Record of Palaeozoic pseudoscorpions

Abstract

PSEUDOSCORPIONS (Class Arachnida; Order Pseudoscor-piones) represent a diverse and abundant group of small predatory arthropods^1–4. Approximately 3,000 living species occupy habitats ranging from sea level to 5,000 metres elevation. Until now, the fossil record of the group extended back only 35 million years, to the Oligocene, where nearly 30 species, all in extant families, have been described from the Baltic Amber⁵. Addition pseudoscorpions have been described from the younger Dominican⁶ and Mexican⁷ ambers, and they too are all assignable to modern families. We now report the discovery of two pseudoscorpion specimens in Middle Devonian sediments near Gilboa, New York, USA. This find increases the documented age of the order more than 10-fold to ∼380 million years. Although the specimens cannot be assigned with certainty to any extant superfamily, their excellent state of preservation allows us to make numerous inferences concerning behaviour and ecology, such as silk use, grooming and tactile behaviour. The presence of certain well preserved structures indicates that Devonian pseudoscorpions were predatory, as are their modern counterparts. Our discovery provides further evidence that fully terrestrial arthropods coexisted with primitive vascular plants during the Middle Devonian.