The parietal and frontal bones of Ixalerpeton polesinensis form a skull roof broader than that of most early dinosaurs. A large postfrontal fits laterally to the frontal, as more common to non-archosaur archosauromorphs []. Unlike dinosaurs [], I. polesinensis retains a frontal not excavated by the supratemporal fossa and a post-temporal opening not reduced to a foramen-sized aperture. Medial to that, a notch in the supraoccipital indicates the path of the middle cerebral vein, which also laterally pierces the braincase, dorsal to the trigeminal foramen. The lateral braincase wall hosts the anterior tympanic recess [] and a shallow depression on the caudoventral surface of the parabasisphenoid (also seen in Lewisuchus admixtus, Saturnalia tupiniquim, and Eodromaeus murphy) that resembles the semilunar depression of non-archosaur archosauriforms []. Comparisons to other dinosauromorphs [] indicate that I. polesinensis preserves pre-sacral vertebrae 6–20, the first two of which are longer and may correspond to the last neck vertebrae. The trunk series starts with transitional morphologies, including a trapezoidal second vertebra as in Marasuchus lilloensis []. Unlike silesaurids [] and most dinosaurs [], the lateral surface of the neural arches lack laminae radiating from the apophyses, and the caudalmost vertebra lacks the cranially inclined neural spines described for Lagerpeton chanarensis []. The two-vertebrae sacrum fits the archosaur plesiomorphic pattern []. The ilium has a fully closed acetabulum, the caudal margin of which bears an antitrochanter. This is continuous to the ischial antitrochanter, which forms the entire acetabular margin of the bone, as in L. chanarensis []. Ixalerpeton polesinensis also shares an extensive ventromedial flange of the ischium with the latter taxon, forming the laminar symphysis and a deep articulation with the pubis. Its femur has various lagerpetid [] traits such as a large caudomedial tuber of the proximal portion, a lateral emargination ventral to the head, and a large tibiofibular crest separated from the lateral condyle by a deep groove. The fourth trochanter forms a large crest, differing from that of Dromomeron spp [].

The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms.

22 Sereno P.C.

Martínez R.N.

Alcober O.A. Osteology of Eoraptor lunensis (Dinosauria, Sauropodomorpha).

14 Nesbitt S.J. The early evolution of archosaurs: relationships and the origin of major clades.

23 Yates A.M. A new theropod dinosaur from the Early Jurassic of South Africa and its implication for the early evolution of theropods.

23 Yates A.M. A new theropod dinosaur from the Early Jurassic of South Africa and its implication for the early evolution of theropods.

24 Yates A.M. The first complete skull of the Triassic dinosaur Melanorosaurus Haughton (Sauropodomorpha:Anchisauria).

25 Pol D.

Garrido A.

Cerda I.A. A new sauropodomorph dinosaur from the Early Jurassic of Patagonia and the origin and evolution of the sauropod-type sacrum.

14 Nesbitt S.J. The early evolution of archosaurs: relationships and the origin of major clades.

15 Langer M.C.

Benton M.J. Early dinosaurs: a phylogenetic study.

15 Langer M.C.

Benton M.J. Early dinosaurs: a phylogenetic study.

14 Nesbitt S.J. The early evolution of archosaurs: relationships and the origin of major clades.

15 Langer M.C.

Benton M.J. Early dinosaurs: a phylogenetic study.

15 Langer M.C.

Benton M.J. Early dinosaurs: a phylogenetic study.

14 Nesbitt S.J. The early evolution of archosaurs: relationships and the origin of major clades.

14 Nesbitt S.J. The early evolution of archosaurs: relationships and the origin of major clades.

15 Langer M.C.

Benton M.J. Early dinosaurs: a phylogenetic study.

Buriolestes schultzi lacks usual sauropodomorph traits such as a reduced skull and an enlarged external naris []. As in all early dinosaurs [], the frontal is excavated by the supratemporal fossa. A sharp ridge forms the ventral border of the antorbital fenestra, as is typical of neotheropods [], but a subnarial gap and/or diastema is lacking in the premaxilla-maxilla junction. The dentary tip resembles those of other Carnian sauropodomorphs, with 2–3 large foramina and the ventrally sloping surface housing the first two teeth. Most teeth are caudally curved, with serrations (six per millimeter) forming straight angles to the crown margin, but these are not seen in the mesial carina of the elongate rostral teeth, a feature also reported for some neotheropods []. As typical of sauropodomorphs [], the humerus is longer than 60% the length of the femur, and the deltopectoral crest extends for more than 40% of its length. The last of the three sacral vertebrae lacks dorsoventrally expanded ribs and, as in Saturnalia tupiniquim and Plateosaurus engelhardti [], was surely incorporated from the tail series. The iliac preacetabular ala is short and dorsoventrally expanded, whereas the long postacetabular ala is ventrally excavated by a brevis fossa. The ventral margin of the acetabular wall is plesiomorphically straight [], as in Panphagia protos and S. tupiniquim. The pubic shaft is straight, laminar, and slightly expanded at the distal end, lacking typical traits found in major dinosaur groups [], e.g., sauropodomorph “apron,” theropod “boot,” ornithischian retroversion. The femoral head is expanded and kinked, as typical of dinosaurs [], but not completely inturned (states 304-2 and 305-1 in []). The iliofemoral musculature attaches to a subtle anterior trochanter and a marked trochanteric shelf. The tibia is slightly longer than the femur, but not as much as in early ornithischians and theropods, which also have an expanded outer malleolus [], absent in B. schultzi. As in most non-theropod saurischians [], the calcaneum is proximodistally flattened and has a reduced tuber. The third metatarsal is the longest, as is typical of dinosaurs [], and the fifth element is proximally expanded. The distalmost of the 42 preserved tail vertebrae lack elongated prezygapophyses, differing from those of Tawa hallae, herrerasaurids, and neotheropods [].