An international scientific team, notably from the Institut de Systématique Évolution et Biodiversité ( ISYEB ), has just identified the smallest species of singing cricket ever described, whether fossil or present-day, in opaque amber from the Cretaceous period (around 100 million years ago - Ma) in the Charentes region of France.
Fossils are essential markers in the study of evolution, validating the presence in the past of zoological groups, morphological characters or behaviours. They are often incomplete, especially the oldest ones. In the case of Orthoptera insects (crickets, grasshoppers, crickets), pre-Cenozoic fossils (prior to 66 Ma) consist mainly of isolated wings or partial footprints, and the few whole fossils found in amber are mostly juveniles.
Non-invasive X-ray microtomography analysis of an opaque amber fragment dating from the Cretaceous (100 Ma) has revealed two remarkably well-preserved adult crickets, belonging to two new species for science. Palaeonemobius occidentalis and Picogryllus carentonensis are thus the oldest known representatives of two worldwide subfamilies of crickets, respectively the Nemobiinae (Trigonidiidae) and the Podoscirtinae (Oecanthidae).
Another rare discovery: with a body length of 3.3 mm, Picogryllus carentonensis is not only the smallest cricket ever found, present or fossil, but also possesses a complete stridulatory apparatus. Given its size, this species must have called at much higher frequencies than present-day crickets. High-frequency emission in insects is often correlated with strong selection pressure, particularly from bats, which didn’t appear until 50 million years later. This species of cricket therefore already had to contend with predators capable of detecting acoustic emissions, attesting to the antiquity of prey-predator relationships and their influence on the evolution of species and their modes of communication.
New Cretaceous crickets of the subfamilies Nemobiinae and Podoscirtinae (Orthoptera, Grylloidea: Trigonidiidae, Oecanthidae) attest the antiquity of these clades Laure Desutter-Grandcolas, Hugo Josse, Marie Laurent, Lucas Denadai de Campos , Sylvain Hugel, Carmen Soriano, André Nel and Vincent Perrichot.
Revelation of the smallest singing cricket in a 100-million-year-old amber fragment from the Charentes region of France