sharks, skates and rays placoid scales ampullary organs chondrichthyes

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