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Prognathodon
''Prognathodon'' is an extinct genus of marine lizard belonging to the mosasaur family. It is classified as part of the Mosasaurinae subfamily, alongside genera like ''Mosasaurus'' and ''Clidastes''. ''Prognathodon'' has been recovered from deposits ranging in age from the Campanian to the Maastrichtian in the Middle East, Europe, New Zealand, and North America. ''Prognathodon'' means "forejaw tooth", which originates from the Latin ''pro''- ("earlier" or "prior"), Greek ''gnathos'' ("jaw") and ''odṓn'' ("tooth"). Twelve nominal species of ''Prognathodon'' are recognised, from North America, northern and western Africa, the Middle East, western Europe and New Zealand. Due to the sometimes clear differences between them and the incomplete nature of many of the specimens, the systematics of the genus and which species should properly be considered ''Prognathodon'' is controversial. Some species have been assigned to other genera, such as ''Dollosaurus'' and ''Brachysaurana'', but ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mosasaurus
''Mosasaurus'' (; "lizard of the Meuse River") is the type genus (defining example) of the mosasaurs, an extinct group of aquatic squamate reptiles. It lived from about 82 to 66 million years ago during the Campanian and Maastrichtian stages of the Late Cretaceous. The earliest fossils of ''Mosasaurus'' known to science were found as skulls in a chalk quarry near the Dutch city of Maastricht in the late 18th century, which were initially thought to have been the bones of crocodiles or whales. One skull discovered around 1780, and which was seized by France during the French Revolutionary Wars for its scientific value, was famously nicknamed the "great animal of Maastricht". In 1808, naturalist Georges Cuvier concluded that it belonged to a giant marine lizard with similarities to monitor lizards but otherwise unlike any known living animal. This concept was revolutionary at the time and helped support the then-developing ideas of extinction. Cuvier did not designate a scientifi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clidastes
''Clidastes'' is an extinct genus of marine lizard belonging to the mosasaur family. It is classified as part of the Mosasaurinae subfamily, alongside genera like ''Mosasaurus'' and ''Prognathodon''. ''Clidastes'' is known from deposits ranging in age from the Coniacian to the early Campanian in the United States. ''Clidastes'' means "locked vertebrae", which originates from the Greek noun κλειδί, or kleid meaning key (akin to Latin ''claudere'' meaning to shut). This refers to how the vertebral processes allow the proximal heads of the vertebrae to interlock for stability and strength during swimming. It was one of the earliest hydropedalIn mosasaurs, the terms "hydropedal" and "plesiopedal" refers to varying limb conditions and varying degrees of adaptations for marine life. Plesiopedal mosasaurs, such as ''Dallasaurus'' or ''Tethysaurus'' were primitive and largely coastal, while later hydropedal mosasaurs were streamlined and well-adapted to marine life. mosasaurs, repr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mosasaurinae
The Mosasaurinae are a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates. Members of the subfamily are informally and collectively known as "mosasaurines" and their fossils have been recovered from every continent except for South America. The lineage first appears in the Turonian and thrived until the K-Pg mass extinction at the end of the Maastrichtian. They ranged in size from some of the smallest known mosasaurs (''Carinodens'', 3–3.5 meters), to medium-sized taxa (''Clidastes'', 6+ meters), to the largest of the mosasaurs (''Mosasaurus hoffmannii'') potentially reaching about 13 m in length. Many genera of mosasaurines were either piscivorous or generalists, preying on fish and other marine reptiles, but one lineage, the Globidensini, evolved specialized crushing teeth, adapting to a diet of ammonites and/or marine turtles. Though represented by relatively small forms throughout the Turonian and Santonian, such as ''Clidastes'', the lineage diver ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mosasaur
Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Greek ' meaning 'lizard') comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. They belong to the order Squamata, which includes lizards and snakes. Mosasaurs probably evolved from an extinct group of aquatic lizards known as aigialosaurs in the Earliest Late Cretaceous with 42 described genera. During the last 20 million years of the Cretaceous period (Turonian–Maastrichtian ages), with the extinction of the ichthyosaurs and pliosaurs, mosasaurs became the dominant marine predators. They themselves became extinct as a result of the K-Pg event at the end of the Cretaceous period, about 66 million years ago. Description Mosasaurs breathed air, were powerful swimmers, and were well-adapted to living in the warm, shallow inland seas prevalent during the Late Cretaceous period. Mosasaurs were so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Liodon
''Liodon'' is a dubious genus of mosasaur from the Late Cretaceous, known from fragmentary fossils discovered in St James' Pit, England and possibly also the Ouled Abdoun Basin of Morocco. Though dubious and of uncertain phylogenetic affinities, ''Liodon'' was historically a highly important taxon in mosasaur systematics, being one of the genera on which the family Mosasauridae was based. History ''Liodon anceps'' was first described as "''Leiodon anceps''" by Richard Owen in 1841, based only on two tooth fragments and a minor portion of the corresponding jaw bone discovered in Essex, England.Benjamin CreislerMosasauridae Translation and Pronunciation Guide. Dinosauria.com. Retrieved 2008-04-07. The name ''Leiodon'' derived from the Greek ''leios'' ("smooth") and ''-odon'' ("tooth"), meaning "smooth tooth" on account of the "smooth and polished surface" of the fossil teeth. The specific name ''anceps'' means "two-edged", referencing the carinae (cutting edges) on both the front ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lacertilian
Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia although some lizards are more closely related to these two excluded groups than they are to other lizards. Lizards range in size from chameleons and geckos a few centimeters long to the 3-meter-long Komodo dragon. Most lizards are quadrupedal, running with a strong side-to-side motion. Some lineages (known as "legless lizards"), have secondarily lost their legs, and have long snake-like bodies. Some such as the forest-dwelling ''Draco'' lizards are able to glide. They are often territorial, the males fighting off other males and signalling, often with bright colours, to attract mates and to intimidate rivals. Lizards are mainly carnivorous, often being sit-and-wait predators; many smaller species eat insects, while the Komodo eats mammals as bi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sclerotic Ring
Sclerotic rings are rings of bone found in the eyes of many animals in several groups of vertebrates, except for mammals and crocodilians. They can be made up of single bones or multiple segments and take their name from the sclera. They are believed to have a role in supporting the eye, especially in animals whose eyes are not spherical, or which live underwater. Fossil sclerotic rings are known for a variety of extinct animals, including ichthyosaurs, pterosaurs, and dinosaurs, but are often not preserved. File:Tawny Frogmouth Skull.jpg, A skull of an extant tawny frogmouth, showing large sclerotic rings. File:Uroplatus_phantasticus_skull1.jpg, A skull of an extant satanic leaf-tailed gecko, showing large sclerotic rings. File:Viatkogorgon skull.png, Skull and sclerotic ring of the gorgonopsian ''Viatkogorgon''. File:Prosaurolophus maximus3.JPG, Sclerotic ring of the hadrosaur ''Prosaurolophus ''Prosaurolophus'' (; meaning "before ''Saurolophus''", in comparison to the late ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is approximately 43 dioptres. The cornea can be reshaped by surgical procedures such as LASIK. While the cornea contributes most of the eye's focusing power, its focus is fixed. Accommodation (the refocusing of light to better view near objects) is accomplished by changing the geometry of the lens. Medical terms related to the cornea often start with the prefix "'' kerat-''" from the Greek word κέρας, ''horn''. Structure The cornea has unmyelinated nerve endings sensitive to touch, temperature and chemicals; a touch of the cornea causes an involuntary reflex to close the eyelid. Because transparency is of prime importance, the healthy cornea does not have or need blood vessels with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sclera
The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some crucial elastic fiber. In humans, and some other vertebrates, the whole sclera is white, contrasting with the coloured iris, but in most mammals, the visible part of the sclera matches the colour of the iris, so the white part does not normally show while other vertebrates have distinct colors for both of them. In the development of the embryo, the sclera is derived from the neural crest. In children, it is thinner and shows some of the underlying pigment, appearing slightly blue. In the elderly, fatty deposits on the sclera can make it appear slightly yellow. People with dark skin can have naturally darkened sclerae, the result of melanin pigmentation. The human eye is relatively rare for having a pale sclera (relative to the iris). This makes it easier for one individual to ide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Campanian
The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian spans the time from 83.6 (± 0.2) to 72.1 (± 0.2) million years ago. It is preceded by the Santonian and it is followed by the Maastrichtian. The Campanian was an age when a worldwide sea level rise covered many coastal areas. The morphology of some of these areas has been preserved: it is an unconformity beneath a cover of marine sedimentary rocks. Etymology The Campanian was introduced in scientific literature by Henri Coquand in 1857. It is named after the French village of Champagne in the department of Charente-Maritime. The original type locality was a series of outcrop near the village of Aubeterre-sur-Dronne in the same region. Definition The base of the Campanian Stage is defined as a place in the stratigraphic column wher ... [...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] |
Prefrontal Bone
The prefrontal bone is a bone separating the lacrimal and frontal bones in many tetrapod skulls. It first evolved in the sarcopterygian clade Rhipidistia, which includes lungfish and the Tetrapodomorpha. The prefrontal is found in most modern and extinct lungfish, amphibians and reptiles. The prefrontal is lost in early mammaliaforms and so is not present in modern mammals either. In dinosaurs The prefrontal bone is a very small bone near the top of the skull, which is lost in many groups of coelurosaurian theropod dinosaurs and is completely absent in their modern descendants, the birds. Conversely, a well developed prefrontal is considered to be a primitive feature in dinosaurs. The prefrontal makes contact with several other bones in the skull. The anterior part of the bone articulates with the nasal bone and the lacrimal bone. The posterior part of the bone articulates with the frontal bone and more rarely the palpebral bone The palpebral bone is a small dermal bone found ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
