1) The lophophorates include phyla with traits of both deuterostomes [tri-coelomate body, radial cleavage, blastopore yields anus (e.g., brachiopods), coeloms via enterocoely (some)] and protostomes [larval protonephridia (some), mouth from blastopore (e.g., bryozoans)]
a) most are sessile with a reduced head and most secrete a protective covering or shell; almost all are suspension feeders
b) two unifying traits are: i) a lophophore (crown of ciliated tentacles around the mouth extended by a distinct coelom: mesocoel), ii) a U-shaped gut (anus typically lies outside lophophore)
c) Ph. BRYOZOA (moss animals) approx. 4,000 marine and freshwater spp; encrusting colonial animals with polyp-like zooids that extend out of a gelatinous, leathery or calcareous exoskeleton; particles are captured by lateral cilia or tentacular flicking
d) Ph. BRACHIOPODA (lamp shells) approx. 300 marine spp; solitary animals enclosed by paired (dorsal and ventral) shells and bearing a stalk-like pedicle; a coiled lophophore maximizes feeding efficiency vs rate; most went extinct 225 MYA; some have a blind gut (no anus!)
2) Ph. HEMICHORDATA (acorn worms) approx. 100 marine spp; the phylum is pivotal to our understanding of chordate origins
a) two classes differ greatly in form and may belong in separate phyla
b) the Cl. Enteropneusta (acorn worms)
- sediment-dwelling animals that also exhibit a clear tri-partite body
- an extensive branchial chamber, with ciliated U-shaped gill slits, is very similar to Cephalochordata (sister group to vertebrates)
- most enteropneusts feed on particles in sediment; some may filter feed; which mode is primitive remains unclear
- have a stomochord (for ultrafiltration), may be related to notochord
c) the Cl. Pterobranchia: tube-dwelling, colonial animals that superficially resemble bryozoans; have a clear tri-partite body, move along tubes on a creeping oral shield; gill slits small (one pair) or absent
3) Echinoderms and hemichordates share several traits:
a) a protocoelic nephridium (=axial complex)
b) a coelomopore (=hydropore) connects the protocoel to the outside
c) similar larval forms (echinoderm auricularia resemble the enteropneust tornaria) and arrangement of major coeloms