Form classification

[1] Form taxonomy is restricted to fossils that preserve too few characters for a conclusive taxonomic definition or assessment of their biological affinity, but whose study is made easier if a binomial name is available by which to identify them.

[3] Such groups are united by a common mode of life, often one that is generalist, in consequence acquiring generally similar body shapes by convergent evolution.

Ediacaran biota — whether they are the precursors of the Cambrian explosion of the fossil record, or are unrelated to any modern phylum — can currently only be grouped in "form taxa".

The latter were initially described as the earliest family of Neornithes but are nowadays recognized to unite a number of unrelated early neornithine lineages, several of which probably later gave rise to the "seabird" form taxon of today.

There are three broad categories in the scheme, on the pattern of organismal phylogenetic classification, called oofamilies, oogenera and oospecies (collectively known as ootaxa).