The skull roof, or the roofing bones of the skull, are a set of bones covering the brain and nostrils in bony fishes and all land-living vertebrates. The bones are derived from bone, hence the alternative name dermatocranium. More or less incorporated in the roof is the upper jaw. The early armoured fish did not have a skull in the understanding of the word. The dermal bones gradually evolved into a fixed unit overlaying the endocranium like a lid, protecting the animals head. Cartilaginous fish whose skeleton is formed from cartilage lack a continuous dermal armour, a more or less full shield of fused dermal bones was common in early bony fishes of the Devonian, and particularly well developed in shallow water species. In early sarcopterygians the skull roof was composed of bony plates, particularly around the nostrils. The skull proper was joined by the bones of the operculum, the skull itself was composed rather loosely, with a joint between the bones covering the brain and the snout. This joint disappeared in the evolving labyrinthodonts, at the time the number of bones were reduced.
In modern amphibians the skull roof is further reduced and has large openings, only in caecilians can a full covering skull roof be found, an adaption for burrowing. The skull roof in lungfish is composed of a number of plates that are not readily compared to those found in early amphibians. In most ray-finned fishes the skull is often reduced to a series of elements. The pattern of plates of the labyrinthodonts formed that basis for that seen in all land-living vertebrates, the roof itself formed a continuous cover over the whole of the head, leaving only openings for nostrils, eyes and a parietal eye between the parietal bones. This type of skull was inherited by the first reptiles as they evolved from labyrinthodont stock in the Carboniferous and this type of skull roof without any above openings behind the eyes is called anapsid. Today anapsid skulls are only found in turtles, though this may be a case of loss of the post orbital openings. In two groups of reptiles the skull roof evolved post orbital openings to allow for greater movement of the jaw muscles.
The two groups evolved the openings independently, The Synapsids having one opening on each side, fairly low on the side of the skull, the Diapsids having two openings on each side, the two openings separated by an arch formed from processes of the postorbital and squamosal bones. The synapsids are the reptiles and the mammals
Dvinosaurus is a genus of extinct temnospondyl amphibian from the Late Permian of Russia. The first three species, D. primus, D. secundus, and D. tertius, were described by Russian paleontologist Vladimir Prokhorovich Amalitskii in 1921. Dvinosaurus was first found near the village of Sokolki in Arkhangelsk and named after the Northern Dvina River, the holotype is cataloged as PIN2005/35, and consists of only a skull. Amalitskiis D. tertius is now considered synonymous with D. secundus, two additional species, D. egregius, and D. purlensis, were named by Mikhail Shishkin in 1968. These were named from a skull and a partial lower jaw
The skull is a bony structure that forms the head of the skeleton in most vertebrates. It supports the structures of the face and provides a cavity for the brain. The skull is composed of two parts, the cranium and the mandible, in the human these two parts are the neurocranium and the viscerocranium or 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, nose, in the human these sensory structures are part of the facial skeleton. In some animals such as horned ungulates, the skull has a function by providing the mount for the horns. The English word skull is probably derived from Old Norse skulle, while the Latin word cranium comes from the Greek root κρανίον, the skull is made up of a number of fused flat bones, and contains many foramina and processes, and several cavities or sinuses. For details and the constituent bones, see neurocranium and viscerocranium, the human skull is the bony structure that forms the head in the human skeleton.
It supports the structures of the face and forms a cavity for the brain, like the skulls of other vertebrates, it protects the brain from injury. The skull consists of two parts, of different embryological origin—the neurocranium and the facial skeleton, the neurocranium forms the protective cranial cavity that surrounds and houses the brain and brainstem. The facial skeleton is formed by the supporting the face. Except for the mandible, all of the bones of the skull are joined together by sutures—synarthrodial joints formed by bony ossification, sometimes there can be extra bone pieces within the suture known as wormian bones or sutural bones. The human skull is considered to consist of twenty-two bones—eight cranial bones. In the neurocranium these are the bone, two temporal bones, two parietal bones, the sphenoid and frontal bones. The bones of the skeleton are the vomer, two nasal conchae, two nasal bones, two maxilla, the mandible, two palatine bones, two zygomatic bones, and two lacrimal bones.
Some of these bones—the occipital, frontal, in the neurocranium, and the nasal, the skull contains sinus cavities and numerous foramina. The sinuses are lined with respiratory epithelium and their known functions are the lessening of the weight of the skull, the aiding of resonance to the voice and the warming and moistening of the air drawn through the nasal cavity. The foramina are openings in the skull, the largest of these is the foramen magnum that allows the passage of the spinal cord as well as nerves and blood vessels. The many processes of the include the mastoid process and the zygomatic process
The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 Mya. It is the last period of the Mesozoic Era, the Cretaceous Period is usually abbreviated K, for its German translation Kreide. The Cretaceous was a period with a warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct marine reptiles and rudists, during this time, new groups of mammals and birds, as well as flowering plants, appeared. The Cretaceous ended with a mass extinction, the Cretaceous–Paleogene extinction event, in which many groups, including non-avian dinosaurs, pterosaurs. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary, the name Cretaceous was derived from Latin creta, meaning chalk. The Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series, in older literature the Cretaceous is sometimes divided into three series, Neocomian and Senonian.
A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide, in many parts of the world, alternative local subdivisions are still in use. As with other geologic periods, the rock beds of the Cretaceous are well identified. No great extinction or burst of diversity separates the Cretaceous from the Jurassic and this layer has been dated at 66.043 Ma. A140 Ma age for the Jurassic-Cretaceous boundary instead of the usually accepted 145 Ma was proposed in 2014 based on a study of Vaca Muerta Formation in Neuquén Basin. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a first step toward formally changing the age in the International Union of Geological Sciences, due to the high sea level there was extensive space for such sedimentation. Because of the young age and great thickness of the system. Chalk is a type characteristic for the Cretaceous. It consists of coccoliths, microscopically small calcite skeletons of coccolithophores, the group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea.
Chalk is not easily consolidated and the Chalk Group still consists of sediments in many places. The group has other limestones and arenites, among the fossils it contains are sea urchins, belemnites and sea reptiles such as Mosasaurus. In southern Europe, the Cretaceous is usually a marine system consisting of competent limestone beds or incompetent marls
A similar concept is used for suprageneric groups called a type genus. In botanical nomenclature, these terms have no standing under the code of nomenclature. In botany, the type of a name is a specimen which is the type of a species name. The species name that has that type can be referred to as the type of the genus name, names of genus and family ranks, the various subdivisions of those ranks, and some higher-rank names based on genus names, have such types. In bacteriology, a species is assigned for each genus. Every named genus or subgenus in zoology, whether or not currently recognized as valid, is associated with a type species. In practice, there is a backlog of untypified names defined in older publications when it was not required to specify a type, a type species is both a concept and a practical system that is used in the classification and nomenclature of animals. The type species represents the species and thus definition for a particular genus name. In the Glossary, type species is defined as The nominal species that is the type of a nominal genus or subgenus.
The type species permanently attaches a formal name to a genus by providing just one species within that genus to which the name is permanently linked. The species name in turn is fixed, in theory, to a type specimen, for example, the type species for the land snail genus Monacha is Monacha cartusiana. That genus is placed within the family Hygromiidae. The type genus for that family is the genus Hygromia, the concept of the type species in zoology was introduced by Pierre André Latreille. The International Code of Zoological Nomenclature states that the name of the type species should always be cited. It gives an example in Article 67.1, Astacus marinus Fabricius,1775 was designated as the type species of the genus Homarus, thus giving it the name Homarus marinus. However, the species of Homarus should always be cited using its original name. 3, the type of the genus name Elodes is quoted as the type of the species name Hypericum aegypticum, Glossary of scientific naming Genetypes – genetic sequence data from type specimens.
Holotype Paratype Principle of Typification Type Type genus
Chigutisauridae is an extinct family of large temnospondyl amphibians. The only genera recognized as belonging to Chigutisauridae at the current time are all from Gondwana and include Koolasuchus, chigutisaurid temnspondyls from the Late Triassic of India and a review of the family Chigutisauridae. Triassic temnospondyls of the Pranhita-Godavari Basin, journal of Asian Earth Sciences 21, 655-662
It is thus a clade, a group consisting of a species and all its descendants. Though formulated in the 1970s, the term was not commonly used until its reintroduction in 2000 by Graham Budd and it is not necessary for a species to have living descendants in order for it to be included in the crown group. Extinct side branches on the tree that are descended from the most recent common ancestor of living members will still be part of a crown group. Although considered to be birds and other groups are not included in the crown group, as they fall outside the Neornithes clade. An alternative definition does not require any members of a group to be extant. The first definition forms the basis of this article, the crown group is given the designation crown-, to separate it from the group as commonly defined. Crown-Aves and Crown-Mammalia therefore differ slightly in content from the definition of Aves. This has caused confusion in the literature. Thus, a host of prefixes have been defined to describe various branches of the phylogenetic tree relative to extant organisms, a pan-group or total group is the crown group and all organisms more closely related to it than to any other extant organisms.
In a tree analogy, it is the group and all branches back to the split with the closest branch to have living members. The Pan-Aves thus contain the living birds and all more closely related to birds than to crocodilians. The phylogenetic lineage leading back from Neornithes to the point where it merges with the crocodilian lineage, pan-Mammalia consists of all mammals and their fossil ancestors back to the phylogenetic split from the remaining amniotes. Pan-Mammalia is thus a name for Synapsida. A stem group is a group composed of a pan-group or total group, above. This leaves primitive relatives of the groups, back along the phylogenetic line to the last common ancestor of the crown group. It follows from the definition that all members of a group are extinct. Alternatively, the stem group is sometimes used in a narrower sense to cover just the members of the traditional taxon falling outside the crown group. Permian synapsids like Dimetrodon and Anteosaurus are stem mammals in the wider sense, stem birds perhaps constitute the most cited example of a stem group, as the phylogeny of this group is fairly well known
Temnospondyli is a diverse subclass of extinct small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous and Triassic periods. A few species continued into the Cretaceous, fossils have been found on every continent. During about 210 million years of history, they adapted to a wide range of habitats, including fresh water, terrestrial. Their life history is understood, with fossils known from the larval stage, metamorphosis. Most temnospondyls were semiaquatic, although some were almost fully terrestrial and these temnospondyls were some of the first vertebrates fully adapted to life on land. Although temnospondyls are considered amphibians, many had characteristics, such as scales and armour-like bony plates, temnospondyls have been known since the early 19th century, and were initially thought to be reptiles. They were described at times as batrachians and labyrinthodonts. Temnospondyli means cut vertebrae, as each vertebra is divided into several parts, experts disagree over whether temnospondyls were ancestral to modern amphibians, or whether the whole group died out without leaving any descendants.
Different hypotheses have placed modern amphibians as the descendants of temnospondyls, another group of early tetrapods called lepospondyls, recent studies place a family of temnospondyls called the amphibamids as the closest relatives of modern amphibians. Similarities in teeth and hearing structures link the two groups, many temnospondyls are much larger than living amphibians, and superficially resemble crocodiles. Others are smaller and resemble salamanders, Most have broad, flat heads that are either blunt or elongated. The skulls are rounded or triangular in shape when viewed from above, the rugged surfaces of bones may have supported blood vessels, which could transfer carbon dioxide to the bones to neutralize acidic build up in the blood. Many temnospondyls have grooves in their skulls called sensory sulci. The sulci, which run around the nostrils and eye sockets, are part of a lateral line system used to detect vibrations in water. As semiaquatic animals, most temnospondyls have small limbs with four toes on each front foot, terrestrial temnospondyls have larger, thicker limbs, and some even have claws.
One unusual terrestrial temnospondyl, has long limbs for its body. Among the most distinguishing features of temnospondyls are the interpterygoid vacuities, another pair of holes, are present in front of these vacuities, and connect the nasal passage with the mouth. Temnospondyls often have teeth on their palates, as well as in their jaws, some of these teeth are so large, they are referred to as tusks
Mesa is a city in Maricopa County, in the U. S. state of Arizona, and is a suburb located about 20 miles east of Phoenix. Mesa is the city of the East Valley section of the Phoenix Metropolitan Area. It is bordered by Tempe on the west, the Salt River Pima-Maricopa Indian Community on the north and Gilbert on the south, as of the 2010 Census Mesa became Arizonas center of population. Mesa is the third-largest city in Arizona, after Phoenix and Tucson, the city is home to 439,041 people as of 2010 according to the Census Bureau. Mesa is home to higher education facilities including the Polytechnic campus of Arizona State University. The history of Mesa dates back at least 2,000 years to the arrival of the Hohokam people, the Hohokam, whose name means All Used Up or The Departed Ones, built the original canal system. The canals were the largest and most sophisticated in the prehistoric New World, some were up to 90 feet wide and ten feet deep at their head gates, extending for as far as 16 miles across the desert.
By A. D.1100 water could be delivered to an area over 110,000 acres, by A. D.1450, the Hohokam had constructed hundreds of miles of canals many of which are still in use today. After the disappearance of the Hohokam and before the arrival of the early settlers little is known, by the late 19th century near present-day Mesa, U. S. Army troops subdued the Apache opening the way for settlement. Mormon pioneer Daniel Webster Jones led an expedition to found a Mormon settlement in Arizona, leaving St. George, Utah in March 1877, Jones and others arrived at Lehi, an area within the northern edge of present-day Mesa. Jones had been asked by Mormon officials to direct a party of people in establishing a settlement in Arizona. This settlement was known as Jonesville and Fort Utah and did not receive the name of Lehi until 1883. At the same time, another group dubbed the First Mesa Company arrived from Utah and their leaders were named Francis Martin Pomeroy, Charles Crismon, George Warren Sirrine and Charles I.
Rather than accepting an invitation to settle at Jones Lehi settlement and they dug irrigation canals, some of which were over the original Hohokam canals, and by April 1878, water was flowing through them. The Second Mesa Company arrived in 1879 and settled to the west of where the First Mesa Company settled in 1880, on July 17,1878, Mesa City was registered as a 1-square-mile townsite. The first school was built in 1879, in 1883, Mesa City was incorporated with a population of 300 people. Dr. A. J. Chandler, who would go on to found the city of Chandler. In 1917, the city of Mesa purchased the utility company, the revenues from the company provided enough for capital expenditures until the 1960s
In biology, a species is the basic unit of biological classification and a taxonomic rank. A species is defined as the largest group of organisms in which two individuals can produce fertile offspring, typically by sexual reproduction. While this definition is often adequate, looked at more closely it is problematic, for example, with hybridisation, in a species complex of hundreds of similar microspecies, or in a ring species, the boundaries between closely related species become unclear. Other ways of defining species include similarity of DNA, all species are given a two-part name, a binomial. The first part of a binomial is the genus to which the species belongs, the second part is called the specific name or the specific epithet. For example, Boa constrictor is one of four species of the Boa genus, Species were seen from the time of Aristotle until the 18th century as fixed kinds that could be arranged in a hierarchy, the great chain of being. In the 19th century, biologists grasped that species could evolve given sufficient time, Charles Darwins 1859 book The Origin of Species explained how species could arise by natural selection.
Genes can sometimes be exchanged between species by horizontal transfer, and species may become extinct for a variety of reasons. In his biology, Aristotle used the term γένος to mean a kind, such as a bird or fish, a kind was distinguished by its attributes, for instance, a bird has feathers, a beak, wings, a hard-shelled egg, and warm blood. A form was distinguished by being shared by all its members, Aristotle believed all kinds and forms to be distinct and unchanging. His approach remained influential until the Renaissance, when observers in the Early Modern period began to develop systems of organization for living things, they placed each kind of animal or plant into a context. Many of these early delineation schemes would now be considered whimsical, animals likewise that differ specifically preserve their distinct species permanently, one species never springs from the seed of another nor vice versa. In the 18th century, the Swedish scientist Carl Linnaeus classified organisms according to shared physical characteristics and he established the idea of a taxonomic hierarchy of classification based upon observable characteristics and intended to reflect natural relationships.
At the time, however, it was widely believed that there was no organic connection between species, no matter how similar they appeared. However, whether or not it was supposed to be fixed, by the 19th century, naturalists understood that species could change form over time, and that the history of the planet provided enough time for major changes. Jean-Baptiste Lamarck, in his 1809 Zoological Philosophy, described the transmutation of species, proposing that a species could change over time, in 1859, Charles Darwin and Alfred Russel Wallace provided a compelling account of evolution and the formation of new species. Darwin argued that it was populations that evolved, not individuals and this required a new definition of species. Darwin concluded that species are what appear to be, ideas
Glen Rose Formation
The Glen Rose Formation is a shallow marine to shoreline geological formation from the lower Cretaceous period exposed over a large area from South Central to North Central Texas. Wells drilled in eastern Travis County have encountered over 1,000 feet of the Glen Rose, in the northern part, the Glen Rose is laterally continuous with the Paluxy Formation. The Glen Rose overlies the Hensel Sand and is overlain in turn by formations of the Fredericksburg division, in 1974, Keith Young concluded, based on ammonite zonation, that the formation ranges from late Upper Aptian into the Lower Albian, about 115-105 million years old. The formation consists mostly of limestone strata alternating with marl or marly limestone. Because of the strengths of the layers, the limestone weathers to form a staircase profile on hills. These strata were originally referred to as the Alternating Beds, which included the overlying Fredericksburg formations. The Glen Rose has been divided into upper and lower portions, separated by a layer of Corbula shells.
The formation was named in 1891 for the town of Glen Rose, the type locality is a near shore section exposed in the Paluxy River near the town of Glen Rose. The stratigraphy of the formation was most recently revised in a 1971 study, a stratigraphic column at the Mount Bonnell location starts with the Lower Cretaceous Trinity Group overlain by the Edwards Group. Upper Cretaceous formations follow, starting with the Del Rio Clay, Buda Limestone, formations within the Trinity Group include the Hammett Formation, Cow Creek Formation, Hensel Formation, and Lower and Upper Glen Rose Formation. The Hammett and the portion of the Upper Glen Rose act as confining units for the Middle Trinity Aquifer. The Upper Glen Rose contains the Upper Trinity Aquifer, which appears to have intra-aquifer groundwater flow with the Edwards Aquifer as water levels are at the same elevation. A variety of fossils are found in the Glen Rose, more abundantly in the lower Glen Rose than the upper, including gastropods, clams.
Many species in the lower portion are not found in the upper portion, Dinosaur tracks have been found in many localities, as well as isolated vertebrate remains. Microfossils are present, including one of the largest foraminifera ever found, a variety of fossil bivalves have been found, usually preserved as internal molds, with the exception of oysters and rudists, which have their shells present although mineralized. Some of the clams are large and round and have given the popular name heart clams. Fossil bivalves include a number of rudists which form reefs in the lower Glen Rose, numerous gastropods are found in the Glen Rose, preserved as internal molds, the shells having dissolved away. Corals formed reefs in the lower Glen Rose and a number of species of corals have been described