|Skeletal reconstruction showing known remains|
Cabreira et al. 2011
Cabreira et al. 2011
Pampadromaeus is known only from the holotype specimen ULBRA-PVT016, a disarticulated, partial but well preserved skeleton from a single individual which includes most of the skull bones and the lower jaws; dorsal, sacral and caudal vertebrae; elements of the shoulder girdle and the forelimbs, an ilium and elements of the hindlimbs. It was collected in the upper Hyperodapedon biozone from the Alemoa Member of the Santa Maria Formation (Rosário do Sul Group) in the "Janner" (also known as "Várzea do Agudo") locality, geopark of Paleorrota, dating to the Carnian faunal stage of the early Late Triassic, about 230-228 million years ago. A U-Pb (Uranium decay) dating found that the Santa Maria Formation dated around 233.23 million years ago, putting it 1.5 million years older than the Ischigualasto Formation, and making the two formations approximately equal as the earliest dinosaur localities.
Pampadromaeus was a small bipedal animal. It shows a mosaic of basal and derived traits. It differs from other sauropodomorphs by a combination of characters. Some of these are shared with members of the Theropoda: the premaxilla is pointed downwards forming a subnarial gap with the maxilla and the anterior-most teeth are unserrated; in the location where with theropods the fenestra promaxillaris is positioned, a small depression is present. Basal traits consist of a large skull, a short thighbone, the possession of just two sacral vertebrae and the presence of fifteen teeth in the pterygoid.
There were four teeth in the premaxilla and about twenty in both the maxilla and the lower jaw for a total of eighty-eight. The teeth were large, elongated, lanceolate, slightly recurved, sharply pointed and coarsely serrated. The lower leg was much longer than the thighbone, indicating Pampadromaeus was a good runner.
Pampadromaeus was first named by Sergio F. Cabreira, Cesar L. Schultz, Jonathas S. Bittencourt, Marina B. Soares, Daniel C. Fortier, Lúcio R. Silva and Max C. Langer in 2011 and the type species is Pampadromaeus barberenai. The generic name is derived from Quechua pampa, "plain", in reference to the present landscape of the site, and Greek δρομεύς, dromeus, "runner", referring to the cursorial habits; the Latinised spelling variant dromaeus is used. The specific name honours the Brazilian paleontologist Mário Costa Barberena.
Pampadromaeus was found to be a basal sauropodomorph in four different cladistic analyses. The describers emphasized however, that this position was not strongly supported, showing the difficulties of determining the affinities of such early forms with the basal Dinosauromorpha, Saurischia, Sauropodomorpha and Theropoda.
Averostra, or "bird snouts", is a clade that includes most theropod dinosaurs that have a promaxillary fenestra (fenestra promaxillaris), an extra opening in the front outer side of the maxilla, the bone that makes up the upper jaw. Two groups of averostrans, the Ceratosauria and the Orionides, survived into the Cretaceous period. When the Cretaceous–Paleogene extinction event occurred, ceratosaurians and two groups of orionideans within the clade Coelurosauria, the Tyrannosauroidea and Maniraptoriformes, were still extant. Only one subgroup of maniraptoriformes, Aves, survived the extinction event and persisted to the present day.Avetheropoda
Avetheropoda, or "bird theropods", is a clade that includes carnosaurians and coelurosaurs to the exclusion of other dinosaurs.Buriolestes
Buriolestes (meaning "Buriol's robber") is a genus of early sauropodomorph dinosaurs from the Late Triassic Santa Maria Formation of the Paraná Basin in southeastern Brazil. It contains one species, B. schultzi, named in 2016. The type specimen was found alongside a specimen of the lagerpetid dinosauromorph Ixalerpeton.Cerapoda
Cerapoda ("ceratopsians and ornithopods") is a clade of the dinosaur order Ornithischia.Dinosauriformes
Dinosauriformes is a clade of archosaurian reptiles that include the dinosaurs and their most immediate relatives. All dinosauriformes are distinguished by several features, such as shortened forelimbs and a partially to fully perforated acetabulum, the hole in the hip socket traditionally used to define dinosaurs. The oldest known member is Asilisaurus, dating to about 245 million years ago in the Anisian age of the middle Triassic period.Guaibasauridae
Guaibasauridae is a family of basal saurischian dinosaurs, known from fossil remains of late Triassic period formations in Brazil and Argentina.Haya griva
Haya is an extinct genus of basal neornithischian dinosaur known from Mongolia.Jeholosauridae
Jeholosaurids were herbivorous neornithischian dinosaurs from the Cretaceous Period (Aptian - Santonian, with a possible Campanian record) of Asia. The family was first proposed by Han et al. in 2012. The jeholosaurids were defined as those ornithischians more closely related to Jeholosaurus shangyuanensis than to Hypsilophodon foxii, Iguanodon bernissartensis, Protoceratops andrewsi, Pachycephalosaurus wyomingensis, or Thescelosaurus neglectus. The Jeholosauridae includes the type genus Jeholosaurus and Yueosaurus.Jingshanosaurus
Jingshanosaurus (meaning "Jingshan lizard") is a genus of sauropodomorph dinosaurs from the early Jurassic period.Melanorosauridae
The Melanorosauridae were a family of sauropodomorph dinosaurs which lived during the Late Triassic and Early Jurassic. The name Melanorosauridae was first coined by Friedrich von Huene in 1929. Huene assigned several families of dinosaurs to the infraorder "Prosauropoda": the Anchisauridae, the Plateosauridae, the Thecodontosauridae, and the Melanorosauridae. Since then, these families have undergone numerous revisions. Galton and Upchurch (2004) considered Camelotia, Lessemsaurus, and Melanorosaurus members of the family Melanorosauridae. A more recent study by Yates (2007) indicates that the melanorosaurids were instead early sauropods.Neotheropoda
Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs, and the only group of theropods who survived the Triassic–Jurassic extinction event. Yet all of the neotheropods became extinct during the early Jurassic period except for Averostra.Orionides
Orionides is a clade of tetanuran theropod dinosaurs from the Middle Jurassic to the Present. The clade includes most theropod dinosaurs, including birds.Orodrominae
Orodrominae is a subfamily of parksosaurid dinosaurs from the Cretaceous of North America and Asia.Riojasauridae
Riojasauridae is a family of sauropod-like dinosaurs from the Upper Triassic. It is known primarily from the genera Riojasaurus and Eucnemesaurus. Sites containing Riojasauridae include the Lower Elliot Formation of Orange Free State, South Africa (where fossils of Eucnemesaurus have been found), and Ischigualasto, in La Rioja Province, Argentina ( where fossils of Riojasaurus have been recovered).Saturnaliinae
Saturnaliinae is a clade of sauropodomorph dinosaurs found in Brazil and Argentina.
In 2010, Martin Ezcurra defined the subfamily Saturnaliinae for the clade containing Saturnalia and Chromogisaurus, which were found to be close relatives in several studies. While they are sometimes found to be a subgroup within the Guaibasauridae, other studies have found the saturnaliines to form an independent lineage at the very base of the sauropodomorph family tree. Langer and colleagues (2019) recovered Pampadromaeus and Panphagia as relatives of Saturnalia and Chromogisaurus, elevating Saturnaliinae to family rank as Saturnaliidae. They recovered Guaibasaurus as a basal theropod.Unaysauridae
Unaysauridae is a family of basal sauropodomorphs from the Late Triassic of India and Brazil.Xixiposaurus
Xixiposaurus is a genus of prosauropod dinosaur which existed in what is now Lower Lufeng Formation, China during the lower Jurassic period. It was first named by Sekiya Toru in 2010 and the type species is Xixiposaurus suni.Yueosaurus
Yueosaurus is an extinct genus of basal ornithopod dinosaur known from Zhejiang Province, China.