In zoology Form taxa are groupings that are based on common overall forms. Early attempts at classification of
labyrinthodonts was based on skull shape (the heavily armoured skulls often being the only preserved part). The amount of convergent evolution in the many groups led to a number of
polyphyletic taxa. 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". Other examples include the
seabirds and the "
Graculavidae". 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. Fossil eggs are classified according to the parataxonomic system called
Veterovata. There are three broad categories in the scheme, on the pattern of organismal phylogenetic classification, called oofamilies, oogenera and oospecies (collectively known as ootaxa). The names of oogenera and oofamilies conventionally contain the root "oolithus" meaning "stone egg", but this rule is not always followed. They are divided up into several basic types: Testudoid, Geckoid, Crocodiloid, Dinosauroid-spherulitic, Dinosauroid-prismatic, and Ornithoid.
In botany In
paleobotany, two terms were formerly used in the
codes of nomenclature, "form genera" and "organ genera", to mean groups of fossils of a particular part of a plant, such as a leaf or seed, whose parent plant is not known because the fossils were preserved unattached to the parent plant. A later term "morphotaxa" also allows for differences in preservational state. These three terms have been replaced as of 2011 by provisions for "fossil-taxa" that are more similar to the provisions for other types of plants. Names given to organ genera could only be applied to the organs in question, and could not be extended to the entire organism. Fossil-taxon names can cover several parts of an organism, or several preservational states, but do not compete for
priority with any names for the same organism that are based on a non-fossil
type. The part of the plant was often, but not universally, indicated by the use of a
suffix in the
generic name: • wood fossils may have generic names ending in
-xylon • leaf fossils generic names ending in '''' • fruit fossils generic names ending in ''
, -carpum
or -carpus'' • pollen fossils generic names ending in ''
or -pollenoides''. ==See also==