Primal mouths

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Primal mouths
In the case of the original mouths, the original mouth (blastopore) becomes the mouth, the anus is newly formed.

In the case of the original mouths, the original mouth (blastopore) becomes the mouth, the anus is newly formed.

without rank: Opisthokonta
without rank: Holozoa
without rank: Multicellular animals (Metazoa)
without rank: Tissue animals (Eumetazoa)
without rank: Bilateria
without rank: Primal mouths
Scientific name
Grobben , 1908

The primal mouths (Protostomia) are a stem group of the tissue animals (Eumetazoa). The majority of animal phyla and the vast majority of all terrestrial animal species belong to the group of protostomia, which is traditionally compared to the other bilateria , the new mouths (deuterostomia). For a few strains ( arrowworms , also Gastrotricha and a few others) the assignment to one of these two large groups has not been conclusively clarified.

Definition and demarcation

The original mouths traditionally include the animal phyla with a complete digestive tract , in which the mouth emerges from the slit-shaped original mouth in the embryonic development , while the anus breaks through secondarily or arises from the rear part of the original mouth. The origin of the mouth of the original mouth can take place in different ways.

Traditionally, they included the molting animals (Ecdysozoa), the Lophotrochozoa (Lophotrochozoa) and the flatworms (Platyzoa). The arrowworms (Chaetognatha) are not (any longer) integrated here because, according to molecular genetic studies, they may occupy an isolated, basal position in the system. Other groups have recently been transferred there, as suggested by analyzes of the classification of the Xenacoelomorpha. In contrast to the new mouths (deuterostomia), according to the prevailing view today , the original mouths are paraphyletic , i.e. they do not represent a natural group in the sense of the phylogenetic system.


Individual evidence

  1. ^ Cannon Johanna Taylor, Cossermelli Vellutini Bruno, Smith Julian, Ronquist Fredrik, Jondelius, Ulf, Hejnol Andreas: Xenacoelomorpha is the sister group to Nephrozoa . In: Nature . No. 530, 2016, pp. 89-93 doi : 10.1038 / nature16520

Web links

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