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?

For now, lampreys considered basal to vertebrates

But..Compelling evidence exists that supports the cyclostome hypothesis

Relationships are uncertain!

Cyclostome Hypothesis Vertebrate Hypothesis

We covered the jawless fishesWhat next?...

Jawed fishesSuperclass Gnathostomata

Class Chondrichthyes

• Subclass Holocephali (etymology?)– Chimaeras

• Subclass Elasmobranchii– Sharks– Skates and Rays

Chondrichthyan characters

• Cartilaginous skeleton• Fin “rays” called ______________• No gas bladder• Oily liver• Spiral valve intestine • Claspers • Ampullae of Lorenzini

Differences

Holocephali ElasmobranchiiJaw fused Jaw protrusibleEver-growing toothplate Serially replaced teethScaleless Placoid ScalesNo cloaca (?) 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/mutual-of-omahas-wild-kingdom-manta-ray-fingerprints.html

http://www.youtube.com/watch?v=rsFVDmFvRbg

Shark Lab1. 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