Nearly 99 million years ago, two harvestmen—known to some as daddy longlegs—decided to have sex. Little did they know that their final act would still be preserved today, enshrined in amber in striking detail. The fossil, which shows one ancient arachnid at the moment its penis was fully extended (above), offers a rare example of Cretaceous copulation. Male harvestmen have a retractable penis that spends most of its time tucked away inside its body—unfortunate for arachnologists, because these genitals are a great way to tell the difference between species. So this new mid-coitus fossil gives researchers a unique look at how ancient harvestmen are related to the species that exist today—and just how these ancestors were different. A study published yesterday in the journal Naturwissenschaften describes the fossil and places it in a new, extinct family of harvestmen, based partially on its unusual penis, which sports a spatula-shaped tip. The specimen also has very large eyes, a trait that the researchers say may have been common in the Dyspnoi suborder to which this ancient harvestmen species belongs.