Marsupionta

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The division of living beings into systematics is a continuous subject of research. Different systematic classifications exist side by side and one after the other. The taxon treated here has become obsolete due to new research or is not part of the group systematics presented in the German-language Wikipedia.

As Marsupionta a postulated by some researchers will taxon of mammals referred that the marsupials (Metatheria) and the egg-laying Ursäuger summarizing (Protheria). The higher mammals (Eutheria) would therefore be the sister taxon of Marsupionta.

This view contradicts the widespread opinion that pouches and higher mammals form a common taxon Theria to the exclusion of the mammals. The theria are described by a number of common derived features ( synapomorphies ), which include viviparity (giving birth to live young animals), the presence of teats, and several features in the structure of the skull and shoulder girdle .

Common morphological features of Marsupionta consist only in the sac bones , two bones protruding forward from the pelvis , which are present in both primeval and saccharine mammals, but are absent in the higher mammals. However, some primeval mammals and fossil ancestors of the higher mammals from the Cretaceous period also have these bones. It can therefore be assumed that these pouch bones were an original feature that was reduced in today's higher mammals and thus no morphological feature exists for the Marsupionta.

The genetic findings, however, are contradictory. Comparisons of mitochondrial DNA support the Marsupionta theory, while genetic studies of the cell nucleus speak in favor of theria. Other studies do not come to a clear conclusion either (Lee 2003), so that due to the morphological findings, the majority of researchers prefer the Theria.

literature

  • W. Westheide, R. Rieger: Special Zoology. Part 2: vertebrates or skulls. Spektrum Akademischer Verlag, Munich 2004, ISBN 3-8274-0307-3 .
  • Tse Yan Alexander Lee: Mammalian Phylogenetic Relationship: Genetics 3003 - Molecular Evolution III; Theria Enthusiasts versus Marsupionta Fans . In: Internet Journal of Genomics & Proteomics . tape 1 , no. 1 , 2003, p. 3 ( abstract [accessed May 6, 2013]).