The 75-foot-long brontosaurus at the newly reopened Yale Peabody Museum in New Haven, Conn., is the same dinosaur that the natural history museum has had on display since 1931. Yet it looks different. A fresh pose. New front ribs. The head is repositioned at a more inquisitive angle. The museum’s four-year renovation not only refreshed the nearly 100-year-old building, but also included an overhaul of the fossil mounts that research has proved to be inaccurate.

The Peabody’s update —…