Scutellosaurus lawleri (Colbert 1981; Breden et al. 2021; Triassic/Jurassic boundary ~200 mya, 1.2 m in length) has long been recognized as a basal thyreophoran, an herbivorous ornithischian dinosaur basal to other armored herbivores including, ankylosaurs and stegosaurs. Here Scutellosaurus was derived from as sister to Lesothosaurus and basal to Stegosaurus. But anklylosaurs like Minmi are derived from Scelidosaurus.

Distinct from Lesothosaurus, the skull of Scutellosaurus had an upturned premaxilla. While the illustration (above) appears to indicate a recessed cheek, that is actually the internal view of the maxilla. The maxillary and dentary teeth are denticulated (coarsely serrated). A tiny predentary may have been present or maybe not. The mandibular fenestra was a mere slit, on its way to disappearing.

The cervicals were smaller with shorter neural spines. Five sacral vertebrae were present. The tail was much longer.

The scapula was more rectangular. The humerus had a reduced proximal surface. Although preserved incompletely, the hand was likely more symmetrical with metatarsal 3 and digit 3 the longest.

The pelvis took a radical departure. The anterior ilium was elongated. The posterior ilium was expanded. The pubis rotated to align with the ischium, which was more slender distally. The femur was relatively shorter, no longer than the tibia. While foot preservation is incomplete PIL analysis indicates a reconstruction like that of Turfanosuchus is likely, but with longer metatarsals.

Ossified dermal scutes covered the torso and spine.

The rotation of the pubis in this herbivore is thought to have expanded the volume of the gut to facilitate the digestion of plant material. A quadrupedal configuration appears likelyt due to the length of the limbs and torso. Even so, Scutellosaurus could have risen to a bipedal configuration whenever necessary, enabled by the expansion of the sacral series and elongation of the ilium.