Ornithopods

Ornithopods were bipedal. This is why their name means 'bird foot'. They were similar to cattle in the fact that they grazed on vegetation using beaks. They then ground up that vegetation with teeth similar to molars. Ornithopods split into five different groups. These are Fabrosauridae, Heterodontisauridae, Hypsilophodontids, Iguanodontids and Hadrosauridae. The  Fabrosauridae were the earliest of these groups and were small and light with an average length of 60-120 centimetres. Heterodontosaurs developed horny beaks and different teeth. Hypsilophodontids were one of the largest dinosaur groups and were likely fast runners. They ranged in length from 1.5-7 metres. Iguanodontids ranged from medium to large sizes with special teeth made especially for grinding food. Hadrosaurs (or duck billed dinosaurs) had beaks like a duck's. Hadrosaurs split down further in to two more groups, one of these being Lambeosaurines with their bony crests placed on the back of their skull. They are believed to have been the most populated group of dinosaurs in North America during their time.  They are known to have cared for their young and live in large herds.