Back to Biodiversity Explorer main pageGo to Iziko Museums of Cape Town home pageAbout Biodiversity Explorer - history, goals, etc.Send us your questions about southern African biodiversityPeople who have contributed content and images.Search Biodiversity Explorer

Metazoa (animals)

Life > Eukaryotes > Opisthokonta


Porifera (sponges)



Ctenophora (comb-jellies) 



Cnidaria (jellyfish, sea anemones, sea fans, soft corals, hard corals)

The unique feature of the Cnidaria is that they have stinging cells, called nematocysts. Each of these cells contains a thread-like sting that is discharged in attack or defense (if you have been stung by a bluebottle while swimming at the beach, you will know all about this). Cnidaria come in two main forms: polyps, that usually stays in one place (e.g. sea anemones), or medusae that have an umbrella shape and float or swim around in the water (e.g. jellyfish). Bluebottles and their relatives (Siphonophora) are unusual in that each of them is basically a colony of floating polyps, one of which is inflated to form the float. So not all polyps are sedentary. Some of the most important members of the Cnidaria are the corals that, in association with symbiotic algae, are able to lay down calcium carbonate and in this way build whole islands that people now live on.



Trichoplax adhaerens, an amoeba-like marine animal about half a centimeter long, is the sole species known from this phylum.








Chordata (vertebrates and relatives, including fish, mammals, birds, reptiles and amphibians).

Have a dorsal nerve cord and a notocord (that becomes the vertebral column in vertebrates).






Marine organisms such as acorn worms.


Echinodermata (starfish, sea urchins, sea cucumbers, etc.) 







About 430 species known, all microscopic.







Nematomorpha (horsehair worms)

About 320 species known.


Nematoda (nematodes or roundworms)

About 12000 species known, but an estimated 200000+ species extant, mostly microscopic. Considered the second most diverse animal phylum after the arthropods.


Cephalorhyncha (= Scalidophora)


Priapula (priapulid worms)

Sixteen species known, about half microscopic.





Kinorhyncha (mud dragons)

About 150 species known, all microscopic.


Loricifera (loriciferans)



      Onychophora (peripatus)






Tardigrada (water bears)



Arthropoda (insects, spiders, scorpions, crustaceans, centipedes, millipedes)  



    Platyhelminthes (flatworms, tapeworms)  

Rotifera (rotifers or "wheel animalcules")

 About 1500 species known, all microscopic.









[= Ectoprocta]



Annelida (segmented worms, including earthworms and leaches) 



Nemertea (ribbon worms)

Marine worms that in some species can reach 30 m in length! Synonyms: Nemertini or Nemertina.


Sipunculida (peanut worms)

[= Sipuncula]


    Mollusca (snails, mussels, squid, etc.)  

Echiura (spoon worms and innkeepers)

Marine. Once placed with the phylum Annelida.


Siboglinidae (beard worms)

[= Pogonophora, Vestimentifera]]

Marine worms living in tubes. Some giant species, 1.5 m long have been found around warm water vents in the Pacific Ocean. Siboglinidae has been placed previously under the Annelida.





Brachiopoda (lamp shells)

Look superficially like clams in that they have a similar shaped shell but they are not molluscs. 



Chaetognatha (arrowworms). About 70 species known.  
Acanthocephala. Spiny-headed parasitic worms; about 1150 species known.  

How animals are given scientific names - a brief introduction

Text by Hamish Robertson 

Contact us if you can contribute information or images to improve this page.

Biodiversity Explorer home   Iziko home   Search