Dinosaurs dominated the Earth during the Mesozoic Era, from 252 to 66 million years ago, thriving on every continent and in many habitats, and although most became extinct, birds survived as their living descendants. Dinosaur Park preserves a Maryland ecosystem from 110 million years ago in which dinosaurs lived alongside crocodiles, insects, fish, and small shrew-like early mammal ancestors. Fossils from this Cretaceous world include Astrodon johnstoni, a long-necked plant-eating sauropod related to Brachiosaurus, with most local finds coming from juveniles; remains of a giant meat-eating theropod probably related to Acrocanthosaurus; feathered dromaeosaurs, swift hunters with hooked claws and stiffened tails; Ornithomimus affinis, an ostrich-like theropod that likely ate seeds, fruits, insects, and other small animals; Arundelconodon bottoni, a rare small Mesozoic mammal from the eastern United States that was probably nocturnal; and Priconodon crassus, a heavily armored plant-eating nodosaur that apparently preferred watery habitats.
