Download Chordates 1

2/24/13
Chordates
Chordates 1
Cephalochordata
Chordates
Origin of Chordates
Tunicates etc
Sharks etc
Bony “fish”
Urochordata
Notochord
Myxini
Common
ancestor of
chordates
Head
Petromyzontida
Chondrichthyes
Vertebral column
–  Osteichthans
–  Lobe fins and lungfish
Actinopterygii
Jaws, mineralized skeleton
Actinistia
Lungs or lung derivatives
Dipnoi
Lobed fins
Reptilia
Amniotic egg
All Chordates have a notochord and a
dorsal, hollow nerve cord
Milk
Mammalia
Tetrapods
Amniotes
Amphibia
Limbs with digits
Feb 25, 2013
Craniates
Vertebrates
Gnathostomes
Osteichthyans
Lobe-fins
• 
• 
• 
• 
Echinodermata
ANCESTRAL
DEUTEROSTOME
Figure 34.2a
Derived features of Chordates
2. Dorsal,
hollow
nerve cord
Echinodermata
Muscle
segments
Cephalochordata
ANCESTRAL
DEUTEROSTOME
1.Notochord
Urochordata
Notochord
Myxini
Common
ancestor of
chordates
Head
Petromyzontida
Mouth
Chondrichthyes
Vertebral column
Jaws, mineralized skeleton
Osteichthyes
Anus
4. Muscular,
post-anal tail
Bony fish &
tetrapods
3. Pharyngeal
slits or clefts
Figure 34.4
Cirri
Mouth
Pharyngeal slits
Atrium
Digestive tract
Notochord
Atriopore
Dorsal,
hollow
nerve cord
Segmental
muscles
1 cm
Cephalochordata- Lancets
Urochordata
Myxini
Petromyzontida
Chondrichthyes
Actinopterygii
Actinistia
Dipnoi
Amphibia
Reptilia
Mammalia
Anus
Tail
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Figure 34.5
Cephalochordata
Urochordata Tunicates
Myxini
Petromyzontida
Chondrichthyes
Actinopterygii
Actinistia
Dipnoi
Amphibia
Reptilia
Mammalia
Notochord
Incurrent
siphon
to mouth
Water flow
Dorsal, hollow
nerve cord
Tail
Excurrent
siphon
Incurrent
siphon
Muscle
segments
Intestine
Stomach
Excurrent
siphon
Excurrent
siphon
Atrium
Pharynx
with
numerous
slits
Tunic
Anus
Intestine
Atrium
Pharynx with slits
(a) Tunicate larva
Esophagus
Stomach
(b) Adult tunicate
(c) Adult tunicate
Derived features of tunicates:
Figure 34.5a
Figure 34.6
Notochord
Water flow
Incurrent
siphon
to mouth
BF1
Dorsal, hollow
nerve cord
Tail
Excurrent
siphon
Incurrent
siphon
Muscle
segments
Intestine
Stomach
Atrium
Pharynx
with
numerous
slits
Anus
Pharynx with slits
(a) Tunicate larva
Hox3
Nerve cord of lancelet embryo
Excurrent
siphon
Intestine
Atrium
Otx
Tunic
Esophagus
Stomach
BF1
Hox3
Otx
Brain of vertebrate embryo
(shown straightened)
Forebrain
Midbrain Hindbrain
(b) Adult tunicate
Figure 34.8
Cambrian
|
Head |
Vertebrae
5 mm
Only 3 cm long
Pharyngeal slits
Segmented
muscles
Cephalochordata
Urochordata
Myxini
Petromyzontida
Chondrichthyes
Actinopterygii
Actinistia
Dipnoi
Amphibia
Reptilia
Mammalia
Hagfish and
Lampreys’
Had a well-formed brain, eyes, and
muscular segments, but not a skull
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Figure 34.9
Figure 34.10
Slime glands
Gnathostomes have jaws that might have
evolved from skeletal supports of the
pharyngeal slits
Gill slits
Cranium
Mouth
Skeletal rods
Sea Lamprey parasitize fish
in Lake Champlain
Gnathostome fossil
Odovician
0.5 m
|
Jaws
Cephalochordata
Urochordata
Myxini
Petromyzontida
Chondrichthyes
Actinopterygii
Actinistia
Dipnoi
Amphibia
Reptilia
Mammalia
Sharks
3
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Figure 34.2b
Sharks and Rays (about 470 species)
Actinopterygii
Actinistia
Lungs or lung derivatives
Dipnoi
Lobed fins
Amphibia
Reptilia
Limbs with digits
Amniotic egg
Mammalia
Milk
Ray-finned fish (about 30,000 species)
“Fish”
Cephalochordata
Urochordata
Myxini
Petromyzontida
Chondrichthyes
Actinopterygii
Actinistia
Dipnoi
Amphibia
Reptilia
Mammalia
|
Bony
endoskeleton
Ray-finned fish
Lobe fin fish
Lungfish
Figure 34.16
Lobe Fins
Brain
Spinal cord
Swim
bladder
Dorsal fin
Adipose fin
Caudal
fin
Nostril
5 cm
Cut
edge of
operculum
Anal fin
Liver
Gills
Kidney
Heart
Stomach
Gonad
Intestine
Anus
Pelvic
fin
Lower
jaw
Scaly
covering
Dorsal
spine
Lateral
line
Urinary
bladder
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Coelocanth
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
Tiktaalik: a fossil with both fish and tetrapod characteristics
Fish
Characters
Scales
Fins
Gills and
lungs
Figure 34.21
Lungfishes
Tetrapod
Characters
Neck
Ribs
Fin skeleton
Flat skull
Eyes on top
of skull
Eusthenopteron
Panderichthys
Tiktaalik
Shoulder bones
Ribs
Neck
Acanthostega
Scales
Head
Eyes on top of skull
Humerus
Limbs
with digits
Ulna
Flat
skull
Elbow
Amphibians
“Wrist”
Amniotes
Radius
Fin
Tulerpeton
Fin skeleton
Key to
limb bones
Ulna
Radius
Humerus
Silurian
PALEOZOIC
Permian
Carboniferous
Devonian
415 400 385 370 355 340 325 310 295 280 265 0
Time (millions of years ago)
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