16 Vertebrates

Chordata

defined by 4 principal features

• nerve cord, notochord, pharyngeal slits or pouches, postanal tail

• muscles arranged in segmented blocks

Basal chordates (no skull or backbone)

lancelets and tunicata

Myxini (hagfish)

only living group with a skull but no bony vertebrae.

• skull , no jaws, no bony vertebrae

• only chordate that us craniate but not vertebrate

Petromyzontida (lampreys)

• most primitive vertebrates

• vertebral column

• no jaws

Vertebrata (subphylum)

skull, vertebral column, neural crest, endoskeleton

8 principal groups of living vertebrates

• all share skull and vertebraes

• but dont share bony skeleton, jaw, limbs, amniotic egg, milk, four chamber heart, swim bladder

Osteichthyes

boney fish, all live in water (actinoptergii, actinistia, dipnoi)

• other groups that also live in water are chondrichthyes sharks and rays

• and petromyzontida which are lampreys

3 groups that are land dwelling tetrapods (four feet)

• amphibia

• reptilia

• mammalia

Amphibia

frogs, salamanders, caecilians

• 1st vertebrates to walk on land

• limbs with digits

Amniotes

reptiles and mammals

• escaping water

• amniotic eggs key innovation for becoming truly terrestrial

What are only amniotes

reptiles like lizards, birds, turtles, snakes, crocodilians and mammals

Reptilia

tetrapods with scales or feathers

Birds

only living reptiles with feathers

• heat loss endothermi

• thin hollow bones

• most diverse living reptiles

Mammals (tetrapods with milk and hair)

Some distinguishing features are

• milk/mammary glands

• hair (modified scales) like porcupines

• heat loss (endothermic)

• camouflage

• sensory structures

• defense weapons

Evolution of 4 chambered heart

• independently evolved in birds and mammals

• allows separation of oxygenated and deoxygenated blood

• like fishes have 1 circuit and 2 chambered hearts while birds have 2 circuits and 4 chambered heart

• and mammals have 2 circuits and 4 chambered hearts

Monoteremes

a lineage of mammals, like platypus. They lay eggs and don’t have nipples (dispersed glands)

metatherians (marsupial mammals)

lineage of mammals like kangaroo and koala which give live birth but very early in development and complete development in pouch

Eutherians (placental mammals)

like elephants and humans where they have more well-developed placenta and have a live birth of more fully developed offspring

Placentals mammals

They are much more diverse than other two they have rabbits bats elephants all in them.