Asterzalia

Asterzalia is the most primitive asterzoan phylum, yet ironically the most "advanced" in terms of intelligence and lifestyle. All extant members have four arms (one of which is modified for waste disposal), a nervous system, chemoreceptive skin patches, and the ability to swim. Though they ancestrally had four-point radial symmetry, some have evolved bilateral symmetry by differentiating their arms as they mature; all bilateral species, particularly those within Lagnodactylia, have radially symmetric larval or embryonic stages.

Cladistically, Asterzalia would also include Asterfolia and Asterstreidia, but these are traditionally not included on account of their differing morphology and not being a part of the crown group.

Class Piktivarelia
Radially symmetric filter-feeding asterzalia which have nervous systems and a waste disposal system, but otherwise lack complex internal organs.

Class Branchiatunica
Bilateral asterzalia with gills and mouths both derived from baits.

Class Triasteria
Bilateral asterzalia derived from a triradial body plan.

Class Lagnodactylia
Asterzalia which have mouths for eating larger prey, bilateral symmetry in adulthood, and flexible digits on their arms used for copulation and sometimes locomotion.