Determining the acoustic ecology of extinct or rare species is challenging due to the inability to record their acoustic signals or hearing thresholds. This species is one of only eight remaining members of an ancient family with over 90 extinct species that dominated the acoustic landscape of the Jurassic. Only a single confirmed specimen of Prophalangopsis obscura is known, the 150-year-old type specimen at the London Natural History Museum.
Using Laser-Doppler Vibrometry, 3D surface scans, and known scaling relationships, we discovered that P. obscura produces a pure-tone song at a frequency of ~4.7 kHz. This frequency range is distinct but comparable to the calls of Jurassic relatives, suggesting a limitation of early acoustic signals in insects to sonic frequencies (<20 kHz).