The three T’s include an 11-foot-tall two-year-old, the youngest known T fossil in the world. A 20-foot-tall, 13-year-old T weighed about 1,800 kg when it died. Thomas is the oldest at 17 and was 34 feet long and weighed nearly 73,200 kg. It is about 70 percent complete and has never been on exhibit before. All three fossils were found in the badlands of Montana. Three hundred fossils and 17 other dinosaur skeletons will be on display in the hall, which nearly doubles the museum’s dinosaur display space. Admission ranges from $5 to $12. Members and children under 4 are free.