1. Gastrulation and neurulation (frog)
Neurulation animation (human)

2. Phylum Chordata Subphylum Urochordata (Tunicata)
Subphylum Cephalochordata
“Craniata” group
Subphylum Vertebrata
Superclass Agnatha
Superclass Gnathostomata
Class Placodermi
Class Chondrichthyes
Class Acanthodii
Class Osteichthyes
Class Amphibia
Class Reptilia
Class Mammalia
Class Aves

4. Urochordata

5. Urochordata
Sessile filter feeder – cilia move water and food, filtering in pharyngeal ‘pouch’ (pharynx)
Water + Food In
Water
Out
Gets
filtered

6. Urochordata Endostyle – ciliated groove within pharynx
secretes mucous for food capture
metabolizes iodine - homologous to thyroid
Endostyle

7. Urochordata
Monoecious (hermaphroditic) - each individual produces male and female gametes.
Gametes
released

8. Tunic – polysacchrides w/tunicin secreted by mantle

9. Urochordata
Adult lacks most chordate synapomorphies

10. Urochordata larvae
Eyespot (ocellus)
and
statocyst

12. Phylum Chordata -Superclass Agnatha Subphylum Urochordata (Tunicata)
Subphylum Cephalochordata
“Craniata” group
Subphylum Vertebrata
-Superclass Agnatha
Superclass Gnathostomata
Class Placodermi
Class Chondrichthyes
Class Acanthodii
Class Osteichthyes
Class Amphibia
Class Reptilia
Class Mammalia
Class Aves

13. Cephalochordata Motile filterfeeders Ciliated wheel organ and pharynx
Notochord – “hydroskeleton”
Stiffness of notochord under neural control
amphioxus
Notochord extends
into anterior end

14. Cephalochordata Amphioxus
Tail musculature and associated nerves & vessels are segmented.
‘Metamerism”
myomeres

15. Cephalochordata Amphioxus
Circulatory system with dorsal and ventral aorta.

16. Cephalochordata
Metapleural fold – stability for swimming

17. In text, Euchordates = Somitichordates

19. What were early chordates like?

20. Pikaia gracilens - 530 million years ago
myomeres (muscle blocks)
skeletal notochord
cephalization

21. Cambrian explosion - ~550 million y.a.
Burgess shale

23. It’s a long way from amphioxus
Kiss off, you dang annelids!
It’s a long way from amphioxus
Oh, a fish-like thing appeared among the annelids one day,
It hadn't any parapods or setae to display.
It hadn't any eyes or jaws or ventral nervous cord.
But it had a lot of gill slits and it had a notochord.
Chorus:
It's a long way from amphioxus, it's a long way to us.
It's a long way from amphioxus to the meanest human cuss.
It's good-bye to fins and gill slits, and welcome lungs and hair.
It's a long, long way from amphioxus, but we all came from there.
It wan't much to look at and it scarce knew how to swim.
And Nories was very sure it hadn't come from him.
The Molluscs wouldn't own it and the Arthropods got sore.
So the poor thing had to burrow in the sand along the shore.
"My notochord shall change into a chain of vertebrae,
And, as fins, my metapleural folds will agitate the sea."
"My tiny dorsal nervous cord shall be a mighty brain.
And the vertebrates shall dominate the animal domain."

24. Phylum Chordata -Superclass Agnatha Subphylum Urochordata (Tunicata)
Subphylum Cephalochordata
“Craniata” group
Subphylum Vertebrata
-Superclass Agnatha
-Superclass Gnathostomata
Class Placodermi
Class Chondrichthyes
Class Acanthodii
Class Osteichthyes
Class Amphibia
Class Reptilia
Class Mammalia
Class Aves

25. Craniata Contains hagfish and all vertebrata
Chordates with skulls, neural crest
Cranium is cartilagenous, fibrous or bony and encases brain and sense organs
Hagfish
Lamprey

26. Craniata
Sensory, digestive and respiratory anatomy

27. Neural crest cells
NC cells are found in all craniates and give rise to a variety of structures

28. It’s nice to have a neural crest….
pigment cells
gill arches, jaw
ganglia in ANS
base of skull
induce skin ‘structures’
cranial meninges

29. Craniata vs. ‘protochordates’
Selection for predatory characteristics
active feeders
muscular gut tube for filtering
Pikaia gracilens Haikouella

30. Conodonts - 540-230 m.y. ago after Pikaia, the next fossil Chordates
microfossils of teeth, probably in pharynx

31. Cool thing about conodonts
A new hard substance appears: mineralized tissue – calcium phosphate (hydroxyapatite)