Convolosaurus marri (Andrzejewski, Winkler and Jacobs 2019; SMU 72834; 2.5m in length) informally nicknamed the "Proctor Lake hypsilophodont", this specimen is known from a flock of subadults. Originally considered a basal ornithopod, here Convolosaurus nests with Agilisaurus at the base of the dome-skulled dinosaurs, the pachycephalosaurs. Note the deep jugal, U-shaped quadratojugal, nearly anterior nares, twin supraoccipitals, tiny hands.

Agilisaurus louderbacki (Peng 1990, Barrett, Butler and Knoll 2005; ZDM T6011; Middle Jurassic) was originally considereded a basal ornithischian, but later considered a sister to Heterodontosaurus. Here it nests between Heterodontosaurus and Stegoceras (below). Note the anteriorly facing nares, the two part palpebral bones, the rise of the posterior skull. A small head, long neck, short torso, long tail and much longer hindlimbs than forelimbs characterize the post-crania of Agilisaurus, precursor traits to the pachycephalosaurs.

Stegoceras validum (Lambe 1902, Late Cretaceous, Late Campanian, 75mya, 2m length) was a dome-head dinosaur, a pachycephalosaur derived from a sister to Agilisaurus. Traditionally pachycephalosaurs have been linked to to stegosaurs, like Stegosaurus, troodontids like Sinornithoides, and ceratopsians, like Triceratops, but those are not supported in the large reptile tree.

In Stegoceras the nares face forward, as in Agilisaurus. Similarly the forelimbs are tiny on this biped. The palpebral bones are incorporated into the skull itself. The antorbital fenestra is no longer visible. The dorsal and caudal ribs are quite wide, giving this dinosaur a wider than deep torso and tail. The posterior tail is stiffened with ossified tendons.