Heterotardigrada And Eutardigrada
Heterotardigrada includes only one known species, Echiniscoides sigismundi, which has a unique morphology and is found primarily in marine environments.
Eutardigrada, on the other hand, is a much larger subclass and includes the majority of tardigrade species. This subclass is further divided into four orders: Apochela, Parachela, Isohypsibioidea, and Hypsibioidea.
Heterotardigrades are characterized by their unique morphology, which includes a set of spines along their body and a pair of claws on each leg. These adaptations allow them to move easily along surfaces and to cling to substrates in the marine environment.
One of the defining characteristics of Eutardigrada is the presence of a pair of stylets, which are used by the tardigrades to pierce plant and animal cells to feed. Tardigrades in this subclass also have an adhesive disk on their ventral side, which allows them to attach to surfaces and move about.