Question

if excretory system is absent in echinodermata then why is anus present

Answer 1

in these type of echinodermata anus is a permanent feature.

Answer 2

Explanation:

Echinoderms have no primary organs for excretion but instead release their nitrogenous waste in the form of ammonia through their respiratory system. The anus though is located in most echinoderms and is used for the removing waste as well.