Back to the sea
Reptiles that had conquered land swim back out
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Ichthyosaurs, plesiosaurs and mosasaurs represent three independent returns to the sea among reptiles, and whales and seals did the same among mammals much later. The convergence is striking: ichthyosaurs evolved a body shape almost identical to a dolphin's without being related. Svalbard has yielded some of the world's richest finds, notably from the Slottsmøya Member of the Agardhfjellet Formation. That they gave live birth is documented in fossils caught at the moment of delivery — the amniotic egg cannot be laid in water.
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It took a hundred million years to get out of the water. Then some reptiles turned around and went back. Legs became flippers, the body became streamlined, and they gave birth in the water instead of laying eggs. Some of the finest fossils of them have been found on Svalbard.
Connects to
Part of Terra Saga — the story of Earth on a timeline. terrasaga.org