dinosauriforms

Dinosauriformes is a clade of archosaurs that includes the earliest relatives of dinosaurs and the dinosaurs themselves. The group comprises several early Triassic genera such as Asilisaurus, Lagosuchus, Marasuchus, and Silesaurus, as well as the broader family Silesauridae. Within Dinosauriformes, the lineage leading to true dinosaurs is one of the major branches, with Dinosauria representing the crown group. In many classifications, Silesaurids are considered close relatives of dinosaurs but lie outside Dinosauria; in others, Lagosuchus and Marasuchus are placed more basally within Dinosauriformes.

Anatomically, dinosauriforms show a mosaic of primitive archosauriform traits and features that foreshadow the dinosaur body plan. They typically exhibit an elongated hind limb and a posture capable of bipedal or facultatively bipedal locomotion, and they possess an astragalus and calcaneum ankle arrangement that is more advanced than in more primitive archosaurs. However, their skeletons are diverse, and not all lineages display the same degree of postural modernization.

The fossil record for dinosauriforms spans the Early to Middle Triassic, roughly 245 to 230 million years ago, with the earliest records found in landmasses of the ancient supercontinent Pangaea. They were generally small to medium-sized carnivorous or omnivorous animals, occupying various ecological niches that foreshadow later dinosaur-dominated ecosystems.

Dinosauriformes are of particular interest because they illuminate the origin and evolution of Dinosauria, highlighting transitional features and the ecological contexts that gave rise to true dinosaurs and their diversification in the Mesozoic.