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 fishes What next?... Jawed fishes Superclass 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 Elasmobranchii Jaw fused Jaw protrusible Ever-growing toothplateSerially replaced teeth ScalelessPlacoid Scales No 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 of-omahas-wild-kingdom-manta-ray- fingerprints.html

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