Epitheria
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Epitherians comprise all the Eutherian Mammals except the Xenarthra. They are primarily characterized by having a stirrup-shaped stapes in the middle ear, which allows for passage of a blood vessel. This is in contrast to the column-shaped stapes found in marsupials, monotremes, and xenarthrans. They are also characterized by having a shorter fibula relative to the tibia.
Monophyly of the Epitheria has been challenged by molecular phylogenetic studies (Springer et al., 2004), but (Kriegs et al., 2006) found evidence for the clade based on a set of retroposons shared by all its members (Presence/absence data).
Epitheres appeared in the early part of the Late Cretaceous age. Before the end of the Mesozoic Era, most of the living order's ancestors have already appeared, such as the Ungulates and the Insectivores. After the extinction of non-avian dinosaurs (in the Early Paleocene), the Epitheres' diversity has exploded, and by the end of the Eocene, all living orders of the infraclass Epitheria had appeared. Epitheres are one of the most successful group of animals.
[edit] References
- Kriegs, Jan Ole, Gennady Churakov, Martin Kiefmann, Ursula Jordan, Juergen Brosius, and Juergen Schmitz. (2006) Retroposed Elements as Archives for the Evolutionary History of Placental Mammals. PLoS Biol 4(4): e91.[1]
- Springer, Mark S., Michael J. Stanhope, Ole Madsen, and Wilfried W. de Jong. 2004. "Molecules consolidate the placental mammal tree". Trends in Ecology and Evolution, 19:430–438. (pdf version)
