Afrotheria

from Wikipedia, the free encyclopedia
Afrotheria
Various members of the Afrotheria

Various members of the Afrotheria

Systematics
without rank: Amniotes (Amniota)
without rank: Synapsids (Synapsida)
Class : Mammals (mammalia)
without rank: Theria
Subclass : Higher mammals (Eutheria)
Superordinate : Afrotheria
Scientific name
Afrotheria
Stanhope , Waddell , Madsen , de Jong , Hedges , even , Kao & Springer , 1998

The Afrotheria are a molecular genetically determined superorder within the subclass of higher mammals . They include 88 species . The group, which appears to be quite inhomogeneous from the outside, shares its ancestral origin from Africa . Apart from the Asian elephants , a Hyrax -Art and manatees is this continent still their habitat.

In the late Cretaceous period, the Afrotheria in Africa separated from their sister group, the Exafroplacentalia ( secondary arthropods and Boreoeutheria ).

features

This group of mammals is very diverse and includes aquatic animals such as manatees, ant-eaters such as the aardvark and giants such as elephants. The dwarf lesser rek ( Microgale parvula ) and the gnome lesser rek ( Microgale pusilla ) are the smallest representatives of the Afrotheria with a weight of up to 4 grams; the African elephant ( Loxodonta africana ), on the other hand, is the largest land mammal with its weight of up to 5 tons.

Apart from the genetic features that define the group, only a few skeletal anatomical features are known to unite the group. All Afrotheria have a higher number of vertebrae in the thoracic and lumbar spine compared to numerous other, especially early representatives of the higher mammals and compared to the marsupials (20 to 31 compared to 19). Another synapomorphy (common feature) could be found in the very late eruption of permanent dentition in the adult stage.

In addition, the group of animals is characterized by some "primitive" characteristics that it shares with primeval groups of animals such as the monastery . The testes of the males of many Afrotherians are in the abdominal cavity and thermoregulation is hardly developed in many species. The latter can also be related to the fact that they come from warm climates.

Tribal history

With the breakup of the southern major continent of Gondwana in the Cretaceous period about 105 million years ago, the Afrotheria probably evolved separately from all other groups of higher mammals. Their common ancestor was probably a forest insect or herbivore.

Very early records of the Afrotheria come from Morocco and are around 60 million years old, thus dating to the end of the Paleocene . These include, for example, Ocepeia , a very primitive representative, or Eritherium , one of the oldest known proboscis. The Afrotheria produced ecological counterparts to many groups of mammals that developed at the same time on the northern major continent of Laurasia . The tenre karts are similar to the insectivores (for example the golden mole to the moles ), the manatees have parallels in their physique to whales and seals , the hyraxes resemble marmots .

When about 30 to 40 million years ago the rapprochement between Africa and Europe and Asia lifted the isolated position of Africa, numerous groups of mammals migrated from Eurasia to Africa; some Afrotherians, such as the elephants and the hyrax, in turn colonized the northern continents.

Systematics

The representatives of Afrotheria carry specific retroposons , so-called AfroSINEs, in their genomes , which prove that they belong together. The group includes six very different looking recent orders:

The lines of the rhino-like Embrithopoda and the amphibious Desmostylia , which became extinct millions of years ago, are also likely to belong to the Afrotheria.

Hyrax, manatees, and elephants are sometimes grouped together as paenungulata because of their close relationship .

literature

  • M. Nikaido, H. Nishihara, Y. Hukumoto, N. Okada: Ancient SINEs from African endemic mammals. In: Mol Biol Evol. 20, 2003, pp. 522-527.
  • William J. Murphy, Eduardo Eizirik, Mark S. Springer et al: Resolution of the Early Placental Mammal Radiation Using Bayesian Phylogenetics. In: Science . Vol 294, Issue 5550, December 14, 2001, pp. 2348-2351.
  • Jan Ole Kriegs, Gennady Churakov, Martin Kiefmann, Ursula Jordan, Juergen Brosius, Juergen Schmitz: Retroposed Elements as Archives for the Evolutionary History of Placental Mammals. In: PLoS Biol . 4 (4), 2006, p. E91. (abstract)
  • David Macdonald: The Great Encyclopedia of Mammals. Könemann in the Tandem Verlag, Königswinter 2004, ISBN 3-8331-1006-6 .

Individual evidence

  1. ↑ Marcelo R. Sanchez-Villàgra, Yuichi Narita, Shigeru Kuratani: Thoracolumbar vertebral number: the first skeletal synapomorphy for afrotherian mammals. In: Systematics and Biodiversity. 5, 2007, pp. 1-7.
  2. ↑ Robert J Asher, Thomas Lehmann: Dental eruption in afrotherian mammals. In: BMC Biology. 6, 2008, p. 14 doi: 10.1186 / 1741-7007-6-14
  3. Jump up ↑ Emmanuel Gheerbrant, Mbarek Amaghzaz, Baadi Bouya, Florent Goussard, Charlène Letenneur: Ocepeia (Middle Paleocene of Morocco): The Oldest Skull of an Afrotherian Mammal. In: PLOSone. 9 (1), 2014, p. E89739 ( plosone.org ).
  4. ↑ Michael Buckley: A Molecular Phylogeny of Plesiorycteropus Reassigns the Extinct Mammalian Order 'Bibymalagasia'. In: PlosOne. 8 (3), 2013, p. E59614 doi: 10.1371 / journal.pone.0059614

Web links