higher frequencies, similar to our native leafhoppers,” reports Jonsson. One species surprised the researchers: it communicated in the ultrasonic range – 100 million years before bats evolved. “This allowed us to demonstrate that the world during the Jurassic Period was acoustically far richer and more diverse than previously thought,” the biologist summarises.
Thorin Jonsson is conducting the research as part of the “Small Wings, Loud Songs” project, funded by the Austrian Science Fund (FWF), in collaboration with colleagues from the UK, China and the USA. The paper “Reconstruction of an extinct soundscape reveals ultrasonic communication in the Jurassic” has been published in the latest issue of the journal PNAS.