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Jugal Bone
The jugal is a skull bone found in most reptiles, amphibians and birds. In mammals, the jugal is often called the malar or zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species. Anatomy The jugal bone is located on either side of the skull in the circumorbital region. It is the origin of several masticatory muscles in the skull. The jugal and lacrimal bones are the only two remaining from the ancestral circumorbital series: the prefrontal, postfrontal, postorbital, jugal, and lacrimal bones. During development, the jugal bone originates from dermal bone. In dinosaurs This bone is considered key in the determination of general traits in cases in which the entire skull has not been found intact (for instance, as with dinosaurs in paleontology). In some dinosaur genera the jugal also forms part of the lower margin of either the antorbital fenestra or the infratemporal fenestra, or both. Most commonly, this bone art ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gegenbaur 1870 Skull Homology Color
Karl Gegenbaur (21 August 1826 – 14 June 1903)"Karl Gegenbaur – Encyclopædia Britannica" (biography), ''Encyclopædia Britannica'', 2006, Britannica.coBritannica-KarlG was a German anatomist and professor who demonstrated that the field of comparative anatomy offers important evidence supporting of the theory of evolution. As a professor of anatomy at the University of Jena (1855–1873) and at the University of Heidelberg (1873–1903), Karl Gegenbaur was a strong supporter of Charles Darwin's theory of organic evolution, having taught and worked, beginning in 1858, with Ernst Haeckel, eight years his junior. Gegenbaur's book ''Grundzüge der vergleichenden Anatomie'' (1859; English translation ''Elements of Comparative Anatomy'' by Francis Jeffrey Bell, 1878) became the standard textbook, at the time, of evolutionary morphology, emphasizing that structural similarities among various animals provide clues to their evolutionary history. Karl Gegenbaur noted that the most re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is the subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya; their dominance continued throughout the Jurassic and Cretaceous periods. The fossil record shows that birds are feathered dinosaurs, having evolved from earlier theropods during the Late Jurassic epoch, and are the only dinosaur lineage known to have survived the Cretaceous–Paleogene extinction event approximately 66 mya. Dinosaurs can therefore be divided into avian dinosaurs—birds—and the extinct non-avian dinosaurs, which are all dinosaurs other than birds. Dinosaurs are varied from taxonomic, morphological and ecological standpoints. Birds, at over 10,700 living species, ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Masseter Muscle
In human anatomy, the masseter is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. The most obvious muscle of mastication is the masseter muscle, since it is the most superficial and one of the strongest. Structure The masseter is a thick, somewhat quadrilateral muscle, consisting of three heads, superficial, deep and coronoid. The fibers of superficial and deep heads are continuous at their insertion. Superficial head The superficial head, the larger, arises by a thick, tendinous aponeurosis from the temporal process of the zygomatic bone, and from the anterior two-thirds of the inferior border of the zygomatic arch. Its fibers pass inferior and posterior, to be inserted into the angle of the mandible and inferior half of the lateral surface of the ramus of the mandible. Deep head The deep head is much smaller, and more muscular in texture. It arises from the posterior third of the low ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cranial Kinesis
Cranial kinesis is the term for significant movement of skull bones relative to each other in addition to movement at the joint between the upper and lower jaw. It is usually taken to mean relative movement between the upper jaw and the braincase. Most vertebrates have some form of kinetic skull. Cranial kinesis, or lack thereof, is usually linked to feeding. Animals which must exert powerful bite forces, such as crocodiles, often have rigid skulls with little or no kinesis, for maximum strength. Animals which swallow large prey whole (snakes), which grip awkwardly shaped food items (parrots eating nuts), or, most often, which feed in the water via suction feeding often have very kinetic skulls, frequently with numerous mobile joints. In the case of mammals, which have akinetic skulls (except for perhaps hares), the lack of kinesis is most likely to be related to the secondary palate, which prevents relative movement. This in turn is a consequence of the need to be able to create ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbit (anatomy)
In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents. In the adult human, the volume of the orbit is , of which the eye occupies . The orbital contents comprise the eye, the orbital and retrobulbar fascia, extraocular muscles, cranial nerves II, III, IV, V, and VI, blood vessels, fat, the lacrimal gland with its sac and duct, the eyelids, medial and lateral palpebral ligaments, cheek ligaments, the suspensory ligament, septum, ciliary ganglion and short ciliary nerves. Structure The orbits are conical or four-sided pyramidal cavities, which open into the midline of the face and point back into the head. Each consists of a base, an apex and four walls."eye, human."Encyclopædia Britannica from Encyclopædia Britannica 2006 Ultimate Reference Suite DVD 2009 Openings There are two important foramina, or windows, two important ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gymnogyps Californianus (Shaw, 1798)
The California condor (''Gymnogyps californianus'') is a New World vulture and the largest North American land bird. It became extinct in the wild in 1987 when all remaining wild individuals were captured, but has since been reintroduced to northern Arizona and southern Utah (including the Grand Canyon area and Zion National Park), the coastal mountains of California, and northern Baja California in Mexico. Although four other fossil members are known, it is the only surviving member of the genus ''Gymnogyps''. The species is listed by the International Union for the Conservation of Nature as Critically Endangered, and similarly considered ''Critically Imperiled'' by NatureServe. The plumage is black with patches of white on the underside of the wings; the head is largely bald, with skin color ranging from gray on young birds to yellow and bright orange on breeding adults. Its wingspan is the widest of any North American bird, and its weight of up to nearly equals that of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentaceratops
''Pentaceratops'' ("five-horned face") is a genus of herbivorous ceratopsid dinosaur from the late Cretaceous Period of what is now North America. Fossils of this animal were first discovered in 1921, but the genus was named in 1923 when its type species, ''Pentaceratops sternbergii'', was described. ''Pentaceratops'' lived around 76–73 million years ago, its remains having been mostly found in the Kirtland Formation in the San Juan Basin in New Mexico. About a dozen skulls and skeletons have been uncovered, so anatomical understanding of ''Pentaceratops'' is fairly complete. One exceptionally large specimen later became its own genus, '' Titanoceratops'', due to its more derived morphology, similarities to ''Triceratops,'' and lack of unique characteristics shared with ''Pentaceratops''. ''Pentaceratops'' was about 6 meters (20 feet) long, and has been estimated to have weighed around . It had a short nose horn, two long brow horns, and long horns on the jugal bones. Its sku ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lacrimal Bone
The lacrimal bone is a small and fragile bone of the facial skeleton; it is roughly the size of the little fingernail. It is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders. Several bony landmarks of the lacrimal bone function in the process of lacrimation or crying. Specifically, the lacrimal bone helps form the nasolacrimal canal necessary for tear translocation. A depression on the anterior inferior portion of the bone, the lacrimal fossa, houses the membranous lacrimal sac. Tears or lacrimal fluid, from the lacrimal glands, collect in this sac during excessive lacrimation. The fluid then flows through the nasolacrimal duct and into the nasopharynx. This drainage results in what is commonly referred to a runny nose during excessive crying or tear production. Injury or fracture of the lacrimal bone can result in posttraumatic obstruction of the lacrimal pathways. Structure Lateral or orbital surface The lateral or orbital surface i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antorbital Fenestra
An antorbital fenestra (plural: fenestrae) is an opening in the skull that is in front of the eye sockets. This skull character is largely associated with archosauriforms, first appearing during the Triassic Period. Among extant archosaurs, birds still possess antorbital fenestrae, whereas crocodylians have lost them. The loss in crocodylians is believed to be related to the structural needs of their skulls for the bite force and feeding behaviours that they employ.Preushscoft, H., Witzel, U. 2002. Biomechanical Investigations on the Skulls of Reptiles and Mammals. Senckenbergiana Lethaea 82:207–222.Rayfield, E.J., Milner, A.C., Xuan, V.B., Young, P.G. 2007. Functional Morphology of Spinosaur "Crocodile Mimic" Dinosaurs. JVP. 27(4):892–901. In some archosaur species, the opening has closed but its location is still marked by a depression, or fossa, on the surface of the skull called the antorbital fossa. The antorbital fenestra houses a paranasal sinus that is confluent with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleontology
Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossils to classify organisms and study their interactions with each other and their environments (their paleoecology). Paleontological observations have been documented as far back as the 5th century BC. The science became established in the 18th century as a result of Georges Cuvier's work on comparative anatomy, and developed rapidly in the 19th century. The term itself originates from Greek (, "old, ancient"), (, (gen. ), "being, creature"), and (, "speech, thought, study"). Paleontology lies on the border between biology and geology, but differs from archaeology in that it excludes the study of anatomically modern humans. It now uses techniques drawn from a wide range of sciences, including biochemistry, mathematics, and engineeri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dermal Bone
A dermal bone or investing bone or membrane bone is a bony structure derived from intramembranous ossification forming components of the vertebrate skeleton including much of the skull, jaws, gill covers, shoulder girdle and fin spines rays ( lepidotrichia), and the shell (of tortoises and turtles). In contrast to endochondral bone, dermal bone does not form from cartilage that then calcifies, and it is often ornamented. Dermal bone is formed within the dermis and grows by accretion only – the outer portion of the bone is deposited by osteoblasts. The function of some dermal bone is conserved throughout vertebrates, although there is variation in shape and in the number of bones in the skull roof and postcranial structures. In bony fish, dermal bone is found in the fin rays and scales. A special example of dermal bone is the clavicle The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Skull
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, these two parts are the neurocranium and the viscerocranium ( facial skeleton) that includes the mandible as its largest bone. The skull forms the anterior-most portion of the skeleton and is a product of cephalisation—housing the brain, and several sensory structures such as the eyes, ears, nose, and mouth. In humans these sensory structures are part of the facial skeleton. Functions of the skull include protection of the brain, fixing the distance between the eyes to allow stereoscopic vision, and fixing the position of the ears to enable sound localisation of the direction and distance of sounds. In some animals, such as horned ungulates (mammals with hooves), the skull also has a defensive function by providing the mount (on the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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