MESOZOIC LIFE

• Periods : Triassic, Jurassic & Cretaceous (251-65 m.y.a.)
• "Age of the _________________________", but many modern forms appear
• _______________ climate - Sea Level low

Mollusk recover after Tr.
Jurassic sea level rise
Modern reef builders and aquatic reptiles

Dinosaurs, birds and mammals in a _______________/________________forest.
Cr biota: both ______________ and __________________ forms

•   Extinct in the Pm: fusulinids, trilobites, rugose corals, lacy bryozoans
•   Stromatolites resurge => Why? _______________________________
•   Gastropods and bivalves: burrowers & sea floor dwellers
•   Brachiopods & sea urchins diversified

Reefs:               initially sponges and algae
                             Tr hexacorals (even deep). (Cr: replaced by rudists)

Plankton:              dinoflagellates diversified in the Jr. What were those? _________________ __________________
                              calcareous nannoplankton _______________ in the Jr

 Ammonoids: (Predators) 2 genera survive Pm extinction. Radiated => guide fossils.

Cretaceous Invertebrates and Protists

•   Brachiopods decline
•   _____________________________ gastropods & mollusks
•   Coiled Oysters
•   Rudist reefs,  ________________ end of MZ
•   Predators: carnivorous gastropods, crabs. (Crush, drill, peel shells)

  => __________________ _______________:   burrow deeper
                                                                               grow spines
                                                                               thick shell

  Plankton:

• diatoms (____________________ oozes)
• dinoflagellates                                                                                          diversified
• calcareous __________________________ (Cr chalk)
• calcareous foraminifera (since 100 mya)

    _______________ _______________ foraminifera.  Appear in Cr

VERTEBRATES

Marine Vertebrates
Early MZ

•   Still "primitive" bony ray finned fish

  evolved swim bladder                                        with crushing teeth
 Sharks
•   Reptiles             Nothosaurs (first ________________ reptiles)

                            Placodonts (_____________ _______________)
                                    Both  extinct  at the end of the Tr.  Not fully marine
                            Plesiosaurs: adapted to ocean, evolved from _______________.
                                                Top __________________ until Cr
                            Ichthyosaurs (resemble __________________)
                            Crocodiles: first ____________________ => marine in Ea Jr

•   Mosasaurs (Late Cr). Characteristics? _________________________
•   Teleost fishes: ______________     round scales

                                                           short jaws
                                                           symmetric tails

Terrestrial vertebrates

The Permian extinction killed most of the therapsids (mammal-like reptiles)
 

•   Therapsids:     _________________________ (herbivore survivor, extinct @ the end of Tr)

                          Diversification of therapsids, most extinct end of Tr, completely disappeared in Jr.
 
•   Mammals: from __________________ in Lt Tr, dominated by ______ _________________.

 
•   Thecodonts: ancestors of the ____________________. Bipedal. Appear in the Tr.

 
•   Frogs, turtles, snakes and lizards appeared in Ea MZ.

 
•   Dinosaurs:  from ___________________, bipedal
•    Pteroaurs: flying,  Lt Tr.
•    diversified after therapsid extinction to __________________ size (Ea Jr)
•    Lt Jr: Archeopterix = first __________________
•   _________________ hipped =  saurischian = carnivore

                                                     herbivore = sauropods
  The sauropods were the largest dinosaurs (Morrison Fm.)
 
•    _________________ hipped = ornithischian = herbivore

 
• American West fauna: _________ _______________dinosaurs and  ______________ dinosaurs (ornithischian, herbivore), preyed upon by T. rex and crocodiles.

MZ Plants
Early change in flora (___________________, why? __________________________) => gymnosperms
Ferns and seed ferns; ____________ ferns become extinct in the Jr

MZ forests:

• cycads (Jr is the "Age of the Cycads")
• _____________________
• ___________________

Advantages:                 double fertilization produces ___________ and ___________
                                     cooperation with ___________________ for pollinization
                                     fruits are eaten by mammals

Pollen and leaf characteristics had diversified by the end of the Cr.
 

MZ Mass Extinctions
Three, one at the end of each period.

Tr:

• Land: __________ _______ _________ extinct.
•  Sea: conodonts & ____________ reptiles extinct.
•  Climate is more ____________: Dicroidium Flora replaced by gymnosperms

Jr:  Unclear reasons;  stegosaurs and sauropods extinct.

End of the MZ :   organisms that became extinct:

•   all the _____________
•   ammonoids
•  _______________ & deep burrowing bivalves
•  calcareous ____________________

 Asteroid hypothesis evidence: Chicxulub crater and...
                         ______________ layer                                         __________________
                         ______________quartz                                        _______________ crystals
 

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