The World’s Largest Stegosaurus Comes to New York City

A hundred and fifty million years ago, an aging Stegosaurus lay down for the last time, settling in the mud of what is now northwestern Colorado. It had lived a comfortable life by dinosaur standards, without major bites or fights, though it did deal with possibly painful infections around the pelvis. It had some arthritis in its joints and the fused vertebrae of a mature adult.

That muddy area is known today as the Morrison Formation, and its geological strata are dense with fossils. (A nearby town is called Dinosaur, Colorado.) A swath of it is owned by Jason Cooper, a dino enthusiast, and a couple of years ago he spotted a bone protruding from an outcrop. It turned out to be a femur from (a) the largest Stegosaurus ever found and (b) a skeleton that was about three-quarters complete. Dug out, reassembled, and fitted with 3-D-printed replicas of its missing bones, the dinosaur was 27 feet long from skull to tail and more than 11 feet high. Cooper named it Apex for its dominating size, even though Stegosauri were vegetarian. We don’t know its precise species (there are at least three types of Stegosaurus) or its sex. Dr. Roger Benson, a paleontologist at the American Museum of Natural History, explained to me that determining the latter is usually almost impossible unless a skeleton has eggs inside.

Apex went up for auction at Sotheby’s this past summer with an estimate of $4 million to $6 million. (There is debate over sales like this. Diggers want a payday; scientists fear losses to their research.) Kenneth Griffin, the Citadel hedge-funder — who has no doubt dealt with a few apex predators himself — paid $44.6 million in a bidding war. He’s an AMNH benefactor, and Apex just went on view there, dramatically posed on its steel mounting at the Gilder Center entrance. It’s a four-year loan, after which Griffin can get Apex back, though it’s likely too big for his den.