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Zhangheotheriidae
Zhangheotheriidae is a possibly paraphyletic family of "symmetrodont" mammals that is currently known from Early Cretaceous deposits in China and Russia. Six genera are currently recognized, ''Anebodon'', ''Kiyatherium'', ''Maotherium'', ''Ningchengodon'', ''Origolestes'', and ''Zhangheotherium''. References Symmetrodonta Prehistoric mammal families Early Cretaceous mammals of Asia {{cretaceous-mammal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Symmetrodonta
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] |
Barremian
The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 125.77 Ma (million years ago) and 121.4 ± 1.0 Ma (Historically, this stage was placed at 129.4 million to approximately 125 million years ago) It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is preceded by the Hauterivian and followed by the Aptian Stage.See Gradstein ''et al.'' (2004) or the online geowhen database (link below) Stratigraphic definitions The original type locality for the Barremian Stage is in the vicinity of the village of Barrême, Alpes-de-Haute-Provence, France. Henri Coquand defined the stage and named it in 1873. The base of the Barremian is determined by the first appearance of the ammonites '' Spitidiscus hugii'' and ''Spitidiscus vandeckii''. The end of the Barremian is determined by the geomagnetic reversal at the start of the M0r chronozone, which is biologically near the first appearance of the ammonite '' Paradesh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aptian
The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), Series and encompasses the time from 121.4 ± 1.0 annum, Ma to 113.0 ± 1.0 Ma (million years ago), approximately. The Aptian succeeds the Barremian and precedes the Albian, all part of the Lower/Early Cretaceous. The Aptian partly overlaps the upper part of the Western Europe, Western European Urgonian Stage. The Selli Event, also known as OAE1a, was one of two oceanic anoxic events in the Cretaceous Period, which occurred around 120 annum, Ma and lasted approximately 1 to 1.3 million years, being marked by enhanced silicate weathering, as well as ocean acidification. The Aptian extinction was a minor extinction event hypothesized to have occurred around 116 to 117 Ma. Stratigraphic definitions The Aptian was named after the small city o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zhangheotherium Quinquecuspidens
''Zhangheotherium'' is an extinct genus of "symmetrodont" mammal from the Early Cretaceous of China. A single species is known, ''Zhangheotherium quinquecuspidens'' from Jianshangou Beds of the Yixian Formation. ''Zhangheotherium'' was the first "symmetrodont" known from a nearly complete skeleton, expanding knowledge of the group beyond isolated teeth and jaws. The genus name honors Zhang He, who collected the holotype fossil from Liaoning, Liaoning Province prior to its 1997 description. The specific name is Latin for "five-cusped teeth". "Symmetrodonts" and other archaic mammals such as multituberculates and monotremes are still being debated on their taxonomical relationships. ''Zhangheotherium'' provided insight into the evolution of "symmetrodonts", revealing a combination of traits similar to modern Theria, therians (such as Placentalia, placentals and Marsupial, marsupials) as well as more "primitive" mammalians. Most likely, "symmetrodonts" are a Evolutionary grade, grade ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maotherium
''Maotherium'' is a genus extinct symmetrodont mammal that was discovered in Early Cretaceous rocks in Liaoning Province, China, in 2003. Its scientific name directly translates to "fur beast", in reference to the impressions of fur around the fossil. ''Maotherium'' belongs to an extinct group of Mesozoic mammals called symmetrodonts. Though little is known about this group, the symmetrodonts have several similarities - specifically their teeth. They have tall pointed, but simple molars in a triangular arrangement. Originally symmetrodonts were known since the 1920s. Now a vast majority have been restored, such as '' Zhangheotherium'' and ''Akidolestes'', during the early 21st century. One of the fossils of ''Maotherium'' preserved the imprints of fur, like the mammals '' Eomaia'' and ''Sinodelphys''. A species described in 2009, ''Maotherium asiaticus'', sheds light on the evolution of the mammalian middle ear. In modern mammals, the Meckel's cartilage appears during developme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ningchengodon
''Ningchengodon'' is an extinct genus of spalacotherioid known from the single species ''Ningchengodon foxi'' that inhabited China during the Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 .... References {{Taxonbar, from=Q131451962 Cretaceous mammals of Asia Symmetrodonta Prehistoric mammal genera Fossil taxa described in 2024 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zhangheotherium
''Zhangheotherium'' is an extinct genus of "symmetrodont" mammal from the Early Cretaceous of China. A single species is known, ''Zhangheotherium quinquecuspidens'' from Jianshangou Beds of the Yixian Formation. ''Zhangheotherium'' was the first "symmetrodont" known from a nearly complete skeleton, expanding knowledge of the group beyond isolated teeth and jaws. The genus name honors Zhang He, who collected the holotype fossil from Liaoning Province prior to its 1997 description. The specific name is Latin for "five-cusped teeth". "Symmetrodonts" and other archaic mammals such as multituberculates and monotremes are still being debated on their taxonomical relationships. ''Zhangheotherium'' provided insight into the evolution of "symmetrodonts", revealing a combination of traits similar to modern therians (such as placentals and marsupials) as well as more "primitive" mammalians. Most likely, "symmetrodonts" are a grade of stem-group therians, with representatives incrementally ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paraphyletic
Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In contrast, a monophyletic grouping (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 synapomorphies and symplesiomorphies. If many subgroups are missing from the named group, it is said to be polyparaphyletic. The term received currency during the debates of the 1960s and 1970s accompanying the rise of cladistics, having been coined by zoologist Willi Hennig to apply to well-known taxa like Reptilia (reptiles), which is paraphyletic with respect to birds. Reptilia contains the last common ancestor of reptiles and all descendants of that ancestor exc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
