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Sinocodon
''Sinoconodon'' is an extinct genus of mammaliamorphs that appears in the fossil record of the Lufeng Formation of China in the Sinemurian stage of the Early Jurassic period, about 193 million years ago. While sharing many plesiomorphic traits with other non-mammaliaform cynodonts, it possessed a special, secondarily evolved jaw joint between the dentary and the squamosal bones, which in more derived taxa would replace the primitive tetrapod one between the articular and quadrate bones. The presence of a dentary-squamosal joint is a trait historically used to define mammals. Description This animal had skull of which suggest a presacral body length of and weight about due to the similar parameters to the European hedgehog. ''Sinoconodon'' closely resembled early mammaliaforms like ''Morganucodon'', but it is regarded as more basal, differing substantially from ''Morganucodon'' in its dentition and growth habits. Like most other non-mammalian tetrapods, such as reptiles and amp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sinemurian
In the geologic timescale, the Sinemurian is an age (geology), age and stage (stratigraphy), stage in the Early Jurassic, Early or Lower Jurassic epoch (geology), Epoch or series (stratigraphy), Series. It spans the time between 199.5 ±0.3 annum, Ma and 192.9 ±0.3 Ma (million years ago). The Sinemurian is preceded by the Hettangian and is followed by the Pliensbachian. In Europe the Sinemurian age, together with the Hettangian age, saw the deposition of the lower Lias Group, Lias, in Great Britain known as the Blue Lias. Stratigraphic definitions The Sinemurian Stage was defined and introduced into scientific literature by French palaeontologist Alcide d'Orbigny in 1842. It takes its name from the French town of Semur-en-Auxois, near Dijon. The calcareous soil formed from the Jurassic limestone of the region is in part responsible for the character of the classic Sancerre (wine), Sancerre wines. The base of the Sinemurian Stage is at the first appearance of the ammonite genu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basal (phylogenetics)
In phylogenetics, basal is the direction of the ''base'' (or root) of a phylogenetic tree#Rooted tree, rooted phylogenetic tree or cladogram. The term may be more strictly applied only to nodes adjacent to the root, or more loosely applied to nodes regarded as being close to the root. Note that extant taxa that lie on branches connecting directly to the root are not more closely related to the root than any other extant taxa. While there must always be two or more equally "basal" clades sprouting from the root of every cladogram, those clades may differ widely in taxonomic rank, Phylogenetic diversity, species diversity, or both. If ''C'' is a basal clade within ''D'' that has the lowest rank of all basal clades within ''D'', ''C'' may be described as ''the'' basal taxon of that rank within ''D''. The concept of a 'key innovation' implies some degree of correlation between evolutionary innovation and cladogenesis, diversification. However, such a correlation does not make a given ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haldanodon
''Haldanodon'' is an extinct docodont mammaliaform which lived in the Upper Jurassic (Kimmeridgian, about 145 million years ago). Its fossil remains have been found in Portugal, in the well-known fossil locality of Guimarota, which is in the Alcobaça Formation. It may have been a semi-aquatic burrowing insectivore, similar in habits to desmans and the platypus. Several specimens are known, include a partial skeleton and well-preserved skulls. Description ''Haldanodon'' was about as long as a desman, and may have had a similar ecology. The skull was low and triangular when seen from above. For many years it had the best-known skull material of any docodont, making it vital for understanding the taxonomic position of that mammaliaform group. It was the first Mesozoic mammaliaform discovered to possess Nasal concha, turbinal plates, a complex feature of mammalian Nasal cavity, nasal cavities. However, it also retained some curiously primitive traits in common with non-mammaliaform ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haramiyida
Haramiyida is a possibly Paraphyly, paraphyletic order of Mammaliaformes, mammaliaform cynodonts or mammals of controversial taxonomic affinites. Their teeth, which are by far the most common remains, resemble those of the multituberculates. However, based on ''Haramiyavia'', the jaw is less derived; and at the level of evolution of earlier basal mammals like ''Morganucodon'' and ''Kuehneotherium'', with a groove for Ossicles, ear ossicles on the dentary. Some authors have placed them in a clade with Multituberculata dubbed Allotheria within Mammalia. Other studies have disputed this and suggested the Haramiyida were not crown group mammals, but were part of an earlier offshoot of Mammaliaformes instead, either closely related or unrelated to Multituberculates. It is also disputed whether the Late Triassic species are closely related to the Jurassic and Cretaceous members belonging to Euharamiyida, Euharamiyida/Eleutherodontida, as some phylogenetic studies recover the two groups a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Megazostrodon
''Megazostrodon'' is an extinct genus of basal mammaliaforms belonging to the order Morganucodonta. It is approximately 200 million years old.Fur and Fangs: Mammal Origins . Palaeobiology and Biodiversity Research Group, University of Bristol. Two species are known: ''M. rudnerae'' from the Early Jurassic of Lesotho and South Africa, and ''M. chenali'' from the Late Triassic of France. Discovery The type species ''M. rudnerae'' was first discovered in 1966 in the Elliot Formation of Lesotho, southern Africa, by palaeontologist and archaeologist Ione Rudner. It was first described by Alfred W. Crompton, A. W. Crompton and Farish Jenkins, F. A. Jenkins Jr. in 1968. The generic name ''Mega ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adelobasileus
''Adelobasileus'' is a genus of mammaliamorph cynodonts from the Late Triassic (Carnian to Rhaetian), about 225 - 220 million years ago. It is known only from a partial skull recovered from the Tecovas Formation in western Texas and partial specimen fossils from the Chinle Formation in Arizona, Southern United States. The species name is ''Adelobasileus cromptoni''. ''Adelobasileus'' predates and descends from the non-mammalian cynodonts Tritylodontidae and Tritheledontidae by 10 million years. Distinct cranial features, especially the housing of the cochlea, suggest that ''Adelobasileus'' is a transitional form in the character transformation from non-mammaliaform cynodonts to mammaliaforms. For this reason, it is thought to be a close relative of the common ancestor of all modern mammals. Though formerly classified as a mammal by trait-based taxonomy, it is outside the crown group In phylogenetics, the crown group or crown assemblage is a collection of species composed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleobiology Database
The Paleobiology Database (PBDB) is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database originated in the NCEAS-funded Phanerozoic Marine Paleofaunal Database initiative, which operated from August 1998 through August 2000. From 2000 to 2015, PBDB received funding from the National Science Foundation. PBDB also received support form the Australian Research Council. From 2000 to 2010 it was housed at the National Center for Ecological Analysis and Synthesis, a cross-disciplinary research center within the University of California, Santa Barbara. It is currently housed at University of Wisconsin-Madison and overseen by an international committee of major data contributors. The Paleobiology Database works closely with the Neotoma Paleoecology Database, which has a similar intellectual history, but has focused on the Quaternary (with an emphasis on the late Pleistocene and Holoc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mammaliaformes
Mammaliaformes ("mammalian forms") is a clade of synapsid tetrapods that includes the crown group mammals and their closest extinct relatives; the group radiated from earlier probainognathian cynodonts during the Late Triassic. It is defined as the clade originating from the most recent common ancestor of Morganucodonta and the crown group mammals; the latter is the clade originating with the most recent common ancestor of extant Monotremata, Marsupialia and Placentalia. Besides Morganucodonta and the crown group mammals, Mammaliaformes also includes Docodonta and ''Hadrocodium''. Mammaliaformes is a term of phylogenetic nomenclature. In contrast, the assignment of organisms to class Mammalia has traditionally been founded on traits and, on this basis, Mammalia is slightly more inclusive than Mammaliaformes. In particular, trait-based taxonomy generally includes ''Adelobasileus'' and '' Sinoconodon'' in Mammalia, though they fall outside the Mammaliaformes definition. These ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mammal
A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three Evolution of mammalian auditory ossicles, middle ear bones. These characteristics distinguish them from reptiles and birds, from which their ancestors Genetic divergence, diverged in the Carboniferous Period over 300 million years ago. Around 6,640 Neontology#Extant taxon, extant species of mammals have been described and divided into 27 Order (biology), orders. The study of mammals is called mammalogy. The largest orders of mammals, by number of species, are the rodents, bats, and eulipotyphlans (including hedgehogs, Mole (animal), moles and shrews). The next three are the primates (including humans, monkeys and lemurs), the Artiodactyl, even-toed ungulates (including pigs, camels, and whales), and the Carnivora (including Felidae, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transitional Fossil
A transitional fossil is any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group. This is especially important where the descendant group is sharply differentiated by gross anatomy and mode of living from the ancestral group. These fossils serve as a reminder that taxonomic divisions are human constructs that have been imposed in hindsight on a continuum of variation. Because of the incompleteness of the fossil record, there is usually no way to know exactly how close a transitional fossil is to the point of divergence. Therefore, it cannot be assumed that transitional fossils are direct ancestors of more recent groups, though they are frequently used as models for such ancestors. In 1859, when Charles Darwin's ''On the Origin of Species'' was first published, the fossil record was poorly known. Darwin described the perceived lack of transitional fossils as "the most obvious and gravest objection which can be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Docodont
Docodonta is an Order (biology), order of extinct Mesozoic Mammaliaformes, mammaliaforms (advanced cynodonts closely related to true Crown group, crown-group mammals). They were among the most common mammaliaforms of their time, persisting from the Early Jurassic to the Early Cretaceous across the continent of Laurasia (modern-day North America, Europe, and Asia). They are distinguished from other early mammaliaforms by their relatively complex Molar (tooth), molar teeth. Docodontan teeth have been described as "pseudotribosphenic": a cusp on the inner half of the upper molar grinds into a basin on the front half of the lower molar, like a Mortar and pestle, mortar-and-pestle. This is a case of convergent evolution with the Tribosphenic molar, tribosphenic teeth of therian mammals. There is much uncertainty for how docodontan teeth developed from their simpler ancestors. Their closest relatives may have been certain Triassic "Symmetrodonta, symmetrodonts", namely ''Woutersia'', an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Morganucodont
Morganucodonta ("Glamorgan teeth") is an extinct order of basal Mammaliaformes, a group including crown-group mammals (Mammalia) and their close relatives. Their remains have been found in Southern Africa, Western Europe, North America, India and China. The morganucodontans were probably insectivorous and nocturnal, though like eutriconodonts some species attained large sizes and were carnivorous. Nocturnality is believed to have evolved in the earliest mammals in the Triassic (called the nocturnal bottleneck) as a specialisation that allowed them to exploit a safer, night-time niche, while most larger predators were likely to have been active during the day (though some dinosaurs, for example, were nocturnal as well). Anatomy and biology Morganucodontans had a double jaw articulation made up of the dentary-squamosal joint as well as a quadrate-articular one. This implies that they also retained one of their postdentary bones: the articular. There is a trough at the back of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
