Sanjuansaurus Temporal range: Carnian ~ | |
---|---|
Holotype | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria (?) |
Clade: | Saurischia (?) |
Family: | † Herrerasauridae |
Genus: | † Sanjuansaurus Alcober & Martinez, 2010 |
Species: | †S. gordilloi |
Binomial name | |
†Sanjuansaurus gordilloi Alcober & Martinez, 2010 | |
Sanjuansaurus ("San Juan Province lizard") is a genus of herrerasaurid dinosaur from the Late Triassic (Carnian) Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina.
Sanjuansaurus was named and described in 2010 by Oscar Alcober and Ricardo Martinez. The type species was named S. gordilloi after Raul Gordillo, the head fossil preparator and artist of the San Juan Museum. It is known from and based on an associated and partially articulated partial skeleton (PVSJ 605) consisting of a jaw fragment, most of the vertebral column from the axis to the anterior tail, the shoulder blades, an ulna, part of the pelvis, most of the long bones of the legs, and a few other bones. [1]
PVSJ 605 was discovered in 1994, in gray-green sandstone 40 meters above the base of the Ischigualasto Formation, in Ischigualasto Provincial Park in San Juan, Argentina. An ash bed from the early part of the formation dates to approximately 231.4 Ma, during the late Carnian Stage of the Late Triassic. [1] The original description indicated that the skeleton was from the earliest part of the Cancha de Bochas Member, [1] though later sources suggested that it was from the upper La Peña member. [2] [3]
Sanjuansaurus was comparable in size to a medium-sized Herrerasaurus , with a thigh bone that was 395 millimetres (15.6 in) long and a tibia that is 360 millimetres (14 in) in length (in the description paper the tibia is listed with 260 mm in length due to a typo). [1] Alcober and Martinez performed a phylogenetic analysis and found Sanjuansaurus to be a herrerasaurid. [1] It was determined that Sanjuansaurus and Herrerasaurus share many similarities in the morphology of the skull, neck vertebrae, back vertebrae, hip vertebrae, scapula, and the hip bones. Alcober and Martinez observed that Sanjuansaurus and Staurikosaurus share many similarities in the morphology of the hip bones, and the tibia. [1] The pubis of Sanjuansaurus, unlike in other herrerasaurids, points toward the cranium.
A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism or group.
According to Alcober and Martinez (2010), Sanjuansaurus can be distinguished based on the following characteristics: [1]
In the Ischigualasto Formation, dinosaurs constituted only about 6% of the total number of fossils, [4] but by the end of the Triassic Period, dinosaurs were becoming the dominant large land animals, and the other archosaurs and synapsids declined in variety and number. [5]
Studies suggest that the paleoenvironment of the Ischigualasto Formation was a volcanically active floodplain covered by forests and subject to strong seasonal rainfalls. The climate was moist and warm, [6] though subject to seasonal variations. [7] Vegetation consisted of ferns ( Cladophlebis ), horsetails, and giant conifers (Protojuniperoxylon). These plants formed highland forests along the banks of rivers. [8] Sanjuansaurus lived in the jungles of Late Triassic South America alongside early dinosaurs, Eoraptor , Herrerasaurus , Chromogisaurus , and Panphagia , as well as Saurosuchus , [9] a giant land-living rauisuchian (a quadrupedal meat eater with a theropod-like skull); the broadly similar but smaller Venaticosuchus , an ornithosuchid; and the predatory chiniquodontids. Herbivores were much more abundant than carnivores and were represented by rhynchosaurs such as Hyperodapedon (a beaked reptile); aetosaurs (spiny armored reptiles); kannemeyeriid dicynodonts (stocky, front-heavy beaked quadrupedal animals) such as Ischigualastia ; and therapsid traversodontids (somewhat similar in overall form to dicynodonts, but lacking beaks) such as Exaeretodon . These non-dinosaurian herbivores were much more abundant than early ornithischian dinosaurs like Pisanosaurus . [10]
Eoraptor is a genus of small, lightly built, basal sauropodomorph dinosaur. One of the earliest-known dinosaurs and one of the earliest members of the sauropod family, it lived approximately 231 to 228 million years ago, during the Late Triassic in Western Gondwana, in the region that is now northwestern Argentina. The type and only species, Eoraptor lunensis, was first described in 1993, and is known from an almost complete and well-preserved skeleton and several fragmentary ones. Eoraptor had multiple tooth shapes, which suggests that it was omnivorous. Eoraptor was 1.5 feet (0.46 m) tall and 3 feet (0.91 m) long.
Sauropodomorpha is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had long necks and tails, were quadrupedal, and became the largest animals to ever walk the Earth. The prosauropods, which preceded the sauropods, were smaller and were often able to walk on two legs. The sauropodomorphs were the dominant terrestrial herbivores throughout much of the Mesozoic Era, from their origins in the Late Triassic until their decline and extinction at the end of the Cretaceous.
Staurikosaurus is a genus of herrerasaurid dinosaur from the Late Triassic of Brazil, found in the Santa Maria Formation.
Herrerasauridae is a family of carnivorous dinosaurs, possibly basal to either theropods or even all of saurischians, or even their own branching from Dracohors, separate from Dinosauria altogether. They are among the oldest known dinosaurs, first appearing in the fossil record around 233.23 million years ago, before becoming extinct by the end of the Carnian stage. Herrerasaurids were relatively small-sized dinosaurs, normally no more than 4 metres (13 ft) long, although the holotype specimen of "Frenguellisaurus ischigualastensis" is thought to have reached around 6 meters long. The best known representatives of this group are from South America, where they were first discovered in the 1930s in relation to Staurikosaurus and 1960s in relation to Herrerasaurus. A nearly complete skeleton of Herrerasaurus ischigualastensis was discovered in the Ischigualasto Formation in San Juan, Argentina, in 1988. Less complete possible herrerasaurids have been found in North America and Africa, and they may have inhabited other continents as well.
Herrerasaurus is likely a genus of saurischian dinosaur from the Late Triassic period. This genus was one of the earliest dinosaurs from the fossil record. Its name means "Herrera's lizard", after the rancher who discovered the first specimen in 1958 in South America. All known fossils of this carnivore have been discovered in the Ischigualasto Formation of Carnian age in northwestern Argentina. The type species, Herrerasaurus ischigualastensis, was described by Osvaldo Reig in 1963 and is the only species assigned to the genus. Ischisaurus and Frenguellisaurus are synonyms.
Ischigualasto Provincial Park, also called Valle de la Luna, due to its moon like appearance, is a provincial protected area in the north-east of San Juan Province, north-western Argentina, limiting to the north with the Talampaya National Park, in La Rioja Province. Both areas belong to the same geological formation, the Ischigualasto Formation . Established on 3 November 1971, the park has an area of 60,370 ha.
Pisanosaurus is an extinct genus of early dinosauriform, likely an ornithischian or silesaurid, from the Late Triassic of Argentina. It was a small, lightly built, ground-dwelling herbivore, that could grow up to an estimated 1 m (3.3 ft) long. Only one species, the type, Pisanosaurus mertii, is known, based on a single partial skeleton discovered in the Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina. This part of the formation has been dated to the late Carnian, approximately 229 million years ago.
Saurosuchus is an extinct genus of large loricatan pseudosuchian archosaurs that lived in South America during the Late Triassic period. It was a heavy, ground-dwelling, quadrupedal carnivore, likely being the apex predator in the Ischigualasto Formation.
Ischigualastia is an extinct genus of large dicynodont therapsids that lived during the Late Carnian age and the Early Norian age of the Late Triassic Period. The genus was found in and named after the Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina. It has been placed in the family Stahleckeriidae.
The Ischigualasto Formation is a Late Triassic geological formation in the Ischigualasto-Villa Unión Basin of southwestern La Rioja Province and northeastern San Juan Province in northwestern Argentina. The formation dates to the late Carnian and early Norian stages of the Late Triassic, according to radiometric dating of ash beds.
Jachaleria was a dicynodont herbivore that lived from the Ladinian to Norian stages of the Middle to Late Triassic, from approximately 240 to 220 million years ago. Jachaleria was one of the last representatives of the dicynodonts, occurring in Argentina and Brazil. It lacked teeth, much like Stahleckeria, but was closer in size to Dinodontosaurus.
Panphagia is a genus of sauropodomorph dinosaur described in 2009. It lived around 231 million years ago, during the Carnian age of the Late Triassic period in what is now northwestern Argentina. Fossils of the genus were found in the La Peña Member of the Ischigualasto Formation in the Ischigualasto-Villa Unión Basin. The name Panphagia comes from the Greek words pan, meaning "all", and phagein, meaning "to eat", in reference to its inferred omnivorous diet. Panphagia is one of the earliest known dinosaurs, and is an important find which may mark the transition of diet in early sauropodomorph dinosaurs.
Promastodonsaurus is an extinct genus of capitosauroid temnospondyls within the family Mastodonsauridae. Fossils of the genus were found in the Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina.
Eodromaeus is an extinct genus of probable basal theropod dinosaurs from the Late Triassic of Argentina. Like many other of the earliest-known dinosaurs, it hails from the Carnian-age Ischigualasto Formation, within the Ischigualasto-Villa Unión Basin of northwestern Argentina. Upon its discovery, it was argued to be one of the oldest true theropods, supplanting its contemporary Eoraptor, which was reinterpreted as a basal sauropodomorph.
Ignotosaurus is an extinct genus of silesaurid dinosauriform known from the Late Triassic (Carnian) Cancha de Bochas Member of the Ischigualasto Formation in the Ischigualasto-Villa Unión Basin in northwestern Argentina. It was therefore contemporary with early dinosaurs such as Herrerasaurus, and lived in the same place.
Buriolestes is a genus of early sauropodomorph dinosaurs from the Late Triassic Santa Maria Formation of the Paraná Basin in southern Brazil. It contains a single species, B. schultzi, named in 2016. The type specimen was found alongside a specimen of the lagerpetid dinosauromorph Ixalerpeton.
Ixalerpeton is a genus of lagerpetid avemetatarsalian containing one species, I. polesinensis. It lived in the Late Triassic of Brazil alongside the sauropodomorph dinosaur Buriolestes.
The Ischigualasto-Villa Unión Basin is a small sedimentary basin located in the Argentine Northwest, Argentina. It is located in the southwestern part of La Rioja Province and the northeastern part of San Juan Province. The basin borders the Sierras Pampeanas in the east, the western boundary of the basin is formed by the Valle Fértil Fault, bordering the Precordillera, and it is bound in the southeast by the El Alto Fault, separating the basin from the Marayes-El Carrizal Basin.
Gnathovorax is a genus of herrerasaurid saurischian dinosaur from the Santa Maria Formation in Rio Grande do Sul, Brazil. The type and only species is Gnathovorax cabreirai, described by Pacheco et al. in 2019.
Incertovenator is an extinct genus of archosauriform reptile, likely an archosaur, of uncertain affinities. Its unstable position is a result of possessing a number features found in both the bird-line avemetatarsalian archosaurs and the crocodylian-line pseudosuchians. The type and only known species is I. longicollum, which is known from single specimen discovered in the Late Triassic Ischigualasto Formation of Argentina. Incertovenator is known almost entirely by its vertebral column. This indicates that it had a relatively long neck, leading to its uncertain classification due to the convergent evolution of elongated neck vertebrae in both avemetatarsalian and pseudosuchian archosaurs.