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Ichthyolestes
''Ichthyolestes'' ("fish thief") is an extinct genus of archaic cetacean that was endemic to Indo-Pakistan during the Lutetian stage. To date, this monotypic genus is only represented by ''Ichthyolestes pinfoldi.'' Like other members of the family Pakicetidae, which are considered the earliest and least specialized of the archaic cetaceans, ''Ichthyolestes'' represents an early quadrupedal phase of the land-to-sea transition which occurs in the cetacean lineage. Discovery and Classification ''I. pinfoldi'' was initially known only from teeth, which were found in the Eocene locality Ganda Kas, Pakistan. Upon their discovery, ''I. pinfoldi'' was placed within the Family Mesonychidae, a group of terrestrial mammals from which cetaceans were previously thought to have evolved. Due to morphological distinctions from other mesonychids, ''I. pinfoldi'' was later acknowledged and described as an archaeocete, making it the first Pakicetid to be described. Cranial and postcranial mate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ichthyolestes
''Ichthyolestes'' ("fish thief") is an extinct genus of archaic cetacean that was endemic to Indo-Pakistan during the Lutetian stage. To date, this monotypic genus is only represented by ''Ichthyolestes pinfoldi.'' Like other members of the family Pakicetidae, which are considered the earliest and least specialized of the archaic cetaceans, ''Ichthyolestes'' represents an early quadrupedal phase of the land-to-sea transition which occurs in the cetacean lineage. Discovery and Classification ''I. pinfoldi'' was initially known only from teeth, which were found in the Eocene locality Ganda Kas, Pakistan. Upon their discovery, ''I. pinfoldi'' was placed within the Family Mesonychidae, a group of terrestrial mammals from which cetaceans were previously thought to have evolved. Due to morphological distinctions from other mesonychids, ''I. pinfoldi'' was later acknowledged and described as an archaeocete, making it the first Pakicetid to be described. Cranial and postcranial mate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pakicetidae
Pakicetidae ("Pakistani whales") is an extinct family of Archaeoceti (early whales) that lived during the Early Eocene in Pakistan. Description described the first pakicetid, '' Ichthyolestes'', but at the time they did not recognize it as a cetacean, identifying it, instead, it as a fish-eating mesonychid. Robert West was the first to identify pakicetids as cetaceans in 1980 and, after discovering a braincase, Phillip Gingerich and Donald Russell described the genus ''Pakicetus'' in 1981. On October 26, 2016, a publication represented the idea that the emergence of cetacea in the Paleogene presents the best idea of microevolution that resulted in the phenotype of pakicetid. During the following two decades, more research resulted in additional pakicetid cranial material and by 2001 postcranial material for the family had been described. Though all parts of pakicetid postcrania are known, no complete skeleton from a single individual has been recovered. The pakicetid goldmine is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaeoceti
Archaeoceti ("ancient whales"), or Zeuglodontes in older literature, is a paraphyletic group of primitive cetaceans that lived from the Early Eocene to the late Oligocene (). Representing the earliest cetacean radiation, they include the initial amphibious stages in cetacean evolution, thus are the ancestors of both modern cetacean suborders, Mysticeti and Odontoceti. This initial diversification occurred in the shallow waters that separated India and Asia , resulting in some 30 species adapted to a fully oceanic life. Echolocation and filter-feeding evolved during a second radiation . All archaeocetes from the Ypresian (56–47.8 mya) and most from the Lutetian (47.8–41.3 mya) are known exclusively from Indo-Pakistan, but Bartonian (41.3–38.0 mya) and Priabonian (38.0–33.9 mya) genera are known from across Earth, including North America, Egypt, New Zealand, and Europe. Although no consensus exists regarding the mode of locomotion of which cetaceans were capable during ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Even-toed Ungulate
The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing posteriorly. By contrast, odd-toed ungulates bear weight on an odd number of the five toes. Another difference between the two is that many other even-toed ungulates (with the exception of Suina) digest plant cellulose in one or more stomach chambers rather than in their intestine as the odd-toed ungulates do. Cetaceans (whales, dolphins, and porpoises) evolved from even-toed ungulates, and are therefore often classified under the same taxonomic branch because a species cannot outgrow its evolutionary ancestry; some modern taxonomists combine the two under the name Cetartiodactyla , while others opt to include cetaceans in the already-existing Artiodactyla. The roughly 270 land-based even-toed ungulate species include pigs, peccaries, hippo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semicircular Canals
The semicircular canals or semicircular ducts are three semicircular, interconnected tubes located in the innermost part of each ear, the inner ear. The three canals are the horizontal, superior and posterior semicircular canals. Structure The semicircular canals are a component of the bony labyrinth that are at right angles from each other. At one end of each of the semicircular canals is a dilated sac called an osseous ampulla, which is more than twice the diameter of the canal. Each ampulla contains an ampullary crest, the crista ampullaris which consists of a thick gelatinous cap called a ampullary cupula, cupula and many hair cells. The superior and posterior semicircular canals are oriented vertically at right angles to each other. The lateral semicircular canal is about a 30-degree angle from the horizontal plane. The orientations of the canals cause a different canal to be stimulated by movement of the head in different planes, and more than one canal is stimulated at onc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nalacetus
''Nalacetus'' is an extinct pakicetid early whale, fossils of which have been found in Lutetian red beds in Punjab, Pakistan (, paleocoordinates ).. Retrieved June 2013.. Retrieved June 2013. ''Nalacetus'' lived in a fresh water environment, was amphibious, and carnivorous. It was considered monophyletic by . It was said to be wolf-sized and one of the earliest forms of the order ''Cetacea Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ....'' ''Nalacetus'' is known mostly from dental remains from the Lutetian of the Kala Chitta Hill, Punjab, Pakistan: * H-GSPHoward University-Geological Survey of Pakistan Project 96055, right palatal fragment with P4 and M1−2. * H-GSP 30306, right maxillary fragment with P2 and partial P3−4; a fragmentary mandible with fragmented teeth toge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supraorbital Shield
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Supraorbital refers to the region immediately above the eye sockets, where in humans the eyebrows are located. It denotes several anatomical features, such as: *Supraorbital artery *Supraorbital foramen *Supraorbital gland *Supraorbital nerve *Supraorbital ridge *Supraorbital vein The supraorbital vein is a vein of the forehead. It communicates with the frontal branch of the superficial temporal vein. It passes through the supraorbital notch, and merges with the angular vein to form the superior ophthalmic vein. The supra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tympanic Bulla
The tympanic part of the temporal bone is a curved plate of bone lying below the squamous part of the temporal bone, in front of the mastoid process, and surrounding the external part of the ear canal. It originates as a separate bone (tympanic bone), which in some mammals stays separate through life. Evolutionarily, a portion of it is derived from the angular bone of the reptilian lower jaw. Surfaces Its postero-superior surface is concave, and forms the anterior wall, the floor, and part of the posterior wall of the bony ear canal. Medially, it presents a narrow furrow, the ''tympanic sulcus'', for the attachment of the tympanic membrane. Its antero-inferior surface is quadrilateral and slightly concave; it constitutes the posterior boundary of the mandibular fossa, and is in contact with the retromandibular part of the parotid gland. Borders Its lateral border is free and rough, and gives attachment to the cartilaginous part of the ear canal. Internally, the tympani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eocene
The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "dawn") and (''kainós'', "new") and refers to the "dawn" of modern ('new') fauna that appeared during the epoch. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period in which the concentration of the carbon isotope Carbon-13, 13C in the atmosphere was exceptionally low in comparison with the more common isotope Carbon-12, 12C. The end is set at a major extinction event called the ''Grande Coupure'' (the "Great Break" in continuity) or the Eocene–Oligocene extinction event, which may be related to the impact of one or more large bolides in Popigai impact structure, Siberia and in what is now ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vestibular Apparatus
The vestibular system, in vertebrates, is a sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating motor coordination, movement with balance. Together with the cochlea, a part of the auditory system, it constitutes the labyrinth of the inner ear in most mammals. As movements consist of rotations and translations, the vestibular system comprises two components: the semicircular canals, which indicate Angular acceleration, rotational movements; and the otoliths, which indicate Acceleration, linear accelerations. The vestibular system sends signals primarily to the neural structures that control eye movement; these provide the anatomical basis of the vestibulo-ocular reflex, which is required for clear vision. Signals are also sent to the muscles that keep an animal upright and in general control Neutral spine, posture; these provide the anatomical means required to enable an animal to maintain its desired position in space. The brai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metacone
A cusp is a pointed, projecting, or elevated feature. In animals, it is usually used to refer to raised points on the crowns of teeth. The concept is also used with regard to the leaflets of the four heart valves. The mitral valve, which has two cusps, is also known as the bicuspid valve, and the tricuspid valve has three cusps. In humans A cusp is an occlusal or incisal eminence on a tooth. Canine teeth, otherwise known as cuspids, each possess a single cusp, while premolars, otherwise known as bicuspids, possess two each. Molars normally possess either four or five cusps. In certain populations the maxillary molars, especially first molars, will possess a fifth cusp situated on the mesiolingual cusp known as the Cusp of Carabelli. Buccal Cusp- One other variation of the upper first premolar is the 'Uto-Aztecan' upper premolar. It is a bulge on the buccal cusp that is only found in Native American Indians, with highest frequencies of occurrence in Arizona. The name is no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
