Chondrichthyes Sharks, skates and rays Placoid scales Ampullary organs

Placoid scales and drag

Chondrichthyes No swim bladder for buoyancy big liver loss of weight lift from tail, pectoral fins

Heterocercal vs. Homocercal tails

Teeth in shark originate from modified placoid scales Enamel Dentine ‘Denticles’

Denticles Placoid scales Teeth

Chondrichthyes Septal gill design

Phylum Chordata Subphylum Urochordata (Tunicata) Subphylum Cephalochordata Craniata group Subphylum Vertebrata Superclass Agnatha Superclass Gnathostomata Class Placodermi Class Chondrichthyes Class Acanthodii Class Osteichthyes Class Amphibia Class Reptilia Class Mammalia Class Aves

Osteichthyes “Bony fish” By far the most diverse class. Swim bladder (or gas bladder) present in in most species

Swim bladder

Opercular gills - bony covering overlying gill slits

Some major groupings in Osteichthyes Actinopterygii Teleostei Sarcopterygii Dipnoi Crossopterygii

2 major groups: Actinopterygians - ray-finned fish dominant form presently fins move via muscles in body wall fins w/ Lepidotrichia

Actinopterygii Teleosts - diverse group of Actinopterygians Recent radiation - 65 million years ago Has a derived swim bladder design (detached from gut)

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

Sarcopterygii 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

Homologies with Amphibia Crossopterygii Homologies 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 Acanthostega Tiktaalik roseae “Labyrinthodont” group

Actinopterygii - Ray-finned Sacropterygii - fleshy-finned

Tetrapods Phylum Chordata Subphylum Urochordata (Tunicata) Subphylum Cephalochordata Craniata group Subphylum Vertebrata Superclass Agnatha Superclass Gnathostomata Class Placodermi Class Chondrichthyes Class Acanthodii Class Osteichthyes Class Amphibia Class Reptilia Class Mammalia Class Aves Tetrapods

From water to land:

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?

Fossil amphibians

Amphibia - have aquatic larval stage Toads and Frogs (Anura) Salmanders (Urodela) Caecilians (Gymnophiona)

Tetrapods Amniotes Phylum Chordata Subphylum Urochordata (Tunicata) Subphylum Cephalochordata Craniata group Subphylum Vertebrata Superclass Agnatha Superclass Gnathostomata Class Placodermi Class Chondrichthyes Class Acanthodii Class Osteichthyes Class Amphibia Class Reptilia Class Mammalia Class Aves Tetrapods Amniotes

Amniotes Amniotes - have embryos with extra-embryonic membranes amnion keeps water from leaving the egg or developing young.

Major living ‘reptile’ groups: Lizards and snakes (Squamata) Crocodiles and alligators (Crocodilia) Turtles (Testudinata)

Aves Most diverse class of tetrapods Feathers modification of skin thermoregulation, flight

Microraptor gui

Endothermy Puts particular requirements on some physiological systems: Circulatory, respiratory systems must be efficient and work at high rates

Mammalia Defining characteristics: Hair - for insulation, sensation. Mammary glands Other glands - sweat and sebaceous glands.

Distinguishing mammal from reptile fossils Via fossil evidence: 1. Three bones make up middle ear: malleus, incus, stapes Theraspid

Distinguishing mammal from reptile fossils 2. Lower jaw a single bone (dentary) 3. Jaw joint is articulation of dentary and squamosal bone.

Major mammal groups: Monotremes - oviparous

Therians - viviparous Marsupials - partial internal - external development

Therians - viviparous Placentals (eutherians) - completely internal development - Most diverse