Embracing for eternity

It is the first time fossils of vertebrates - animals with backbones that include ourselves - have been caught in the act!Nine pairs of frisky fossils - the females identified by their shorter tails - were found in a the Messel Pit, near Darmstadt in Germany.
It is believed the copulating couples were overcome by poisonous gas at the bottom of a volcanic crater.

Dr Walter Joyce, of the University of Tuebingen, Germany, said the turtles belonged to an extinct species known as Allaeochelys crassesculpta.Anatomical evidence revealed that each couple contained male and a female. Their upper shell would have reached almost two feet in length and been more than a foot wide.

Males had much longer tails protruding beyond the margin of the shell, whereas the females' were short enough to remain inside.Dr Joyce said: 'We demonstrate for the first time all couples contain one male and one female individual and the tails of some males are aligned with those of the female.'
It is believed volcanic gases were emitted from the lake from time to time and caused the death of many animals that lived in and around it which is why so many fossil vertebrates have been found in the sediment.

Dr Joyce, whose findings are published in the Royal Society journal Biology Letters, said: 'The behaviour of fossil organisms can typically be inferred only indirectly, but rare fossil finds can provide surprising insights.

'Here, we report numerous pairs of the fossil turtle Allaeochelys crassesculpta that represent for the first time among fossil vertebrates couples that perished during copulation.
'In our opinion, it is implausible that the A. crassesculpta couples found at Messel would actively swim, court and finally mate in poisonous surface waters or ingest poisonous surface waters only while mating.

'We propose, instead, that the turtles initiated copulation in habitable surface waters, perished when their skin started to absorb poisons while sinking during their embrace into deeper portions of the lake made toxic from the build up of volcanic gases or decay of organic matter, and fully or partially separated once they reached the bottom of the lake.'
He added: 'The mating pairs from Messel are therefore more consistent with a stratified, volcanic maar lake with inhabitable surface waters and a deadly abyss.'

Fifty million years ago the Messel Pit comprised a large series of lakes surrounded by lush, sub-tropical forests that supported an incredibly diverse range of lifeforms.

While most other such sites are lucky to contain partial skeletons, the pit boasts extensive preservation, even going so far as to preserve the fur, feathers, and 'skin shadows' of some species. And the diversity is no less astonishing, thanks in part to the periodic gas attacks.

This includes more than 10,000 fossilized fish of numerous species, thousands of aquatic and terrestrial insects, some with distinct colours still preserved, a plethora of small mammals including pygmy horses, large mice and armadillos, along with bats.

A large number of birds, particularly predatory species, have also been discovered as well as crocodiles, frogs, salamanders and other reptiles or amphibians.
The Messel Pit was declared a UNESCO World Heritage site in December 1995.