Marine Life
- mollusks (pelecypods
[bivalves] and gastropods) took over the seafloor; echinoids
common
- ammonoids: late Pz ammonoids had
goniatitic suture; most extinct at end of Permian
Triassic ammonoids had ceratitic suture; most
extinct at end of Triassic
Jur & K ammonoids had
ammonitic suture; all extinct at end of
Cretaceous
- belemnites were squidl-ike
cephalopods with internal rods for support and counterbalance
- Teleost (modern ray-fins) bony fishes with
swim bladders
- aquatic and marine reptiles
plesiosaurs - lock ness monster
ichthyosaurs - Mesozoic "flipper"
marine crocodiles and turtles
Terrestrial Life
Plant Life
- gymnosperms were the dominant plant life,
esp. cycads (palm-like) and ginkoes
(fan-leafed)
- angiosperms (flowering plants) evolved
in the Cretaceous
angiosperms grow and reproduce more quickly
than gymnosperms because
1. flowers attract pollinators
2. fruit or nut grown around seed attracts animals which eat fruit and spread seed
- pollinators, bees and moths, apparently co-evolved with angiosperms during the Cretaceous
Late Cretaceous palms, holly, oak, walnut,
birch
Animal Life
- the dominant Permian fauna of synapsids and
amphibians was replaced in the Mesozoic by archosaurs:
which included the lineages of crocodilians, dinosaurs, pterosaurs,
and others
-therapsids (synapsid reptiles) remained the dominant reptile of the Triassic. However, therapsids became extinct at the end of the Triassic coincident with a large increase of CO2 in the beginning of the Jurassic caused by the onset of rifting of Pangea and formation of the North Atlantic Igneous Province. Extinction of the therapsids made way for the dinosaurs to become the dominant land animals.
- primitive pterosaurs and dinosaurs appeared in the Late Triassic
- ornithischian ("bird-hipped") dinosaurs -> stegosaurs, ceratopsids (triceratops; Late Cretaceous), hadrosaurs (duck-billed; Jurassic Park's poison spitters)
- saurischian ("lizard-hipped)
dinosaurs included sauropods (brontosaurus - now called apatosaurus) and tyrannosaurs (e.g., T. rex)
- Birds arose during the Jurassic; Archaeopteryx (the oldest fossil birds; Late Jurassic)
they apparently evolved from small carnivorous saurischian dinosaurs (raptors of Jurassic Park fame)
-fish-eating toothed birds were common in the Late Cretaceous- great diversification of herbivorous
(plant-eating) dinosaurs in Late Cretaceous with the rise of
angiosperms (flowering plants) [to delight of T. rex]
- amphibians: frogs and salamanders appeared in
Triassic
- reptiles: crocodiles and turtles, Triassic; lizards, Jur-Cret; first snakes
(constrictors), Cretaceous
- mammals descended from last synapsids
(therapsids) in Late Triassic
remained shrew-like or mouse-like for ~150 m.y.
marsupials and placental mammals established by
Late Cretaceous
Cretaceous/Tertiary (66 m.y.) Mass Extinction
- many marine microplankton, some brachiopods,
mollusks, echinoids, fish, and land plants went extinct
- all ammonites and dinosaurs (except for
birds!) went extinct
The Dinosaur Extinction
Controversy
- gradual or sudden?
- Impact vs Volcanic
iridium anomaly, glass spherules, shocked
quartz found at K/T stratigraphic horizon
all three are consistent with impact; only
first two may result from volcanoes