Dual origin of tribosphenic mammals

  title={Dual origin of tribosphenic mammals},
  author={Zhe‐Xi Luo and Richard. Cifelli and Zofia Kielan-Jaworowska},
Marsupials, placentals and their close therian relatives possess complex (tribosphenic) molars that are capable of versatile occlusal functions. This functional complex is widely thought to be a key to the early diversification and evolutionary success of extant therians and their close relatives (tribosphenidans). Long thought to have arisen on northern continents, tribosphenic mammals have recently been reported from southern landmasses. The great age and advanced morphology of these new… 

The Gondwanan Origin of Tribosphenida (Mammalia)

Abstract A review of the Southern Hemisphere Mesozoic tribosphenic mammal fossil record supports the hypothesis that Tribosphenida arose in the Southern Hemisphere during the Early Jurassic, around

Marsupial and monotreme evolution and biogeography

The known fossil record and biogeography of both radiations is summarised, with particular attention given to a recent paradigm shift on monotreme evolution, with the latest research suggesting that monotremes are part of an ancient, Gondwanan radiation of mammals that independently evolved a tribosphenic dentition.

Convergent dental adaptations in pseudo-tribosphenic and tribosphenic mammals

The find reveals a much greater range of dental evolution in Mesozoic mammals than in their extant descendants, and strengthens the hypothesis of homoplasy of ‘tribosphenic-like’ molars among mammals.

The origin and early evolution of metatherian mammals: the Cretaceous record

Metatherian diversification patterns suggest that they were not strongly affected by a Cretaceous Terrestrial Revolution, but they clearly underwent a severe extinction across the K-Pg boundary.

An Early Cretaceous Tribosphenic Mammal and Metatherian Evolution

New data from this fossil support the view that Asia was likely the center for the diversification of the earliest metatherians and eutherians during the Early Cretaceous.

In quest for a phylogeny of Mesozoic mammals

A phylogeny of all major groups of Mesozoic mammals based on phylogenetic analyses of 46 taxa and 275 osteological and dental characters, using parsimony methods is proposed, suggesting that the “obtuse−angle symmetrodonts” are paraphyletic, and that they lack reliable and unambiguous synapomorphies.

The earliest known eutherian mammal

The skeleton of a eutherian (placental) mammal found in northeastern China has limb and foot features that are known only from scansorial and arboreal extant mammals, in contrast to the terrestrial or cursorial features of other Cretaceous eutherians.

A Jurassic eutherian mammal and divergence of marsupials and placentals

This mammal has scansorial forelimb features, and provides the ancestral condition for dental and other anatomical features of eutherians, reducing and resolving a discrepancy between the previous fossil record and the molecular estimate for the placental–marsupial divergence.


Herein we describe two new tribosphenic mammals from the Cedar Mountain Formation of Emery County, Utah, USA. The fossils occur in a narrow stratigraphic interval near the top of the unit



Tribosphenic mammal from the North American Early Cretaceous

  • R. Cifelli
  • Environmental Science, Geography
  • 1999
A new tribosphenic mammal from the Early Cretaceous of North America is described, based on an unusually complete specimen, and its molar structure is primitive, emphasizing the need for caution in interpretation of isolated teeth.

A new symmetrodont mammal from China and its implications for mammalian evolution

This analysis suggests that this new taxon represents a part of the early therian radiation before the divergence of living marsupials and placentals; that therians and multituberculates are more closely related to each other than either group is to other mammalian lineages.

Implications of Deltatheridium specimens for early marsupial history

The presence of specialized marsupial patterns of tooth replacement and cranial vascularization in Deltatheridium and the basal phylogenetic position of this taxon indicate that these features are characteristic of Metatheria as a whole.

Modern mammal origins: evolutionary grades in the Early Cretaceous of North America.

A tooth from the Early Cretaceous of Texas test previous predictions (based on lower molars) of the morphology of upper molars in early tribosphenic dentitions and demonstrates unexpected morphological diversity at a strategic stage of mammalian evolution.

A Middle Jurassic mammal from Madagascar

The lower molars of tribosphenic mammals (marsupials, placentals and their extinct allies) are marked, primitively, by a basined heel (talonid) acting as the mortar to the pestle of a large inner

Eutherian mammals from the Early Cretaceous of Mongolia

A collection of eutherian mammals consisting of 39 specimens (teeth and jaw fragments) from the ?Aptian or Albian Khoboor Beds in the Gobi Desert, Mongolia, is described. It contains 3 taxa:

First Mesozoic mammal from Australia—an early Cretaceous monotreme

Here we describe Australia's first known Mesozoic mammal and the first known early Cretaceous mammal from Gondwanaland. Steropodon galmani n. gen. and sp., discovered in early Cretaceous sediments at

The origin of egg-laying mammals

Steropodon appears to have been derived from therians before the development of tribosphenic teeth, possibly during the Jurassic period, and radically alters currently held opinion that monotremes and therians diverged at the earliest stage of mammalian evolution.

A probable pseudo-tribosphenic upper molar from the late Jurassic of China and the early radiation of the Holotheria

A three-cusped, mammalian upper molar recovered from the type locality of Shuotherium dongi Chow and Rich, 1982 in the Late Jurassic, Upper Shaximiao Formation Sichuan, China indicates a greater antiquity and diversity of the Tribosphenida than previously thought.

A Chinese triconodont mammal and mosaic evolution of the mammalian skeleton

The derived pectoral girdle of this new triconodont indicates that homoplasies are as common in the postcranial skeleton as they are in the skull and dentition in the evolution of Mesozoic mammals.