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Weigeltaspis
''Weigeltaspis'' is a genus of extinct heterostracan agnathan fish known from the Late Silurian and Early Devonian periods. Fossils are known primarily from Early Devonian-aged marine strata of Europe and Canada. Fragments and disarticulated plates of what may be of ''Weigeltaspis'' are known from Late Silurian-aged marine strata of Arctic Canada. Rare articulated fossils, plus the overall anatomy of its plates suggest the living animals were, at least superficially, similar to psammosteids, some authorities, such as Tarlo, place them within Psammosteida.Tarlo, Halstead. "LB t1965) Psammosteiformes tAgnatha)—A review with descriptions of new material from the Lower Devonian of Poland, II. Systematic Part." Palaeontologia Polonica 15: 168. Pages 20-21 Because the ornamentation on the plates and scales are very similar to the ornamentation seen on the plates and scales of '' Traquairaspis'' to the point of constant confusion, other authorities follow the lead of Obruchev, and pl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traquairaspis
''Traquairaspis'' is a genus of extinct heterostracan agnathan fish known from the Silurian and Early Devonian periods. It is predominantly known from Late Silurian fluvial deposits from Wales and England: some species were also found in shallow water marine environment in Canada and North America. The head-shield and body armor of most species form an almond shape. Plates have a distinctive ornamentation of tubercles: this ornamentation is very similar to the plate ornamentation of the heterostracan ''Weigeltaspis''. This similarity of ornamentation creates much confusion over the taxonomical placement of ''Weigeltaspis'', in addition to confusion over whether or not an isolated plate is of ''Traquairaspis'', or of ''Weigeltaspis''.Tarlo, Halstead. "LB t1965) Psammosteiformes tAgnatha)—A review with descriptions of new material from the Lower Devonian of Poland, II. Systematic Part." Palaeontologia Polonica 15: 168. Pages 20-21 The generic name honors Ramsay Heatley Traqu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Psammosteida
Psammosteida also called as Psammosteoidei is a suborder of pteraspidid heterostracan agnathans. The psammosteids had broad, flattened bodies, suggesting a predominantly benthic habit. The earliest unequivocal psammosteid is '' Drepanaspis'' of Early Devonian Germany, which is either included in the family Psammosteidae, or placed within its own family, Drepanaspididae. If the late Silurian/Early Devonian '' Weigeltaspis'' is a psammosteid, as opposed to being a traquairaspid, then that genus, instead, would be the oldest psammosteid. However, its placement within Heterostraci remains a matter of debate. Other notable psammosteids include '' Psammosteus'', and '' Obruchevia'', two genera of enormous species with dorsal shields around one meter in diameter. The Psammosteids were the only heterostracans to survive to the end of the Devonian, where they finally perish during the Hangenberg event The Hangenberg event, also known as the Hangenberg crisis or end-Devonian extinct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Animal
Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motility, able to move, can Sexual reproduction, reproduce sexually, and go through an ontogenetic stage in which their body consists of a hollow sphere of Cell (biology), cells, the blastula, during Embryogenesis, embryonic development. Over 1.5 million Extant taxon, living animal species have been Species description, described—of which around 1 million are Insecta, insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from to . They have Ecology, complex interactions with each other and their environments, forming intricate food webs. The scientific study of animals is known as zoology. Most living animal species are in Bilateria, a clade whose members have a Symmetry in biology#Bilate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fossils Of Canada
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood and DNA remnants. The totality of fossils is known as the ''fossil record''. Paleontology is the study of fossils: their age, method of formation, and evolutionary significance. Specimens are usually considered to be fossils if they are over 10,000 years old. The oldest fossils are around 3.48 billion years old to 4.1 billion years old. Early edition, published online before print. The observation in the 19th century that certain fossils were associated with certain rock strata led to the recognition of a geological timescale and the relative ages of different fossils. The development of radiometric dating techniques in the early 20th century allowed scientists to quantitatively measure the absolut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Devonian Fish Of North America
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, where rocks from this period were first studied. The first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. The arthropod groups of myriapods, arachnids and hexapods also became well-established early in this period, after starting their expansion to land at least from the Ordovician period. Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fishes. The placoderms began dominating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Early Devonian Fish Of Europe
{{disambiguation, geo ...
Early may refer to: History * The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.: ** Early Christianity ** Early modern Europe Places in the United States * Early, Iowa * Early, Texas * Early Branch, a stream in Missouri * Early County, Georgia Other uses * ''Early'' (Scritti Politti album), 2005 * ''Early'' (A Certain Ratio album), 2002 * Early (name) * Early effect, an effect in transistor physics * Early Records, a record label * the early part of the morning See also * Earley (other) Earley is a town in England. Earley may also refer to: * Earley (surname), a list of people with the surname Earley * Earley (given name), a variant of the given name Earlene * Earley Lake, a lake in Minnesota *Earley parser, an algorithm *Earley ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterostraci Enigmatic Taxa
Heterostraci (Ancient Greek, ἕτερος+ὄστρακον "those itha different shell" i is pl. of -us is an extinct subclass of pteraspidomorph jawless vertebrate that lived primarily in marine and estuary environments. Heterostraci existed from the mid-Ordovician to the conclusion of the Devonian. Description and anatomy The Heterostracans differed from other Paleozoic agnathan taxa both in the arrangement and histology of their scales. Most heterostracans had two plates which form a large dorsal shield and a large ventral shield, and had series of scales arranged in various patterns on the sides of their bodies, the exact pattern differing from one group to another. In a few primitive forms, such as ''Lepidaspis'', the dorsal and ventral shields are composed of a mosaic of tiny scales. In most other known forms, though, these tiny scales have fused together to form the shield-plates. The scales of heterostracans are histologically distinct from other vertebrates, ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterostraci Genera
Heterostraci (Ancient Greek, ἕτερος+ὄστρακον "those itha different shell" i is pl. of -us is an extinct subclass of pteraspidomorph jawless vertebrate that lived primarily in marine and estuary environments. Heterostraci existed from the mid-Ordovician to the conclusion of the Devonian. Description and anatomy The Heterostracans differed from other Paleozoic agnathan taxa both in the arrangement and histology of their scales. Most heterostracans had two plates which form a large dorsal shield and a large ventral shield, and had series of scales arranged in various patterns on the sides of their bodies, the exact pattern differing from one group to another. In a few primitive forms, such as '' Lepidaspis'', the dorsal and ventral shields are composed of a mosaic of tiny scales. In most other known forms, though, these tiny scales have fused together to form the shield-plates. The scales of heterostracans are histologically distinct from other vertebrate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silurian Jawless Fish
The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozoic Era. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out. One important event in this period was the initial establishment of terrestrial life in what is known as the Silurian-Devonian Terrestrial Revolution: vascular plants emerged from more primitive land plants, dikaryan fungi started expanding and diversifying along with glomeromycotan fungi, and three groups of arthropods (myriapods, arachnids and hexapods) became fully terrestrialized. A significant evolutionary milestone during th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Devonian Jawless Fish
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, where rocks from this period were first studied. The first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. The arthropod groups of myriapods, arachnids and hexapods also became well-established early in this period, after starting their expansion to land at least from the Ordovician period. Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fishes. The placoderms began dominating al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beverly Halstead
Lambert Beverly Halstead (13 June 1933 – 30 April 1991), who also went by Lambert Beverly Halstead Tarlo or just Beverly Halstead, was a British paleontology, paleontologist and professor of Geology & Zoology and popular science, popularizer of science. He was noted for his candid theories of dinosaur sexual habits, and also for a prolonged assault on phylogenetic systematics (or Cladistics, "cladism", as he referred to it), in a series of letters and editorials to the journal Nature (journal), Nature in the late 1970s and early 1980s. He was President of the Geologists' Association for 1990–91. References * Republished in W.A.S. Sarjeant (ed.), Vertebrate fossils and the evolution of scientific concepts. Writings in tribute to Beverly Halstead. Reading, England: Gordon & Breach Publishers, 1995. * 1933 births 1991 deaths British palaeontologists Presidents of the Geologists' Association {{paleontologist-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by total area. Its southern and western border with the United States, stretching , is the world's longest binational land border. Canada's capital is Ottawa, and its three largest metropolitan areas are Toronto, Montreal, and Vancouver. Indigenous peoples have continuously inhabited what is now Canada for thousands of years. Beginning in the 16th century, British and French expeditions explored and later settled along the Atlantic coast. As a consequence of various armed conflicts, France ceded nearly all of its colonies in North America in 1763. In 1867, with the union of three British North American colonies through Confederation, Canada was formed as a federal dominion of four provinces. This began an accretion of provinces an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
