|
Tritylodontids
Tritylodontidae ("three-knob teeth", named after the shape of their cheek teeth) is an extinct family of small to medium-sized, highly specialized mammal-like cynodonts, bearing several mammalian traits like erect limbs, endothermy and details of the skeleton. They were the last-known family of the non-mammaliaform synapsids, persisting into the Early Cretaceous. Most tritylodontids are thought to have been herbivorous, feeding on vegetation, such as stems, leaves, and roots, although at least one may have had a more omnivorous diet. Tritylodontid fossils are found in the Americas, South Africa, and Eurasia—they appear to have had an almost global distribution, including Antarctica. Description The skull of tritylodontids had a high sagittal crest. They retained the primitive condition of the joint between the quadrate bone of the skull and the articular bone of the lower jaw—the retention of the joint is one of the reasons they are technically regarded to not be mammals, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oligokyphus Triserialis
''Oligokyphus'' ("few cusps") is an extinct genus of advanced herbivorous cynodonts of the late Triassic to early Jurassic periods. Originally considered to be an early mammal, it is now classified as a Mammaliamorph (nearly a mammal) because ''Oligokyphus'' does not have the mammalian jaw attachments and it retains a vestigial joint between the quadrate bone and the squamosal bone in the skull. Discovery and naming ''Oligokyphus'' was named by Edwin Hennig in 1922 on the basis of two teeth from Württemberg, Germany. The name of the genus is derived from Greek "few" and "hump", and is a calque of Paucituberculata, the group in which ''Oligokyphus'' was initially classified, from Latin into Greek. Like ''Tritylodon'', ''Oligokyphus'' was originally classified as a mammal. Hennig initially recognized two species, which he named ''Oligokyphus triserialis'' and ''Oligokyphus biserialis'' based on the number of rows of cusps, though he acknowledged this distiction as provisional. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kayentatherium Wellesi
''Kayentatherium'' is an extinct genus of tritylodontid cynodonts that lived during the Early Jurassic. It is one of two tritylodonts from the Kayenta Formation of northern Arizona, United States. ''Kayentatherium'' means "Kayenta Beast", and is named for the geological formation in which it was found, the Kayenta Formation. ''Kayentatherium'' is known from several specimens.Kermack, D. 1982. A new tritylodont from the Kayenta Formation of Arizona. Zoological Journal of the Linnean Society, 76. 1-17.Sues, Hans-Dieter & F. A. Jenkins. 2006. The Postcranial Skeleton of Kayentatherium Wellesi from the Lower Jurassic Kayenta Formation of Arizona and the Phylogenetic Significance of Postcranial Features in Tritylodontid Cynodonts in: Carrano, Matthew T., Gaudin, T. J., Blob, R. W. and Wible, J. R., Amniote Paleobiology: Perspectives on the Evolution of Mammals, Birds, and Reptiles: The University of Chicago Press. pp. 114-152. The specific name honors paleontologist Samuel Welles, who ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Triassic
The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. The corresponding series (stratigraphy), series of rock beds is known as the Upper Triassic. The Late Triassic is divided into the Carnian, Norian and Rhaetian Geologic time scale, Ages. Many of the first dinosaurs evolved during the Late Triassic, including ''Plateosaurus'', ''Coelophysis'', and ''Eoraptor''. The Triassic–Jurassic extinction event began during this epoch and is one of the five major mass extinction events of the Earth. Etymology The Triassic was named in 1834 by Friedrich August von Namoh, Friedrich von Alberti, after a succession of three distinct rock layers (Greek meaning 'triad') that are widespread in southern Germany: the lower Buntsandstein (colourful sandstone'')'', t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest continent, being about 40% larger than Europe, and has an area of . Most of Antarctica is covered by the Antarctic ice sheet, with an average thickness of . Antarctica is, on average, the coldest, driest, and windiest of the continents, and it has the highest average elevation. It is mainly a polar desert, with annual precipitation of over along the coast and far less inland. About 70% of the world's freshwater reserves are frozen in Antarctica, which, if melted, would raise global sea levels by almost . Antarctica holds the record for the lowest measured temperature on Earth, . The coastal regions can reach temperatures over in summer. Native species of animals include mites, nematodes, penguins, seals and tardigrades. Where vegetation o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Matter
In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic particles, and in everyday as well as scientific usage, "matter" generally includes atoms and anything made up of them, and any particles (or combination of particles) that act as if they have both rest mass and volume. However it does not include massless particles such as photons, or other energy phenomena or waves such as light or heat. Matter exists in various states (also known as phases). These include classical everyday phases such as solid, liquid, and gas – for example water exists as ice, liquid water, and gaseous steam – but other states are possible, including plasma, Bose–Einstein condensates, fermionic condensates, and quark–gluon plasma. Usually atoms can be imagined as a nucleus of protons and neutrons, and a surro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plant
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclude the fungi and some algae, as well as the prokaryotes (the archaea and bacteria). By one definition, plants form the clade Viridiplantae (Latin name for "green plants") which is sister of the Glaucophyta, and consists of the green algae and Embryophyta (land plants). The latter includes the flowering plants, conifers and other gymnosperms, ferns and their allies, hornworts, liverworts, and mosses. Most plants are multicellular organisms. Green plants obtain most of their energy from sunlight via photosynthesis by primary chloroplasts that are derived from endosymbiosis with cyanobacteria. Their chloroplasts contain chlorophylls a and b, which gives them their green color. Some plants are parasitic or mycotrophic and have lost the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Food
Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is ingested by an organism and assimilated by the organism's cells to provide energy, maintain life, or stimulate growth. Different species of animals have different feeding behaviours that satisfy the needs of their unique metabolisms, often evolved to fill a specific ecological niche within specific geographical contexts. Omnivorous humans are highly adaptable and have adapted to obtain food in many different ecosystems. The majority of the food energy required is supplied by the industrial food industry, which produces food with intensive agriculture and distributes it through complex food processing and food distribution systems. This system of conventional agriculture relies heavily on fossil fuels, which means that the food and agricu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Occlusion (dentistry)
Occlusion, in a dental context, means simply the contact between teeth. More technically, it is the relationship between the maxillary (upper) and mandibular (lower) teeth when they approach each other, as occurs during chewing or at rest. Static occlusion refers to contact between teeth when the jaw is closed and stationary, while dynamic occlusion refers to occlusal contacts made when the jaw is moving. The masticatory system also involves the periodontium, the TMJ (and other skeletal components) and the neuromusculature, therefore the tooth contacts should not be looked at in isolation, but in relation to the overall masticatory system. Anatomy of Masticatory System One cannot fully understand occlusion without an in depth understanding of the anatomy including that of the teeth, TMJ, musculature surrounding this and the skeletal components. The Dentition and Surrounding Structures The human dentition consists of 32 permanent teeth and these are distributed between the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diastema
A diastema (plural diastemata, from Greek διάστημα, space) is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars. More colloquially, the condition may be referred to as gap teeth or tooth gap. In humans, the term is most commonly applied to an open space between the upper incisors (front teeth). It happens when there is an unequal relationship between the size of the teeth and the jaw. Diastemata are common for children and can exist in adult teeth as well. In humans Causes 1. Oversized Labial Frenulum: Diastema is sometimes caused or exacerbated by the action of a labial frenulum (the tissue connecting the lip to the gum), causing high mucosal attachment and less attached keratinized tissue. This is more prone to recession or by tongue thrusting, which can push the teeth apart. 2. Periodontal Disease: Periodontal disease, also known as gum disease, can result in bone loss that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Incisor
Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, whereas armadillos have none. Structure Adult humans normally have eight incisors, two of each type. The types of incisor are: * maxillary central incisor (upper jaw, closest to the center of the lips) * maxillary lateral incisor (upper jaw, beside the maxillary central incisor) * mandibular central incisor (lower jaw, closest to the center of the lips) * mandibular lateral incisor (lower jaw, beside the mandibular central incisor) Children with a full set of deciduous teeth (primary teeth) also have eight incisors, named the same way as in permanent teeth. Young children may have from zero to eight incisors depending on the stage of their tooth eruption and tooth development. Typically, the mandibular central incisors erupt first, followed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canine Tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dog teeth, or (in the context of the upper jaw) fangs, eye teeth, vampire teeth, or vampire fangs, are the relatively long, pointed teeth. They can appear more flattened however, causing them to resemble incisors and leading them to be called ''incisiform''. They developed and are used primarily for firmly holding food in order to tear it apart, and occasionally as weapons. They are often the largest teeth in a mammal's mouth. Individuals of most species that develop them normally have four, two in the upper jaw and two in the lower, separated within each jaw by incisors; humans and dogs are examples. In most species, canines are the anterior-most teeth in the maxillary bone. The four canines in humans are the two maxillary canines and the two mandibular canines. Details There are generally four canine teeth: two in the upper (maxillary) and two in the lower (mandibular) arch. A canine is placed laterally to ... [...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)Dudas et al. (2007): Palatal fusion – Where do the midline cells go? A review on cleft palate, a major hum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
