Why aren't Myxozoans within Hydrozoa?

[ATJ]

In the week 3 lecture, you cite Sidall et al (1997) analysis that the rDNA of Myxozoans puts them in Hydrozoa and yet they are given their own class.

 

[rshimek]

Hi,

This is one "conservative" approach. The nucleic acid data are only one set of data, there are a lot of other factors to weigh as well.

Similar "fence straddling" is seen in many phyla. For example, there is no reason to separate birds from reptiles - they are small feathered dinosaurs. However, it will take a while for this to be accepted.

There is a LOT of inertia against making major changes too rapidly, and we will see some other examples. So... you get to weigh the data and decide whether various taxa get lumped or split...

Even though most hobbyists consider name change or even scientific data to somewhat capricious, the set of rules (International Code of Zoological Nomenclature) is really very detailed (it runs to well over 150 pages now, I believe). Generally, changes at the phylum or class level are slow to gain acceptance.