Trechnotheria

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Trechnotheria
Temporal range: Middle JurassicRecent
Zhangheotherium quinquecuspidens.jpg
Fossil of Zhangheotherium , a "symmetrodont"
Fox - British Wildlife Centre (17429406401).jpg
Red fox, a modern-day trechnotherian
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Clade: Theriiformes
Clade: Trechnotheria
McKenna, 1975
Subgroups [1]

Trechnotheria is a group of mammals that includes the therians and some fossil mammals from the Mesozoic Era. It includes both the extinct symmetrodonts and the living Cladotheria.

Contents

Trechnotheria has been assigned various ranks, but was originally described as a "superlegion" by the naming authority. [2] A later node-based definition for Trechnotheria was the clade comprising the last common ancestor of Zhangheotherium and living therian mammals, and all its descendants. [3] Alternatively it can be defined as the group with true symmetrodontia, being defined as an apomorphy rather than being defined as a node, the redefinition includes the Tinodontids. [4]

Characteristics

Like most Mesozoic mammal groups, early trechnotherians are known mainly from their teeth. Hence, one of the most prominent features of this group is the "hypertrophied postvallum/prevallid shearing mechanism", along with other dental characters. Features of the shoulder blade, tibia, humerus, and ankle joint also diagnose this clade. [1]

Phylogeny

A cladogram based on Luo, Cifelli & Kielan-Jaworowska, 2001, Luo, Kielan-Jaworowska & Cifelli, 2002 and, Kielan-Jaworowska, Cifelli & Luo, 2004. [5]

Alternatively, the zanjeotherids would be ancestral to both the spalacotherids and the cladotherians (driolestoids and prototribosphenids), with the tinodontids equally paraphyletic. The group that contains the Spalacotheriidae and Cladotheria is called Alethinotheria (sensu Alexander O Averianov. 2013 [6] ), which was initially proposed to highlight the closeness between the spalacotherids and the meridiolestids. [4]

Theriimorpha

Sources

  1. 1 2 Luo, Z.−X.; Kielan−Jaworowska, Z.; Cifelli, R.L (2002). "In quest for a phylogeny of Mesozoic mammals" (PDF). Acta Palaeontologica Polonica. 47 (1): 1–78.
  2. McKenna, Malcolm C.; Bell, Susan K. (1997). Classification of Mammals: Above the Species Level. Columbia University Press. p. 43. ISBN   978-0-231-52853-5.
  3. Kielan-Jaworowska, Zofia; Cifelli, Richard; Luo Zhe-Xi (5 February 2005). Mammals from the age of dinosaurs: origins, evolution, and structure. Columbia University Press. p. 366. ISBN   978-0-231-11918-4.
  4. 1 2 Lasseron, Maxime; Martin, Thomas; Allain, Ronan; Haddoumi, Hamid; Jalil, Nour-Eddine; Zouhri, Samir; Gheerbrant, Emmanuel (2022-06-02). "An African Radiation of 'Dryolestoidea' (Donodontidae, Cladotheria) and its Significance for Mammalian Evolution" (PDF). Journal of Mammalian Evolution. 29 (4): 733–761. doi:10.1007/s10914-022-09613-9. ISSN   1064-7554. S2CID   249324444.
  5. Haaramo, Mikko. "Holotheria – holotheres". Mikko's Phylogeny Archive.
  6. Averianov, Alexander O.; Martin, Thomas; Lopatin, Alexey V. (April 2013). "A new phylogeny for basal Trechnotheria and Cladotheria and affinities of South American endemic Late Cretaceous mammals". Die Naturwissenschaften. 100 (4): 311–326. Bibcode:2013NW....100..311A. doi:10.1007/s00114-013-1028-3. ISSN   1432-1904. PMID   23494201.

See also