Parifüleetiline

Parifüleetiline refers to a taxonomic classification that includes a common ancestor but not all of its descendants. This type of classification is in contrast to a monophyletic group, which includes an ancestor and all of its descendants, or a polyphyletic group, which includes organisms descended from more than one common ancestor. The term itself is derived from Greek roots.

In phylogenetic studies, the goal is generally to identify monophyletic groups, also known as clades, as these represent natural evolutionary lineages. Parifüleetiline groupings, while sometimes historically used, are considered problematic because they do not fully reflect evolutionary history. They can arise when certain lineages are excluded from a group, often due to a loss of distinguishing features or because they have evolved in a very different direction.

An example often cited to illustrate a parifüleetiline group is the traditional classification of reptiles. This group historically included lizards, snakes, turtles, and crocodilians, but excluded birds. However, birds evolved from within the reptilian lineage (specifically, from theropod dinosaurs). Therefore, classifying reptiles without birds creates a parifüleetiline group. Modern cladistic classifications, which prioritize monophyly, would include birds within the broader group of dinosaurs or sauropsids to create a monophyletic entity. Understanding parifüleetiline groups is important for recognizing the evolution of classification systems and the principles of modern phylogenetic analysis.