Hybodontiformes

The Hybodontiformes radiated in the Triassic, and lived alongside modern elasmobranchs until the Late Cretaceous. The paired fins show signs of intrinsic musculature, and greater flexibility, implying that they were used in steering. They had a heterocercal tail, an anal fin and amphistylic jaw suspension. Hybodonts were also the first group to possess a heterodont dentition (= different shaped teeth along the length of the jaw). For instance, having sharp cutting teeth in the front part of their jaw and flat crushing teeth in the back part of the jaw allowed them to feed on a variety of food types. The Hybodontiforms also possessed a full set of hemal, as well as neural, arches around the notochord.