Riojasuchus Temporal range: Norian ~ | |
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Holotype skull and diagram | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Clade: | Archosauria |
Clade: | Pseudosuchia |
Family: | † Ornithosuchidae |
Genus: | † Riojasuchus Bonaparte 1969 |
Type species | |
Riojasuchus tenuisceps Bonaparte 1969 |
Riojasuchus is an extinct genus of ornithosuchid archosaur from the Late Triassic (Norian) of Argentina. Ornithosuchidae was a widespread family of facultatively bipedal pseudosuchians (crocodilian-line archosaurs) with adaptations for scavenging. [1] [2] Riojasuchus is notable as one of the youngest and most complete members of the family. The type and only known species, Riojasuchus tenuisceps, was named and described by José Bonaparte in 1967. [3] It was one of the first of many well-preserved Triassic archosaurs to be discovered in Argentina. The holotype specimen, PVL 3827, was found in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina. [4] [5]
The holotype specimen is PVL 3827, consisting of a complete skull and mandibles, as well as a nearly complete postcranial skeleton, and it was collected during the late 1960s. [4] Three other specimens are known. PVL 3828 is almost as complete as the holotype, including a nearly complete skull. PVL 3826 consists of articulated vertebrae and limb fragments. PVL 3814 only involves a few fragments of vertebrae, limb bones, and osteoderms. [5]
All four specimens were found close together in the upper section of the Los Colorados Formation. [3] The formation's diverse fossil beds have been radiometrically dated to the mid-Norian stage of the Late Triassic. [6] The fossils are stored in the vertebrate paleontology collection (PVL) at Instituto Miguel Lillo in San Miguel de Tucumán. [4] [5]
Riojasuchus and its fossils were initially described in papers by José Bonaparte in 1967 [3] and 1972. The skull was redescribed by M. Belén von Baczko, Julia B. Desojo, and Denis Ponce in 2016. [4] The postcranial skeleton was redescribed by von Baczko and Desojo in 2019. [5]
The skull of the type specimen is 25 centimetres (9.8 in) long, and has a large, curved snout and short mandibles.
Many characteristics were identified by Bonaparte in 1969. They are listed below: [3]
Riojasuchus is a member of Ornithosuchidae, a family of facultatively bipedal carnivores that were geographically widespread during the Late Triassic. [3] Two other genera, Ornithosuchus and Venaticosuchus , are currently known. The group was originally considered to be related to dinosaurs, before many phylogenetical analyses. [1]
Below is a phylogenetic cladogram by Butler et al. in 2011 showing the cladistics of Archosauriformes, focusing mostly on Pseudosuchia: [7] Clade names follow Nesbitt 2011. [8]
Fossils of Riojasuchas are found in the Los Colorados Formation, a Late Triassic unit in Argentina, [3] and date to approximately 217 to 215 million years ago. [1] At that age, it is the youngest ornithosuchid known. [1] It lived alongside the protosuchid Hemiprotosuchus ; the sphenosuchid Pseudohesperosuchus ; the stagonolepidid Neoaetosauroides ; the melanorosaurid Strenusaurus ; and the riojasaurid Riojasaurus . [3]
Postosuchus, meaning "Crocodile from Post", is an extinct genus of rauisuchid reptiles comprising two species, P. kirkpatricki and P. alisonae, that lived in what is now North America during the Late Triassic. Postosuchus is a member of the clade Pseudosuchia, the lineage of archosaurs that includes modern crocodilians. Its name refers to Post Quarry, a place in Texas where many fossils of the type species, P. kirkpatricki, were found. It was one of the apex predators of its area during the Triassic, larger than the small dinosaur predators of its time. It was a hunter which probably preyed on large bulky herbivores like dicynodonts and many other creatures smaller than itself.
Marasuchus is a genus of basal dinosauriform archosaur which is possibly synonymous with Lagosuchus. Both genera lived during the Late Triassic in what is now La Rioja Province, Argentina. Marasuchus contains a single species, Marasuchus lilloensis.
Dasygnathoides is an extinct genus of pseudosuchian from the Late Triassic (Carnian) Lossiemouth Sandstone of Scotland.
Ornithosuchus is an extinct genus of pseudosuchians from the Late Triassic (Carnian) Lossiemouth Sandstone of Scotland. It was originally thought to be the ancestor to the carnosaurian dinosaurs, but it is now known to be more closely related to crocodilians than to dinosaurs.
Venaticosuchus is a genus of pseudosuchian archosaurs from the family Ornithosuchidae. Known from a single species, Venaticosuchus rusconii, this genus is described based on an incomplete skull and jaw collected from the Late Triassic (Carnian) Ischigualasto Formation in the Ischigualasto-Villa Unión Basin in northwestern Argentina, which was deposited around 230 million years ago. This fossil material has been termed the holotype specimen PVL 2578. Venaticosuchus incorporated a myriad of features present in the other two genera of ornithosuchids, Ornithosuchus and Riojasuchus. However, it also had several unique traits, relating to the lower jaw.
Gracilisuchus is an extinct genus of tiny pseudosuchian from the Late Triassic of Argentina. It contains a single species, G. stipanicicorum, which is placed in the clade Suchia, close to the ancestry of crocodylomorphs. Both the genus and the species were first described by Alfred Romer in 1972.
Lewisuchus is a genus of archosaur that lived during the Late Triassic. As a silesaurid dinosauriform, it was a member of the group of reptiles most commonly considered to be the closest relatives of dinosaurs. Lewisuchus was about 1 metre (3.3 ft) long. Fossils have been found in the Chañares Formation of Argentina. It exhibited osteoderms along its back.
Prestosuchidae is a polyphyletic grouping of carnivorous archosaurs that lived during the Triassic. They were large active terrestrial apex predators, ranging from around 2.5 to 7 metres in length. They succeeded the Erythrosuchidae as the largest archosaurs of their time. While resembling erythrosuchids in size and some features of the skull and skeleton, they were more advanced in their erect posture and crocodile-like ankle, indicating more efficient gait. "Prestosuchids" flourished throughout the whole of the middle, and the early part of the late Triassic, and fossils are so far known from Europe, India, Africa (Tanzania), Argentina, and Paleorrota in Brazil. However, for a long time experts disagree regarding the phylogenetic relationships of the group, what genera should be included, and whether indeed the "Prestosuchidae" constitute a distinct family.
Hesperosuchus is an extinct genus of crocodylomorph reptile that contains a single species, Hesperosuchus agilis. Remains of this pseudosuchian have been found in Late Triassic (Carnian) strata from Arizona and New Mexico. Because of similarities in skull and neck anatomy and the presence of hollow bones Hesperosuchus was formerly thought to be an ancestor of later carnosaurian dinosaurs, but based on more recent findings and research it is now known to be more closely related to crocodilians rather than dinosaurs.
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.
Ornithosuchidae is an extinct family of pseudosuchian archosaurs from the Triassic period. Ornithosuchids were quadrupedal and facultatively bipedal, meaning that they had the ability to walk on two legs for short periods of time. They had distinctive, downturned snouts, unique, "crocodile-reversed" ankle bones, and several other features that distinguish them from other archosaurs. Ornithosuchids were geographically widespread during the Carnian and Norian stages of the Late Triassic with members known from Argentina, Brazil, and the United Kingdom. Four genera, comprising Ornithosuchus, Venaticosuchus, Dynamosuchus, and Riojasuchus are presently known. The family was first erected by German paleontologist Friedrich von Huene in 1908.
The Los Colorados Formation is a sedimentary rock formation of the Ischigualasto-Villa Unión Basin, found in the provinces of San Juan and La Rioja in Argentina. The formation dates back to the Norian age of the Late Triassic.
Luperosuchus is an extinct genus of loricatan pseudosuchian reptile which contains only a single species, Luperosuchus fractus. It is known from the Chañares Formation of Argentina, within strata belonging to the latest Ladinian stage of the late Middle Triassic, or the earliest Carnian of the Late Triassic. Luperosuchus was one of the largest carnivores of the Chañares Formation, although its remains are fragmentary and primarily represented by a skull with similarities to Prestosuchus and Saurosuchus.
Sillosuchus is a genus of shuvosaurid poposauroid archosaur that lived in South America during the Late Triassic period. Shuvosaurids were an unusual family of reptiles belonging to the group Poposauroidea; although their closest modern relatives are crocodilians, they were bipedal and lightly armored, with dinosaur-like hip and skull structures. Based on skull remains from members of the family such as Effigia, they were also toothless and likely beaked herbivores.
Stagonosuchus is an extinct genus of loricatan, or possibly a species of Prestosuchus. Fossils have been found from the Late Triassic Manda Formation in Tanzania that are Anisian in age.
Decuriasuchus is an extinct genus of loricatan from the Middle Triassic period. It is a carnivorous archosaur that lived in what is now southern Brazil, in Paleorrota. It was first named by Marco Aurélio G. França, Jorge Ferigolo and Max C. Langer in 2011 and the type species is Decuriasuchus quartacolonia. The generic name means "unit of ten crocodiles" in Latin and Greek in reference to the ten known specimens and the animal's possible group behavior. The specific name refers to the Quarta Colonia region where the fossils were collected.
Erpetosuchidae is an extinct family of pseudosuchian archosaurs. Erpetosuchidae was named by D. M. S. Watson in 1917 to include Erpetosuchus. It includes the type species Erpetosuchus granti from the Late Triassic of Scotland, Erpetosuchus sp. from the Late Triassic of eastern United States and Parringtonia gracilis from the middle Middle Triassic of Tanzania; the group might also include Dyoplax arenaceus from the Late Triassic of Germany, Archeopelta arborensis and Pagosvenator candelariensis from Brazil and Tarjadia ruthae from Argentina.
Aenigmaspina is an extinct genus of enigmatic pseudosuchian (=crurotarsan) archosaur from the Late Triassic of the United Kingdom. Its fossils are known from the Pant-y-ffynnon Quarry in South Wales, of which its type and only known species is named after, A. pantyffynnonensis. Aenigmaspina is characterised by the unusual spines on its vertebrae, which are broad and flat on top with a unique 'Y' shape. Although parts of its skeleton is relatively well known, the affinities of Aenigmaspina to other pseudosuchians are unclear, although it is possibly related to families Ornithosuchidae, Erpetosuchidae or Gracilisuchidae.
Dynamosuchus is an extinct genus of pseudosuchian archosaurs from the family Ornithosuchidae. It is known from a single species, Dynamosuchus collisensis, which is based on a partial skeleton from the Santa Maria Formation of Brazil. Dynamosuchus is considered a close relative of Venaticosuchus, which is known from the Ischigualasto Formation of Argentina. Ornithosuchids are one of many groups which lived in the Santa Maria and Ischigualasto Formations, which formed at approximately the same time and were ecologically similar. As a large scavenging reptile, Dynamosuchus helps to illuminate the trophic structure of the Santa Maria Formation. It also supports the hypothesis that ornithosuchids had diversified throughout South America by the start of the Carnian, and were not originally endemic to the Ischigualasto-Villa Unión Basin.
Mambawakale is a genus of large sized basal paracrocodylomorph, possibly a poposauroid, from the Manda Beds of Tanzania. It was informally named Pallisteria before being officially published under its current name almost 60 years after its discovery. It contains a single species, Mambawakale ruhuhu.