Dinosauromorpha is a clade of avemetatarsalians (archosaurs closer to birds than to crocodilians) that includes the Dinosauria (dinosaurs) and some of their close relatives.

[7] Contrary to Novas, most paleontologists since 1992 have considered herrerasaurids to be true dinosaurs, though many other dinosaur-like reptiles still fall within his definition of Dinosauriformes.

[7] Nesbitt (2011) provided a roughly equivalent definition, using Marasuchus and Passer domesticus (the house sparrow, a representative of dinosaurs).

A phylogenetic analysis by Andrea Cau in 2018 resolved two different topologies for dinosaur origins, depending on whether it was run using parsimony or bayesian inference.

Cau coined the term Dracohors for the clade uniting all taxa closer to the theropod Megalosaurus bucklandi than the basal form Marasuchus lilloensis.

However, under bayesian results, Herrerasauria placed outside Dinosauria within Dracohors, and Dinosauriformes, Dinosauromorpha, and Pan-Aves were synonyms, with Marasuchus in a clade with lagerpetids.

Cau identified the synapomorphies of Dracohors as:[8]The anterior tympanic recess, the axial epipophyses, the centrodiapophyseal laminae in the presacral vertebrae, the relative size enlargement of the postacetabular process of ilium, the elongation of the pubis, the proximal sulcus and the reduction of the ligament tuber in the femoral head, and the further reduction in length of the fourth metatarsal and toe compared to the third.

Following the discovery and description of more cranial and postcranial material of the genera Kongonaphon, Ixalerpeton and Lagerpeton, it was found that lagerpetids shared many features with the basal taxa of Pterosauria.

Features of the maxillary bone, teeth, braincase and forelimb meant that the 2020 phylogenetic analysis of Ezcurra and colleagues placed Lagerpetidae next to pterosaurs within Pterosauromorpha, removing the family from Dinosauromorpha.

[9] Simultaneously, Rodrigo Müller and Maurício Garcia published novel results that reduced the family Silesauridae to a grade of basal dinosaurs in Ornithischia.

It has been variously found as the direct sister taxon of Dinosauria, the basalmost ornithischian, a basal theropod,[17] or a deeply-nested sauropodomorph.