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Better Terrestrial living – origin of the amniotes
Part 7
Amniotes
Amphibians
2 terrestrial tetrapod groups
2 terrestrial tetrapod groups
Amniotes reptile/bird, mammal + (many extinct things)
(Lepospondyli)
1.
Temnospondyli
2.
Amphibians + (many) extinct things
Amniota
lobe-fin fish
†early tetrapods: labyrinthodonts, ichthyostegans, “fish-o-pods”
Lepospondyli, †Anthracosaurs
Amnoita
Temnospondyli
Class Amphibia
† various dead ends
† various dead ends
† various dead ends
not quite amniotes
Lepospondyli, †Anthracosaurs
Amnoita
Amnoita (living)
Deriving Amniotes
Carboniferous – warm and wet
Carboniferous – “amphibian” paradise
Permian – cooler and drier
Paleozoic is the age of fishes and “amphibians”
Post-Paleozoic is the age of amniotes
Amnoita
Patterns in Skull Evolution
Pre-Amniote
/early amniote
Captorhinus
Captorhinus aguti
Pre-Amniote / early amniote
Early Amniote
anapsid
SkullsPre- & early Amniote
AnapsidPre- & early Amniote
Captorhinus aguti
jaw muscles
Jaw muscles
anapsid skull and jaw muscles (beneath skull bones)
pre-amniote / early amniote
anapsid skull and jaw muscles
pre-amniote
Anapsid condition
amniote
foramen
pre-amniote
Anapsid condition Synapsid condition
Proto-mammal
Modern mammal
Skull re-arranged to accommodate jaw muscles
Old
NEW
NEW
Anapsid
Diapsid
SkullsRe-arranged to accommodate jaw muscles
No foramen foramena present
diapsid – 2 openingsanapsid
Early diapsidPetrolacosaurus
Anapsid
Synapsid
SkullsRe-arranged to accommodate jaw muscles
No foramen foramen present
Synapsid – 1 openinganapsid
Anapsid
DiapsidSynapsid
Synapsida Diapsida
Anapsid
DiapsidSynapsid
Anapsid
Diapsid
Synapsid
Amniote ancestor
Mammals and ancestors
Reptiles, birds, dinosaurs, etc.
Anapsid
anamniotes, stem amniotes
Synapsid
orbit
fenestra joined with orbit
Modern mammal
Synapsid
Diapsid
Diapsidtuatara
orbit
Diapsid Modern Lizard
Diapsid
Modern snake
DiapsidModern bird
orbit
Diapsid
Mesozoic reptile
orbit
Turtles
Turtles are diapsids with a (secondarily acquired) anapsid skull
Fenestration
Clear proof of diapsids on Mars
NASA Photos
As seen on the internet
Moving away from water
Amniotic Egg
Amniotic Egg
FishAmphibian
Amniote
Internal Fertilization
No more gill breathing – even in larvae
amphibian larvae
Body covering
Dry and dead
Amniote skin
Scales
…. Not all the same
Scales
fish scales = dermal
amniote scales = epidermal
Keratin
present in anamniotes – but not widely employed
Respiration
Anamniotes – Positive Pressure Breathing
Amniotes – negative pressure breathing
Amniotes – No more cutaneous respiration
Jaw rearrangements
amphibians
lungs
lungs and gills
gills
Circulation
lungs lungs
amphibians reptiles
lungs and gills
Osmotic balance and waste elimination
evolution of kidneys
Locomotion
Lobe fin fish
Senses
The big splitanapsid anamniote
synapsid
diapsid
The big split
The big split
Synapsid lineage
Diapsid radiation
Endothermy
Greater Mobility
Greater Mobility
Higher metabolism
More heat generation
better respiration
better circulation
heat conservation / utilization
waste heat elimination
diet / digestion
What do we do with the heat?
Diet
Respiration
Circulation
