Evolution of Tetrapod Vertebrates
inferred from fossil record
Labyrinthodonts – first tetrapod amphibians

Rhipidistians – crossopterygian lobe-finned fish
(Sarcopterygii)

Placoderms – first jawed fishes

Ostracoderms – jawless fishes
Cladogram of key taxa in evolution of tetrapods
Eusthenopteron foordi (Sarcopterygii: Crossopterygii) Devonian Quebec
Panderichthys rhombolepis (Sarcopterygi: Crossopterygii)
Devonian Latvia
Tiktaalik rosseae
Sarcopterygian Fish
Devonian 375 MY
Labyrinthodont amphibians - the earliest tetrapods
Carboniferous
Acanthostega
Ichthyostega
Acanthostega
Labyrinthodont Amphibian
facweb.furman.edu
Eusthenopteron and Acanthostega
classical reconstruction
Behavior of fossil species can be difficult to interpret
Frogfishes (Antennarius)
have limb-like fins but
they never leave the
water …
Periophthalmus
…but mudskippers
do, and they don’t
even have lungs
Sarcopterygians do
Sarcopterygians,
do have
have
lungs
caught
African lungfishes cuaght
in small water-hole
Ichthyostega – a temnospondyl labyrinthodont
Ichthyostega – a temnospondyl labyrinthodont
...had 7 toes!
facweb.furman.edu
Sclerocephalus - a temnospondyl labyrinthodont
Eryops – a temnospondyl labyrinthodont
fin-foot intermediates
Eusthenopteron
Panderichthys
Tiktaalik
Acanthostega
CA Boisvert et al. Nature (2008) doi:10.1038/nature07339
Evolution of Reptiles from Amphibians
inferred from fossil record
Synapsids
– mammal-like reptiles
Diapsids
– Lepidosaurs (lizards, snakes)
and Archosaurs (“ruling reptiles” dinosaurs, crocodiles, birds)

Cotylosaurs (Anapsids
) – stem reptiles

Anthracosaur Labyrinthodonts –tetrapod amphibians