Darwinius is a genus within the infraorder Adapiformes, a group of basal strepsirrhine primates from the middle Eocene epoch.
Darwinius is the only known species, Darwinius masillae, lived approximately 47 million years ago (Lutetian stage) based on dating of the fossil site.
The only known fossil, called Ida, was discovered in 1983 at the Messel pit, a disused quarry near the village of Messel, about 35 km (22 mi) southeast of Frankfurt, Germany. The fossil, divided into a slab and partial counterslab after the amateur excavation and sold separately, was not reassembled until 2007. The fossil is of a juvenile female, approximately 58 cm (23 in) overall length, with the head and body length excluding the tail being about 24 cm (9.4 in). It is estimated that Ida died at about 80–85% of her projected adult body and limb length.
The genus Darwinius was named in commemoration of the bicentenary of the birth of Charles Darwin, and the species name masillae honors Messel where the specimen was found. The creature appeared superficially similar to a modern lemur.
The authors of the paper describing Darwinius classified it as a member of the primate family Notharctidae, subfamily Cercamoniinae, suggesting that it has the status of a significant transitional form (a "link") between the prosimian and simian ("anthropoid") primate lineages. Others have disagreed with this placement.
Concerns have been raised about the claims made about the fossil's relative importance and the publicising of the fossil before adequate information was available for scrutiny by the academic community.
Some of Norway's leading biologists, among them Nils Christian Stenseth, have called the fossil an "exaggerated hoax" and stated that its presentation and popular dissemination "fundamentally violate scientific principles and ethics."