Dysalotosaurus

Type Species: Dysalotosaurus lettowvorbecki

Classification: Dinosauria – Ornithischia – Ornithopoda – Iguanodontia – Dryosauridae 

Time Period: Late Jurassic 

Location: Africa

Diet: Herbivore   

The ‘uncatchable lizard’ lived in Africa during the Tithonian stage of the Late Jurassic. This gazelle-like ornithopod traveled in herds and lived in the shadow of larger herbivores such as the stegosaur Kentrosaurus and the sauropods Dicraeosaurus and Giraffatitan. As flocks of Dysalotosaurus scurried about the semi-arid coastal environment laced with lagoons and brackish rivers and lakes, they would need to keep an eye out for predators such as the spinosaurid Ostafrikasaurus and the carcharodontosaur Veterupristisaurus. This small ornithopod was only eight feet long and weighed 180 pounds, and it lacked the thumb spikes associated with later iguanodonts. It was adapted for running about on two legs, as implied by its short front limbs, powerful and long hind limbs, and long, counter-balancing tail. That this lithe ornithopod was numerous is seen in the thousands of bones and fragments that have been recovered from the Tendaguru Formation in Tanzania; some scientists believe these remains are from a herd that died and was buried in a cataclysmic event (not too noteworthy, given the intense volcanism of the Jurassic). Interestingly, all rather complete specimens of this dinosaur belong to juveniles; from their specimens we can determine that their dentition (teeth and jaws) changed as they grew, changes that would make sense if juveniles had an omnivorous diet whereas more mature individuals were herbivorous. Bone analysis indicates that their growth rates were similar to that of a modern kangaroo. In one specimen, evidence of scoliosis was present; while all vertebrates are known to suffer this defect, Dysalotosaurus was the first dinosaur to have evidence of it.

For much of the 1900s, Dysalotosaurus was believed to be synonymous with its closely-related cousin Dryosaurus of North America; more recent studies, however, have determined that it was its own genera. It’s classified as a dryosaurid, a type of primitive iguanodont. Iguanodonts belong to a clade that includes most ornithopods, as well as the duck-billed hadrosaurs. The iguanodonts became the most widespread and diverse herbivore lineage of the Cretaceous, but in the Jurassic they were Little Leaguers compared to the stegosaurs and sauropods.