An insect † Archaeopteryx : Cretaceous amber fossil elucidates the evolution of complex host detection and ovipositor mechanisms in parasitoid woodwasps (Hymenoptera: Orussoidea)

Abstract We describe † Cretovelona orussopteryx n. gen. & sp., a female orussoid from mid‐Cretaceous Kachin amber. We examine the fossil with synchrotron scanning and integrate it into an existing morphological data set for Orussoidea. † Cretovelona is placed as sister to crown group Orussoidea by Bayesian phylogenetic analyses. It is unique in displaying a combination of plesiomorphic (e.g. 12 antennomeres, exposed ovipositor sheaths, partly internalized ovipositor that does not extend further than anterior part of abdomen) and apomorphic characters (e.g. antenna with club, fore tarsus 3‐segmented) that display intermediate stages in the evolution of the host detection mechanism and the fully internalized ovipositor in extant Orussidae. The wing venation of † Cretovelona is even more reduced than observed in extant Orussidae, likely correlated with the small body size (<2 mm). Tracing the changes in body size across the orussoid tree indicates that the stem group underwent a size reduction event in the Cretaceous, something that might have influenced character evolution in for example wing venation and internalization of the ovipositor. † Cretovelona is a rare example of a transitional fossil that elucidates the evolution of complex features when adapting to a highly specialized lifestyle, in this case detecting and targeting hosts deep inside wood. We propose to recognize only the family Orussidae within Orussoidea. Orussidae comprises the crown group Orussoidea, including all Cenozoic fossils described so far. The stem group taxa, all Mesozoic fossils, are not assigned to any specific family within Orussoidea. Zoobank Registration: urn:lsid: zoobank.org :pub:397F76A5‐7467‐4BCA‐9963‐6A380EC05200.