Ch 34: The Origin and Evolution of Vertebrates (Abridged)

All Vertebrae Classes 

• Chordates = Notochord / Dorsal, hollow nerve cord / Pharyngeal slits or clefts / Muscular, post-anal tail

• Vertebrates = enclosed spinal cord, neural crest, skeletal system + nervous system

• Cyclostomes = “circular mouth”, jawless invertebrates

• Gnathostomes = “jaw mouth” → jaws (hinged structures) with teeth, enlarged forebrain, lateral line system (vibration sensing)

• Osteichthyans = “boney fish”

• Lobe-fins (Sarcopterygii) = rod-shaped bones surrounded by a thick layer of muscle in their pelvic and pectoral fins

• Tetrapods = 4 limbs+digits, neck, pelvic girdle fused to backbone, absence of gills, ears

• Amniotes = amniotic egg

• Chordates

Notochord / Dorsal, hollow nerve cord / Pharyngeal slits or clefts / Muscular, post-anal tail

• Cephalochordata

lancelets (not vertebrae)

• Urochordata

tunicates (not vertebrae)

• Vertebrates

enclosed spinal cord, neural crest, skeletal system + nervous system

• Cyclostomes

“circular mouth”, jawless invertebrates (lampreys & hagfish)

• Myxini

hagfishes (jawless & rudimentary vertebrae)

• Petromyzontida

lampreys (jawless & rudimentary vertebrae)

• Gnathostomes

“jaw mouth” → jaws (hinged structures) with teeth, enlarged forebrain, lateral line system (vibration sensing)

• Chondrichthyans

shark, rays, and relatives (mostly cartilage skeleton)

• Oviparous

egg hatch outside

• Ovoviviparous

eggs are retained, young hatch in the uterus

• Viviparous

embryo develops within the uterus nourished through a yolk sac placenta

• Osteichthyans

“boney fish”

• Actinopterygii

(Ray-Finned Fishes)

tuna, lionfish, sea horse, moray eel
* Boney rays that support their fins

• Sarcopterygii

(Lobe-Fins)

coelacanths (Actinistia), lungfishes (Dipnoi), and tetrapods
* rod-shaped bones surrounded by a thick layer of muscle in their pelvic and pectoral fins

• Tetrapods

4 limbs+digits, neck, pelvic girdle fused to backbone, absence of gills, ears

• Amphibia

salamanders, frog, caecilians (metamorphosis from aquatic larva to terrestrial adult)

• Amniotes

amniotic egg

• Diapsids

pair of holes on each side of the skull behind the eye socket through which muscles pass to attach to the jaw

• Lepidosaurs

tuataras, squamates (snakes, lizards)

• Archosaurs

turtles, crocodilians, birds, *Pterosaurs, *Ornithischian dinosaurs, *Saurischian dinosaurs

• Birds

(keratin feathers)

Neorithes, ratites (flightless birds)

• Synapsid

a single hole behind the eye socket on each side of the skull for attachment of the jaw muscle

• Monotremata

(egg-laying mammals)

echidnas, platypus

• Marsupials

(marsupium maternal pouch)

opossums, kangaroos, koala

• Eutherians

(complex placenta)

primates, rodents, cetaceans (whales, dolphins)…

• Primates

lemurs, tarsiers, monkeys, apes

• Humans/Homo sapiens

upright posture & bipedal locomotion, large brains, reduced jaws, shorter digestive tracts, & descended from African ancestors

• Hominins

extinct human relatives, closer than chimpanzees