Ancient Turtles Fossilized During Sex
Nine ancient turtles died mid-coitus 47 million ago and became fossilized, giving scientists the earliest known glimpse into vertebrate sex. The turtles, described in the latest edition of the journal Biology Letters, did not all die at the same time, but likely drifted into poisonous waters during the act at separate times, researchers said.
"Many animals enter a trance-like state when mating or laying eggs and it is possible that these turtles simply did not notice that they were entering poisonous waters before it was too late," Walter Joyce, study author and researcher at the University of Tübingen in Germany, told Discovery News.
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Researchers discovered the fossils at the Messel Pit Fossil Site in Frankfurt, Germany, an area that consisted of a poisonous lake millions of years ago. Fossils of various animals that died there, such as birds, bats, fish, frogs, snakes, insects, have been found there.
Researchers analyzed the turtle fossils and found that each pair was made up of a male and female, which they were able to determine based on the animal's size. In addition, each pair had their rear-ends oriented to each other, much like modern turtles do when they mate. It's exceedingly rare for animals to be fossilized in the middle of any kind of act, but fossilization during sex has never been seen before, researchers said.
"No other vertebrates have ever been found like these, so these are truly exceptional fossils," Joyce told LiveScience. "The chances of both partners dying while mating are extremely low, and the chances of both partners being preserved as fossils afterward even lower. These fossils show that the fossil record has the potential to document even the most unlikely event if the conditions are right."
Researchers said it's odd that so many turtle pairs died while mating there, but said the turtles, which have permeable skin, likely died quickly due to the lack of oxygen in the ancient lake.
Tyler Lyson, director and president of the Marmarth Research Foundation, told Discovery News that the researcher's conclusion is sound, and that the fossils really do show ancient turtles having sex -- something never seen before.
"The argument is strong and the conclusions sound," he said. "We see similar sexual morphism in living turtles and the fact that there are so many pairs of turtles indicates they were copulating, sunk and died in the more anoxic waters."
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