Dryosaurus

a family group of Dryosaurus drink at a river beside a Stegosaurus
(never mind the presence of grass, which had yet to evolve)

Type Species: Dryosaurus altus  

Classification: Dinosauria – Ornithischia – Ornithopoda – Iguanodontia – Dryomorpha – Dryosauridae 

Time Period: Late Jurassic 

Location: United States 

Diet: Herbivore

Dryosaurus was an iguanodont ornithopod, though it was formerly classified as a hypsilophodont. Its name means ‘tree lizard,’ referring to the forested environment it inhabited (some people erroneously believe the name refers to its vague oak-leaf shaped cheek teeth). Dryosaurus could grow between eight to fourteen feet in length and could weigh up to two hundred pounds; because all known specimens are of creatures in various stages of growth, the maximum adult size is unknown. Dryosaurus had a long neck, slender legs, and a long, stiff tail that acted as a counterbalance when running. Its short arms had five fingers on each hand. Dryosaurus had a horny beak and cheek teeth, and some paleontologists believe it had cheek-like structures to prevent the loss of food while chewing. Living in the Morrison Formation, Dryosaurus was dwarfed by its titanic herbivorous brethren, sauropods such as Diplodocus, Brachiosaurus, and Supersaurus; larger ornithopods such as Camptosaurus; and massive stegosaurs such as Stegosaurus. It likely used speed as its best defense against large predators such as Allosaurus and Ceratosaurus, and it’s speculated that with its small size, it stuck to the overgrown conifer forests that would be difficult for larger animals to navigate. Thus if we were to step back in time to the Late Jurassic western United States and tour a deep conifer forest cut by streams with overgrown banks and littered with deep ponds teeming with crocodylomorphs and early amphibians, we might spy small herds of Dryosaurus roaming like deer through the trees and munching on ferns and cycads, safely tucked away from the giant theropods roaming the neighboring floodplains and valleys.