ECHO (Evolutionary Convergence in Historical Oceans)

Ichthyosaurs evolved a fish-shaped body like whales, but with unexpectedly dense, heavy ribs

Thin sections from two ichthyosaur fossils and two toothed whales in Oslo found the extinct reptiles' ribs nonporous where a porpoise's and a beluga's are hollowed out, which points to two routes to one shape.