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Squalodontidae
Squalodontidae or the shark-toothed dolphins is an extinct family of large toothed whales who had long narrow jaws. Squalodontids are known from all continents except Antarctica, from the Oligocene to the Neogene, but they had a maximal diversity and global distribution during the Late Oligocene and Early to Middle Miocene (). With their cosmopolitan Miocene distribution and heterodont dentition, squalodontids are the most common and basal platanistoids. They are relatively large odontocetes, comparable in size to extant mesoplodont whales. The premaxillae on their elongated rostrum have large and slightly convex fossae for the air sacs associated with the presence of a melon, indicating the ability for echolocation. ''Squalodon'' and '' Eosqualodon'' are based on partial or complete skulls. The synapomorphic traits of the family are, however, based mostly on one of the bones of the inner ear, the periotic bone, which is unknown in these genera except in ''Squalodon''. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Squalodon
''Squalodon'' is an extinct genus of whales of the Oligocene and Miocene epochs, belonging to the family Squalodontidae. Named by Jean-Pierre Sylvestre de Grateloup in 1840, it was originally believed to be an iguanodontid dinosaur but has since been reclassified. The name ''Squalodon'' comes from ''Squalus'', a genus of shark. As a result, its name means "shark tooth". Its closest modern relative is the South Asian river dolphin (with its two subspecies the Ganges river dolphin and Indus river dolphin). Description Species of ''Squalodon'' are odontocetes that lived during the late Oligocene into the middle Miocene, about 28 to 15 million years ago. The genus ''Squalodon'' belongs to the order Odontoceti, the toothed whales. They are named after the shark ''Squalus'' because their cheek teeth look like the teeth of a squalus shark. The largest species, ''Squalodon whitmorei'', reached up to 5.5 meters in length. The unique-looking squalodontids were likely distributed throug ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eosqualodon
''Eosqualodon'' is a genus of squalodontid odontocete from the Late Oligocene to Early Miocene (Chattian-Aquitanian) of northwestern Germany and northeastern Italy. Taxonomy and description Two species are recognized, ''E. langewieschei'' and ''E. latirostris''. The latter was originally described as a subspecies of ''Squalodon bariensis'', ''S. b. latirostris'', but is distinct from ''S. bariensis''. ''Eosqualodon'' can be distinguished from ''Squalodon ''Squalodon'' is an extinct genus of whales of the Oligocene and Miocene epochs, belonging to the family Squalodontidae. Named by Jean-Pierre Sylvestre de Grateloup in 1840, it was originally believed to be an iguanodontid dinosaur but has sinc ...'' in having a broader rostral base, the caudal border of the external nares (blowhole) at the height of the caudal part of the orbits, and weakly developed intertemporal construction.G. Capellini. 1903. Avanzi di squalodonte nella Arenaria di Grumi dei Frati Presso Schio. Memorie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tangaroasaurus
''Tangaroasaurus'' is an extinct genus of squalodontid whale from the Miocene of New Zealand. It contains a single species, ''Tangaroasaurus kakanuiensis''. Similar to ''Basilosaurus'' and its close relative ''Squalodon'', it was originally thought to be a species of marine reptile. Parts of the Holotype are presumably lost. Its name comes from Tangaroa, the Maori god of the sea, while the suffix ''-saurus'' comes from the Latin word for reptile, the group that Tangaroasaurus was originally placed in. The type fossil was found in a grey clay deposit at All Day Bay and consists of a jaw bearing a few teeth, measuring each. The original describer of the type specimen, William Blaxland Benham, described it as a reptile, either a dinosaur such as Megalosaurus or an late surviving ichthyosaur. The genus was described as an odontocete cetacean in 1979 by R. E. Fordyce. The status of the genus as a cetacean remains under discussion. Fossils known from the same geological format ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phoberodon
''Phoberodon'' is a genus of archaic odontocete cetacean from the Early Miocene (Burdigalian) of Patagonia, Argentina. Taxonomy and description ''Phoberodon'' was described in 1926 from a partially complete skeleton lacking the earbones, which was found in the Colhuehuapian Gaiman Formation of Chubut Province, Argentina. Subsequent authors either followed Cabrera (1926) in classifying ''Phoberodon'' as a squalodontid, or considered it a relative of ''Waipatia'' although the genus was included in any cladistic analysis of archaic odontocetes. However, known specimens lack a periotic, which incorporates most defining synapomorphies of Squalodontidae, and Viglino et al. (2018) recovered ''Phoberodon'' as distantly related to ''Squalodon ''Squalodon'' is an extinct genus of whales of the Oligocene and Miocene epochs, belonging to the family Squalodontidae. Named by Jean-Pierre Sylvestre de Grateloup in 1840, it was originally believed to be an iguanodontid dinosaur but has si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Toothed Whales
The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales possessing teeth, such as the beaked whales and sperm whales. Seventy-three species of toothed whales are described. They are one of two living groups of cetaceans, the other being the baleen whales (Mysticeti), which have baleen instead of teeth. The two groups are thought to have diverged around 34 million years ago (mya). Toothed whales range in size from the and vaquita to the and sperm whale. Several species of odontocetes exhibit sexual dimorphism, in that there are size or other morphological differences between females and males. They have streamlined bodies and two limbs that are modified into flippers. Some can travel at up to 20 knots. Odontocetes have conical teeth designed for catching fish or squid. They have well-developed hearing, that is well adapted for both air and water, so much so that some can surviv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monophyly
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic groups are typically characterised by shared derived characteristics ( synapomorphies), which distinguish organisms in the clade from other organisms. An equivalent term is holophyly. The word "mono-phyly" means "one-tribe" in Greek. Monophyly is contrasted with paraphyly and polyphyly as shown in the second diagram. A ''paraphyletic group'' consists of all of the descendants of a common ancestor minus one or more monophyletic groups. A '' polyphyletic group'' is characterized by convergent features or habits of scientific interest (for example, night-active primates, fruit trees, aquatic insects). The features by which a polyphyletic group is differentiated from others are not inherited from a common ancestor. These definitions have taken ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chattian First Appearances
The Chattian is, in the geologic timescale, the younger of two ages or upper of two stages of the Oligocene Epoch/Series. It spans the time between . The Chattian is preceded by the Rupelian and is followed by the Aquitanian (the lowest stage of the Miocene). Stratigraphic definition The Chattian was introduced by Austrian palaeontologist Theodor Fuchs in 1894. Fuchs named the stage after the Chatti, a Germanic tribe.Berry, Edward W"The Mayence Basin, a Chapter of Geologic History" ''The Scientific Monthly'', Vol. 16, No. 2, February 1923. pp. 114. Retrieved March 18, 2020. The original type locality was near the German city of Kassel. The base of the Chattian is at the extinction of the foram genus ''Chiloguembelina'' (which is also the base of foram biozone P21b). An official GSSP for the Chattian Stage was ratified in October of 2016. The top of the Chattian Stage (which is the base of the Aquitanian Stage, Miocene Series and Neogene System) is at the first appearanc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prehistoric Toothed Whales
Prehistory, also known as pre-literary history, is the period of human history between the use of the first stone tools by hominins 3.3 million years ago and the beginning of recorded history with the invention of writing systems. The use of symbols, marks, and images appears very early among humans, but the earliest known writing systems appeared 5000 years ago. It took thousands of years for writing systems to be widely adopted, with writing spreading to almost all cultures by the 19th century. The end of prehistory therefore came at very different times in different places, and the term is less often used in discussing societies where prehistory ended relatively recently. In the early Bronze Age, Sumer in Mesopotamia, the Indus Valley Civilisation, and ancient Egypt were the first civilizations to develop their own scripts and to keep historical records, with their neighbors following. Most other civilizations reached the end of prehistory during the following Iron Age. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaeoceti
Archaeoceti ("ancient whales"), or Zeuglodontes in older literature, is a paraphyletic group of primitive cetaceans that lived from the Early Eocene to the late Oligocene (). Representing the earliest cetacean radiation, they include the initial amphibious stages in cetacean evolution, thus are the ancestors of both modern cetacean suborders, Mysticeti and Odontoceti. This initial diversification occurred in the shallow waters that separated India and Asia , resulting in some 30 species adapted to a fully oceanic life. Echolocation and filter-feeding evolved during a second radiation . All archaeocetes from the Ypresian (56–47.8 mya) and most from the Lutetian (47.8–41.3 mya) are known exclusively from Indo-Pakistan, but Bartonian (41.3–38.0 mya) and Priabonian (38.0–33.9 mya) genera are known from across Earth, including North America, Egypt, New Zealand, and Europe. Although no consensus exists regarding the mode of locomotion of which cetaceans were capable during ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atavism
In biology, an atavism is a modification of a biological structure whereby an ancestral genetic trait reappears after having been lost through evolutionary change in previous generations. Atavisms can occur in several ways; one of which is when genes for previously existing phenotypic features are preserved in DNA, and these become expressed through a mutation that either knocks out the dominant genes for the new traits or makes the old traits dominate the new one. A number of traits can vary as a result of shortening of the fetal development of a trait (neoteny) or by prolongation of the same. In such a case, a shift in the time a trait is allowed to develop before it is fixed can bring forth an ancestral phenotype. Atavisms are often seen as evidence of evolution. In social sciences, atavism is the tendency of reversion. For example, people in the modern era reverting to the ways of thinking and acting of a former time. The word ''atavism'' is derived from the Latin ''atavus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jean-Pierre Sylvestre De Grateloup
Jean-Pierre Sylvestre de Grateloup (31 December 1782 – 25 August 1862) was a French physician and naturalist. He completed his medical studies at Montpellier and remained attached to the countryside of the southwest of France. In company with his childhood friend Jean-Marie Léon Dufour (1780–1865) and Dufour's friend Jean-Baptiste Bory de Saint-Vincent (1778–1846) he expressed his enthusiasm for botany specializing in the study of cryptogams, the ferns and other plants that reproduce through spores. Then the shells found in the region attracted his attention, in particular those from the Adour.Grateloup, "Tableau des coquilles Fossiles qu'on rencontre dans des terrains calcaires tertiaires (faluns) des environs de Dax" in ''Actes de la Société linnéenne de Bordeaux'', 183;: ''Mémoire de géo-zoologie sur les oursins fossiles (échinides) qui se rencontrent dans les terrains caleaires des environs de Dax'', 1836; Conchyliologie fossile des terrains tertiaires du bassin d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South Asian River Dolphin
South Asian river dolphins are toothed whales in the genus ''Platanista'', which inhabit fresh water habitats in the northern Indian subcontinent. They were historically considered to be one species (''P. gangetica'') with the Ganges river dolphin and the Indus river dolphin being subspecies (''P. g. gangetica'' and ''P. g. minor'' respectively). Genetic and morphological evidence in 2021 has shown them to be separate species. The Ganges and Indus river dolphins are estimated to have diverged 550,000 years ago. They are the only living members of the family Platanistidae and the superfamily Platanistoidea. Fossils of ancient relatives date to the late Oligocene. South Asian river dolphins are small but stocky cetaceans with long snouts or rostra, broad flippers, and small dorsal fins. They have several unusual features. Living in murky river waters, their eyes are tiny and lensless, relying instead on echolocation for navigation. The skull has large crests over the melon, w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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