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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 and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 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, 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 wines. The base of the Sinemurian Stage is at the first appearance of the ammonite genera ''Vermiceras'' and '' Metophioceras'' in the stratigraphic record. A global reference profile ( GSSP or golden spike) for ... [...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] |
Castorocauda
''Castorocauda'' is an extinct, semi-aquatic, superficially otter-like genus of docodont mammaliaforms with one species, ''C. lutrasimilis''. It is part of the Yanliao Biota, found in the Daohugou Beds of Inner Mongolia, China dating to the Middle to Late Jurassic. It was part of an explosive Middle Jurassic radiation of Mammaliaformes moving into diverse habitats and niches. Its discovery in 2006, along with the discovery of other unusual mammaliaforms, disproves the previous hypothesis of Mammaliaformes remaining evolutionarily stagnant until the extinction of the non-avian dinosaurs. Weighing an estimated , ''Castorocauda'' is the largest known Jurassic mammaliaform. It is the earliest known mammaliaform with aquatic adaptations or a fur pelt. It was also adapted for digging, and its teeth are similar to those of seals and Eocene whales, collectively suggesting it behaved similarly to the modern-day platypus and river otters and ate primarily fish. It lived in a wet, seaso ... [...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 turbinal plates, a complex feature of mammalian nasal cavities. However, it also retained some curiously primitive traits in common with non-mammaliaform cynodonts. The body was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haramiyida
Haramiyida ("thief" from Arabic الحرامية (al ḥarāmiyah), "thief, bandit") is a possibly polyphyletic order of 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 ear ossicles on the dentary. If they are early multituberculates, they would be the longest lived mammalian clade of all time. However, a more recent study in November 2015 may dispute this and suggested the Haramiyida were not crown mammals, but were part of an earlier offshoot of mammaliaformes instead. It is also disputed whether the Late Triassic species are closely related to the Jurassic and Cretaceous members belonging to Euharamiyida/Eleutherodontida, as some phylogenetic studies recover the two groups as unrelate ... [...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 of and , and ''M. chenali'' from the |
Adelobasileus
''Adelobasileus'' is a genus of mammaliamorph cynodonts from the Late Triassic (Carnian), about 225 million years ago. It is known only from a partial skull recovered from the Tecovas Formation in western Texas, southern United States, referred to the species ''Adelobasileus cromptoni''. Roughly contemporary with the mammaliaform '' Tikitherium'', ''Adelobasileus'' predates 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 Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time. All living beings are in fact descendants of a unique ancestor commonly referred to as the last universal comm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mammaliaformes
Mammaliaformes ("mammalian forms") is a clade that contains the crown group mammals and their closest Extinction, extinct relatives; the group adaptive radiation, radiated from earlier probainognathian cynodonts. 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 includes Docodonta and ''Hadrocodium'' as well as the Triassic ''Tikitherium'', the earliest known member of the group. Mammaliaformes is a term of phylogenetic nomenclature. In contrast, the assignment of organisms to 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 fa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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, together with Saur ... [...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 of extinct mammaliaforms that lived during the Mesozoic, from the Middle Jurassic to Early Cretaceous. They are distinguished from other early mammaliaforms by their relatively complex molar teeth, from which the order gets its name. Until recently, Docodonta were represented primarily by teeth and jaws found across former Laurasia, (modern-day North America, Europe, and Asia). However, recent discoveries in China include some exceptionally well preserved, almost complete body fossils. Description Skeletal traits Docodonts have a long and low mandible (lower jaw), formed primarily by the tooth-bearing dentary bone. The dentary connects to the cranium via a joint with the squamosal, a connection which is strengthened relative to earlier mammaliaforms. The other bones in the jaw, known as postdentary elements, are still connected to the dentary and lie within a groove (the postdentary trough) in the rear part of the dentary’s inner edge. Nevertheless, ... [...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 the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
