Eutriconodonta
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Eutriconodonta
Eutriconodonta is an order of early mammals. Eutriconodonts existed in Asia, Africa, Europe, North and South America during the Jurassic and the Cretaceous periods. The order was named by Kermack ''et al.'' in 1973 as a replacement name for the paraphyletic Triconodonta. Traditionally seen as the classical Mesozoic small mammalian insectivores, discoveries over the years have shown them to be among the best examples of the diversity of mammals in this time period, including a vast variety of bodyplans, ecological niches and locomotion methods. Classification "Triconodonta" had long been used as the name for an order of early mammals which were close relatives of the ancestors of all present-day mammals, characterized by molar teeth with three main cusps on a crown that were arranged in a row. The group originally included only the family Triconodontidae and taxa that were later assigned to the separate family Amphilestidae, but was later expanded to include other taxa such ...
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Gobiconodonta
Gobiconodonta is an order (biology), order of extinct mammals known from the Early Jurassic (such as ''Huasteconodon'') to early Late Cretaceous. They are generally held to be part of Eutriconodonta. Biology Like many other non-therian mammals, gobiconodonts retained classical mammalian synapomorphies like epipubic bones (and likely the associated reproductive constrictions), Venomous mammal, venomous spurs and sprawling limbs. However, the forelimb and shoulder anatomy of at least some species like ''Jeholodens'' are similar to those of therian mammals, though the hindlimbs remain more conservative. Gobiconodonts had Evolution of mammalian auditory ossicles, a modern ear anatomy, the main difference from therians being that the ear ossicles were still somewhat connected to the jaw via the Meckel's cartilage. Some information on gobiconodont soft-tissues can be seen in ''Spinolestes'', which was very well preserved, showing evidence of fur and internal organs. ''Spinolestes'' sh ...
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Triconodon Owen
''Triconodon'' ("three coned tooth") is a genus of extinct mammal from the Early Cretaceous of England and France with two known species: ''T. mordax'' and ''T. averianovi''. First described in 1859 by Richard Owen,R. Owen. 1859. Palaeontology. '' Encyclopedia Britannica, 8th ed.'' 17:91-176 . Wagner/P. Wagner it is the type genus for the order Triconodonta, a group of mammals characterised by their three-cusped (triconodont) molar teeth. Since then, this "simplistic" type of dentition has been understood to be either ancestral for mammals or else to have evolved multiple times, rendering "triconodonts" a paraphyletic or polyphyletic assemblage respectively, but several lineages of "triconodont" mammals do form a natural, monophyletic group, known as Eutriconodonta, of which ''Triconodon'' is indeed part of. ''Triconodon'', therefore, is significant in the understanding of the evolution of mammals by originating the understanding of the "triconodont" grade and eutriconodon ...
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Dyskritodon
''Dyskritodon'' ("tooth of unknown origin", from Greek δυσκρίτος, "''dyskritos''"Sigogneau-Russell, D. (1995) Two possibly aquatic triconodont mammals from the Early Cretaceous of Morocco. Acta Palaeontologica Polonica. 40(2), p.149-162.) is a genus of extinct mammal from the Early Cretaceous of Morocco, and possibly the Early Jurassic of India. Of uncertain affinities, it is tentatively described as a eutriconodont. Description The type species, ''D. amazighi'', is known from the Ksar Metlili Formation in the Atlas Mountains, dating to the Berriasian. It is known from several molars, about 1.85 mm long. These teeth are noted for being rather high and narrow crowned, bearing three main cusps that decrease in height posteriorly, as well as two minuscule mesial cusps. ''D. indicus'' is known from a single lower molar tooth from the Kota Formation, dating to the Hettangian-Pliensbachian. It is very similar to ''D. amazighi'', differing in being smaller (1.24  ...
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Volaticotherini
Volaticotherini is a clade of eutriconodont mammals from the Mesozoic. In addition to the type genus '' Volaticotherium'', it includes the genera '' Argentoconodon'', '' Ichthyoconodon'', and potentially '' Triconolestes''. Since most remains are primarily teeth, they are foremostly diagnosticated by their highly distinctive molars. However, the remains of one species, '' Volaticotherium antiquum'', show that at least some members of this clade were capable of gliding. and '' Argentoconodon'' shares similar post-cranial features that also indicate aerial locomotion. As such, this clade contains some of the oldest known aerial mammals, alongside the various gliding haramiyidans. Definition Volaticotherini is phylogenetically defined as the clade derived from the most recent common ancestor of ''Argentoconodon'', ''Ichthyoconodon,'' and ''Volaticotherium''. History '' Ichthyoconodon'' was the first described member of this group, back in 1995, previously usually ranked among ...
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Jeholodens
''Jeholodens'' was a primitive mammal belonging to the order Eutriconodonta, and which lived in present-day China during the Middle Cretaceous about 125 million years ago. Only one specimen has been formally described. This specimen (the holotype) consists of a virtually complete articulated skull and skeleton, it shared its corporal characteristics with most other Mesozoic mammals; it was a long-tailed, nocturnal tetrapod (with prehensile fingers and toes) which hunted insects, its food, during the night. It is suspected to be a Nocturnality, nocturnal creature because it had very large eyes which were roughly 5 mm across. This would have allowed it to have better night vision for catching insects. It is notable for its relatively derived forelimb morphology, having shoulder blades and other pectoral girdle elements comparable to those of modern therians like opossums. It also had grasping hands. By contrast, however, the hindlimbs retained primitive characters, suggestin ...
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Yanoconodon
''Yanoconodon'' is a monotypic genus of extinct early mammal whose representative species ''Yanoconodon allini'' lived during the Mesozoic in what is now China. The holotype fossil of ''Yanoconodon'' was excavated in the Yan Mountains about 300 kilometres from Beijing in the Qiaotou member of the Huajiying Formation (which the original authors considered part of the Yixian Formation) of Hebei Province, China, and is therefore of uncertain age. The Qiaotou Member may correlate with the more well-known Early Cretaceous Yixian Formation, and so probably dates to around 122 Ma ago.Jin, F., Zhang, F.C., Li, Z.H., Zhang, J.Y., Li, C. and Zhou, Z.H. (2008). "On the horizon of ''Protopteryx'' and the early vertebrate fossil assemblages of the Jehol Biota." ''Chinese Science Bulletin'', 53(18): 2820-2827. ''Yanoconodon'' was a eutriconodont, a group composing most taxa once classified as "triconodonts" which lived during the time of the dinosaurs. These were a highly ecologically dive ...
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Mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or hair, and three middle ear bones. These characteristics distinguish them from reptiles (including birds) from which they diverged in the Carboniferous, over 300 million years ago. Around 6,400 extant species of mammals have been described divided into 29 orders. The largest orders, in terms of number of species, are the rodents, bats, and Eulipotyphla ( hedgehogs, moles, shrews, and others). The next three are the Primates (including humans, apes, monkeys, and others), the Artiodactyla (cetaceans and even-toed ungulates), and the Carnivora ( cats, dogs, seals, and others). In terms of cladistics, which reflects evolutionary history, mammals are the only living members of the Synapsida (synapsids); this clade, toget ...
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Liaoconodon
''Liaoconodon'' is an extinct genus of early mammal from the early Cretaceous (early Aptian stage, approximately 120 Ma). It is a eutriconodont which lived in what is now the Jianchang of Liaoning Province, eastern China. It is known from the holotype IVPP V 16051, which consists of nearly complete skeleton and skull. It was found in the Jiufotang Formation (Jehol Biota) near Xiaotaizi, Lamadong. It was first named by Jin Meng, Yuanqing Wang and Chuankui Li in 2011 and the type species is ''Liaoconodon hui''. Studies on its anatomy show that it was a semi-aquatic mammal, having a long body and paddle-like limbs. Phylogeny Cladogram after Thomas Martin Thomas or Tom Martin may refer to: Born 16th century *Thomas Martin (politician, died 1583) (1530–1583), MP for Dorchester * Thomas Martin (lawyer) (1521–1593), MP for Ludgershall, Saltash and Hindon Born 17th century *Thomas Martin of Pa ... et al. 2015Thomas Martin, Jesús Marugán-Lobón, Romain Vu ...
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Volaticotherium
''Volaticotherium antiquum'' (meaning "ancient gliding beast") is an extinct, gliding, insectivorous mammal that lived in Asia during the Jurassic period, around 164 mya. It is the only member of the genus ''Volaticotherium''. The discovery of ''Volaticotherium'' provided the earliest-known record of a gliding mammal (70 million years older than the next oldest example), until the discovery of the contemporary haramiyidans '' Maiopatagium'', '' Vilevolodon'' and '' Xianshou'', and provided further evidence of mammalian diversity during the Mesozoic Era. The closely related and significantly older '' Argentoconodon'' shows similar post-cranial adaptations for aerial locomotion also seen in ''Volaticotherium''. Discovery The only known fossil of ''Volaticotherium'' was recovered from the Daohugou Beds of Ningcheng County, Inner Mongolia, China. The age of the Daohugou Beds is currently uncertain and the subject of debate, but most studies suggest an age of around 164 plus or mi ...
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Jurassic
The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of the Mesozoic Era and is named after the Jura Mountains, where limestone strata from the period were first identified. The start of the Jurassic was marked by the major Triassic–Jurassic extinction event, associated with the eruption of the Central Atlantic Magmatic Province. The beginning of the Toarcian Stage started around 183 million years ago and is marked by an extinction event associated with widespread oceanic anoxia, ocean acidification, and elevated temperatures likely caused by the eruption of the Karoo-Ferrar large igneous provinces. The end of the Jurassic, however, has no clear boundary with the Cretaceous and is the only boundary between geological periods to remain formally undefined. By the beginning of the Jurassi ...
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Triconodontidae
Triconodontidae is an extinct family of small, carnivorous mammals belonging to the order Eutriconodonta, endemic to what would become Asia, Europe, North America and probably also Africa and South America during the Jurassic through Cretaceous periods at least from 190–70.6 mya. Triconodontids can be distinguished from other eutriconodonts by the shape of their molars, which bore three main cusps of roughly equal size. During occlusion, the upper and lower molars interlocked tightly, producing a self-sharpening cutting edge. Historically, the triconodontids were thought to have a different occlusion pattern than other eutriconodonts, with the middle cusp of the lower molar (cusp a) fitting between the middle cusp (cusp A) and the front cusp (cusp B) of the upper molar, as in the basal mammaliaform ''Morganucodon''. However, a 2020 study on ''Priacodon'' suggests that triconodontids occluded their molars in the same manner as other eutriconodonts (so-called "embrasure occlus ...
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Jeholodentidae
The family Jeholodentidae is a possible eutriconodont family that was present in China around 125 million years ago during the time of the dinosaurs. There are currently two genera assigned to the family, '' Yanoconodon'' and '' Jeholodens''. However, recent studies have shown it to be paraphyletic in relation to Triconodontidae Triconodontidae is an extinct family of small, carnivorous mammals belonging to the order Eutriconodonta, endemic to what would become Asia, Europe, North America and probably also Africa and South America during the Jurassic through Cretaceous p ..., with '' Yanoconodon'' being closer to them than to '' Jeholodens''. Taxonomy * Family †Jeholodentidae Luo et al. 2007Mikko's Phylogeny ArchivPaleofile.com (net, info) . ** Genus †'' Yanoconodon'' Luo, Chen, Li & Chen 2007 *** Species †'' Yanoconodon allini'' Luo, Chen, Li & Chen 2007 ** Genus †'' Jeholodens'' Ji, Luo & Ji 1999 *** Species †'' Jeholodens jenkinsi'' Ji, Luo & Ji 1999 Re ...
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