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Meridiolestida
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 (mammal), Cronopio,supplementary information '' as well as the clade Mesungulatoidea/Mesungulatomorpha, which ranged in size from the shrew-sized ''Reigitherium'' to the dog-sized ''Peligrotherium.'' Mesungulatoideans had highly modified dentition with bunodont (low and rounded) teeth, and were likely herbivores/omnivores. Meridiolestidans are generally classified within Cladotheria, more c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dryolestida
Dryolestida is an extinct order of mammals, known from the Jurassic and Cretaceous. They are considered basal 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 group contains Dryolestidae and the possibly paraphyletic Paurodontidae, and some other unplaced genera, which were small insectivores, known from the Middle Jurassic to Early Cretaceous of Laurasia, primarily Europe and North America, with a single record from Asia. During the Late Jurassic in North America and from the Late Jurassic to Early Cretaceous in Europe, they were among the most diverse mammal groups. They have sometimes been placed as part of a broader group, the "Dryolestoidea", which typically includes Dryolestida and Meridiolestida, a diverse group of mammals in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peligrotherium
''Peligrotherium'' is an extinct meridiolestidan mammal 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 Around the size of a , it was among the largest of all non- therian mammals, and the largest non-therian mammal known from South America. It is a member of Mesungulatoidea, a clade of herbivorous meridiolestidans with molars that had ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Groebertherium
''Groebertherium'' is a genus of dryolestoid mammal from the Late Cretaceous Los Alamitos Formation, Los Alamitos and Allen Formations of Argentina. It is not closely related to other contemporary dryolestoids, all of which are part of the clade Meridiolestida. Classification ''Groebertherium'' has been consistently recovered as a dryolestoid within Dryolestida and outside of Meridiolestida, though its exact positioning varies among several studies. Rougier ''et al.'' 2011, for example, recovers it as a member of Dryolestidae, rendering it a relictual survivor of this clade with a gap of 40 million years in relation to the youngest northern dryolestids, while Harper ''et al.'' 2018 recovers it as slightly closer to Meridiolestida than to northern dryolestoids. Palaeobiology Unlike meridiolestidans, it retains a parastylar hook on its molariform teeth. Therefore, it was likely less specialised to transverse (side-to-side) mastication. It was rather similar to ''Dryolestes'', ind ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Austrotriconodon
''Austrotriconodon'' is a mammal genus from the Campanian and Maastrichtian of South America. It currently contains only the type species, ''A. mckennai''. Originally assumed to be a eutriconodont, more recent studies have recovered it as a meridiolestidan dryolestoid. Description ''Austrotriconodon'' is known only from its teeth. Their similarity to the triconodont teeth of mammals such as eutriconodonts has caused taxonomic confusion and referral of this taxon to eutriconodonta; however, discovery of similar teeth in animals such as '' Cronopio'' has led to its reinterpretation as a meridolestidan. Discovery and species ''Austrotriconodon'' fossils were found in the Argentinean Los Alamitos Formation, dating to the Campanian or Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretace ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. Antarctica is the fifth-largest continent, being about 40% larger than Europe, and has an area of . Most of Antarctica is covered by the Antarctic ice sheet, with an average thickness of . Antarctica is, on average, the coldest, driest, and windiest of the continents, and it has the highest average elevation. It is mainly a polar desert, with annual Climate of Antarctica#Precipitation, precipitation of over along the coast and far less inland. About 70% of the world's freshwater reserves are frozen in Antarctica, which, if melted, would raise global sea levels by almost . Antarctica holds the record for the Lowest temperature recorded on Earth, lowest measured temperature on Earth, . The coastal regions can reach temperatures over in the ... [...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, which were the dominant mammals in 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 |
Miocene
The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" because it has 18% fewer modern marine invertebrates than the Pliocene has. The Miocene followed the Oligocene and preceded the Pliocene. As Earth went from the Oligocene through the Miocene and into the Pliocene, the climate slowly cooled towards a series of ice ages. The Miocene boundaries are not marked by distinct global events but by regionally defined transitions from the warmer Oligocene to the cooler Pliocene Epoch. During the Early Miocene, Afro-Arabia collided with Eurasia, severing the connection between the Mediterranean and Indian Oceans, and allowing the interchange of fauna between Eurasia and Africa, including the dispersal of proboscideans and Ape, hominoids into Eurasia. During the late Miocene, the conn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Symmetrodont
Symmetrodonta is a group of Mesozoic mammals and mammal-like synapsids characterized by the triangular aspect of the molars when viewed from above, and the absence of a well-developed talonid. The traditional group of 'symmetrodonts' ranges in age from the latest Triassic to the Late Cretaceous, but most research in the last 20-30 years has concluded that they are not a true taxonomic group, but include several unrelated branches of the mammal tree. Despite this, the name is still used informally by some researchers for convenience, usually restricted to the spalacotheriids and zhangheotheriids. Martin, T., 2018. 6. Mesozoic mammals—early mammalian diversity and ecomorphological adaptations. In Mammalian evolution, diversity and systematics (pp. 199-300). De Gruyter. There are some symmetrodonts with acutely-triangulated molar cusps (“acute-angled symmetrodonts”) that seem to form a true monophyletic group, and lasted from the Early Cretaceous to the Campanian, although ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antarctic Peninsula
The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martin in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctica. The Antarctic Peninsula is part of the larger peninsula of West Antarctica, protruding from a line between Cape Adams (Weddell Sea) and a point on the mainland south of the Eklund Islands. Beneath the ice sheet that covers it, the Antarctic Peninsula consists of a string of bedrock islands; these are separated by deep channels whose bottoms lie at depths considerably below current sea level. They are joined by a grounded ice sheet. Tierra del Fuego, the southernmost tip of South America, is about away across the Drake Passage. The Antarctic Peninsula is in area and 80% ice-covered. The marine ecosystem around the western continental shelf of the Antarctic Peninsula (WAP) has been subjected to rapid Climate change in Antarctica, clima ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
La Meseta Formation
The La Meseta Formation is a sedimentary sequence deposited during much of the Paleogene on Seymour Island off the coast of the Antarctic Peninsula. It is noted for its fossils, which include both marine organisms and the only terrestrial vertebrate fossils from the Cenozoic of Antarctica. In some treatments, the La Meseta Formation is restricted to just the older Thanetian to Lutetian-aged strata, with the younger Bartonian to Rupelian strata treated as the overlying Submeseta Formation. However, other papers instead treat the Submeseta Formation as an allomember of the La Meseta Formation. 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
