Theria

Giant Anteater ( Myrmecophaga tridactyla)

• Marsupial ( Metatheria )
• Higher mammals ( Eutheria )

The Theria ( gr θηρίον - therion " wild animal ") constitute a taxon within the Mammals ( Mammalia) dar. It summarizes the marsupial ( Metatheria ) and the higher mammals ( Eutheria ) together and is the sister taxon of the monotremes.

Features

The Theria are defined by, among other synapomorphies that are shared derived characteristics, but in individual cases may well be reduced:

• They are viviparous, so they bring in contrast to the egg-laying monotremes living offspring into the world.
• The hole of the urinary and genital apparatus and the anal opening are separated by a dam ( perineum ). Contrast, monotremes have a common outlet opening, the cloaca.
• The shoulder girdle has only shoulder blade (scapula ) and collarbone ( clavicle ) on - the clavicle is reduced but in many species. The monotremes do not have extra bones in the shoulder area as the coracoid.
• The mammary glands lead to the teats, the monotremes, in contrast, zitzenlos.
• The (secondary) side of the skull wall is composed mainly of the wing of the sphenoid bone ( Alisphenoid ) together with the monotremes it is mainly composed of the temporal bone.
• Theria have whiskers ( vibrissae ).
• The molars have a common ( " tribosphenisches " ) pattern.

History of development

The Theria are phylogenetically classified within the Tribosphenida, one in comparison to the early primitive mammals highly developed group. In addition to the Theria These include some extinct and little-known side lines as the Aegialodontidae, who lived primarily in the early Cretaceous period. Within the Theria it came later than 125 million years ago to split into bag and Higher mammals because of two taxa of the earliest known representatives ( Sinodelphys szalayi or Eomaia scan soria ) lived at that time.

Some researchers, however, reject the Theria, they keep the monotremes and marsupials for closely related to each other and put them into a taxon Marsupionta. Probably are but a primitive mammalian feature - - For this taxon morphological features such as the marsupial bones are, and certain genetic data cited. However, the overwhelming morphological and genetic data argue against this thesis, so the Marsupionta be represented only by a minority.