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| Reconstructed skeleton of P. avelasi | |
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| Genus: | †Priosphenodon Apesteguia & Novas 2003 [1] |
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Priosphenodon is an extinct, large herbiviorous eilenodontine rhynchocephalian known from the mid-Cretaceous (Albian-Turonian) of Argentina. [1] [2] It is one of the largest known sphenodontians.
The type species of Priosphenodon, P. avelasi, was described in 2003 from the Late Cretaceous (Cenomanian-Turonian) aged Candeleros Formation of Argentina. [1] In 2014, a second smaller species, P. minimus was described from the same formation, though from an earlier unit suggested to be Early Cretaceous (Albian) in age. [2] Other authors have disputed the use of the genus Priosphenodon, with some authors treating P. avelasi and P. minimus as members of the previously named genus Kaikaifilusaurus instead. [3]
With some individuals reaching over 1 metre (3.3 ft) in total length, Priosphenodon avelasi is the largest known terrestrial sphenodontian. [1] The skull is around 15 centimetres (5.9 in) long. [2] The front of the upper jaw has a large beak-like structure probably formed from fused teeth on the premaxilla. [1] The teeth are densely packed with a cone-in-cone structure, and have prismatic enamel structure similar to those of mammals and the lizard Uromastyx, which was likely an adaptation to wear resistance in the absence of tooth replacement. [4] There is a large elongate tooth row on the palatine bones on the roof of the mouth that runs parallel to the maxillary tooth row. [1] The ungual phalanges are square in shape, and are expanded towards their distal ends, a condition unlike those known in other lepidosaurs, which typically have pointed ungual phalanges. [1]
P. avelasi exhibited variable but generally slow growth rates, with a probably sexually mature individual confirmed to be at least 13 years old by bone histology was still growing and only around 40% maximum size at the time of death. [5]
P. minimus differs from P. avelasi by having a proportionally shorter skull in addition to a considerably smaller body size, among a variety of differences in the arrangement and shape of the skull bones. [2]
During feeding the dentary teeth of Priosphenodon slotted between the maxillary and palatine tooth rows, which in turn with backward and forward (propalinal) motion of the jaw, served to shred plant material. The Candeleros Formation is suggested to have been deposited in an arid environment. Remains of P. avelasi are the most abundant of any terrestrial vertebrate at the sites it is found, and the lack of other herbivores found at the localities suggests that it may have been the only resident herbivore. [4]
Lesothosaurus is a monospecific genus of ornithischian dinosaur that lived during the Early Jurassic in what is now South Africa and Lesotho. It was named by paleontologist Peter Galton in 1978, the name meaning "lizard from Lesotho". The genus has only one valid species, Lesothosaurus diagnosticus. Lesothosaurus is one of the most completely-known early ornithischians, based on numerous skull and postcranial fossils from the Upper Elliot Formation. It had a simpler tooth and jaw anatomy than later ornithischians, and may have been omnivorous in some parts of the year.
Rhynchocephalia is an order of lizard-like reptiles that includes only one living species, the tuatara of New Zealand. Despite its current lack of diversity, during the Mesozoic rhynchocephalians were a speciose group with high morphological and ecological diversity. The oldest record of the group is dated to the Middle Triassic around 238 to 240 million years ago, and they had achieved global distribution by the Early Jurassic. Most rhynchocephalians belong to the group Sphenodontia ('wedge-teeth'). Their closest living relatives are lizards and snakes in the order Squamata, with the two orders being grouped together in the superorder Lepidosauria.
Buitreraptor is a genus of dromaeosaurid dinosaurs that lived during the Late Cretaceous of Argentina at the Candeleros Formation. Buitreraptor was described in 2005 and the type species is Buitreraptor gonzalezorum. It was rooster-sized and had a very elongated head with many small teeth.
The Candeleros Formation is a geologic formation that crops out in the Río Negro, Neuquén, and Mendoza provinces of northern Patagonia, Argentina. It is the oldest formation in the Neuquén Group and belongs to the Rio Limay Subgroup. Formerly that subgroup was treated as a formation, and the Candeleros Formation was known as the Candeleros Member.
Ekrixinatosaurus is a genus of abelisaurid theropod which lived approximately 100 to 97 million years ago during the Late Cretaceous period. Its fossils have been found in Argentina. Only one species is currently recognized, Ekrixinatosaurus novasi, from which the specific name honors of Dr. Fernando Novas for his contributions to the study of abelisaurid theropods, while the genus name refers to the dynamiting of the holotype specimen. It was a large abelisaur, measuring between 6.5 and 8 m in length and weighing 800 kg (1,800 lb).
Najash is an extinct genus of basal snake from the Late Cretaceous Candeleros Formation of Patagonia. Like a number of other Cretaceous and living snakes it retained hindlimbs, but Najash is unusual in having well-developed legs that extend outside the rib cage, and a pelvis connected to the spine.
Eilenodon is an extinct genus of rhynchocephalian reptile from the Late Jurassic Morrison Formation of western North America, present in stratigraphic zone 4. The only known species of this genus is Eilenodon robustus. It was a member of a group of rhynchocephalians called the eilenodontines, which were large, herbivorous members of Rhynchocephalia, the order of reptiles which contains the modern tuatara (Sphenodon). The generic name "Eilenodon" is Greek for "packed teeth", in reference to its closely packed teeth. The specific name, "robustus", refers to the strong build of the jaws.
Reigitherium was a mammal that lived during the Late Cretaceous, in the. Its fossils have been found in the Los Alamitos and the La Colonia Formations of Argentina.
Opisthodontia is a proposed clade of sphenodontian reptiles, uniting Opisthias from the Late Jurassic-earliest Cretaceous of Europe and North America with the Eilenodontinae, a group of herbivorous sphenodontians known from the Late Triassic to Late Cretaceous.
Clevosaurs are an extinct group of rhynchocephalian reptiles from the Triassic and Jurassic periods.
Sapheosaurs are an extinct group of rhynchocephalian reptiles from the Late Jurassic period. "Sapheosaurs" is an informal name for a group of rhynchocephalians closely related to the genus Sapheosaurus. It was first recognized as a group containing multiple genera by Hoffstetter in 1955. The group has sometimes been given a formal taxonomic name as the family Sapheosauridae, although in some analyses this group belongs to the family Sphenodontidae and thus cannot be assigned its own family. They were fairly advanced rhynchocephalians which may have had semiaquatic habits.
Lamarquesaurus is an extinct genus of sphenodontian from the Late Cretaceous (Campanian) of Patagonia. It is known from a single species, Lamarquesaurus cabazai. This genus and species is represented by MML-PV-42, a well-preserved right maxillary bone. This bone was found at the Cerro Tortuga site near Lamarque, Argentina, which preserves fossils from the Cretaceous Allen Formation. The discoverer of the Cerro Tortuga locality, Tito Cabaza, is the namesake of the species.
Tralkasaurus is a genus of abelisaurid dinosaur from the Huincul Formation from Río Negro Province in Argentina. The type and only species is Tralkasaurus cuyi, named in 2020 by Mauricio Cerroni and colleagues based on an incomplete skeleton. A medium-sized abelisaurid, Tralkasaurus exhibits a conflicting blend of characteristics found among the early-diverging abelisauroids with others that characterize the highly specialized clade Brachyrostra, and thus its position within the clade is poorly-resolved.
Kaikaifilusaurus is an extinct genus of rhynchocephalians in the family Sphenodontidae from the Late Cretaceous of South America. Fossils of the genus were found in Cenomanian sediments of the Candeleros Formation and Turonian layers of the Huincul Formation, both of the Neuquén Basin and the Albian strata of the Cerro Barcino Formation in the Cañadón Asfalto Basin, all in Patagonia, Argentina. The genus contains two species, K. minimus and the type species K. calvoi.
Overoraptor is an extinct genus of paravian theropod of uncertain affinities from the Late Cretaceous Huincul Formation of Argentinian Patagonia. The genus contains a single species, O. chimentoi, known from several bones of the hands, feet, and hips alongside some vertebrae.
Eilenodontinae are an extinct clade of reptiles belonging to Sphenodontia. They are either considered a subgroup of Opisthodontia, or Sphenodontidae. They had deep jaws with broad, closely packed teeth with thick enamel and noticeable wear facets. They were likely herbivorous, and probably chewed with a proal movement, with food shredded between the edges of opposing sharp-edged wear facets. Members of the group are known from South America, North America and Europe. The earliest known member of the group, Sphenotitan, is known from the Late Triassic of South America. while the youngest members are known from the Late Cretaceous of South America. The group contains some of the largest known sphenodontians, with Priosphenodon suggested to be the largest known non aquatic sphenodontian, with an estimated body length of over 1 metre (3.3 ft).
Kawasphenodon is an extinct genus of sphenodontian reptile, known from the Late Cretaceous and Paleocene of Patagonia in South America. The type species, K. expectatus, was described in 2005 from jaw fragments found in late Campanian aged sediments in the Los Alamitos Formation, the jaw when complete was estimated to be 11 cm long, making it among the largest known sphenodontians. A second species, K. peligrensis, around 1/3 the size of the type species, was described in 2014 also from jaw fragments in early Paleocene (Danian) sediments of the Salamanca Formation, making it the youngest known definitive representative of Rhynchocephalia outside of New Zealand. In the original description, it was found to be a member of Sphenodontidae, in some other subsequent analyses it was found to be a member of Opisthodontia. A 2020 analysis of rhyncocephalian relationships found it to be outside Opisthodontia, and instead a member of the Sphenodontinae as the closest known relative of the tuatara, with an estimated divergence between the two genera in the Early Cretaceous. Other subsequent studies have endorsed its placement as a member of Sphenodontidae. Like most other rhynchocephalians, the teeth are acrodont, with a deep dentary, and it probably had an omnivorous habit.
Tika is an extinct genus of sphenodontian from the Late Cretaceous Candeleros Formation of Argentina. The type species is Tika giacchinoi. It is considered to be closely related to the tuatara,, and a member of the Sphenodontinae. It is the oldest member of Sphenodontinae known from South America.
Meraxes is a genus of large carcharodontosaurid theropod dinosaur from the Late Cretaceous Huincul Formation of Patagonia, Argentina. The genus contains a single species, Meraxes gigas.
Sidersaura is an extinct genus of rebbachisaurid sauropod dinosaur from the Late Cretaceous Huincul Formation of Argentina. The genus contains a single species, S. marae, known from the remains of four individuals. Sidersaura represents one of the largest known rebbachisaurids.
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