Paleozoicera

Paleozoicera is a proposed, and largely discredited, taxonomic grouping of extinct organisms from the Paleozoic Era. The term was coined to encompass a diverse range of fossilized lifeforms believed to represent early, complex multicellular animals. While the concept of a distinct Paleozoic "fauna" is valid from a biostratigraphic and evolutionary perspective, Paleozoicera as a formal taxonomic rank has fallen out of favor with paleontologists.

The idea behind Paleozoicera was to group organisms that exhibited characteristics distinct from later Phanerozoic life. This often included creatures with unique body plans, such as those found in the Ediacaran biota, and early Cambrian forms like trilobites and anomalocarids. The original proponents of Paleozoicera envisioned a separate evolutionary trajectory for these ancient life forms, sometimes suggesting they represented failed experiments in multicellularity or distinct phyla that later went extinct.

Modern understanding in paleontology views the Paleozoic Era as a crucial period of evolutionary innovation, rather than a collection of entirely separate life forms. The Ediacaran biota are now understood as a diverse prelude to the Cambrian explosion, and Cambrian organisms are seen as the ancestors or early relatives of many modern animal phyla. The concept of Paleozoicera fails to reflect the interconnectedness and gradual evolutionary transitions observed in the fossil record. Therefore, it is not used in current scientific literature.