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Whitakersaurus
''Whitakersaurus'' is a genus of sphenodontid rhynchocephalian reptile dated to be late Triassic in age and is from the Ghost Ranch fossil quarry in New Mexico, USA. It is named after the discoverer of the Ghost Ranch quarry, George O. Whitaker. The fossil was described in 2007. Features The left and right dentary are preserved, along with a fragmentary left maxilla and probable palatal bone, on two blocks of stone. Dentary bones The left dentary is fragmented but still has almost all teeth present, whereas the right dentary is incomplete and has most of the teeth. The left dentary is 11 mm long and has multiple broken teeth or tooth positions. The coronoid process is missing, but there may be a suture present where the dentary was joined to the surangular. A small groove is present on the lingual side of teeth 16-18. The right dentary is only partial, unlike the left dentary where all the fragments are present, but the piece preserved is 9 mm long. The posterior ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhynchocephalia
Rhynchocephalia (; ) is an order of lizard-like reptiles that includes only one living species, the tuatara (''Sphenodon punctatus'') 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. Rhynchocephalians are distinguished from squamates by a number of traits, including the retention of rib-like gastralia bones in the belly, as well as most rhynchocephalians having acrodont teeth that are fused to the crests of the jaws (the latter also found among a small number of modern lizard grou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nutrient Canal
All bones possess larger or smaller foramina (openings) for the entrance of blood-vessels; these are known as the nutrient foramina, and are particularly large in the shafts of the larger long bones, where they lead into a nutrient canal, which extends into the medullary cavity. The nutrient canal (foramen) is directed away from the growing end of bone. The growing ends of bones in upper limb are upper end of humerus and lower ends of radius and ulna. In lower limb, the lower end of femur and upper end of tibia are the growing ends. The nutrient arteries along with nutrient veins pass through this canal. A nutrient canal is found in long bones, in the mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ..., and in dental alveoli. In long bones the nutrient canal is found in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chinle Formation
The Chinle Formation is an Upper Triassic continental geological formation of fluvial, lacustrine, and palustrine to eolian deposits spread across the U.S. states of Nevada, Utah, northern Arizona, western New Mexico, and western Colorado. In New Mexico, it is often raised to the status of a geological group, the Chinle Group. Some authors have controversially considered the Chinle to be synonymous to the Dockum Group of eastern Colorado and New Mexico, western Texas, the Oklahoma panhandle, and southwestern Kansas. The Chinle Formation is part of the Colorado Plateau, Basin and Range, and the southern section of the Interior Plains.GEOLEX database entry for Chinle USGS (viewed 19 March 2006) A probable separate depositional basin within the Chinle is found in northwestern Colorado and northeaste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Juvenile (organism)
A juvenile is an individual organism (especially an animal) that has not yet reached its adult form, sexual maturity or size. Juveniles can look very different from the adult form, particularly in colour, and may not fill the same niche as the adult form. In many organisms the juvenile has a different name from the adult (see List of animal names). Some organisms reach sexual maturity in a short metamorphosis, such as ecdysis in many insects and some other arthropods. For others, the transition from juvenile to fully mature is a more prolonged process—puberty in humans and other species (like higher primates and whales), for example. In such cases, juveniles during this transformation are sometimes called subadults. Many invertebrates cease development upon reaching adulthood. The stages of such invertebrates are larvae or nymphs. In vertebrates and some invertebrates (e.g. spiders), larval forms (e.g. tadpoles) are usually considered a development stage of their own, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood and DNA remnants. The totality of fossils is known as the ''fossil record''. Though the fossil record is incomplete, numerous studies have demonstrated that there is enough information available to give a good understanding of the pattern of diversification of life on Earth. In addition, the record can predict and fill gaps such as the discovery of '' Tiktaalik'' in the arctic of Canada. Paleontology includes the study of fossils: their age, method of formation, and evolutionary significance. Specimens are sometimes considered to be fossils if they are over 10,000 years old. The oldest fossils are around 3.48 billion years to 4.1 billion years old. Early edition, published online before prin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crown (tooth)
In dentistry, the crown is the visible part of the tooth above the gingival margin and is an essential component of dental anatomy. Covered by Tooth enamel, enamel, the crown plays a crucial role in cutting, tearing, and grinding food. Its shape and structure vary depending on the type and function of the tooth (incisors, Canine tooth, canines, premolars, or Molar (tooth), molars), and differ between Deciduous teeth, primary dentition and Permanent teeth, permanent dentition. The crown also contributes to facial aesthetics, speech, and oral health. Anatomical crown vs clinical crown The anatomical crown refers to the portion of the tooth covered by enamel, regardless of whether it is visible. The clinical crown is the part of the tooth that is visible in the mouth. In a healthy young adult, the gums typically follow the contour where enamel meets the root, so the clinical and anatomical crowns are similar in size. However, with age or periodontal disease, this may change. Te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Striated
Striations means a series of ridges, furrows or linear marks, and is used in several ways: * Glacial striation * Striation (fatigue), in material * Striation (geology), a ''striation'' as a result of a geological fault * Striation Valley, in Antarctica * In hyperbolic geometry, a ''striation'' is a reflection across two parallel mirrors. * In anatomy, striated muscle * In acoustic phonetics, ''striations'' are vertical bands on a spectrogram associated with pulses of the vocal folds when producing voiced periodic sounds. * Striations can be found in certain glasses. These have been caused by turbulent flow during teeming (pouring) of the glass. * Striations can be observed in clouds. See Barber's pole. * Ballistic fingerprinting Forensic firearm examination is the forensic process of examining the characteristics of firearms or bullets left behind at a crime scene. Specialists in this field try to link bullets to weapons and weapons to individuals. They can raise and r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterodont
In anatomy, a heterodont (from Greek, meaning 'different teeth') is an animal which possesses more than a single tooth morphology. Human dentition is heterodont and diphyodont as an example. In vertebrates, heterodont pertains to animals where teeth are differentiated into different forms. For example, members of the Synapsida generally possess incisors, canines ("dogteeth"), premolars, and molars. The presence of heterodont dentition is evidence of some degree of feeding and or hunting specialization in a species. In contrast, homodont or isodont dentition refers to a set of teeth that possess the same tooth morphology. In invertebrates, the term heterodont refers to a condition where teeth of differing sizes occur in the hinge plate, a part of the Bivalvia Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pleurodont
Pleurodont is a form of tooth implantation common in reptiles of the order Squamata, as well as in at least one temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') or temnospondyls is a diverse ancient order (biology), order of small to giant tetrapods—often considered Labyrinth .... The vestibular (outer) side of pleurodont teeth are fused ( ankylosed) to the inner surface of the jaw bones which host them. The lingual (tongue) side of pleurodont teeth are not attached to bone, and instead are typically held in place by connective ligaments. This contrasts with thecodont implantation, in which the teeth are set in sockets and surrounded by bone on all sides. References External links Tooth Implantation at palaeos.comOral Cavity of Reptiles - Anatomy and Physiology Dentition types Reptile anatomy {{Vertebrate anatomy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acrodont
Acrodonty (from Greek ''akros'' 'highest' + ''odont-'' 'tooth') is an anatomical placement of the teeth at the summit of the alveolar ridge of the jaw, without sockets, characteristic of bony fish. Functionally, acrodont tooth implantation may be related to greater bite force. However, this result is not supported when size and phylogeny is taken into account. Examples Squamata Within squamate reptiles, acrodont tooth implantation is best known in Acrodonta and some species of amphisbaenians, though some snakes are also referred to as being acrodont. Acrodonta is unique in that the name of the clade is based upon this trait. Most other squamate reptiles have pleurodont dentition, though some snakes are occasionally described as having acrodont dentition. Rhynchocephalia Acrodont tooth implantation is common within Rhynchocephalia, including '' Sphenodon''. Amphibia Acrodont tooth implantation also present in some frogs and the temnospondyl Temnospondyli (from Greek l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diphydontosaurus
''Diphydontosaurus'' is an extinct genus of small Rhynchocephalia, rhynchocephalian reptile from the Late Triassic of Europe. It is the most primitive known member of Sphenodontia. Description ''Diphydontosaurus'' was one of the smallest sphenodontia, sphenodontians, measuring up to long. It had long, sharp claws to help it catch its prey. The skull, which was around long, had large Orbit (anatomy), orbits (eye sockets), as well as a combination of 17 regularly replaced conical pleurodont teeth on the front of the jaws and 11 larger permanent acrodont teeth in the posterior jaws. It was likely an insectivore which used its acrodont posterior teeth to dismember prey. Classification ''Diphydontosaurus avonis'' is known from abundant remains covering most of the skeleton found in fissure fill deposits in Southwest Britain. A skeleton of a juvenile sphenodontian tentatively referred to ''Diphydontosaurus'' was reported in 1996 from the Norian of Lombardy in Italy.Renesto, S., 1995 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
