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Oegophiurida
The Oegophiurida are an order of brittle stars, class Ophiuroidea. The physical characteristics of this order include well separated lateral plates, which expose the oral surface of radial ossicles. It also has vertebrae with streptospondylous (hourglass) articulation, which thus allow for vertical and horizontal movements. The order has neither oral nor radial shields. They have paired serial gonads arranged segmentally along the arm. The hyponeural groove is covered by soft integument, which forms a spacious epineural canal that is not closed over by ventral arm plates. The disk is covered by naked or granulated skin, or by imbricating scales. The Oegophiurida are extinct except for a recent species, '' Ophiocanops fugiens'', which has several remarkable features. In each arm is a single digestive caecum. The caecum wall has many folds which enlarge the absorbing surface. This is similar to the structure in asteroids. Nothing, however, is known of this species' microsc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ophiocanops Fugiens
''Ophiocanops fugiens'' is a living species in the brittle star family Ophiocanopidae. Though once considered to be the only one living species in this brittle star family, recent research has brought to light three specimens of ''Ophiocanops'' that differ substantially from ''O. fugiens.'' It has been regarded as the most primitive brittle star, close to Paleozoic forms, though other authors have disagreed with the view. Classification of ''O. fugiens'' is highly argued. ''Ophiocanops'' is usually placed in the order Oegophiurida (suborder Zeugophiurina) or regarded as a genus '' incertae sedis'' or even given its own subclass Oegophiuridea. Some recent data suggest its relationship to the extant family Ophiomyxidae (it would thus belong to the order Phrynophiurida). Characteristics ''Ophiocanops fugiens'' displays a central, armored, disk-shape body that is clearly demarcated from the arms and is 3mm in diameter. Brittle Stars, including ''O. fugiens'', have long flexible ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zeugophiurina
Zeugophiurina is a suborder of primitive brittle stars with three extinct families. The family Ophiocanopidae with only one living genus and species, ''Ophiocanops fugiens ''Ophiocanops fugiens'' is a living species in the brittle star family Ophiocanopidae. Though once considered to be the only one living species in this brittle star family, recent research has brought to light three specimens of ''Ophiocanops'' ...'' has been placed here but recent studies have challenged this classification.Pawson,D.L.,Phylum Echinodermata, Zootaxa 1668: 749–764 (2007) References Oegophiurida Animal suborders {{ophiuroidea-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ophiuroidea
Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomotion. The ophiuroids generally have five long, slender, whip-like arms which may reach up to in length on the largest specimens. The Ophiuroidea contain two large clades, Ophiurida (brittle stars) and Euryalida (basket stars). Over 2,000 species of brittle stars live today. More than 1,200 of these species are found in deep waters, greater than 200 m deep. Range The ophiuroids diverged in the Early Ordovician, about 500 million years ago. Ophiuroids can be found today in all of the major marine provinces, from the poles to the tropics. Basket stars are usually confined to the deeper parts of this range; Ophiuroids are known even from abyssal (>6,000 m) depths. However, brittle stars are also common members of reef communities, where ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ossicle (echinoderm)
Ossicles are small calcareous elements embedded in the dermis of the body wall of echinoderms. They form part of the endoskeleton and provide rigidity and protection. They are found in different forms and arrangements in sea urchins, starfish, brittle stars, sea cucumbers, and crinoids. The ossicles and spines (which are specialised sharp ossicles) are the only parts of the animal likely to be fossilized after an echinoderm dies. Formation Ossicles are created intracellularly by specialised secretory cells known as sclerocytes in the dermis of the body wall of echinoderms. Each ossicle is composed of microcrystals of calcite arranged in a three-dimensional lattice known as a stereom. Under polarized light the ossicle behaves as if it were a single crystal because the axes of all the crystals are parallel. The space between the crystals is known as the stroma and allows entry to sclerocytes for enlargement and repair. The honeycomb structure is light but tough and collagenou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordovician
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. The Ordovician, named after the Welsh tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same rock beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed strata were different from those of either the Cambrian or the Silurian systems, and placed them in a system of their own. The Ordovician received international approval in 1960 (forty years after Lapworth's death), when it was adopted as an official period of the Paleozoic Era by the International Geological Congress. Life continued to flourish during the Ordovician as it did in the earlier C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago (Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferous'' means "coal-bearing", from the Latin '' carbō'' (" coal") and '' ferō'' ("bear, carry"), and refers to the many coal beds formed globally during that time. The first of the modern 'system' names, it was coined by geologists William Conybeare and William Phillips in 1822, based on a study of the British rock succession. The Carboniferous is often treated in North America as two geological periods, the earlier Mississippian and the later Pennsylvanian. Terrestrial animal life was well established by the Carboniferous Period. Tetrapods (four limbed vertebrates), which had originated from lobe-finned fish during the preceding Devonian, became pentadactylous in and diversified during the Carboniferous, including early amphibian lin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
