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Craniates
Vertebrates
Gnathostomes
Lobe fins
Tetrapods
Amniotes
Mammalia (mammals)
Reptilia (turtles, lizards,
R
sn
nakes, crocodiles, birds)
Amphibia (amphibians)
A
Dipnoi (lungfishes)
Actinistia (coelacanths)
A
Actinoptery
ygii (ray-finned fishes)
Chondrichthyes (cartilaginous fishes)
Section 4
S i Petro
omyzontida (lampreys)
Myxini (hagfish)
Reptilia
Milk,
hair
Amniotic egg
Professor Donald McFarlane
Legs
Lungs
Lobed fins
KEY
Critical innovations
Lecture 15 Craniates 1:
Hagfish to Amphbians.
Bony skeleton
Jaws, internal skeleton
Vertebral column
Cranium
2
1.
2.
„
„
2 defining characteristics compared to
invertebrate chordates
Cranium - p
protective bony
y or
cartilaginous housing for brain
Neural crest - embryonic cells that will
disperse throughout the embryo
contributing to the development of the
skeleton, jaws, and teeth
Also, at least 2 Hox clusters
„
„
„
„
3
Hagfish
Jawless, finless,
marine fish that lack
vertebrae
Notoshord and
cartilaginous skull
Essentially blind with
a keen sense of smell
Copious amounts of
slime
Mammalia
Dipnoi
Reptilia
Actinistia
Amphibia
Actinopterygii
Myxini
„
Class Myxini
Petromyzontida
Craniates
Chondrichthyes
Ancestral chordate
Ancestral chordate
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Vertebrates
Lampreys
„ Lack hinged jaw and
true appendages
„
Agnathan=
„
Reptilia
5
6
Mammalia
Class Petromyzontida
Dipnoi
Liver unique to vertebrates
Heart, kidneys, and endocrine system are more
complex than analogous structures in other taxa
Amphibia
Actinistia
Actinopterygii
3.
Chondrichthyes
2.
All chordate and craniate characteristics plus
Vertebral column - notochord is replaced by a
bony or cartilaginous column of interlocking
vertebrae
Endoskeleton of cartilage or bone – most also
have two pairs of appendages
Internal organs - liver, kidneys, endocrine
glands, and a heart with at least two chambers
Myxini
1.
Petromyzontida
„
Vertebrae
jawless
Do possess a
notochord and
rudimentary vertebral
column
One of earliest diverging groups of
vertebrates
„ Found in marine and freshwater
„ Marine lampreys parasitic as adults
„
Ancestral chordate
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8
2
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Skull
(cartilage)
Extinct
3
9 8 7 6 5 4
Derived
(b) Early jawed fishes (placoderms)
„
Living forms
9 8
7 6
5
4
Reptilia
Mammalia
Dipnoi
Amphibia
not ancestral character
Sharks among earliest fish to
develop teeth
Not
3
Actinistia
Cartilaginous fish
„ Sharks, skates, rays
„ Skeleton composed of flexible
cartilage
„
(a) Primitive jawless fishes
Actinopterygii
Myxini
Gill slits
(8)
Chondrichthyes
Class Chondricthyes
Gill arches
(9)
1
3 2
9 8 7 6 5 4
Petromyzontida
Gnathostome
s: Jawed
vertebrates
„ Hinged jaws
developed
from the
pharnygeal
arches
„ Modification
of existing
deature
„
set into jaw
Ancestral chordate
9
(c) Modern jawed fishes (cartilaginous and bony fishes)
10
2-chambered versus 4-chambered
hearts
Denser than water – swim to maintain
buoyancy and breathing
„ 2 chambered heart – single circulation
„ Powerful sense of smell
„ Lateral line – p
pressure wave detection
„ Internal fertilization
„
Oviparous
– lay eggs
Ovoviparous – egg retained in female, no
placenta
Viviparous – eggs develop in uterus, placenta
nourishes young
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12
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Bony fish
Caudal fin
„
Dorsal fin
3 living classes
(b) Rows of shark teeth
„
Pelvic fin
3 features different from Chondricthyes
1.
Pectoral fin
2.
3.
(a) Silvertip shark
Actinopterygii – ray-finned fish
Actinistia – coelacanths
Dipnoi – lungfish
Bony skeleton
Operculum covers gills
Swim bladder for buoyancy
(c) Shark egg pouch
a: © Valerie & Ron Taylor/ardea.com; b: © Jeff Rotman/naturepl.com; c: © OSF/Photolibrary
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14
„
Actinopterygii – ray-finned fish
Includes
all bony fish but coelocanths and
lungfish
Fins supported by thin, bony, flexible rays
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16
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„
„
Actinistia – coelacanths
Dipnoi – lungfish
3
genera with 6 species
Live in oxygen-poor freshwater
Both gills and lungs
Will drown if unable to breathe air
Muscular lobe fins
Believed
extinct until 1938
Special joint in skull gives powerful bite
Swim bladder filled with oil rather than gas –
still used for bouyancy
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Tetrapods
Transition to land meant adaptations to
prevent desiccation, locomotion and
reproduction on land possible
„ Sturdy lobe-finned fishes became fishes
with four limbs
„ Vertebral column strengthened, hip and
shoulder bones braced against backbone
„ Relatively simple changes in gene
expression, especially Hox genes
„
„
19
Hox genes 9–13 work together to specify limb
formation from the proximal to the distal
direction, meaning from close to the point of
attachment to the body to the terminal end of the
limb
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Davis, Capecchi, and Colleagues Provide a
Genetic-Developmental Explanation for Limb Length
in Tetrapods
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
„
„
„
„
„
Transitional taxa
Tiktaalik rosae
Fishapods had broad
skulls, eyes on top,
lungs, pectoral fins
with 5 finger-like
bones
Species increasingly
fed on land but tied to
water for reproduction
320mya Cacops was
similar to modern
amphibians
Expanded ribs
Flat head,
eyes on top
Neck
Specific Hox genes are responsible for
determining limb formation in mice
„ Mutations in the genes HoxA
HoxA-11
11 and HoxD
HoxD11 resulted in the loss of the radius, ulna,
and some of the carpals
„ Relatively simple mutations can control
relatively large changes in limb
development
„
Scales
Tiktaalik
roseae
Fins
21
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Amphibians
„
„
„
„
„
„
Reptilia
Order Anura – frog and toads
Nearly
90% of amphibians
Carnivorous adults, herbivorous larva
Mammalia
Dipnoi
Amphibia
Actinistia
Actinopterygii
Successfully invaded land but must
return to water to reproduce
Buccal pumping to force air into
lungs
Skin can absorb oxygen
3 chambered heart
Fertilization external
Larval stages aquatic
Metamorphosis regulated by
thyroid hormones
Chondrichthyes
Myxini
„
Petromyzontida
„
„
Order Caudata – salamanders
Paedomorphosis
– adult has larval
characteristics
„
Order Gymnophiona – caecilians
Nearly
blind tropical burrowers
legless
Uterine milk nourishes young inside mother’s
body
Secondarily
Ancestral chordate
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