Examples include ceratopsians, "Bistahieversor", ornithopods, and sauropods. Neornithischia includes ornithopods, pachycephalosaurs, and ceratopsians. The main groups of ornithischians are ankylosaurians, ornithopods, ceratopsians, and pachycephalosaurians. The ornithischians divided into armoured thyreophorans and unarmoured ornithopods and marginocephalians. Historically, most indeterminate ornithischian bipeds were lumped in as ornithopods. Potential prey included ornithopods, stegosaurids, and sauropods. Paleontologists have discovered tracks or fossils from ankylosauria, ornithopods (including a Hadrosaurus), and theropods. Pleurokinesis refers to the complex multiple jointing thought to occur in ornithopods, such as hadrosaurs. Ankylosaurians and ornithopods were also becoming more common, but prosauropods had become extinct. Footprints indicate the presence of large ornithopods and pterosaurs as well. Other herbivorous groups like ornithomimids, therizinosaurs, pachycephalosaurs, small ornithopods, nodosaurids and ankylosaurids were also represented. It is a derived clade of iguanodontian ornithopods and contains the subgroup Styracosterna. Heterodontosaurids have also been seen as basal to both ornithopods and marginocephalians. Such plates are known from several other ornithopods and their cerapodan relatives. Ornithopods, bipedal herbivores, came in several types.