vertebrates Flashcards
chordates
Nerve chord and gill arches
Gnathostomes
Jawed vertebrates, craniates, first appear early Silurian
First appearance of modern fish groups
Early Devonain
The transition to land begins….
during the Late Devonian. The evolution of tetrapods, probably from lobe finned fishes
Amphibians
can live on land, must reproduce in water
First amniotes and development of the amniotic egg was during the…
Early carboniferous
3 major groups of land dwelling amniotes
Anapsid, diapsid, synapsid
Anapsid
No openings (primative reptiles, turtles)
Diapsid
1 opening (lizards, snakes, crocodiles, pterosaurs, dinosaurs, birds)
Synapsid
2 openings “mammal like reptiles”, mammals
Did dinosaurs and mammals coexist?
Yes, throughout most of the mesozoic
When were synapsids the dominant group?
Late Carboniferous-end Triassic
The first mammals
Many were small, nocturnal, insect-eatting. The need to be active at night may be why they are warm blooded
When was the oldest definite mammal?
Jurassic
monotremes
egg-laying mammals. Platyupus and echidnas. Have a poor fossil record
Marsupials
pouched mammals (opossums, kangaroos, koalas)
Placentals
Bear live young, nourished before birth through a specialized embryotic sack.
Therian mammals
marsupials and placentals
Great American Interchange
The Isthmus of Panama was closed and became a complete land bridge for the first time. Animals from both continents began to interact.
Why did North American species win during the great interchange?
Tropical climate zones, north american mammal groups had been shaped by millions of years of competition, size
Hypsodont
High crowned teeth
When did primates evolve?
Paleogene
When were the big 5 extinctions?
End ordovician, end Devonian, Permo-Triassic, end Triassic, KT boundary
Causes of Mass Extinction
glaciation, volcanic eruptions, impact
Mammals during the Pleistocene
grew to be huge (ex-giant sloth)
