2. Phylum Chordata

3. Phylum Chordata common characteristics segmented muscles
 ventral heart
 complete digestive system
Five defining chordate characteristics
 pharyngeal gill slits
 dorsal, hollow nerve cord
post anal tail
endostyle/thyroid gland
 notochord

4. Body Structure pharyngeal slits & atriopore Notochord with myomeres
post-anal tail
dorsal, hollow nerve cord

5. Subphylum Urochordata (Tunicates)
“tail string”
all are filter feeders
sessile & pelagic; solitary & colonial
tadpole-like larva
Adult
Larva

6. Three Classes
Ascidiacea
Larvacea
Thaliacea

7. Class Ascidiacea
“sea squirts”
u-shaped gut, with incurrent oral and excurrent atrial siphons
large central chamber (atrium)

8. Larval Ascidean

9. Class Thaliacea

10. Class Larvacea

11. Subphylum Cephalochordata
“head string”
Lancelets (Amphioxus)
burrow into sand & shell gravels
filter feeders

12. Closed Circulatory System
flow pattern similar to fishes
no “heart”
peristaltic contractions of blood vessels

13. Filter Feeders

14. larval notochord replaced by vertebral column in adults
Phylum Chordata
Subphylum Vertebrata
larval notochord replaced by vertebral column in adults
dorsal nerve cord
pharyngeal gill slits

15. Trends in Vertebrate Evolution
Living Endoskeleton
Pharynx and Efficient Respiration
Advanced Nervous System
Paired Limbs

16. Early Chordata Fossils
Pikaia
Resembles Amphioxus
Distinct notochord
Chevron shaped muscle