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Sharks, skates and rays
Placoid scales Ampullary organs
Chondrichthyes
Placoid scales and drag
No swim bladder for buoyancy big liver loss of weight lift from tail, pectoral fins
Chondrichthyes
Heterocercal vs. Homocercal tails
Heterocercal
Homocercal
Teeth in shark originate from modified placoid scales
‘Denticles’
Enamel
Dentine
DenticlesPlacoid scalesTeeth
Septal gill design
Chondrichthyes
Phylum Chordata Subphylum Urochordata (Tunicata) Subphylum CephalochordataCraniata group Subphylum Vertebrata
Superclass Agnatha Superclass Gnathostomata
Class PlacodermiClass ChondrichthyesClass AcanthodiiClass OsteichthyesClass AmphibiaClass ReptiliaClass MammaliaClass Aves
“Bony fish”By far the most diverse class.
Swim bladder (or gas bladder) present in in most species
Osteichthyes
Swim bladder
Opercular gills - bony covering overlying gill slits
Actinopterygii Teleostei
Sarcopterygii Dipnoi Crossopterygii
Some major groupings in Osteichthyes
Actinopterygians - ray-finned fish dominant form presently fins move via muscles in body wall fins w/ Lepidotrichia
2 major groups:
Teleosts - diverse group of Actinopterygians
Recent radiation - 65 million years ago Has a derived swim bladder design
(detached from gut)
Actinopterygii
Sarcopterygians - fleshy-finned fish Thicker fins - muscles within fins Swim bladder connected to gut
(ancestral) Internal nostril (choana) first arose in
this group fossil sarcopterygian w/choana
Early choanates
Dipnoi - lungfish Paired lungs Survive in mud by breathing air. In warm waters - not as much
dissolved oxygen
Sarcopterygii
Crossopterygii - Several fossil forms with swim
bladders used as “lungs” One living - Coelacanth
Sarcopterygii
CrossopterygiiHomologies with Amphibia
Bones in fins correspond to bones in early tetrapods
Labyrithodont teeth
Crossopterygian and Labyrinthodont skulls
Crossopterygian fish
Early tetrapod
Fossil organisms showing a fish/tetrapod transition
Tiktaalik roseae Acanthostega
“Labyrinthodont” group
Actinopterygii - Ray-finned Sacropterygii - fleshy-finned
Phylum Chordata Subphylum Urochordata (Tunicata) Subphylum CephalochordataCraniata group Subphylum Vertebrata
Superclass Agnatha Superclass Gnathostomata
Class PlacodermiClass ChondrichthyesClass AcanthodiiClass OsteichthyesClass AmphibiaClass ReptiliaClass MammaliaClass Aves
Tetrapods
From water to land:
“Problems”:Support - Air is a thinner medium.
From water to land:
“Problems”:Support - Air is a thinner medium.Gas exchange - Oxygen in a different
state.
From water to land:
“Problems”:Support - Air is a thinner medium.Gas exchange - Oxygen in a different
state.Temperature - Fluctuates more in air.
From water to land:
“Problems”:Support - Air is a thinner medium.Gas exchange - Oxygen in a different
state.Temperature - Fluctuates more in air.Keeping moist - How to keep tissues,
eggs, young moist?
From water to land:
Fossil amphibians
Amphibia - have aquatic larval stage
Toads and Frogs (Anura) Salmanders (Urodela) Caecilians (Gymnophiona)
Phylum Chordata Subphylum Urochordata (Tunicata) Subphylum CephalochordataCraniata group Subphylum Vertebrata
Superclass Agnatha Superclass Gnathostomata
Class PlacodermiClass ChondrichthyesClass AcanthodiiClass OsteichthyesClass AmphibiaClass ReptiliaClass MammaliaClass Aves
TetrapodsAmniotes
Amniotes - have embryos with extra-embryonic membranes
amnion keeps water from leaving the egg or developing young.
Amniotes
Major living ‘reptile’ groups:
Lizards and snakes (Squamata) Crocodiles and alligators (Crocodilia) Turtles (Testudinata)
Most diverse class of tetrapods
Feathers modification of skin thermoregulation, flight
Aves
Microraptor gui
Puts particular requirements on
some physiological systems:
Circulatory, respiratory systems must be efficient and work at high rates
Endothermy
Defining characteristics:
Hair - for insulation, sensation.
Mammary glands
Other glands - sweat and sebaceous glands.
Mammalia
Via fossil evidence:
1. Three bones make up middle ear:malleus, incus, stapes
Distinguishing mammal from reptile fossils
Theraspid
2. Lower jaw a single bone (dentary)
3. Jaw joint is articulation of dentary and squamosal bone.
Distinguishing mammal from reptile fossils
Major mammal groups:
Monotremes - oviparous
Therians - viviparous Marsupials - partial internal -
external development
Therians - viviparous Placentals (eutherians) -
completely internal development - Most diverse