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Chordates
Chordates 2
Echinodermata
Cephalochordata
ANCESTRAL
DEUTEROSTOME
Chordates
•  Sharks etc
•  Bony “fish”
Urochordata
Notochord
–  Osteichthans
–  Lobe fins and lungfish
Petromyzontida
Chondrichthyes
Vertebral column
•  Tetrapods
Actinopterygii
Jaws, mineralized skeleton
Actinistia
Lungs or lung derivatives
Dipnoi
Lobed fins
Amphibia
Reptilia
Limbs with digits
Amniotic egg
Feb 27, 2013
All Chordates have a notochord and a
dorsal, hollow nerve cord
Milk
Mammalia
Tetrapods
Amniotes
–  Amphibians
–  Reptiles
–  Birds
Craniates
Vertebrates
Gnathostomes
Osteichthyans
Lobe-fins
Myxini
Common
ancestor of
chordates
Head
Sharks and Rays (about 470 species)
|
Jaws
Cephalochordata
Urochordata
Myxini
Petromyzontida
Chondrichthyes
Actinopterygii
Actinistia
Dipnoi
Amphibia
Reptilia
Mammalia
Sharks
Figure 34.2b
“Fish”
Actinopterygii
Actinistia
Lungs or lung derivatives
Dipnoi
Lobed fins
Amphibia
Reptilia
Limbs with digits
Amniotic egg
Mammalia
Milk
|
Bony
endoskeleton
Cephalochordata
Urochordata
Myxini
Petromyzontida
Chondrichthyes
Actinopterygii
Actinistia
Dipnoi
Amphibia
Reptilia
Mammalia
Ray-finned fish
Lobe fin fish
Lungfish
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Figure 34.16
Ray-finned fish (about 30,000 species)
Brain
Swim
bladder
Spinal cord
Dorsal fin
Adipose fin
Caudal
fin
Nostril
Cut
edge of
operculum
Anal fin
Liver
Gills
Stomach
Kidney
Intestine
Heart
Lobe Fins
Gonad
Anus
Lateral
line
Pelvic
fin
Urinary
bladder
Coelocanth
5 cm
Lower
jaw
Scaly
covering
Dorsal
spine
Tiktaalik: a fossil with both fish and tetrapod characteristics
Derived Characters of Tetrapods
•  Tetrapods have some specific adaptations
–  Four limbs, and feet with digits
–  A neck, which allows separate movement of
the head
–  Fusion of the pelvic girdle to the backbone
–  The absence of gills (except some aquatic
species)
–  Ears for detecting airborne sounds
Fish
Characters
Scales
Fins
Gills and
lungs
Tetrapod
Characters
Neck
Ribs
Fin skeleton
Flat skull
Eyes on top
of skull
Shoulder bones
Ribs
Neck
Scales
Head
Eyes on top of skull
Humerus
Ulna
Flat
skull
Elbow
“Wrist”
Radius
Fin
Fin skeleton
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Figure 34.21
Lungfishes
Eusthenopteron
Panderichthys
Tiktaalik
Acanthostega
Limbs
with digits
Tulerpeton
Amphibians
Amniotes
Key to
limb bones
Ulna
Radius
Humerus
Silurian
|
4 limbs
PALEOZOIC
Permian
Carboniferous
Devonian
415 400 385 370 355 340 325 310 295 280 265 0
Time (millions of years ago)
Cephalochordata
Urochordata
Myxini
Petromyzontida
Chondrichthyes
Actinopterygii
Actinistia
Dipnoi
Amphibia
Frogs, Salamanders
Reptilia
about 6,150 species
Mammalia
(a) Tadpole
Amphibians
Metamorphosis
Order Urodela
(salamanders)
(b) During metamorphosis
Order Anura
(frogs)
(c) Mating adults
Many Amphibian
Populations have been
declining
Glass frogs show biparental
care of eggs
Other species have male
“pregnancy”
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Figure 34.25
Parareptiles
Archosaurs
Crocodilians
Pterosaurs
Saurischians
Dinosaurs
Diapsids
ANCESTRAL
AMNIOTE
Ornithischian
dinosaurs
Saurischian dinosaurs
other than birds
Birds
Plesiosaurs
Ichthyosaurs
Lepidosaurs
Synapsids
Figure 34.26
Turtles
Reptiles
|
Amniotic Egg
Cephalochordata
Urochordata
Myxini
Petromyzontida
Chondrichthyes
Actinopterygii
Actinistia
Dipnoi
Amphibia
Reptilia
Lizards, Birds
Mammalia
Tuataras
Squamates
Mammals
Figure 34.28
Extraembryonic membranes
Amnion
Allantois
Chorion
Yolk sac
Embryo
Amniotic cavity
with amniotic
fluid
Shell
Yolk
(nutrients)
Albumen
Lepidosauria
Turtles
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Lepidosaurs
Archosaurs
Two surviving lineages
•  Tuataras (2 spp)
•  Dinosaurs
•  Birds
•  Crocodilians
•  Squamates (the lizards
and snakes, many spp)
Birds are the only surviving Dinosaurs
The Origin of Birds
Toothed beak
Wing claw
Early feathers might have
evolved for insulation,
camouflage, or courtship display
Airfoil wing
with contour
feathers
Long tail with
many vertebrae
Derived Characters of Birds
Finger 1
(b) Bone structure
Palm
Finger 2
(a) Wing
Forearm
Shaft
Vane
Wrist
Finger 3
Shaft
Barb
Barbule
Hook
(c) Feather structure
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