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McGraw Hill Financial, Inc. is an American publicly traded corporation headquartered in Rockefeller Center in New York City. Its primary areas of business are financial, publishing, and business services.
A group of extinct flying birds known exclusively from the latest stages of the Cretaceous (80–65 million years ago) in North America. Along with Hesperornithiformes, Ichthyornithiforms are some of the earliest nonmodern bird taxa known to science. Indeed, alongside <i>Archaeopteryx</i> (from much earlier Jurassic rocks in Germany, about 140 million years old), the ichthyornithiformes <i>Ichthyornis</i>, <i>Apatornis</i>, and their kin formed the basis for knowledge of avian evolution for almost a century. Although the fossil record of these birds has improved in recent years, Ichthyornithiformes are still poorly understood.
Industry:Science
A group of extinct invertebrate organisms normally having an elongate, four-sided pyramidal exoskeleton of calcium phosphate composition. Due to poor preservation of key biological structures, the evolutionary affinities and classification of conulariids are uncertain; however, they are often regarded as an unusual group of cnidarians.
Industry:Science
A group of extinct mammals that range from the Late Triassic to Late Cretaceous. Their fossil remains have been found in Mesozoic deposits worldwide. These small insectivorous or carnivorous mammals are the size of a shrew or mouse. They are considered to be distant relatives of the more derived therian mammals, including the extinct eupantotheres, such as dryolestids and the living placental and marsupial mammals.
Industry:Science
A group of extinct marine animals that are often abundant in strata of Late Cambrian to Late Triassic age, a time span of about 300 million years. Only the mineralized elements, which are usually 0.2 to 2 mm (0.008 to 0.08 in.) in dimension (the largest known reach 14 mm or 0.6 in.), are normally preserved. They are routinely extracted as isolated discrete specimens by chemical degradation of the rock in which they occur. The apatite (calcium phosphate) of which conodont elements are composed is laid down as lamellae. In the earliest euconodonts (“true” conodonts, as opposed to the more primitive, and possibly unrelated, protoconodonts and paraconodonts), the elements comprise an upper crown and a basal body. The basal body occupies a cavity in the base of the crown, but is not present in the majority of post-Devonian species. In advanced conodonts the crown incorporates regular patches of opaque, finely crystalline, white matter.
Industry:Science
A group of fossil jawless fishes, roughly similar in appearance to extant lampreys, known from Early Silurian–Early Devonian deposits (about 410–430 million years ago) that represent marine, coastal environments. Anaspid fossils are known predominantly from the Northern Hemisphere.
Industry:Science
A group of fungi consisting of yeasts that reproduce asexually by budding or splitting of single cells. In spite of simple morphology, these yeasts are quite diverse in terms of evolutionary origins and environmental roles. The group contains the yeasts used in baking and brewing. Some other yeasts are responsible for infections in humans and animals, while others occur on leaves or fruits. A few species are used for biological control of microbial plant pathogens. A very small number are pathogens of plants.
Industry:Science
A group of laboratory and production operations whereby the components of a polyphase mixture are separated by mechanical methods into two or more fractions of different mechanical characteristics. The separated fractions may be homogeneous or heterogeneous, particulate or nonparticulate. Mechanical separations are differentiated from two other classes of separations of major importance: those that depend on separation at the molecular level on the basis of thermodynamic or physicochemical properties and by means of such mass-transfer processes as evaporation, dissolution, precipitation, absorption, and intraphase or interphase diffusion; and those that depend on chemical reaction of a component and subsequent separation of the product by mass-transfer or mechanical methods.
Industry:Science
A group of late archaic humans from Europe, the Near East, and central Asia that immediately preceded the first modern humans in those regions. The Neandertals are included by some within the species <i>Homo sapiens</i>, recognizing their close affinities to modern humans; others place them in their own species, <i>Homo neanderthalensis</i>, emphasizing the differences between them and modern humans.
Industry:Science
A group of lobe-finned fishes, distantly related to tetrapods, that spans some 375 million years of geological time from the first known fossil in the Middle Devonian to the living fish <i>Latimeria chalumnae</i>. There is, however, a gap of some 70 million years in the fossil record between the most recent known fossil and the living fish. Indeed, coelacanths had long been thought to have become extinct with the dinosaurs at the end of the Cretaceous. Great excitement therefore ensued when the first living coelacanth was found off East London, South Africa, in 1938. Much debate followed concerning the status of the living species: for example, where does <i>Latimeria</i> live, how has it survived, and how many are there now are still issues. Recently a new population of the species has been discovered in the western Pacific Ocean, throwing many previously held theories into disarray.
Industry:Science
A group of marine protists, regarded as a subclass of Actinopodea in older classifications, but not recognized as a natural group in some modern systems owing to its heterogeneity. Radiolarians occur almost exclusively in the open ocean as part of the plankton community, and are widely recognized for their ornate siliceous skeletons produced by most of the groups (<b>illus. <i>a</i>–<i>c</i></b>). Their skeletons occur abundantly in ocean sediments and are used in analyzing the layers of the sedimentary record (biostratigraphy). Although most radiolarians occur only in open ocean locations, a unique skeleton-bearing nasselarian radiolarian (<i>Lophophaena rioplatensis</i>) has been identified in a coastal location in the Rio de la Plata estuary in South America.
Industry:Science
