Post on 11-May-2015
Chapter 34:
Vertebrates
(sea squirtsthrough birds)
Chor
date
Phy
loge
ny
Chordate Characteristics
Subp
hylu
m U
roch
orda
ta
The urochordates include the tunicates, a.k.a., sea
squirts
The tunicates are mostly
sessile, filter feeding animals that look almost
nothing like a chordate
However, their larval form possesses all of
the basic characteristics of a
chordate
Tunicate: Urochordate
Tuni
cate
Lar
va
The notochord serves as a primitive internal support
structure
Subp
hylu
m
Ceph
aloc
hord
ata
Cephalochordates, the lancelets, retain a chordate body plan
throughout life
In addition to the four defining chordate
characteristics, lancelets, as well as
tunicate larvae, have somites
Somites are blocks of musculature arranged in
segments along the bodies of lancelets and fishes (as well as
derivations of this segmentation found in
tetrapods)
Lancelet: Cephalochordate
Clas
s M
yxin
i
Class Myxini are represented in
modern times by the hagfish
Technically hagfish are not fish; they
are more like “sophisticated”
lancelets
Hagfish, a Craniate
Not
ocho
rd, N
erve
Cor
d, E
tc.
In more modern forms, the notochord exists during development but is modified with development, e.g., into the gelatinous material of the intra-vertebral disks
Clas
s Ce
phal
aspi
dom
orph
i
Class cephalaspidomorphi
is represented in extant lineages by
lampreys
Jawless fish were the vertebrate
forerunners of the jawed fish
Lampreys in addition lack paired fins
Lamprey: Jawless Vertebrate
Lamprey have vertebrae (backbones) but no jaw
As vertebrates, lampreys are (just barely) members
of subphylum Vertebrata
Lamprey Larvae are like Lancelets
Lamprey larvae are suspension feeders that resemble lancelets, even burying themselves
in sediment as to lancelets
Early (and armored) Jawless Fish
Supe
rcla
ss G
nath
som
ata
Jawed fish are referred to as gnathostomes
(superclass gnathsomata) for
their defining feature: jaws
Jawed fish also have skulls, vertebrae, and
paired appendages (fins)
Early
Gna
thos
tom
es
Many vertebrate characteristics are
adaptations to vigorous
swimming
Jaws, of course, aid in
eating
Especially carnivorous
eating…
Clas
s Ch
ondr
icht
hyes
Class Chondrichthyes includes the sharks and
rays
Members of this class are named for their
cartilaginous skeletons, i.e., unmineralized (or
less mineralized/ossified) skeletons
Class Chondrichthyes Members
The
Ost
eich
thya
ns
These are bony fish, both ray-
finned and lobe-finned fish
Ost
eich
thya
ns a
re B
ony
Fish The bony fish are all of the fish you are familiar with
except the sharks, rays, and chimaeras The skeleton of bony fish displays ossification, i.e.,
calcium phosphate in addition to the cartilaginous base Bony fish additionally possess flattened scales Bony fish
also secrete mucus onto their skin to aid in reducing their coefficient of drag
Bony fish additionally possess a gas-filled swim bladder that allows them to adjust their buoyancy to match that of the water
• Sharks and rays lack a swim bladder and consequently sink when not moving
Clas
s Ac
tinop
tery
gii
Members of class Actinopterygii are
the ray-finned
The lobe-finned fish are members of
Sarcopterygii
Anatomy of a Ray-Finned Fish
Clas
s Ac
tinis
tia
A Coelacanth
Lobe fins are supported by musculature and a bony skeleton; they may be employed for “walking” upon the bottom and other substrate found within bodies
of water
Clas
s D
ipno
i
Members of class Dipnoi are the lung
fish
The lungfish are named for the lungs they retain and use
for gulping air, especially when air is less readily available
within the freshwaters in which
they reside
Vario
us E
xtan
t Lun
gfish
Clas
s Am
phib
ia
Amphibians are the lineage descended from the earliest
tetrapods: the terrestrial
vertebrates
Vario
us E
xtan
t Am
phib
ians
The amphibians were the dominant terrestrial vertebrates during the
Carboniferous period, i.e., the same time the seed-less, vascular plants dominated
the land
Most amphibians are dependent on the water, minimally for reproduction; this is
because their eggs are not desiccation resistant
In addition, many amphibians employ their skin for gas exchange, thus
requiring that their skin remain moist
Thus, amphibians tend to be not as well-adapted to long term, especially multi-
generational excursions away from moist habitats
Tetr
apod
s The tetrapods are the
terrestrial descendants of
some lobe-finned fish,
starting approximately
with the amphibians
Reconstruction of an Extinct Tetrapod
Clas
s Re
ptilia
Note how the reptiles are indicated as
sister group to the mammals
In fact, the reptiles and mammals
together form a clade known as the
amniotes
The defining features of the amniotes are keratinized
(waterproof) skin and the amniotic
(shelled) egg
Class Reptilia, Examples
Clas
s Re
ptilia
is P
arap
hyle
tic
Class Reptilia, if it excludes the birds, is paraphyletic
The Amniotes
The amniotes were the first fully
terrestrial vertebrates,
achieving true freedom from
water except, of course, for the need to drink
Amniotic Egg
The amniotic egg is shelled, an adaptation to desiccation
prevention
The amniotic egg employs extraembryonic membranes to transfer stored nutrients and water,
exchange gasses, and remove wastes
The
Amni
ote
Phyl
ogen
y
Gia
nt A
quati
c Re
ptile
s
Non-Archosaur Giant Reptiles (i.e., these are
lizards!)
Clas
s Av
es –
Bird
s Members of class Aves (birds) have…• Feathers• Forelimbs modified as wings• Horny bills made of keratin (feathers and hair are
also made of keratin)• No teeth (reduces weight)• Grind their food in a gizzard (since no teeth)• Reduced or absent organs (reduces weight)• Hollow bones (reduces weight)• Acute vision (e.g., high-speed tree-branch avoidance) Some of these adaptations were present in the
dinosaur ancestors of birds (e.g., possessing gizzard, bipedalism, feathers, etc.)
Feathers and Light-Weight Bones
Archaeop
teryx
More primitive extinct birds were more saurischian
dinosaur like