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Eutheriodont
Eutheriodontia is a clade of therapsids which appear during the Middle Permian and which includes therocephalians and cynodonts, this latter group including mammals and related forms. With the dicynodonts, they form one of two lineages of therapsids that survived the End-Permian extinction and which diversified again during the Triassic, before the majority of them disappeared before or during the Triassic–Jurassic extinction, except for a lineage of cynodonts that later gave rise to mammals. Classification The clade was named in 1986 by James Allen Hopson and Herbert Richard Barghusen, the name meaning the "true Theriodontia". Within Hopson's system, the Eutheriodontia are the sister group of the Gorgonopsia within the Theriodontia. A close relationship between therocephalians and cynodonts had been recognized for many years. In 2001 the Eutheriodontia were defined as the least inclusive clade including Mammalia and '' Bauria''.James A. Hopson and James W. Kitching, 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gorgonopsia
Gorgonopsia (from the Greek Gorgon, a mythological beast, and 'aspect') is an extinct clade of Saber-toothed predator, sabre-toothed therapsids from the Middle Permian, Middle to the Upper Permian, roughly between 270 and 252 million years ago. They are characterised by a long and narrow skull, as well as elongated upper and sometimes lower canine teeth and incisors which were likely used as slashing and stabbing weapons. Postcanine teeth are generally reduced or absent. For hunting large prey, they possibly used a bite-and-retreat tactic, ambushing and taking a debilitating bite out of the target, and following it at a safe distance before its injuries exhausted it, whereupon the gorgonopsian would grapple the animal and deliver a killing bite. They would have had an exorbitant gape, possibly in excess of 90°, without having to unhinge the jaw. They markedly increased in size as time went on, growing from small skull lengths of in the Middle Permian to bear-like proportions of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theriodontia
The theriodonts (clade Theriodontia) are a major group of therapsids which appeared during the Middle Permian and which includes the gorgonopsians and the eutheriodonts, itself including the therocephalians and the cynodonts. Naming In 1876, Richard Owen named a suborder Theriodontia, which he divided into the Cynodontia and the Gomphodontia. In 1956, D. M. S. Watson and Alfred Romer divided Therapsida into Theriodontia, which predominantly included carnivorous species, and the mostly herbivorous Anomodontia, defined as comprising Dinocephalia as well as Venyukovioidea and Dicynodontia. The modern clade concept was devised by James Allen Hopson. In his system, Theriodontia fall into two main groups: the Gorgonopsia and the Eutheriodontia. The latter consist of the Therocephalia and Cynodontia.J.A. Hopson. 1999. "Therapsids". ''Encyclopedia of Paleontology'' 2: 1256-1266 Evolution Theriodonts appeared at the same time as their sister group within the Neotherapsida, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permian–Triassic Extinction Event
The Permian–Triassic extinction event (also known as the P–T extinction event, the Late Permian extinction event, the Latest Permian extinction event, the End-Permian extinction event, and colloquially as the Great Dying,) was an extinction event that occurred approximately 251.9 Million years ago, million years ago (mya), at the boundary between the Permian and Triassic geologic periods, and with them the Paleozoic and Mesozoic eras. It is Earth's most severe known extinction event, with the extinction of 57% of Family (biology), biological families, 62% of genera and 81% of marine biology, marine species, (previous estimates of 90–96% marine species extinction were due to historical conflation with the End-Capitanian mass extinction event, end-Capitanian mass extinction which occurred 7–10 million years earlier) and 70% of terrestrial vertebrate species. It is also the greatest known mass extinction of insects. It is the greatest of the "Big Five" mass extinctions of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cynodont
Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 Megaannum, mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extinct ancestors and close relatives (Mammaliaformes), having evolved from advanced probainognathian cynodonts during the Late Triassic. Non-mammalian cynodonts occupied a variety of ecological niches, both as carnivores and as herbivores. Following the emergence of mammals, most other cynodont lines went extinct, with the last known non-mammaliaform cynodont group, the Tritylodontidae, having its youngest records in the Early Cretaceous. Description Early cynodonts have many of the skeletal characteristics of mammals. The teeth were fully differentiated and the braincase bulged at the back of the head. Outside of some Crown group, crown-group mammals (notably the therians), all cynodonts probably laid eggs. The temporal fenestrae#Fenestra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Middle Permian
The Guadalupian is the second and middle series/epoch of the Permian. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. It is named after the Guadalupe Mountains of New Mexico and Texas, and dates between 272.95 ± 0.5 – 259.1 ± 0.4 Mya. The series saw the rise of the therapsids, a minor extinction event called Olson's Extinction and a significant mass extinction called the end-Capitanian extinction event. The Guadalupian is also known as the Middle Permian. Name and background The Guadalupian is the second and middle series or epoch of the Permian. Previously called Middle Permian, the name of this epoch is part of a revision of Permian stratigraphy for standard global correlation. The name "Guadalupian" was first proposed in the early 1900s, and approved by the International Subcommission on Permian Stratigraphy in 1996. References to the Middle Permian still exist. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mammalia
A mammal () is a vertebrate animal of the class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle ear bones. These characteristics distinguish them from reptiles and birds, from which their ancestors diverged in the Carboniferous Period over 300 million years ago. Around 6,640 extant species of mammals have been described and divided into 27 orders. The study of mammals is called mammalogy. The largest orders of mammals, by number of species, are the rodents, bats, and eulipotyphlans (including hedgehogs, moles and shrews). The next three are the primates (including humans, monkeys and lemurs), the even-toed ungulates (including pigs, camels, and whales), and the Carnivora (including cats, dogs, and seals). Mammals are the only living members of Synapsida; this clade, together with Sauropsida (reptiles and birds), constitut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sister Group
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and taxon B are sister groups to each other. Taxa A and B, together with any other extant or extinct descendants of their most recent common ancestor (MRCA), form a monophyletic group, the clade AB. Clade AB and taxon C are also sister groups. Taxa A, B, and C, together with all other descendants of their MRCA form the clade ABC. The whole clade ABC is itself a subtree of a larger tree which offers yet more sister group relationships, both among the leaves and among larger, more deeply rooted clades. The tree structure shown connects through its root to the rest of the universal tree of life. In cladistic standards, taxa A, B, and C may represent specimens, species, genera, or any other taxonomic units. If A and B are at the same taxono ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secondary Palate
The secondary palate is an anatomical structure that divides the nasal cavity from the oral cavity in many vertebrates. In human embryology, it refers to that portion of the hard palate that is formed by the growth of the two palatine shelves medially and their mutual fusion in the midline. It forms the majority of the adult palate and meets the primary palate at the incisive foramen. Clinical significance Secondary palate development begins in the sixth week of pregnancy and can lead to cleft palate when development goes awry. There are three major mechanisms known to cause this failure: #Growth retardation — Palatal shelves do not grow enough to meet each other. #Mechanical obstruction — Improper mouth size, or abnormal anatomical structures in the embryonic mouth prevent fully grown shelves from meeting each other. #Midline epithelial dysfunction (MED) - The surface mucosa of embryonic shelves is impaired, which causes a failure of palatal fusion. Evolution T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bauria
''Bauria'' is an extinct genus of the suborder Therocephalia that existed during the Early Triassic, Early and Middle Triassic period, around 246-251 million years ago. It belonged to the family Bauriidae. ''Bauria'' was probably a herbivore or omnivore. It lived in South Africa, specifically in the Burgersdorp Formation in South Africa. Taxonomy ''Bauria'' was named by Robert Broom in 1909 and found at Winnaarsbaken, South Africa. The first species Broom discovered, ''Bauria cynops'', was a reasonably complete skull, but according to the first description somewhat poorly preserved, and apparently equally poorly prepared. Five other specimens were later found at different points in time, with mostly skulls being found. There have only been two known species of ''Bauria'' that have been discovered so far, with the first species, ''Bauria cynops'', being known from 6 different skulls in varying conditions of poor to excellent. The second species, ''Bauria robusta'' is known f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
James Hopson
James Allen Hopson (born 1935) is an American paleontologist and professor (now retired) at the University of Chicago. His work has focused on the evolution of the synapsids (a group of amniotes that includes the mammals), and has been focused on the transition from basal synapsids to mammals, from the late Paleozoic through the Mesozoic Eras. He received his doctorate at Chicago in 1965, and worked at Yale before returning to Chicago in 1967 as a faculty member in Anatomy, and has also been a research associate at the Field Museum of Natural History since 1971. He has also worked on the paleobiology of dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...s, and his work, along with that of Peter Dodson, has become a foundation piece for the modern understanding of duckbi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Postorbital Bar
The postorbital bar (or postorbital bone) is a bony arched structure that connects the frontal bone of the skull to the zygomatic arch, which runs laterally around the eye socket. It is a trait that only occurs in mammalian taxa, such as most strepsirrhine primates and the hyrax, while haplorhine primates have evolved fully enclosed sockets. One theory for this evolutionary difference is the relative importance of vision to both orders. As haplorrhines (tarsiers and simians) tend to be diurnal, and rely heavily on visual input, many strepsirrhines are nocturnal and have a decreased reliance on visual input. Postorbital bars evolved several times independently during mammalian evolution and the evolutionary histories of several other clades. Some species, such as tarsiers, have a postorbital septum. This septum can be considered as joined processes with a small articulation between the frontal bone, the zygomatic bone and the alisphenoid bone and is therefore different from the p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
