3 Classes down, 2 more to go
• Myxini (hagfishes)
• Petromyzontida (lampreys)
• Chondrichthyes (sharks, rays and chimaeras)
– How many?
What do you think?
• Is the lancelet a fish?
Fish-like characters of lancelets
-myomeres
-nerve cord
-post-anal tail
-notochord
-pharyngeal slits (gills?)
*Compare to lamprey ammocoete
Where are we?
Phylum Chordata
Lancelets- Subphylum Cephalochordata
Everything else- Subphylum Craniata
What are we?
What makes a craniate?
-cranium
-red blood cells
-bone (or cartilage)
What makes a vertebrate?
-vertebrae
-dermal bones
-neural crest
Hagfish vs. Lamprey
• Compare and contrast the specimens
Shark inner ear has 3 semicircular canals
How are they related?
Cyclostome Hypothesis
Vertebrate Hypothesis
For now, lampreys considered basal to vertebrates
But..
Compelling evidence exists that supports the cyclostome
hypothesis
Relationships are uncertain!
We covered the jawless fishes
What next?...
Jawed fishes
Superclass Gnathostomata
Class Chondrichthyes
• Subclass Holocephali (etymology?)
– Chimaeras
• Subclass Elasmobranchii
– Sharks
– Skates and Rays
Chondrichthyan characters
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Cartilaginous skeleton
Fin “rays” called ______________
No gas bladder
Oily liver
Spiral valve intestine
Claspers
Ampullae of Lorenzini
Differences
Holocephali
Jaw fused
Ever-growing toothplate
Scaleless
No cloaca (?)
Elasmobranchii
Jaw protrusible
Serially replaced teeth
Placoid Scales
Cloaca
Sharks vs. Rays
• Division Neoselachii
– Subdivision Selachii – Sharks
• Pectorals not fused to head
• Some with anal fin
• Gill slits lateral
– Subdivision Batoidea – Rays and skates
• Pectorals fused to head
• No anal fin
• Gill slits ventral
Videos
• http://animal.discovery.com/videos/mutualof-omahas-wild-kingdom-manta-rayfingerprints.html
http://www.youtube.com/watch?v=rsFVDmFvRbg
Shark Lab
1. What does Gnathostomata mean? And what taxonomic
level is it?
2. How do you tell gender of shark, ray or chimaera?
3. How do you tell a shark apart from a ray (harder than you
may think)?
4. Terms (what they are and what they look like):
palatoquadrate, ceratotrichia, Ampullae of lorenzini,
placoid scales
5. Know how to identify all orders (families for
Myliobatiformes). Know names of representative
families.
6. 2 differences between Holocephali and Elasmobranchii