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Dimacrodon
''Dimacrodon'' is an extinct genus of non-mammalian synapsid from the latest Early Permian San Angelo Formation of Texas. It is distinguished by toothless, possibly beaked jaw tips, large lower canines and a thin bony crest on top of its head. Previously thought to be an anomodont therapsid related to dicynodonts, it was later found to lack any diagnostic features of anomodonts or even therapsids and instead appears to be a 'pelycosaur'-grade synapsid of uncertain classification. Description Three specimens of ''D. hottoni'' are known, although they only comprise incomplete portions of the lower jaw and skull. The holotype specimen consists of a single partial mandible with teeth. The jaw is long with an unusually broad and deep mandibular symphysis, while the jaw rami are slender (although the additional material from ''D.'' sp. below suggests that the back of the jaws was also deeper). Unusually, the front of the jaw is toothless and has a rough bone texture, possibly support ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dinocephalia
Dinocephalians (terrible heads) are a clade of large-bodied early therapsids that flourished in the Early and Middle Permian between 279.5 and 260 million years ago (Ma), but became extinct during the Capitanian mass extinction event. Dinocephalians included herbivorous, carnivorous, and omnivorous forms. Many species had thickened skulls with many knobs and bony projections. Dinocephalians were the first non-mammalian therapsids to be scientifically described and their fossils are known from Russia, China, Brazil, South Africa, Zimbabwe, and Tanzania. Description Apart from the Biarmosuchians, the dinocephalians are the least advanced therapsids, although still uniquely specialised in their own way. They retain a number of primitive characteristics (e.g. no secondary palate, small dentary) shared with their pelycosaur ancestors, although they are also more advanced in possessing therapsid adaptations like the expansion of the ilium and more erect limbs. They include carnivo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
San Angelo Formation
The San Angelo Formation is a geologic formation in Texas. It preserves fossils dating back to the Permian period. It is one of the geologically youngest formations to preserve fossils of pelycosaurs. Stratigraphy and age The San Angelo Formation belongs to the Kungurian stage of the Cisuralian series. It underlies the Blaine Formation, which is either upper Kungurian or lower Guadalupian. Fossil content Everett C. Olson regarded the San Angelo Formation as preserving some of the oldest known therapsids, several of which he classified in a taxon he called Eotheriodonta. These taxa are now interpreted as caseids and sphenacodontids, not therapsids. Synapsids See also * List of fossiliferous stratigraphic units in Texas * Paleontology in Texas Paleontology in Texas refers to paleontological research occurring within or conducted by people from the U.S. state of Texas. Author Marian Murray has remarked that "Texas is as big for fossils as it is for everything else." Some o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Early Permian
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Mandibular Symphysis
In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular symphysis (Latin: ''symphysis menti'') or line of junction where the two lateral halves of the mandible typically fuse at an early period of life (1-2 years). It is not a true symphysis as there is no cartilage between the two sides of the mandible. This ridge divides below and encloses a triangular eminence, the mental protuberance, the base of which is depressed in the center but raised on either side to form the mental tubercle. The lowest (most inferior) end of the mandibular symphysis — the point of the chin — is called the "menton". It serves as the origin for the geniohyoid and the genioglossus The genioglossus is one of the paired extrinsic muscles of the tongue. The genioglossus is the major muscle responsible for protruding (or sticking out) the tongue. Structure Genioglossus is the fan-shaped extrinsic t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Venyukovioidea
Venyukovioidea is an infraorder of anomodont therapsids related to dicynodonts from the Permian of Russia. They have also known as Venjukovioidea, as well as by the similar names Venyukoviamorpha or Venjukoviamorpha in literature. This in part owes to a misspelling by Russian palaeontologist Ivan Efremov in 1940 when he mistakenly spelt '' Venyukovia'', the namesake of the group, with a 'j' instead of a 'y' (i.e. ''Venjukovia''), which permeated through subsequent therapsid literature before the mistake was caught and corrected. The order Ulemicia has also been coined for a similar taxonomic concept in Russian scientific literature, which notably excludes ''Suminia'' and ''Parasuminia''. Venyukovioidea includes the genera ''Venyukovia'', '' Otsheria'', '' Ulemica'', '' Suminia'' and ''Parasuminia'', all from Western Siberia. Historically, some of these genera have been placed in various families and subfamilies, including the Venyukoviidae/Venjukoviidae, Otsheriidae, and Ule ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infraorder
Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. An immediately higher rank, superorder, is sometimes added directly above order, with suborder directly beneath order. An order can also be defined as a group of related families. What does and does not belong to each order is determined by a taxonomist, as is whether a particular order should be recognized at all. Often there is no exact agreement, with different taxonomists each taking a different position. There are no hard rules that a taxonomist needs to follow in describing or recognizing an order. Some taxa are accepted almost universally, while others are recognized only rarely. The name of an order is usually written with a capital letter. For some groups of organisms, their orders may follo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cladistics
Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived characteristics ( synapomorphies'')'' that are not present in more distant groups and ancestors. However, from an empirical perspective, common ancestors are inferences based on a cladistic hypothesis of relationships of taxa whose character states can be observed. Theoretically, a last common ancestor and all its descendants constitute a (minimal) clade. Importantly, all descendants stay in their overarching ancestral clade. For example, if the terms ''worms'' or ''fishes'' were used within a ''strict'' cladistic framework, these terms would include humans. Many of these terms are normally used paraphyletically, outside of cladistics, e.g. as a ' grade', which are fruitless to precisely delineate, especially when including extinct species. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gorgonopsia
Gorgonopsia (from the Greek Gorgon, a mythological beast, and 'aspect') is an extinct clade of sabre-toothed therapsids from the Middle to Upper Permian roughly 265 to 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 up to in the Upper Permian. The latest gorgonopsia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Titanophoneus
''Titanophoneus'' ("titanic murderer") is an extinct genus of carnivorous dinocephalian therapsid from the Middle Permian. It is classified within the family Anteosauridae. The type species is ''Titanophoneus potens''. Remains of ''Titanophoneus'' have been found at Isheevo in Russia. Description An adult skull would have reached 80 cm with a heavy long snout. The long tail and short limbs show the species to be a primitive therapsid unlike ''Inostrancevia'' which was more advanced. The structure of the limbs and the density of the bone are designed for a sprawling stance. The temporal opening is more advanced than Estemmenosuchidae but less advanced than ''Inostrancevia''. The teeth are large with 12 large palate incisors followed by 2 canines and various smaller back teeth. The lower palate is the same as the upper but without the canine teeth. The appearance of ''Titanophoneus'' is reminiscent to the sphenacodontid pelycosaurs, which included ''Dimetrodon''. Gallery ima ... [...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] |
Temporal Fenestra
An infratemporal fenestra, also called the lateral temporal fenestra or simply temporal fenestra, is an opening in the skull behind the orbit in some animals. It is ventrally bordered by a zygomatic arch. An opening in front of the eye sockets, conversely, is called an antorbital fenestra. Both of these openings reduce the weight of the skull. Infratemporal fenestrae are commonly (although not universally) seen in the fossilized skulls of dinosaurs. Synapsids, including mammals, have one temporal fenestra, while sauropsids Sauropsida ("lizard faces") is a clade of amniotes, broadly equivalent to the class Reptilia. Sauropsida is the sister taxon to Synapsida, the other clade of amniotes which includes mammals as its only modern representatives. Although early sy ..., the birds and reptiles, have two. References {{ref list Dinosaur anatomy Foramina of the skull ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thecodont Dentition
Thecodont dentition is a morphological arrangement in which the base of the tooth is completely enclosed in a deep socket of bone, as seen in crocodilians, dinosaurs and mammals, and opposed to acrodont and pleurodont dentition seen in squamate reptiles. Notably, this appears to be the ancestral tooth condition in Amniota. This morphology was once used as a basis for the now-defunct taxonomic group Thecodontia Thecodontia (meaning 'socket-teeth'), now considered an obsolete taxonomic grouping, was formerly used to describe a diverse "order" of early archosaurian reptiles that first appeared in the latest Permian period and flourished until the end of t .... References Dentition types Archosaurs {{Vertebrate anatomy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
