SURVEY OF THE TETRAPODS

“LABYRINTODONTIA”Eusthenopteron

Panderichtyes

Ichthyostega Te

mno

spon

dyli

Liss

amph

ibia

Lepo

spon

dyli

Am

niot

a

Ant

hrac

osau

ria

Rhipidistia Ichthyostegalia

Class

Subclass LISSAMPHIBIA

URODELA SALIENTIA GYMNOPHIONA

Class AMPHIBIA

Acanthostega

Fish (“Rhipidistian”) - Tetrapod Transition & Fossil Record

Generalized“Rhipidistian”

Early Amphibian

Transitional“Rhipidistian”

• Reduction of fins• Reduction of gills• Shift of eyes (dorsally)• Dactylous appendages

History of the AMPHIBIA

Stem Tetrapods

Derived “labyrinthodonts”Terrestrial & ancestral to “reptiles”

Surviving amphibians (Lissamphibians)

Primitive “amphibians” (aquatic & terrestrial)

Earliest Tetrapod: Acanthostega

Polydactylous LimbsTail fin with skeletal supports

Poorly formed joints (limbs)Weak vertebral column

Eyes face upward

Retains internal gills

Primitive & Derived Labyrinthodonts

Stronger backboneBetter formed joints (limbs)Skull narrowed; eyes lateralLimbs pentadactylous

Anthracosaur

Amphibious

Mostly terrestrial (as adults)

Icthyostegalian

Subclass LISSAMPHIBIA (modern amphibians)

Order SALIENTIA (=Anura)

Order URODELA (=Caudata)

Order GYMNOPHONIA (APODA)

(Tropical, burrowers)

Amniote Skull Types & Classification

Class REPTILIA Subclass PARAREPTILIA = (“Anapsida”) Subclass SYNAPSIDA = (“Synapsida”) Subclass EUREPTILIA = (“Diapsida”)

Modified diapsid skull

Specialized “Anapsids”: Turtles & Pareiosaurs

Subclass PARAREPTILIA

Order TESTUDINATA Order PARIESAURIA

LEPIDOSAURS: Most Successful Group Modern Reptiles

Superorder LEPIDOSAURIA

Order SQUAMATA

(Lizards)

(Snakes)

Order SPHENODONTIA

(Tuatara - New Zealand)

Order AMPHISBAENIA (tropical burrowers)

“Living Fossil”

Subclass ARCHOSAURIA

Order CROCODILIA

Order PTEROSAURIA

Order ORNITHISCHIA

Dinosaur Pelvic Structure & Classification

Convergent with birds

Bird - Therapod Connection

Infraclass ARCHAEORNITHYES

Infraclass NEORNITHYES

Infraclass ENANTIORNITHYES

Infraclass NEORNITHYESInfraclass ODONTORNITHYES

Superorder Paleognathae

Superorder Neognathae

Synapsids & Origin of Mammals

Cynodont Therapsids= sister group of mammals

Pelycosaurs = basal mammal-like reptiles

Primitive Therapsids

Fossils from S. Africa &S. America

Cynodont Therapsids PROTOTHERIA METATHERIA EUTHERIA

MAMMALIA

“REPTILIA”

Basic mammal features

• Hair• Mammary glands• 3 ear ossicles, etc.

• Placenta & viviparity• Therian shoulder complex• Tribosphenic molars

Basic therian features

THERIA

Prototherians Order Monotremata (Australia)

Metatherians Order Marsupialia(Australia, Americas)

Eutheria: Placental Mammals (world-wide distribution)