Caught in the act: the first record of copulating fossil vertebrates

Fossilized pairs of the carettochelyid turtle Allaeochelys crassesculpta from the Eocene Messel Pit Fossil Site, Germany, represent the first recorded instances of fossil vertebrates caught in copulation. This discovery challenges assumptions about taphonomy and lake ecology at Messel. Unlike typical indirect behavioral inferences, these mating pairs suggest that the turtles initiated copulation in habitable surface waters before perishing when their skin absorbed toxins while sinking into deeper, lethal layers. The findings support a stratified volcanic maar lake model with distinct inhabitable and toxic zones, providing unprecedented insight into ancient vertebrate behavior and paleoenvironmental conditions.

Joyce, W. G., Micklich, N., Schaal, S. F. K., & Scheyer, T. M. (2012). Caught in the act: the first record of copulating fossil vertebrates. Biology Letters, 8(5), 846–848. https://doi.org/10.1098/rsbl.2012.0361