Show Summary Details
Page of

date: 24 October 2021

p. 244. Basal animals: sponges, corals, and jellyfishlocked

p. 244. Basal animals: sponges, corals, and jellyfishlocked

  • Peter Holland


‘Basal animals: sponges, corals, and jellyfish’ describes the four non-bilaterian phyla — Porifera (sponges), Cnidaria (sea anemones, corals, and jellyfish), Ctenophora (comb jellies), and the Placozoa — that separated from other animal groups early in evolution. The key characteristics of each phylum and their subdivisions are outlined. Sponges and placozoans lack precise symmetry, while comb jellies have ‘biradial’ symmetry, meaning that their bodies are symmetrical by a 180-degree rotation. The fourth and largest of the non-bilaterian phyla, the Cnidaria, contains animals whose bodies also lack head-to-tail, top-to-bottom, and left-to-right axes, and with few exceptions also have radial or rotational symmetry.

Access to the complete content on Very Short Introductions online requires a subscription or purchase. Public users are able to search the site and view the abstracts and keywords for each book and chapter without a subscription.

Please subscribe or login to access full text content.

If you have purchased a print title that contains an access token, please see the token for information about how to register your code.

For questions on access or troubleshooting, please check our FAQs, and if you can't find the answer there, please contact us.