There are two families of hadrosaurs.
Hadrosaurs take their popular name from their toothless duck-like beaks at the front of their jaws.
Farther back into their jaws, however, lay hundreds of teeth, arranged in batteries to aid in the grinding of food. Most duckbills had the same general body plan, many weighing as much as an elephant. Their hind legs tended to be longer than their forelimbs and their toes were sometimes webbed and ended in hooves. They were probably placid animals, possibly travelling in herds. Halysiocrinus Halysiocrinus was a crinoid with a slender calyx and branching arms.