Boom and bust for ancient sea dragons

A new study by scientists from the University of Bristol's School of Earth Sciences, shows a well-known group of extinct marine reptiles had an early burst in their diversity and evolution - but that a failure to adapt in the long-run may have led to their extinction. Ichthyosaurs were fish-like reptiles that first appeared about 250 million years ago and quickly diversified into highly capable swimmers, filling a broad range of sizes and ecologies in the early Mesozoic oceans. However, this rapid pace didn't last long and an evolutionary bottleneck 200 million years ago, through which only one lineage of ichthyosaurs survived, led to much slower evolution in much of their long history. Dr Ben Moon , who led the research, published in the journal , said: "Ichthyosaurs are a fascinating group of animals to work on because they evolved so many adaptations for living in water very quickly: a fish-like body and tail fin, giving birth to live young rather than laying eggs, and lots of different feeding styles. "Because of this we expected to see a rapid evolution early after ichthyosaurs first appeared, but we were staggered by just how big this early burst was and how relatively short it was." There are over 100 known species of ichthyosaur from between 250-90 million years ago in the Mesozoic Era, when the infamous dinosaurs ruled the land and the seas were full of marine reptiles, the top predators that filled comparable roles to dolphins, orcas, and sharks in modern seas. The study used state-of-the-art computational methods and looked at two types of data, one covering skull size and the other including many features of ichthyosaurs' skeleton.