Tribrachidium heraldicum is a tri-radially symmetric fossil animal that lived in the late Ediacaran (Vendian) seas. In life, it was hemispherical in form. T. heraldicum is the best known member of the extinct group Trilobozoa.
Tribrachidium
Reconstruction of Tribrachidium and other organisms: Tribrachidium heraldicum (top); Wigwamiella enigmatica,a taphomorph of aspidella (left); and Rugoconites enigmatica (right).
Pomoria Corolliformis was once thought to be a Cnidarian polyp, although it has been disproven as instead being a poorly preserved Tribrachidium.
Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, the face of a human being has a plane of symmetry down its centre, or a pine cone displays a clear symmetrical spiral pattern. Internal features can also show symmetry, for example the tubes in the human body which are cylindrical and have several planes of symmetry.
A selection of animals showing a range of possible body symmetries, including asymmetry, radial, and bilateral body plans
Illustration depicting the difference between bilateral (Drosophila), radial (actinomorphic flowers) and spherical (coccus bacteria) symmetry
Lilium bulbiferum displays hexamerism with repeated parts arranged around the axis of the flower.
Apple cut horizontally showing that pentamerism also occurs in fruit