[7] The stem group of Medusozoa also includes Auroralumina attenboroughii, the earliest known animal predator from the late Ediacaran.

It has traditionally been considered to be a cnidarian because of its possession of nematocysts, but molecular studies using 18S rDNA sequences have placed it closer to Myxozoa.

Further studies involving 28S rDNA sequences suggest that it is either part of the hydrozoan clade Leptothecata, or a sister taxon to Hydrozoa, and does not group with myxozoans.

[12] The cnidae, the explosive cells characteristic of the Cnidaria and used in prey capture and defence, are of a single type, there being nematocysts but no spirocysts or ptychocysts.

[4] In contrast, the anthozoan life cycle involves a planula larva which settles and becomes a sessile polyp, which is the adult or sexual phase.

[11] Scyphozoa is the group commonly known as "true jellyfish" and occur in tropical, temperate and polar seas worldwide.

Hydrozoans exhibit the greatest variety of life cycles among medusozoans, with either the polyp or the medusa stage being missing in some groups.

[4] In general, medusae are budded laterally from polyps, become mature and spawn, releasing gametes into the water.