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Asilisaurus
''Asilisaurus'' ( ); from Swahili, ''asili'' ("ancestor" or "foundation"), and Greek, (, "lizard") is an extinct genus of silesaurid archosaur. The type species is ''Asilisaurus kongwe.'' ''Asilisaurus'' fossils were uncovered in the Manda Beds of Tanzania and date back to the middle Ladinian-early Carnian, making it one of the oldest known members of the Avemetatarsalia (animals on the dinosaur/pterosaur side of the archosaurian family tree). It was the first non-dinosaurian dinosauriform recovered from Africa. The discovery of ''Asilisaurus'' has provided evidence for a rapid diversification of avemetatarsalians during the Middle Triassic, with the diversification of archosaurs during this time previously only documented in pseudosuchians ( crocodylian-line archosaurs). ''Asilisaurus'' is known from a relatively large amount of fossils compared to most non-dinosaur dinosauromorphs. This has allowed it to provide important information for the evolution of other silesaurids an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asilisaurus Kongwe Nesbitt Et Al
''Asilisaurus'' ( ); from Swahili, ''asili'' ("ancestor" or "foundation"), and Greek, (, "lizard") is an extinct genus of silesaurid archosaur. The type species is ''Asilisaurus kongwe.'' ''Asilisaurus'' fossils were uncovered in the Manda Beds of Tanzania and date back to the middle Ladinian-early Carnian, making it one of the oldest known members of the Avemetatarsalia (animals on the dinosaur/pterosaur side of the archosaurian family tree). It was the first non-dinosaurian dinosauriform recovered from Africa. The discovery of ''Asilisaurus'' has provided evidence for a rapid diversification of avemetatarsalians during the Middle Triassic, with the diversification of archosaurs during this time previously only documented in pseudosuchians ( crocodylian-line archosaurs). ''Asilisaurus'' is known from a relatively large amount of fossils compared to most non-dinosaur dinosauromorphs. This has allowed it to provide important information for the evolution of other silesaurids and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dinosauriformes
Dinosauromorpha is a clade of avemetatarsalian archosaurs (reptiles closer to birds than to crocodilians) that includes the Dinosauria (dinosaurs) and some of their close relatives. It was originally defined to include dinosauriforms and lagerpetids, with later formulations specifically excluding pterosaurs from the group. Birds are the only dinosauromorphs which survive to the present day. Classification The name "Dinosauromorpha" was briefly coined by Michael J. Benton in 1985. It was considered an alternative name for the group "Ornithosuchia", which was named by Jacques Gauthier to correspond to archosaurs closer to dinosaurs than to crocodilians. Although "Ornithosuchia" was later recognized as a misnomer (since ornithosuchids are now considered closer to crocodilians than to dinosaurs), it was still a more popular term than Dinosauromorpha in the 1980s. The group encompassed by Gauthier's "Ornithosuchia" and Benton's "Dinosauromorpha" is now given the name Avemetatar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dinosauromorpha
Dinosauromorpha is a clade of avemetatarsalian archosaurs (reptiles closer to birds than to crocodilians) that includes the Dinosauria (dinosaurs) and some of their close relatives. It was originally defined to include dinosauriforms and lagerpetids, with later formulations specifically excluding pterosaurs from the group. Birds are the only dinosauromorphs which survive to the present day. Classification The name "Dinosauromorpha" was briefly coined by Michael J. Benton in 1985. It was considered an alternative name for the group "Ornithosuchia", which was named by Jacques Gauthier to correspond to archosaurs closer to dinosaurs than to crocodilians. Although "Ornithosuchia" was later recognized as a misnomer (since ornithosuchids are now considered closer to crocodilians than to dinosaurs), it was still a more popular term than Dinosauromorpha in the 1980s. The group encompassed by Gauthier's "Ornithosuchia" and Benton's "Dinosauromorpha" is now given the name Avemetatars ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silesauridae
Silesauridae is an extinct family of Triassic dinosauriforms. It is most commonly considered to be a clade of non-dinosaur dinosauriforms, and the sister group of dinosaurs. Some studies have instead suggested that most or all silesaurids comprised an early diverging clade or a paraphyletic grade within ornithischian dinosaurs. Silesaurids have a consistent general body plan, with a fairly long neck and legs and possibly quadrupedal habits, but most silesaurids are heavily fragmentary nonetheless. Furthermore, they occupied a variety of ecological niches, with early silesaurids (such as '' Lewisuchus'') being carnivorous and later taxa (such as ''Kwanasaurus'') having adaptations for specialized herbivory. As indicated by the contents of referred coprolites, '' Silesaurus'' may have been insectivorous, feeding selectively on small beetles and other arthropods. Classification Silesauridae is typically considered the sister group to Dinosauria. The group was named in 2010 by Ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archosaur
Archosauria () is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term which includes birds. Extinct archosaurs include non-avian dinosaurs, pterosaurs, and extinct relatives of crocodilians. Modern paleontologists define Archosauria as a crown group that includes the most recent common ancestor of living birds and crocodilians, and all of its descendants. The base of Archosauria splits into two clades: Pseudosuchia, which includes crocodilians and their extinct relatives, and Avemetatarsalia, which includes birds and their extinct relatives (such as non-avian dinosaurs and pterosaurs). Older definitions of the group Archosauria rely on shared morphological characteristics, such as an antorbital fenestra in the skull, serrated teeth, and an upright stance. Some extinct reptiles, such as proterosuchids and euparkeriids, possessed these features yet originated pri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Manda Beds
The Manda Formation (also known as the Manda Beds) is a Middle Triassic (Anisian?) or possibly Late Triassic (Carnian?) geologic formation in Tanzania. It preserves fossils of many terrestrial vertebrates from the Triassic, including some of the earliest dinosauromorph archosaurs. The formation is often considered to be Anisian in age according to general tetrapod biochronology hypotheses and correlations to the ''Cynognathus'' Assemblage Zone of South Africa. However, some recent studies cast doubt to this age, suggesting that parts deposits may actually be younger (Carnian) in age. History of study One of the first to study rocks of the Manda Formation was British geologist G. M. Stockley. In 1932, Stockley explored the geology of the Ruhuhu Basin in Tanzania. He called a series of layers dating from the Late Carboniferous to the Middle Triassic the Songea Series and divided it into eight units labelled K1-K8. Stockley was also the first to describe fossils from these rocks, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sterling Nesbitt
Sterling Nesbitt (born March 25, 1982, in Mesa, Arizona) is an American paleontologist best known for his work on the origin and early evolutionary patterns of archosaurs. He is currently an associate professor at Virginia Tech in the Department of Geosciences. Biography Sterling Nesbitt received his B.A. in integrative biology with a minor in geology from the University of California Berkeley in 2004. He received his PhD from Columbia University in 2009, completing the majority of his research at the American Museum of Natural History in New York City. He subsequently held postdoctoral researcher positions at the University of Texas at Austin, the University of Washington, and the Field Museum. He is currently an associate professor in thDepartment of Geosciencesat Virginia Tech in Blacksburg, Virginia. He is also a research associate/affiliate of the American Museum of Natural History, the Vertebrate Paleontology Lab at The University of Texas at Austin, the Virginia Museum of Nat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Avemetatarsalia
Avemetatarsalia (meaning "bird metatarsals") is a clade of diapsid reptiles containing all archosaurs more closely related to birds than to crocodilians. The two most successful groups of avemetatarsalians were the dinosaurs and pterosaurs. Dinosaurs were the largest terrestrial animals for much of the Mesozoic Era, and one group of small feathered dinosaurs (Aves, i.e. birds) has survived up to the present day. Pterosaurs were the first flying vertebrates and persisted through the Mesozoic before dying out at the Cretaceous-Paleogene (K-Pg) extinction event. Both dinosaurs and pterosaurs appeared in the Triassic Period, shortly after avemetatarsalians as a whole. The name Avemetatarsalia was first established by British palaeontologist Michael Benton in 1999. An alternate name is Panaves, or "all birds", in reference to its definition containing all animals, living or extinct, which are more closely related to birds than to crocodilians. Although dinosaurs and pterosaurs were th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Squamosal Bone
The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral component of the dermal roof and is typically thin compared to other skull bones. The squamosal bone lies ventral to the temporal series and otic notch, and is bordered anteriorly by the postorbital. Posteriorly, the squamosal articulates with the quadrate and pterygoid bones. The squamosal is bordered anteroventrally by the jugal and ventrally by the quadratojugal. Function in reptiles In reptiles, the quadrate and articular bones of the skull articulate to form the jaw joint. The squamosal bone lies anterior to the quadrate bone. Anatomy in synapsids Non-mammalian synapsids In non-mammalian synapsids, the jaw is composed of four bony elements and referred to as a quadro-articular jaw because the joint is between the articular an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Premaxilla
The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has been usually termed as the incisive bone. Other terms used for this structure include premaxillary bone or ''os premaxillare'', intermaxillary bone or ''os intermaxillare'', and Goethe's bone. Human anatomy In human anatomy, the premaxilla is referred to as the incisive bone (') and is the part of the maxilla which bears the incisor teeth, and encompasses the anterior nasal spine and alar region. In the nasal cavity, the premaxillary element projects higher than the maxillary element behind. The palatal portion of the premaxilla is a bony plate with a generally transverse orientation. The incisive foramen is bound anteriorly and laterally by the premaxilla and posteriorly by the palatine process of the maxilla. It is formed from the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quadrate Bone
The quadrate bone is a skull bone in most tetrapods, including amphibians, sauropsids (reptiles, birds), and early synapsids. In most tetrapods, the quadrate bone connects to the quadratojugal and squamosal bones in the skull, and forms upper part of the jaw joint. The lower jaw articulates at the articular bone, located at the rear end of the lower jaw. The quadrate bone forms the lower jaw articulation in all classes except mammals. Evolutionarily, it is derived from the hindmost part of the primitive cartilaginous upper jaw. Function in reptiles In certain extinct reptiles, the variation and stability of the morphology of the quadrate bone has helped paleontologists in the species-level taxonomy and identification of mosasaur squamates and spinosaurine dinosaurs. In some lizards and dinosaurs, the quadrate is articulated at both ends and movable. In snakes, the quadrate bone has become elongated and very mobile, and contributes greatly to their ability to swallow very ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triassic
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic Period is subdivided into three epochs: Early Triassic, Middle Triassic and Late Triassic. The Triassic began in the wake of the Permian–Triassic extinction event, which left the Earth's biosphere impoverished; it was well into the middle of the Triassic before life recovered its former diversity. Three categories of organisms can be distinguished in the Triassic record: survivors from the extinction event, new groups that flourished briefly, and other new groups that went on to dominate the Mesozoic Era. Reptiles, especially archosaurs, were the chief terrestrial vertebrates during this time. A specialized subgroup of archo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
