1. Last Wednesday… began our final phylum - Chordata

2. A taxon within the Deuterostomia, and the Bilateria…
Calcarea
Silicarea
Ctenophora
Cnidaria
Echinodermata
Chordata
Brachiopoda
Phoronida
Ectoprocta
Platyhelminthes
Nemertea
Mollusca
Annelida
Rotifera
Nematoda
Arthropoda
“Radiata”
“Porifera”
Deuterostomia
Lophotrochozoa
Ecdysozoa
Bilateria
Eumetazoa
Metazoa
Ancestral colonial
flagellate
A taxon within the Deuterostomia, and the Bilateria…

3. After describing chordate characters, looked at
Cephalochordata & Urochordata
- do share defining chordate characters...

4. Chordate Phylogeny
Also introduced ‘Craniates’ (vague hierarchical rank)
– have a ‘head’ w. skull, more regulatory genes, gill slits &
neural crest cells

5. Class Myxini - Hagfishes
Predators of invertebrates & scavenge on dead
vertebrates in deep, cold marine waters
- about 30 spp.
- cartilaginous skull &
small brain but no jaws
or vertebrae
- ‘teeth’ of keratin
- small eyes, ears & single
nostril
have lateral line system for detecting vibrations in water
& sensory tentacles

6. - but also (over)fished for ‘eelskin’ and meat
Famous for slime
production…
- but also (over)fished for
‘eelskin’ and meat
hagfish slime scone

7. next step… evolution of vertebral column

8. Subphylum Vertebrata Earliest vertebrates prob. sometime in Cambrian
- initially some skeletal
elements above notochord
protecting nerve cord,
later replacing notochord
& surrounding nerve cord
more gene duplication
(Dlx family) may have
allowed greater
complexity

9. Class Petromyzontida - Lampreys
About 40 spp. in marine & fresh water
- parasites of fish, attach with round sucking mouth
No jaws, but rasping teeth
on tongue create hole
Larvae are suspension
feeders in streams
Have notochord with
covering, plus cartilages
along nerve cord (no collagen)

10. Sea lampreys invaded the Great Lakes, feed on trout,
whitefish, etc.

11. Next characters… jaws & mineralized skeleton

12. Gnathostomes have true jaws, hinged structures that enable
Mouth
Gill slits
Cranium
Skeletal rods
Gnathostomes have true jaws,
hinged structures that enable
them to grasp food firmly
- jaws thought to have evolved by
modification of the arches that
previously supported anterior
pharyngeal gill slits.
- remaining gill slits no longer
required for suspension feeding
& remained as main site of
respiratory gas exchange.

13. More Gnathostome Characteristics
Another duplication of the Hox genes (now 4 clusters) & other developmental genes
- forebrain enlarged, associated with enhanced vision
& smell
- mineralized axial skeleton, shoulder girdle, & 2 sets of
paired appendages

14. Gnathostomes appear in fossil record in mid-Ordovician,
about 470 MYA, & steadily diversified
Dunkleosteus - Devonian
Bothriolepis - Devonian

15. Class Chondrichthyes - Sharks & rays
Basking Shark
Manta Ray
Spotted Ratfish
Fairly diverse, w. about 460+ sharks,
460 rays & 30 chimeras
- many predators, but filter feeders
too

16. Shark & Ray Characteristics
Skeletons (mostly) cartilaginous, although ancestors
had mineralized skeleton
well developed jaws, paired fins, streamlined
bodies, dorsal fin for stability
- water flow over gills
maintained by swimming,
or by pumping of
mouth/pharynx if still
- well-developed sight & smell,
also lateral line system &
electrical field detectors
Shortfin Mako

17. Next group is ‘Osteicthyes’, known traditionally as
‘the bony fishes’, but includes tetrapods …& us!
a key character is lungs or derivative (e.g. swim bladder)

18. Class Actinopterygii – Ray-finned Fishes

19. Actinopterygii - Characteristics
About 27,000 spp., make up > half of all vertebrates
- throughout oceans, but 40% occur in fresh water
- most have bony (ossified) skeleton w. calcium phosphate
matrix
- skin usually with thin, flat bony scales (vs. tooth-like
scales of sharks)
- fins supported by long,
semiflexible rays
- mucus covering reduces drag,
prevents infection
- respire with 4-5 pairs of gills
in chamber w. protective
flap: operculum
Bluegill

20. Most have swim bladder for buoyancy (off digestive tract)
Nostril
Brain
Spinal cord
Swim bladder
Dorsal fin
Adipose fin (characteristic of trout)
Caudal fin
Cut edge of operculum
Gills
Heart
Liver
Kidney
Stomach
Intestine
Gonad
Anus
Urinary bladder
Lateral line
Anal fin
Pelvic fin
Body plan of a typical ray-finned fish – trout
Most have swim bladder for buoyancy (off digestive tract)
- originally, & often still, functioned as simple lung

21. ‘Lobe-fins’ - Sarcopterygii
Originally referred to as lobe-finned fish, but
includes tetrapods now
- originated as aquatic forms in Devonian
- short linear bones & thick muscles support base
of fins, could be useful for moving in shallows
Eusthenopteron

22. Two aquatic classes of ‘lobe-fins’ survive:
1) Class Actinistia - coelacanths & relatives
Known from Devonian fossils, 2 spp. discovered off
Comoros Islands (1938) & Indonesia (1999)
- large deep-water predators
- move limbs alternately when swimming

23. 2) Class Dipnoi - lungfishes
Six spp., in Australia, Africa (4), & South America
- live in rivers & swamps, African spp. at least must
use lungs
- some estivate in mud burrow in dry season
African lungfish

24. Next… evolution of limbs with feet

25. Tetrapods Evolution of limbs that could support weight
about 365 MYA, e.g. Acanthostega
- still basically aquatic,
w. gills, tail fin, etc.
Acanthostega

26. Now many fossils
known of
transitional forms
between
lobe-finned fish
& tetrapods

27. Tetrapoda - the tetrapods
Tetrapods have feet with digits,
transfer muscular forces to
ground
Pelvic girdle fused to vertebral
column, allowing transfer of
forces to body
Neck to allow head to move
separately from body
No pharyngeal clefts in adults,
ears adapted for airborne sounds

28. Class Amphibia Present day amphibians are highly specialized groups
not necessarily very similar to early tetrapods
- most dependent on H2O
at least part of life, or
in moist habitats
- moist skin important for
gas exchange, some
lack lungs
- skin may also be toxic
to varying degrees
Cobalt Poison Dart Frog

29. Amphibian: ‘both lives’ - metamorphosis
(a) The male grasps the female, stimulating her to release eggs. The eggs are laid and fertilized in water. They have a jelly coat but lack a shell and would desiccate in air.
(b) The tadpole is an aquatic herbivore with a fishlike tail and internal gills.
(c) During metamorphosis, the gills and tail are resorbed, and walking legs develop.
Amphibian: ‘both lives’ - metamorphosis
- most species breed, develop as larvae in fresh water
but typically terrestrial as adults

30. Exceptions to standard life cycle fairly numerous,
Eastern Red-backed Salamander
Southern Gastric Brooding Frog
Exceptions to standard life cycle fairly numerous,
& sometimes bizarre…

31. Order Urodela - Salamanders
Over 600 spp., many in eastern US
- some entirely aquatic, but often live on land as adults, or sometimes throughout life
On land, most walk with
side-to-side bending of
body, may resemble
movement of early
terrestrial tetrapods.
Spotted Salamander

32. Order Anura – Frogs &Toads
By far largest order, w. > 6,000 spp., worldwide except
many ocean islands, cold climates
- specialized for hopping
on land (legs, urostyle)
but swim well too
- catch insects with sticky
tongue (attached in
front)
American Toad

33. Many species toxic, & may have aposematic
Golden Mantella
Many species toxic, & may have aposematic
coloration (warning colors, easy to recognize &
learn)

34. Order Apoda - Caecilians
About 190 species, legless & nearly blind
- short tentacles on front of
head
- reduction of legs evolved
secondarily
- superficially resemble
big earthworms, most
burrow in moist soil in
tropical forests
- some South American
spp. live in ponds &
streams
Bannan Caecilian

35. The Amniotes
Amniota consists of mammals, turtles, crocodilians, birds, tuataras & squamates (lizards & snakes), plus many extinct groups

36. Extraembryonic membranes
Shell
Albumen
Yolk (nutrients)
Amniotic cavity with amniotic fluid
Embryo
Yolk sac. The yolk sac contains the yolk, a stockpile of nutrients. Blood vessels in the yolk sac membrane transport nutrients from the yolk into the embryo. Other nutrients are stored in the albumen (“egg white”).
Allantois. The allantois is a disposal
sac for certain metabolic wastes pro-
duced by the embryo. The membrane
of the allantois also functions with
the chorion as a respiratory organ.
Amnion. The amnion protects the embryo in a fluid-filled cavity that cushions against mechanical shock.
Chorion. The chorion and the membrane of the allantois exchange gases between the embryo and the air. Oxygen and carbon dioxide diffuse freely across the shell.
Extraembryonic membranes
Amniotic Egg - major derived trait

37. Amniotic egg allowed life completely on land
- shell retains water, but
allows gas exchange
Great Tinamou eggs
Eggs of birds calcareous,
of most ‘reptiles’ more
leathery
Leatherback Turtle
hatching
- most mammals have lost
shell & retain egg in
uterus
echidna ‘puggle’

38. evolved less permeable skin with keratin & scales
Other amniote traits...
evolved less permeable skin with keratin & scales
(lost in mammals & only on legs of birds)
lungs almost exclusively for respiration &
increasing use of rib cage to ventilate lungs
- adopted more elevated stance than earlier tetrapods
Komodo
Dragon

39. Ornithischian dinosaurs
Synapsids
Ancestral amniote
Reptiles
Diapsids
Archosaurs
Saurischians
Lepidosaurs
Dinosaurs
Parareptiles
Turtles
Crocodilians
Pterosaurs
Ornithischian dinosaurs
Saurischian
dinosaurs other
than birds
Birds
Plesiosaurs
Ichthyosaurs
Tuatara
Squamates
Mammals
An Amniote Phylogenetic Tree

40. Class Testudinia - Turtles
Highly distinctive group - shell formed by bony
shields fused to vertebrae, ribs, clavicles, &
covered with horny scutes
- over 300 species, most associated
with water but some in arid areas
Green Sea Turtle
- respiration in water aided by
cloaca (common excretory &
reproductive opening) or pharynx
- relationships
uncertain, but
perhaps closer
to crocs &
birds
Ornate Box Turtle