Oak Lizard

Dryosaurus altus was a graceful ornithopod dinosaur that inhabited the lush river valleys and fern prairies of Late Jurassic North America approximately 155-150 million years ago. Standing about 1.2 meters tall at the hip and reaching lengths of 3-4 meters, this lightweight herbivore possessed a slender, athletic build perfectly adapted for rapid locomotion. Its elongated hind limbs, with tibiae longer than femora, indicate exceptional running capabilities—a crucial adaptation for evading formidable predators like Allosaurus and Ceratosaurus that shared its ecosystem.

The skull of Dryosaurus featured a distinctive beaked premaxilla lacking teeth, ideal for cropping vegetation, while rows of leaf-shaped cheek teeth processed tough Jurassic plants. Large orbits suggest keen eyesight, likely beneficial for detecting approaching threats. The forelimbs were proportionally short with five-fingered hands, though the animal was obligately bipedal.

Discovered during the famous Bone Wars era, Dryosaurus remains have been recovered primarily from Dinosaur National Monument and other Morrison Formation localities. The genus holds scientific significance as a key representative of basal ornithopods, helping paleontologists understand the evolutionary trajectory leading to later ornithopods like Iguanodon and the hadrosaurs. Multiple growth stages are known, providing valuable insights into ornithopod ontogeny and population dynamics in Jurassic ecosystems.