3 classes down, 2 more to go myxini (hagfishes) petromyzontida (lampreys) chondrichthyes (sharks,...
TRANSCRIPT
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3 Classes down, 2 more to go
• Myxini (hagfishes)
• Petromyzontida (lampreys)
• Chondrichthyes (sharks, rays and chimaeras) – How many?
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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
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Where are we?
Phylum Chordata
Lancelets- Subphylum Cephalochordata
Everything else- Subphylum Craniata
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What are we?
What makes a craniate?-cranium-red blood cells-bone (or cartilage)
What makes a vertebrate?-vertebrae-dermal bones-neural crest
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Hagfish vs. Lamprey
•Compare and contrast the specimens
Shark inner ear has 3 semicircular canals
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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
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We covered the jawless fishesWhat next?...
Jawed fishesSuperclass Gnathostomata
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Class Chondrichthyes
• Subclass Holocephali (etymology?)– Chimaeras
• Subclass Elasmobranchii– Sharks– Skates and Rays
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Chondrichthyan characters
• Cartilaginous skeleton• Fin “rays” called ______________• No gas bladder• Oily liver• Spiral valve intestine • Claspers • Ampullae of Lorenzini
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Differences
Holocephali ElasmobranchiiJaw fused Jaw protrusibleEver-growing toothplate Serially replaced teethScaleless Placoid ScalesNo cloaca (?) Cloaca
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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
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Videos
• http://animal.discovery.com/videos/mutual-of-omahas-wild-kingdom-manta-ray-fingerprints.html
http://www.youtube.com/watch?v=rsFVDmFvRbg
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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