1. The Prechordates Phyla that have some chordate features but not all
Considered to be possible ancestors to the phylum Chordata

2. Phylum Chaetognatha Arrow worms
Approximately 70 species; 1-10 cm long
All marine, free-living, planktonic
bilaterally symmetrical, as are all of the rest of the phyla

3. Phylum Chaetognatha Arrow worms
body of three regions: head, trunk, tail
has lateral and caudal fins
has circumesophogeal ganglia

4. Phylum Chaetognatha Arrow worms
no circulatory system, excretory system, respiratory
skeleton is hydrostatic type
are hermaphroditic; with cross-fertilization, and internal
are carnivorous - predators of plankton

5. Phylum Hemichordata (the acorn worms)
about 100 species, all marine, 0.5 cm - 2 m
benthic (live on the bottom) and free living
solitary or colonial
vermiform- elongate

6. Phylum Hemichordata (the acorn worms)
body in three parts; proboscis, collar and trunk
are gill slits for respiration
no post-anal tail

7. Phylum Hemichordata (the acorn worms)
have free living larvae called tornaria
Resemble echinoderm larvae

8. Phylum Hemichordata (the acorn worms)
primarily feeding on detritus and microscopic organisms
have circulatory system; two main blood vessels and a central sinus (heart)
sexes are separate; fertilization is external