Geology 105: History of Life
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Lecture Notes
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Introduction and Overview
Fossils 1
Fossils 2
Geologic Principles
Relative Time
Absolute Time
Diversity of Life
Evolution
Evolution and Diversity
Rates of Evolution
Extinction
Plate Tectonics
Origin of the Earth
Origin of Life
Early Precambrian (Archean) Life
Late Precambrian (Proterozoic) Life
The Cambrian Explosion
Early Paleozoic Life
Late Paleozoic Marine Life
The Invasion of Land 1
The Invasion of Land 2
The Permo-Triassic Extinctions
Mesozoic Marine Life
Mesozoic Terrestrial Life
Cretaceous-Tertiary Extinctions
Cenozoic Life

Mesozoic Marine Life

Lecture 23
5/4/98

Introduction
 We start our look at the Mesozoic by examining the Marine communities that developed in the Mesozoic.
Key Points
 The Permo-Triassic extinctions openned up opportunities for marine invertebrate to radiate into.
 Modern marine invertebrate faunas were developed during the Mesozoic
 Reptiles radiated into the marine realm as well, occupying niches now taken by whales & dolphins
Mesozoic Paleogeography
 Splitting up Gondwanaland
 Openning of Atlantic Ocean
 beginning the the Triassic
 return of shallow epi-contintental seas
 Movement of North America & Europe north
 begins in the Triassic and continues throughout the Mesozoic
Marine Biosphere
 Development of the Modern Fauna
 Molluscs
 Ammonites
 swimming predators
 extensive radiation during the Jurassic and Cretaceous
 Disappear suddenly at the end of the Cretaceous (65 Ma)
 Gastropods (snails)
 Bivalves
 corals
 Modern corals first appear in the Middle Triassic in Tethys sea
 by the middle Jurassic (180 Ma) they are world-wide and forming reefs
 fish
 Ray-Fin boney fishes (teleost)
 increasing abundance through the Triassic and Jurassic
 have a major radiation in the Cretaceous (140-65 Ma)
 Marine Reptiles
 ichthyosaurs
 stream-lined dolphin like reptile
 Triassic to Jurassic (250-140 Ma)
 placodonts
 Triassic (250-205 Ma)
 a walrus-like life style
 plesiosaurs
 Late Cretaceous
 Large bodied reptile with a long neck and small head
 mososaurs
 Late Cretaceous
 marine lizards
 sea turtles
 Archelon
 late Cretaceous
 10 feet long (3m)
 flipper span of 13 ft (4m)