Trechnotheria is a group of mammals that includes the therians and some fossil mammals from the Mesozoic Era. In the Jurassic through Cretaceous periods, the group was endemic to what would be Asia and Africa.[2]

Trechnotherians
Temporal range: Late Triassic - Holocene, 216.5–0 Ma
Kangaroo and joey03.jpg
Kangaroo with her joey
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Clade: Holotheria
Clade: Trechnotheria
McKenna, 1975
Subgroups[1]

Trechnotheria has been assigned various ranks, but was originally described as a "superlegion" by the naming authority.[3] A later stem-baed definition for Trechnotheria was the clade comprising the last common ancestor of Zhangheotherium and living therian mammals, and all its descendants.[4]

CharacteristicsEdit

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]

PhylogenyEdit

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

Gobiconodonta

Amphilestidae

Amphidontidae

Eutriconodonta

Trechnotheria

Spalacotheriida

Cladotheria

Dryolestida

Zatheria

Vincelestidae

Amphitheriida

Peramuridae

Boreosphenida

Aegialodontia

Pappotheriidae

Theria

Protodelphia

MetatheriaMarsupialia

EutheriaPlacentalia

SourcesEdit

  1. ^ a b Luo, Z.−X., Kielan−Jaworowska, Z., and Cifelli, R.L. (2002). "In quest for a phylogeny of Mesozoic mammals" (PDF). Acta Palaeontologica Polonica. 47 (1): 1–78.CS1 maint: uses authors parameter (link)
  2. ^ "Trechnotheria - Mammalia". Paleobiology Database. Retrieved 2009-10-21.
  3. ^ McKenna, Malcolm C.; Bell, Susan K. (1997). Classification of Mammals: Above the Species Level. Columbia University Press. p. 43.
  4. ^ Kielan-Jaworowska, Zofia; Cifelli, Richard; & Luo Zhe-Xi. Mammals from the age of dinosaurs: origins, evolution, and structure. Columbia University Press. p. 366. ISBN 978-0-231-11918-4.CS1 maint: uses authors parameter (link)
  5. ^ Haaramo, Mikko. "Holotheria – holotheres". Mikko's Phylogeny Archive.

See alsoEdit