Notes on Tunicates and Amphioxus

1. The most recently evolved animalThe most recently evolved animal
phylum is called Chordata.phylum is called Chordata.

2. Chordates are characterized by …Chordates are characterized by …

3. Chordates are characterized by …Chordates are characterized by …
1.1. A dorsal, hollow nerve chord.A dorsal, hollow nerve chord.

4. Chordates are characterized by …Chordates are characterized by …
1.1. A dorsal, hollow nerve chord.A dorsal, hollow nerve chord.
2.2. A dorsal notochord to support theA dorsal notochord to support the
body.body.

5. Chordates are characterized by …Chordates are characterized by …
1.1. A dorsal, hollow nerve chord.A dorsal, hollow nerve chord.
2.2. A dorsal notochord to support theA dorsal notochord to support the
body.body.
3.3. A post anal tail at some stage ofA post anal tail at some stage of
development.development.

6. Chordates are characterized by …Chordates are characterized by …
1.1. A dorsal, hollow nerve chord.A dorsal, hollow nerve chord.
2.2. A dorsal notochord to support theA dorsal notochord to support the
body.body.
3.3. A post anal tail at some stage ofA post anal tail at some stage of
development.development.
4.4. Seven pharyngeal clefts (gills) atSeven pharyngeal clefts (gills) at
some stage of development.some stage of development.

7. About 0.5% of humans have a vestigial remnant of the anterior –most
gill slit. It appears as a tiny opening at the front edge of the ear on one
or both sides of the head.

8. Phylum Chordata is divided into three
subphyla, two of which are invertebrates.
Subphylum Urochordata

9. Phylum Chordata is divided into three
subphyla, two of which are invertebrates.
Subphylum Urochordata

10. Phylum Chordata is divided into three
subphyla, two of which are invertebrates.
Subphylum Urochordata
Subphylum Cephalochordata

11. Tunicate larvae are somewhat fish-like.Tunicate larvae are somewhat fish-like.

22. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.

23. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes

24. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes
• Cephalaspidomorphi -Cephalaspidomorphi -
lampreyslampreys

25. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes
• Cephalaspidomorphi -Cephalaspidomorphi -
lampreyslampreys
• OstracodermiOstracodermi

26. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes
• Cephalaspidomorphi -Cephalaspidomorphi -
lampreyslampreys
• OstracodermiOstracodermi
• PlacodermiPlacodermi

27. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes
• Cephalaspidomorphi -Cephalaspidomorphi -
lampreyslampreys
• OstracodermiOstracodermi
• PlacodermiPlacodermi
• Elasmobranchomorphi –Elasmobranchomorphi –
cartilaginous fishescartilaginous fishes

28. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes
• Cephalaspidomorphi -Cephalaspidomorphi -
lampreyslampreys
• OstracodermiOstracodermi
• PlacodermiPlacodermi
• Elasmobranchomorphi –Elasmobranchomorphi –
cartilaginous fishescartilaginous fishes
• Osteichthyes – bonyOsteichthyes – bony
fishesfishes

29. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes
• Cephalaspidomorphi -Cephalaspidomorphi -
lampreyslampreys
• OstracodermiOstracodermi
• PlacodermiPlacodermi
• Elasmobranchomorphi –Elasmobranchomorphi –
cartilaginous fishescartilaginous fishes
• Osteichthyes – bonyOsteichthyes – bony
fishesfishes
• AmphibiaAmphibia

30. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes
• Cephalaspidomorphi -Cephalaspidomorphi -
lampreyslampreys
• OstracodermiOstracodermi
• PlacodermiPlacodermi
• Elasmobranchomorphi –Elasmobranchomorphi –
cartilaginous fishescartilaginous fishes
• Osteichthyes – bonyOsteichthyes – bony
fishesfishes
• AmphibiaAmphibia
• ReptiliaReptilia

31. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes
• Cephalaspidomorphi -Cephalaspidomorphi -
lampreyslampreys
• OstracodermiOstracodermi
• PlacodermiPlacodermi
• Elasmobranchomorphi –Elasmobranchomorphi –
cartilaginous fishescartilaginous fishes
• Osteichthyes – bonyOsteichthyes – bony
fishesfishes
• AmphibiaAmphibia
• ReptiliaReptilia
• AvesAves

32. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes
• Cephalaspidomorphi -Cephalaspidomorphi -
lampreyslampreys
• OstracodermiOstracodermi
• PlacodermiPlacodermi
• Elasmobranchomorphi –Elasmobranchomorphi –
cartilaginous fishescartilaginous fishes
• Osteichthyes – bonyOsteichthyes – bony
fishesfishes
• AmphibiaAmphibia
• ReptiliaReptilia
• Aves - birdsAves - birds

33. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes
• Cephalaspidomorphi -Cephalaspidomorphi -
lampreyslampreys
• OstracodermiOstracodermi
• PlacodermiPlacodermi
• Elasmobranchomorphi –Elasmobranchomorphi –
cartilaginous fishescartilaginous fishes
• Osteichthyes – bonyOsteichthyes – bony
fishesfishes
• AmphibiaAmphibia
• ReptiliaReptilia
• Aves - birdsAves - birds
• MammaliaMammalia

34. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes
• Cephalaspidomorphi -Cephalaspidomorphi -
lampreyslampreys
• OstracodermiOstracodermi

35. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes
• Cephalaspidomorphi -Cephalaspidomorphi -
lampreyslampreys
• OstracodermiOstracodermi
These three vertebrateThese three vertebrate
classes lack jaws. Theyclasses lack jaws. They
cannot close their mouth.cannot close their mouth.

36. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes
• Cephalaspidomorphi -Cephalaspidomorphi -
lampreyslampreys
• OstracodermiOstracodermi
These three vertebrateThese three vertebrate
classes lack jaws. Theyclasses lack jaws. They
cannot close their mouth.cannot close their mouth.
Such animals are calledSuch animals are called
AgnathansAgnathans..

37. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes
• Cephalaspidomorphi -Cephalaspidomorphi -
lampreyslampreys
• OstracodermiOstracodermi
These three vertebrateThese three vertebrate
classes lack jaws. Theyclasses lack jaws. They
cannot close their mouth.cannot close their mouth.
Such animals are calledSuch animals are called
AgnathansAgnathans..
A – withoutA – without

38. The third subyphylum, called Vertebrata, isThe third subyphylum, called Vertebrata, is
divided into 10 classes, 2 of which are extinct.divided into 10 classes, 2 of which are extinct.
• Myxini – hagfishesMyxini – hagfishes
• Cephalaspidomorphi -Cephalaspidomorphi -
lampreyslampreys
• OstracodermiOstracodermi
These three vertebrateThese three vertebrate
classes lack jaws. Theyclasses lack jaws. They
cannot close their mouth.cannot close their mouth.
Such animals are calledSuch animals are called
AgnathansAgnathans..
A – withoutA – without
gnath - jawgnath - jaw

39. The remaining seven classes (one of which is
extinct) have jaws.

40. The remaining seven classes (one of which is
extinct) have jaws. Vertebrates with jaws are
called gnathostomes.

41. The remaining seven classes (one of which is
extinct) have jaws. Vertebrates with jaws are
called gnathostomes.
Gnath – jaws

42. The remaining seven classes (one of which is
extinct) have jaws. Vertebrates with jaws are
called gnathostomes.
Gnath – jaws
Stome – hole (referring to the mouth)

43. The remaining seven classes (one of which is
extinct) have jaws. Vertebrates with jaws are
called gnathostomes.
Gnath – jaws
Stome – hole (referring to the mouth)
Literally a mouth with jaws.

47. Gill slit
Gill cleft

49. If you think about this, it means thatIf you think about this, it means that
you are closely related to tunicatesyou are closely related to tunicates
and amphioxus as a spider is to anand amphioxus as a spider is to an
insect.insect.