Symplesiomorphy

As Plesiomorphie (from Greek plesio " adjacent ", and morphe "shape" ) is referred to in the systematics and cladistics an original characteristic value. A feature is referred to in evolutionary biology as plesiomorphic, if it arose before the considered lineage, so compared to the characteristic state of the ancestors remained unchanged. The antonym for Plesiomorphie is a newly acquired feature, apomorphy. Classification as a " newly acquired " " original " or is relative, because it always depends on the two taxa under consideration.

For example, the feature of the Vierfüßigkeit in the development of fossil reptiles from fossil amphibians is a Plesiomorphie as all the sub groups of land vertebrates originally had four limbs. In a comparison of terrestrial vertebrates with the fossil Fleischflossern is in contrast to a Vierfüßigkeit apomorphy since the feature relative to the bony fish belonging to the core group has been newly acquired. Similarly, the subsequent recovery of the limbs in snakes is an apomorphy, because the fossil reptiles originally have four extremities.

Symplesiomorphie

As Symplesiomorphie (from the Greek sym - "with", "together" ) is called a homologous consensus on a common feature original condition in different taxa. Symplesiomorphe features are evolutionarily old, they have their roots in an ancestor which is the ancestor of other taxa simultaneously. Because of this, Symplesiomorphien are not the creation of a monophyletic group in most cases; Instead of such reasoned taxa usually lead to ( in cladistics unwanted ) Education paraphyletischer groups.

For example, the feature Vierfüßigkeit is not in support of the taxon reptiles, because on the one hand belonging to the reptiles snakes have lost this original feature and also the taxa amphibians and mammals have the feature Vierfüßigkeit also, but without counting the reptiles. Vierfüßigkeit is based on a Symplesiomorphie reptiles, the feature is evolutionarily much older than the reptiles. The taxon reptiles is, moreover, no monophyletic group, because the birds taxon is not included.