Dracohors

Dracohors is a clade of dinosauriform archosaurs that includes dinosaurs and silesaurids.[1] The oldest known dracohorsian is Asilisaurus, dating to about 245 million years ago in the Anisian age of the middle Triassic period.[2] According to Andrea Cau (2018), the synapomorphies of dracohorsians are:[1]

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.

Dracohors Temporal range: Middle Triassic–Present, 245–0 Ma PreЄ Є O S D C P T J K Pg N
Mounted skeleton of Asilisaurus, the oldest known dracohorsian.
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauriformes
Clade:	Dracohors Cau, 2018
Subgroups
†Saltopus †Silesauridae Dinosauria

Cau defined the group as the "most inclusive clade containing Megalosaurus bucklandii Mantell, 1827, but excluding Marasuchus lilloensis (Romer, 1971)."[1] A good consensus of phylogenetic work supports the sister grouping of silesaurids and dinosaurs,[2][3][4] but the interrelationships within Dinosauria have been debated. Of particular debate are the positions of various basal Triassic dinosaurs such as Eodromaeus, Daemonosaurus, Pisanosaurus,[5][6][7] and herrerasaurids;[1][8] and the interrelationships of the major dinosaur groups Sauropodomorpha, Theropoda, and Ornithischia.[9] The reason for this uncertainty is the taxon sampling size and the implications of how they affect the coding for the phylogenetic tree.[10] In his paper about the stepwise evolution of the avian bauplan, Cau (2018) found in the parsimony analysis polytomy between herrerasaur-grade taxa, Sauropodomorpha and the controversial Ornithoscelida. The Bayesian analysis, however, found a weak support for the sister grouping of a Dinosauria and Herrerasauria, but showed strong support for the dichotomy between Sauropodomorpha and Ornithoscelida as shown below:[1]