Evolution & Systematics

The Hydrozoa are classified morphologcally as either A-form (athecate) or L-form (thecate), based on the presence of a theca. 


Figure 11. The phylogeny of Hydrozoa, with Myrionema classified as Anthoathecata. Adapted from Ruppert et al (2004).


The Anthoathecates are further classifed into Aplanulata, Filifera and Capitata.



Figure 12. Anthoathecata is further divided based on tentacle shape, with Myrionema classifed as Filifera, with long, filiform tentacles.