biradially

Biradially is a term used in biology to describe a type of symmetry. Organisms that exhibit biradial symmetry have a body plan that can be divided into two identical halves along two different planes. This is distinct from radial symmetry, which can be divided into identical halves along any plane passing through the central axis.

Biradial symmetry is found in certain groups of invertebrates, most notably the phylum Cnidaria, which includes jellyfish, corals, and sea anemones. Within Cnidaria, some species, like the comb jellies (ctenophores), display biradial symmetry. These animals typically have two comb rows that are arranged in a particular way, and other structures are also oriented relative to these comb rows.

In essence, biradial symmetry is a compromise between bilateral symmetry (having a distinct left and right side) and radial symmetry. It implies a certain level of organization and specialization within the organism's body, often related to feeding or locomotion. While not as common as radial or bilateral symmetry, biradial symmetry is a significant characteristic for classifying and understanding the evolutionary relationships of certain marine life.