Phylum Chordata
the chordates
Phylum Chordata
chordates
• Primary
characters
include:
– Notochord
Phylum Chordata
Primary Characters
• pharyngeal
gill slits
• dorsal nerve
cord
• ventral heart
• post anal tail
Phylum Chordata
Secondary Characters
• tailed larvae or
direct development
• dorsal and ventral
blood vessels;
closed circulatory
system
• endoskeleton
Phylum Chordata
• Includes two groups:
– Protochordata or Acraniata – those without a
cranium
– Craniata – those with a cranium
Phylum Chordata
Group Protochordata (=Acraniata)
(the first chordates)
• Includes two subphyla:
– Urochordata – tunicates or sea squirts
– Cephalochordata- lancelets
Subphylum Urochordata
(tunicates or sea squirts)
• about 2000
species
• all marine, freeliving or sessile,
solitary or
colonial
• adult has no
coelom; no
segmentation, no
bones
• have a test or
tunic; made of
cellulose
Subphylum Urochordata
(tunicates or sea squirts)
• dorsal atrium,
chamber used for
filter feeding
• there is a heart,
with colorless
blood
• respiration is
probably
function of
pharynx
Subphylum Urochordata
(tunicates or sea squirts)
• notochord is
restricted to tail,
and is found only
in larvae (except
for one classthere are 3
classes)
• larvae are called
"tadpole larvae“
Subphylum Urochordata
(tunicates or sea squirts)
• most species are
hermaphroditic,
fertilization is
external
• some species
reproduce asexually
through budding
Subphylum Cephalochordata
(lancelets)
• about 23 species
• all marine, freeliving or sessile,
solitary or colonial,
live on bottom
• no well developed
head
Subphylum Cephalochordata
(lancelets)
• many gill slits in
pharyngeal basket,
act in excretion and
respiration
• have a tail; projects
behind anus
• muscles arranged in
blocks- myotomes
• have a notochord
made of muscle
fibers
Subphylum Cephalochordata
(lancelets)
• are microscopic
suspension feeders
• has closed
circulatory system,
with colorless blood
• sexes are separate;
fertilization is
external
Phylum Chordata
Group Craniata
(the vertebrates)
• Includes one subphylum:
– Subphylum Vertebrata
Phylum Chordata
Subphylum Vertebrata
• Contains a wide variety of animals that
include:
–
–
–
–
–
–
–
–
Class Myxini – hagfishes
Class Cephalaspidomorphi – lampreys
Class Chondrichthyes – sharks and rays
Class Osteichthyes- bony fishes
Class Amphibia – amphibians
Class Reptilia – reptiles
Class Aves – birds
Class Mammalia - mammals
Subphylum Vertebrata
• Divided into:
– Without useable jaws
• Agnatha
– With useable jaws
• Gnathostomata
Subphylum Vertebrata
• Earliest
vertebrates were
jawless:
– Agnathans
• Earliest of these
were
Ostracoderms
– 500 million years
ago
Subphylum Vertebrata
• Earliest jawed
vertebrates or
Gnathastomes
• Earliest of these
were Placoderms
– 400 million years
ago