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Schizorhiza
''Schizorhiza'' is a fossil genus of cartilaginous fish, containing a single accepted species ''Schizorhiza stromeri''. Its fossils are found in rocks dating from the Campanian and Maastrichtian stages; it thus lived between about and million years ago. Like other sawfish-like rays from the Mesozoic, it probably did not survive the Cretaceous–Paleogene extinction event; there are a few remains from the Paleogene but these seem to have been reworked from Late Cretaceous deposits. (2002): ''Schizorhiza'': a unique sawfish paradigm from the Difunta Group, Coahuila, Mexico. ''Revista Mexicana de Ciencias Geológicas'' 19(1): 16-24 nglish with Spanish abstractbr>PDF fulltext/ref> Taxonomy Due to its unique rostral teeth, ''Schizorhiza'' is placed in the monotypic subfamily Schizorhizinae. Despite formerly being classified within a family of extinct sawfish-like rays known as Sclerorhynchidae, phylogenetic analyses indicate that ''Ischyrhiza, Schizorhiza'', and ''Onchopristis'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sclerorhynchoidei
Sclerorhynchoidei is an extinct suborder of rajiform rays that had long rostra with large denticles similar to sawfishes and sawsharks. This feature was convergently evolved and their closest living relatives are actually skates. While they are often called "sawfishes", sawskates is a more accurate common name for sclerorhynchoids. The suborder contains five named families: Ganopristidae, Ischyrhizidae, Onchopristidae, Ptychotrygonidae, and Schizorhizidae. Several genera (see below) are not currently placed in any of these families. Sclerorhynchoids first appeared in the Barremian and went extinct during the Cretaceous–Paleogene extinction event, with former Paleocene occurrences being misidentifications or reworked specimens. Phylogeny Below is a cladogram of Sclerorhynchoidei, with the topology based on Villalobos-Segura ''et al.'' (2021b) and the family taxonomy based on Greenfield (2021). Other genera *†''Agaleorhynchus'' *†''Ankistrorhynchus'' *†''Arc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ischyrhiza
''Ischyrhiza'' is an extinct genus of sclerorhynchoid ray from the Late Cretaceous and Early Paleogene. It had a large, toothed rostrum closely resembling that of a modern-day sawfish. Despite formerly being classified within a family of extinct sawfish-like rays known as Sclerorhynchidae, phylogenetic analyses indicate that ''Ischyrhiza, Schizorhiza'', and '' Onchopristis'' form a distinct clade that groups closer with the extant family Rajidae, which contains the true skates, possibly rendering the suborder Sclerorhynchoidei paraphyletic. Fossils of the genus have been found in Canada, the United States, the Aguja Formation of Mexico, the Bissekty Formation of Uzbekistan, the Tamayama Formation of Japan, the Dukamaje Formation of Niger, the El Molino Formation of Bolivia, the Quiriquina Formation of Chile, and the Chota Formation The Chota Formation is an Early Campanian to Late Eocene geologic formation of the Cajamarca and western Amazonas Region in northern Pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the Latin word for the white limestone known as chalk. The chalk of northern France and the white cliffs of south-eastern England date from the Cretaceous Period. Climate During the Late Cretaceous, the climate was warmer than present, although throughout the period a cooling trend is evident. The tropics became restricted to equatorial regions and northern latitudes experienced markedly more seasonal climatic conditions. Geography Due to plate tectonics, the Americas were gradually moving westward, causing the Atlantic Ocean to expand. The Western Interior Seaway divided North America into eastern and western halves; Appalachia and Laramidia. India maintained a northward course towards Asia. In the Southern Hemisphere, Australia and Ant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rostrum (anatomy)
Rostrum (from Latin ', meaning ''beak'') is a term used in anatomy for a number of phylogenetically unrelated structures in different groups of animals. Invertebrates * In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes. It is generally a rigid structure, but can be connected by a hinged joint, as seen in Leptostraca. * Among insects, the rostrum is the name for the piercing mouthparts of the order Hemiptera as well as those of the snow scorpionflies, among many others. The long snout of weevils is also called a rostrum. * Gastropod molluscs have a rostrum or proboscis. * Cephalopod molluscs have hard beak-like mouthparts referred to as the rostrum. File:Washington DC Zoo - Macrobrachium rosenbergii 6.jpg, Crustacean: the rostrum of the shrimp ''Macrobrachium rosenbergii'' is serrated along both edges. File:Gminatus australis with Beetle.jpg, Insect: assassin bug piercing its prey with its rostrum File:Architeuthis beak.jpg, Cephalopod: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhomboidal
Traditionally, in two-dimensional geometry, a rhomboid is a parallelogram in which adjacent sides are of unequal lengths and angles are non-right angled. A parallelogram with sides of equal length (equilateral) is a rhombus but not a rhomboid. A parallelogram with right angled corners is a rectangle but not a rhomboid. The term ''rhomboid'' is now more often used for a rhombohedron or a more general parallelepiped, a solid figure with six faces in which each face is a parallelogram and pairs of opposite faces lie in parallel planes. Some crystals are formed in three-dimensional rhomboids. This solid is also sometimes called a rhombic prism. The term occurs frequently in science terminology referring to both its two- and three-dimensional meaning. History Euclid introduced the term in his '' Elements'' in Book I, Definition 22, Euclid never used the definition of rhomboid again and introduced the word parallelogram in Proposition 34 of Book I; ''"In parallelogrammic areas the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triangular
A triangle is a polygon with three edges and three vertices. It is one of the basic shapes in geometry. A triangle with vertices ''A'', ''B'', and ''C'' is denoted \triangle ABC. In Euclidean geometry, any three points, when non- collinear, determine a unique triangle and simultaneously, a unique plane (i.e. a two-dimensional Euclidean space). In other words, there is only one plane that contains that triangle, and every triangle is contained in some plane. If the entire geometry is only the Euclidean plane, there is only one plane and all triangles are contained in it; however, in higher-dimensional Euclidean spaces, this is no longer true. This article is about triangles in Euclidean geometry, and in particular, the Euclidean plane, except where otherwise noted. Types of triangle The terminology for categorizing triangles is more than two thousand years old, having been defined on the very first page of Euclid's Elements. The names used for modern classification are ei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tooth Enamel
Tooth enamel is one of the four major Tissue (biology), tissues that make up the tooth in humans and many other animals, including some species of fish. It makes up the normally visible part of the tooth, covering the Crown (tooth), crown. The other major tissues are dentin, cementum, and Pulp (tooth), dental pulp. It is a very hard, white to off-white, highly mineralised substance that acts as a barrier to protect the tooth but can become susceptible to degradation, especially by acids from food and drink. Calcium hardens the tooth enamel. In rare circumstances enamel fails to form, leaving the underlying dentin exposed on the surface. Features Enamel is the hardest substance in the human body and contains the highest percentage of minerals (at 96%),Ross ''et al.'', p. 485 with water and organic material composing the rest.Ten Cate's Oral Histology, Nancy, Elsevier, pp. 70–94 The primary mineral is hydroxyapatite, which is a crystalline calcium phosphate. Enamel is formed o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elasmobranchii
Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including sharks (superorder Selachii), rays, skates, and sawfish (superorder Batoidea). Members of this subclass are characterised by having five to seven pairs of gill clefts opening individually to the exterior, rigid dorsal fins and small placoid scales on the skin. The teeth are in several series; the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper. The details of this jaw anatomy vary between species, and help distinguish the different elasmobranch clades. The pelvic fins in males are modified to create claspers for the transfer of sperm. There is no swim bladder; instead, these fish maintain buoyancy with large livers rich in oil. The definition of the clade is unclear with respect to fossil chondrichthyans. It has been used by different authors as equivalent to Neoselachii (the clade including modern sharks and rays and their last common ancestor) or for al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Camille Arambourg
Camille Arambourg ( February 3, 1885– November 19, 1969) was a French vertebrate paleontologist. He conducted extensive field work in North Africa. In the 1950s he argued against the prevailing model of Neanderthals as brutish and simian. During World War I he was in Military service. After that he was a professor of Geology at the Institut Agricole d'Alger, and after that a professor of Paleontology at Muséum National d'Histoire Naturelle in Paris, where he succeeded his teacher Marcellin Boule. The pterosaur ''Arambourgiania'' is named after him. He was President of the PanAfrican Archaeological Association from 1959 to 1963. Publications * (1942) "L’ Elephas recki ''Palaeoloxodon recki'' is an extinct species of elephant native to Africa during the Pliocene and Pleistocene. At up to 14 feet (4.27 metres) in shoulder height, it was one of the largest elephant species to have ever lived. It is believed that ... Dietrich. Exposition systématique et ses affinités". ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ernst Stromer
Ernst Freiherr Stromer von Reichenbach (12 June 1871 in Nürnberg – 18 December 1952 in Erlangen) was a German paleontologist. He is best remembered for his expedition to Egypt, during which the first known remains of ''Spinosaurus'' were discovered. He described the following Cretaceous dinosaurs from Egypt: ''Aegyptosaurus'', ''Bahariasaurus'', '' Carcharodontosaurus'', and the enigmatic theropod, ''Spinosaurus aegyptiacus''. Stromer also described the giant crocodilian, ''Stomatosuchus''. The fossil bird genus ''Stromeria'' (now included in the genus ''Eremopezus'') and the sauropod ''Paralititan stromeri'' were named in his honor (by Kálmán Lambrecht in 1929 and Smith et al. 2001,Smith JB, Lamanna MC, Lacovara KJ, Dodson P, Smith JR, Poole JC, Giegengack R, Attia Y (June 2001). "A giant sauropod dinosaur from an Upper Cretaceous mangrove deposit in Egypt". Science. 292 (5522): 1704–6. Bibcode:2001Sci...292.1704S. doi:10.1126/science.1060561. respectively). The m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paraphyly
In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In contrast, a monophyletic group (a clade) includes a common ancestor and ''all'' of its descendants. The terms are commonly used in phylogenetics (a subfield of biology) and in the tree model of historical linguistics. Paraphyletic groups are identified by a combination of synapomorphies and symplesiomorphies. If many subgroups are missing from the named group, it is said to be polyparaphyletic. The term was coined by Willi Hennig to apply to well-known taxa like Reptilia ( reptiles) which, as commonly named and traditionally defined, is paraphyletic with respect to mammals and birds. Reptilia contains the last common ancestor of reptiles and all descendants of that ancestor, including all extant reptiles as well as the extinct synapsids, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Skate (fish)
Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. More than 150 species have been described, in 17 genera.LAST, P.R. & SÉRET, B. & STEHMANN, M.F.W. & WEIGMANN, S. (2016) Skates, Family Rajidae. In: Last, P.R., White, W.T., Carvalho, M.R. de, Séret, B., Stehmann, M.F.W & Naylor, G.J.P (Eds.) Rays of the World. CSIRO Publishing, Melbourne: 204–363 Softnose skates and pygmy skates were previously treated as subfamilies of Rajidae (Arhynchobatinae and Gurgesiellinae), but are now considered as distinct families. Alternatively, the name "skate" is used to refer to the entire order of Rajiformes (families Anacanthobatidae, Arhynchobatidae, Gurgesiellidae and Rajidae). Members of Rajidae are distinguished by a stiff snout and a rostrum that is not reduced. Taxonomy and systematics Evolution Skates belong to the ancient lineage of cartilaginous fishes. Fossil denticles (tooth-like scales in the skin) resembling those of today's ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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