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ILLUSTRATION BY BOB NICHOLLS
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By Victoria Jaggard, SCIENCE Executive Editor
I’ve been told on more than one occasion that I live with a large cat. Felix is not a chonker—he weighs just nine pounds—but he is built tall and lanky, coming in at about 32 inches from head to tail tip. His size is even more noticeable in my petite presence: A neighbor who saw me carrying him said had never seen such a large cat-to-human ratio. Amazingly, though, domestic cats can get much bigger, as the caretakers of any ragdolls, Maine Coons, or Norwegian forest cats can no doubt attest. And within the feline family, Siberian tigers reign supreme as the biggest of the big cats, stretching more than 10 feet long.
So what spurs groups of animals to go through evolutionary growth spurts? It’s a fascinating question, especially when you dive into the fossil record. Today’s blue whale holds the crown for heaviest animal that ever lived, but getting there was not a linear path. Based on ancient bones, we know that multiple lineages of whales grew large relatively recently in their evolutionary history, perhaps due to changes in climate that affected their food supply.
This week paleontologists in the U.K. added more fuel to the fire with the discovery of a prehistoric “sea monster” called an ichthyosaur that is now one of the largest and most complete of its kind. This leviathan (illustrated above) was more than 30 feet long and lived 180 million years ago during the Jurassic period. The combo of age and size makes this animal particularly exciting, Riley Black reports, because until now most of the giant ichthyosaurs dated to a much older time period in the Triassic. “As in whales, ichthyosaurs reached gigantic sizes more than once in different lineages throughout their history,” says Jorge Velez-Juarbe of the Natural History Museum of Los Angeles County.
Studying the newfound fossil and what it was eating can offer insights into why ichthyosaurs repeatedly ballooned in size. That in turn can help scientists better understand the role large marine predators played in the prehistoric seas—and how changes to modern oceans might affect the giants that ply the seas today.
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