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Mesungulatoidea
Meridiolestida is an extinct clade of mammals known from the Cretaceous and Cenozoic of South America and possibly Antarctica. They represented the dominant group of mammals in South America during the Late Cretaceous. Meridiolestidans were morphologically diverse, containing both small insectivores such as the "sabretooth-squirrel" '' Cronopio,supplementary information '' as well as the clade Mesungulatoidea/Mesungulatomorpha, which ranged in size from the shrew-sized '''' to the dog-sized '' |
Dryolestoidea
Dryolestida is an extinct order of mammals, primarily and possibly exclusively known from the Jurassic and Cretaceous. They are considered members of the clade Cladotheria, close to the ancestry of therian mammals. It is also believed that they developed a fully mammalian jaw and also had the three middle ear bones. Most members of the group, as with most Mesozoic mammals, are only known from fragmentary tooth and jaw remains. The taxonomic composition of the group is contested. Aside from the uncontroversial Dryolestidae and the possibly paraphyletic Paurodontidae, which were small insectivores, known from the Middle Jurassic to Early Cretaceous of Laurasia, the Meridiolestida, a diverse group of mammals including both small insectivores and mid-large sized herbivores known from the Late Cretaceous to Miocene of South America and possibly Antarctica, are also often included. However, in many phylogenetic analyses, Meridiolestida are recovered as an unrelated group of cladotheri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cladotheria
Cladotheria is a clade (sometimes ranked as a legion) of mammals. It contains modern therian mammals (marsupials and placentals) and several extinct groups, such as the dryolestoids, amphitheriids and peramurids. The clade was named in 1975 by Malcolm McKenna. In 2002, it was defined as a node-based taxon containing "the common ancestor of dryolestids and living therians, plus all its descendants". A different, stem-based definition was given in 2013, in which Cladotheria contains all taxa that are closer to ''Mus musculus'' (the house mouse) than to the "symmetrodont" '' Spalacotherium tricuspidens''. Description Early cladotherians can be distinguished from other mammals by a number of derived traits (apomorphies). Their teeth differed from those of the "symmetrodonts" by the evolution of a talonid shelf ( hypoflexid) on the lower molars, which occluded with the paracone of the corresponding upper molars. A true talonid basin, allowing for the crushing and grinding of f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peligrotherium
''Peligrotherium'' is an extinct meridiolestidan, and the sole member of the family Peligrotheriidae, from the Paleocene of Patagonia, originally interpreted as a stem-ungulate (though it did co-exist with early meridiungulates). Its remains have been found in the Salamanca Formation.''Peligrotherium'' at .org It was a -sized mammal, among the largest of all dryolestoids (as well as the largest South American mammal), and closely related to [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cronopio (mammal)
''Cronopio'' is an extinct genus of small insectivorous mammal known from the early Late Cretaceous of the Río Negro region in Argentina. Its only species is ''Cronopio dentiacutus''.supplementary information It belongs to the Meridiolestida, an extinct group of mammals widespread in South America during the Late Cretaceous, which are more closely related to modern s and [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reigitherium
''Reigitherium'' was a mammal that lived during the Late Cretaceous, in the (Late Campanian-Maastrichtian). Its fossils have been found in the Los Alamitos and the La Colonia Formations of Argentina. Description The original specimen of ''Reigitherium'' was a fragmentary single molar tooth, with a lot of the surface detail damaged. It was mistakenly identified as an upper left molar, but new material - including a whole tooth row of this species - clarifies that it was a lower right tooth. ''Reigitherium'' was a small mammal with simple premolars that increased in size along the tooth row to an enlarged fourth premolar. The molar teeth them decreased in size along the tooth row. Taxonomy ''Reigitherium'' has proven difficult to classify until recently, because the original fossil material was sparse, damaged, and difficult to identify. It was initially thought to be a dryolestid mammal when described in 1990. Ten years later, Pascual et al. argued that it was a docodont base ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Necrolestes
''Necrolestes'' ("grave robber" or "thief of the dead") is an extinct genus of mammals, which lived during the Early Miocene in what is now Argentine Patagonia. It is the most recent known genus of Meridiolestida, an extinct group of mammals more closely related to therians (marsupials and placentals) than to monotremes that dominated South America during the Late Cretaceous. It contains two species, ''N. patagonensis'' and ''N. mirabilis,'' The type species ''N. patagonensis'' was named by Florentino Ameghino in 1891 based on remains found by his brother, Carlos Ameghino in Patagonia. Fossils of ''Necrolestes'' have been found in the Sarmiento and Santa Cruz Formations.''Necrolestes'' at Fossilworks.org Its morph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paurodontidae
Paurodontidae is a family of Late Jurassic to Early Cretaceous mammals in the order Dryolestida. Remains of paurodontids have been found in the United States, Britain, Portugal, and Tanzania. The group likely represents a paraphyletic group of basal non dryolestid dryolestidans. ''Paurodon'' has been suggested to have been a specilast feeder on earthworms due to the morphology of its teeth closely resembling that of the golden mole genus ''Amblysomus ''Amblysomus'' (also narrow-headed golden mole or South African golden mole) is a genus of the golden mole family, Chrysochloridae, comprising five species of the small, insect-eating, burrowing mammals endemic to Southern Africa. All five spec ...''.A.O. Averianov and T. Martin (2015). "Ontogeny and taxonomy of Paurodon valens (Mammalia, Cladotheria) from the Upper Jurassic Morrison Formation of USA" (PDF). Proceedings of the Zoological Institute of the Russian Academy of Sciences 319 (3): 326–340. References Dryolesti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paraphyletic
In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, 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 Synapomorphy and apomorphy, synapomorphies and symplesiomorphy, 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 a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molar (tooth)
The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone tooth", from ''mola'', millstone and ''dens'', tooth. Molars show a great deal of diversity in size and shape across mammal groups. The third molar of humans is sometimes vestigial. Human anatomy In humans, the molar teeth have either four or five cusps. Adult humans have 12 molars, in four groups of three at the back of the mouth. The third, rearmost molar in each group is called a wisdom tooth. It is the last tooth to appear, breaking through the front of the gum at about the age of 20, although this varies from individual to individual. Race can also affect the age at which this occurs, with statistical variations between groups. In some cases, it may not even erupt at all. The human mouth contains upper (maxillary) and lower (mandib ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meckelian Groove
The Meckelian groove (or Meckel's groove, Meckelian fossa, or Meckelian foramen, or Meckelian canal) is an opening in the medial (inner) surface of the mandible (lower jaw) which exposes the Meckelian cartilage. Modern mammals (which includes placental
Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguishe ... mammals) do not have a Meckeli ...
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La Meseta Formation
The La Meseta Formation is a sedimentary sequence deposited during the Eocene. The formation is found on Seymour Island, Antarctica. Description La Meseta Formation lies unconformably on the Cretaceous Lopez de Bertodano Formation. It is an approximately thick sequence of poorly consolidated sandstones and siltstones. The depositional environment was probably coastal, deltaic or estuarine in character. The top of the sequence is an erosional unconformity to Pleistocene glacial gravels. La Meseta Formation is one of the sequences that make up the fill of the Late Jurassic to Paleogene James Ross Basin. Fossil content La Meseta Formation is extremely rich in fossils. Among mammals, the meridiungulata ''Antarctodon'' and ''Trigonostylops'' have been found in the formation.''Antarctodon'' at Fossilworks.org ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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