Acanthopholis: Akylosaur from the early Cretaceous period found in England; this quadruped plant-eater measured approximately 4.5m / 14 feet long.
Acrocanthosaurus: Carnosaur from the early Cretaceous period found in North America; this bipedal meat-eater measured approximately 12m / 40 feet
Alamosaurus Sauropod from the late Cretaceous period found in North America; this quadruped plant-eater measured approximately 15m / 50 feet long.
Albertosaurus / Gorgosaurus: Carnosaur from the late Cretaceous period found in North America; this bipedal meat-eater measured approximately 9m / 30 feet long.
Allosaurus: Carnosaur from the Jurassic period found in North America, Australia, Africa & Asia; this bipedal meat-eater measured approximately 13m / 45 feet long.
Anatosaurus: Hadrosaur from the late Cretaceous period found in North America & England; this bipedal duck-billed plant-eater measured approximately 9m / 30 feet long.
Ammosaurus: Prosauropod from the late Triassic or early Jurassic period found in North America; this quadruped plant-eater measured approximately 2m / 7 feet and could walk on two legs.
Anchiceratops: Ceratopsian from the late Cretaceous period found in North America; this quadruped plant-eater measured approximately 5m / 16 feet.
Andylosaurus: Andylosaur from the early Cretaceous period found in North America; this quadruped plant-eater measured approximately 7.5m / 25 feet long and 1.2m / 4 feet tall.
Archaeopteryx: European crow-size bird from the Jurassic period discovered in Germany; this bird looked like a small dinosaur with wings and feathers.
Bagaceratops: Ceratopsian from the late Cretaceous period found in Mongolia; this quadruped plant-eater measured approximately 1m / 3 feet long.
Barosaurus: Sauropod from the late Jurassic period found in North America & East Africa; this quadruped plant-eater measured approximately 27m / 90 feet long.