If anything could be more embarrassing than dying while having sex, it might be being preserved in flagrante delicto for millions of years so that members of an advanced species could dig you up, gawk at you, and write a journal paper about your final romantic encounter. For a group of ancient turtles, this nightmare just came true.
Online Wednesday in Biology Letters, paleontologists describe nine couples of a species of aquatic turtle that perished while copulating and that were then preserved -- the first such record among vertebrates, the researchers say. Far from a mere salacious look at the unfortunate reptiles, the fossils provide critical clues about the environment in which they lived.
For decades the Messel pit, a fossil site in west-central Germany, has yielded extraordinarily well-preserved remains. The fossils include complete skeletons of creatures ranging in size from rodents to pygmy horses, as well as insects and feathers that still have hints of their original colors. The oily shale that entombs those fossils was laid down as lake sediments about 47 million years ago, says Walter Joyce, a vertebrate paleontologist at the University of Tübingen in Germany. Although the site has yielded tens of thousands of fossils, only the saucer-sized turtles have been found in pairs.
While some researchers have speculated that the animals died while copulating, the new analysis is the first to provide strong evidence -- revealing, for instance, that each pair includes a male and a female. Male turtles of this species, like many of their modern relatives, have longer tails than females, says Joyce. Also, males are typically smaller than females, a trend clearly seen in the fossils. Finally, in seven of the nine pairs, the turtles are in direct contact along the edge of their shells just above their tails -- and in two of those pairs, the male's tail wraps below the female's shell in mating position.