What advantages do organisms with hard "shells" have?
Gave them protection against UV rays, allows them to move into shallower waters, helps prevent drying, and provides protection.
Cambrian Events in NA
- Most of the shield exposed to erosion
- No land plants to hold soil, so erosion was deep and extensive.
- First major recorded transgression onto continent. Late
Proterozoic through Cambrian and early Ordovician
(Sauk Sequence)
Sauk Sedimentary Sequence
- Record of the first transgression onto the craton
- Seds are shallow water sands, carbonates, and shales
What are the most common Cambrian invertebrate fossils?
Trilobites, anthropods, brachiopods, and archaeocyathids (reef builders), gastropods (marine snails), chordates (vertebrate ancestors), foraminifers (shelled amoebas), and mollusks.
Almost all the major invertebrate physically evolved during the Cambrian
What is the Burgess Shale Biota and why is it important?
Is located in the Canadian Rockies of British Columbia � is one of the world's most celebrated fossil fields as animals preserved here are well-known for their soft-tissue preservation�lived in and on mud banks. The reason they look so strange is that no
What major event marks the end of the Cambrian?
The Cambrian Explosion, which also marks the beginning of the Paleozoic Era, where there occurs a sudden and rapid (only in context of geologic time) appearance of new animals in the fossil record. Near end, a massive extinction took place which severely
During the Ordovician the Appalachians begin to build. Why do they build?
Taconic Oregeny began as Baltica & Laurentia move closer together. Resulted from plate convergence, oceanic crust caught up in this (called clastic wedge of sediment), gets incorporated into mountains themselves. In Appalachia, is called the Queenston Del
Devonian Mass Extinction
Stromatoporoids, and many corals impacted.
- This late Devonian crisis affected these organisms so severely that reef-building was relatively uncommon until much later (Mesozoic era).
Among other marine invertebrates, 70% of the taxa did not survive into
the Devonian, which orogeny is responsible for building up the Appalachians?
Collectively, this constitutes the Acadian Orogeny, the second in the Appalachian-building series. Thick deposits of sediment eroded from these mountains were deposited to the west, in low-lying flood plains and shallow seas where the Appalachians now sta
Which shelled organisms become common in the Devonian, are good guide fossils, and
have distinctive suture patterns? They are extinct now.
Ammonoids:
- Devonian through
Cretaceous
- distinctive suturepatterns
- short stratigraphicranges
- widespread distribution
What are cyclothems, how are they created, and why are they important to us?!
Alternating stratigraphic sequences of marine and
non-marine sediments, interbedded with coal
seams.
- related to rise and fall of sea level during Gondwanan
glacial cycles
- often contain commercial coal--are indicative of
cyclic depositional regimes
Know all about the Permian marine invertebrate extinction event. What groups were
impacted? How big was this extinction event?
The greatest recorded mass extinction to affect Earth
occurred at the end of the Permian
- about 50% of all marine invertebrate families
- about 90% of all marine invertebrate species
- fusulinids, rugose and tabulate corals, many bryozoan and
brachiopod
Ordovician Marine Community
The major transgression that began during the Middle Ordovician (Tippecanoe sequence)
- resulted in the most widespread inundation of the N. A. craton
This vast epeiric sea, which experienced a uniformly warm climate during this time
- opened numerous new
What is a vertebrate (how is it defined)?
Chordates have, during at least part of their life,
a notochord, a dorsal hollow nerve cord, and gill
slits
- Vertebrates have backbones and are a sub-phylum of
chordates
- ancestors were soft-bodied and left few fossils
When do the first fish appear in the fossil record (Era and Period)?
Fish range from the Late Cambrian to the present
and consist of five classes
What are the five major groups of fish? What are the basic characteristics of these?
1) Agnathans (early members are Ostracoderms) - Jawless fish
2) Acanthodians - First fish with jaws
3) Placoderms -Armored jawed fish4) Cartilaginous fish - Sharks, rays, skates
5) Bony fish - Lobe finned and ray-finned fish
Two major groups of living fish
- Cartilaginous fish (sharks
and rays)
- Bony fish (all other living
jawed fish)
Two major groups of bony fish
- Ray-finned fish (most
fish you know and love)
appear in the Silurian
- Lobe-finned fish
(lungfish, coelocanths,
tetrapods) appear in the
Devonian
What are tetrapods and what group of fish do they come from?
Tetrapoda
- vertebrates whose
ancestors had hands and
feet with fingers and toes- Lobe-finned fish with
hands and feet with
fingers and toes
- Common ancestor of all
tetrapods was a fish
with regular lobe-fins
What was the earliest and most primitive tetrapod discussed in class?
Acanthostega. Fish/reptile; had feet. Latest Devonian, Greenland. Found anywhere these rocks exist.
What are the major barriers that vertebrates had to deal with when they made the transition
from water to land?
Barriers they had to deal with:
- desiccation
- reproduction
- effects of gravity
- extraction of oxygen by lungs
rather than gills
Why is the evolution of the shelled amniotic egg important in the evolution of terrestrial
vertebrates?
The evolution of the amniote egg
freed reptiles from the
constraint of returning to water
to reproduce
- amnion - liquid filled sac
surrounding the embryo
- allantois - waste sac
- a tough shell protects the
developing fetus
- reptiles were able to coloni
When do the earliest reptiles appear?
The earliest reptiles are from
the Carboniferous
- success due to advanced
reproductive methods, more
advanced jaws and teeth, and
speed
- Pelycosaurs evolved from this
group and were the dominant
reptile by Permian
When were pelycosaurs around and what did they look like? When did they go extinct?
("mammal-like reptiles")
Pelycosaurs were the dominant terrestrial vertebrates in
Pangea during the late Paleozoic
- 50% of late Pennsylvanian species
- 70% of Early Permian species
The most famous pelycosaurs had sail backs, but most
specied di
What are therapsids and how did they differ from pelycosaurs?
Therapsids succeeded the pelycosaurs during the
Permian
- mammal-like reptiles that quickly evolved into herbivorous and
carnivorous forms
- they displayed fewer bones in the skull, enlargement of the
lower jawbone, differentiation of the teeth, and a mor
What is the earliest record of land plants?
Silurian and Devonian Floras
The earliest land plants are from the
Silurian
- small, simple leafless stalks with a spore-producing
structure at the tip
- a rhizome (the underground part of the stem) transferred water from the soil to the plant and
anchore
When do seed plants first show up in the fossil record? Does this allow plants to spread to
drier areas away from water?
Late Carboniferous and
Permian Floras
Seed-bearing vascular
- Gymnosperm trees (or
flowerless seed plants) -
Glossopteris and others
were able to colonize
large areas of land
- many of these became
extinct in the Permian;
those that survived were
able to
Plant Evolution
Plants had the same water-to-land transition
problems that animals did
Dessication, support, reproduction, gravity
- vascular land plants - have a tissue system to move
water
- nonvascular plants do not, usually small and live in
moist environments
- seed
When was the largest recorded extinction event? About what % of marine invertebrate
species were impacted? What about terrestrial species?
The Permian Extinction Event
The greatest recorded mass extinction to affect Earth occurred at
the end of the Permian
- about 50% of all marine invertebrate families
- about 90% of all marine invertebrate species
- fusulinids, rugose and tabulate corals,
What are potential causes of this extinction?
- causes for this thought to be primarily from:
- reduction in marine shelf due to regression
- climatic changes--possible meteorite
When did the Mesozoic begin and end?
The Mesozoic began 245 mya and ended 66-65 mya
How many periods make up the Mesozoic and what is their order?
Three periods - Triassic, Jurassic, Cretaceous
What was the Major geologic event during this time?
breakup of Pangaea; tectonism and sedimentation are used to classify the Mesozoic in N. America; affected global climate and oceanic regimes as well as that of individual continents
- spans the entire Mesozoic and into the Cenozoic
- ocean basins were cre
What caused the Cordilleran Orogeny? Where and when did it occur? Give an example
of mountains that are the result of this?
- Complex history, involving the subduction of western
oceanic plates under the N. American plate
- Laramide - built the present day Rockies K-Tertiary
- Sevier - J-K thrust faulting to the east
- Nevadan - Jurassic batholith intrusion in the Sierra Nevad
What types of deposits were layed down as the continents separated? Note, these deposits
occur when water evaporates over and over again leaving salts behind.
Triassic
- red bedsJurassic
- marine sediments in the Sundance Sea
- clean cross-bedded sandstones (e.g., Navajo SS)Gulf of Mexico begins to form and experiences evaporite deposition
What ocean is created as Africa separated from the Americas
Atlantic
What caused the rift basins up and down the east coast of North America?
Pangea
During much of the Mesozoic the middle part of North America was covered by an
epeiric sea. Based on this, what types of rocks and
Fossils of large ocean fish, mastodon bones and teeth, trilobites, and even dinosaurs have been recorded. Limestone, sandstone, chalk, and coal.
Why is the Mesozoic known as the age of reptiles?
Because they were the most diverse and abundant land dwellers
During what period of the Mesozoic do angiosperms appear? What are angiosperms?
- Angiosperms
(flowering plants)
appear in Early Cretaceous, similar to magnolias
evolution of flowers and an enclosed seed ensured their success
When do dinosaurs first appear? During what periods of the Mesozoic are dinos most
abundant?
Appear in Late Triassic
Most abundant during Jurassic and Cretaceous
What are three characteristics that separate dinosaurs from living reptiles?
Had teeth in individual sockets
Ball-like head on upper leg bone (femur)
Fully upright posture with limbs directly beneath the body
What are the two main groupings of dinosaurs (Saurischia and Ornithischia) and how are
these two groups separated?
Saurischians
- theropods were bipedal
carnivores
- sauropods were the giant,
quadrupedal herbivores
Ornithischians
- Pachycephalosaurs
- Ceratopsians
- ornithopods
- ankylosaurs
- stegosaurs Order Saurischa: The bipedal Carnivores and giant quardrpedal Or
What are the two main groups of suarischians and what did they look like?
The bipedal Carnivores and giant quardrpedal
What are the first vertebrates to fly? Describe some of their adaptations for flight?
Describe their wing structure?
The pterosaurs were the first vertebrates to fly
- common from Late Triassic to Cretaceous
- wing membrane supported by an elongated fourth
finger
- light hollow bones
- development of brain areas associated with
coordination and sight
- likely to have be
There are 3 main groups of marine reptiles during the Mesozoic (plesiosaurs,
ichthyosaurs, and mosasaurs). What were these like in their overall appearance and
biology?
Ichthyosaurs Fully aquatic carnivores (one species reached 12 m), Plesiosaurs Short-necked and long-necked
types. Carnivorous (One species up to 15 m), Mosasaurs - Late Cretaceous predatory marine lizards.- Closely related to monitor lizards. (up to 9 m)
What group of dinosaurs to birds come from?
�Birds are a specialized group of theropod dinosaurs
Closely related to dromaeosaurs (which includes the raptors) and troodontids
What is the earliest known bird and when did it first appear?
Earliest known bird is Late Jurassic Archaeopteryx. Many skeletal features are shared
between birds and dromaeosaurs.
Examples seen in Archaeopteryx
are...
Wishbones (fused clavicles)
Feathers
Note: No birds retained teeth into the Cenozoic� Birds are jus
Crocodilians (crocodile like forms) are evolutionarily conservative. What does this mean?
When (what period) did crocodilians first appear in the fossil record?
�Archosaurs (like birds, dinosaurs, and pterosaurs)
�Very successful group but evolutionarily conservativeToday's crocodilians represent a fraction of those that
have lived since they appeared in the Triassic (over 220
mya)
During what period did turtles first appear?
First ones appear some 200 million years ago in the Triassic,
well before dinosaurs
�Shell formed from broadly expanded ribs
�Very successful group but evolutionarily conservative, �Example of giant sea turtle from the Cretaceous. By this time turtles had
Have any dinosaurs been found in TN? If you were in extreme western TN during the
Cretaceous would you need a boat?
Exposed Cretaceous of Tennessee
-Covered by shallow sea
-State fossil: small bivalve (Pterotrigonia thoracica) from
these rocks
-Only dinos found are from the hadrosaur Edmontosaurus
When do snakes first appear in the fossil record? Did early snakes have legs?
�Evolved from lizard ancestor in the early Cretaceous.
�Early snakes had legs, Some living snakes have vestigial legs
How are early mammals distinguished from reptiles in the fossil record?
skeletal structure is used to identify mammals in the fossil record
Dentary/squamosal jaw joint
differences in the lower jaw and ear in particular distinguishes mammals, Evolved from
Permian Therapsids
(mammal-like reptiles)
�(most diverse and numerous
te
When do mammals first appear (what period of the Mesozoic?)
First appear in late Triassic
�Usually shrew-sized insectivores Triconodont mammal
�Two evolutionary branches, one ancestral to monotremes and one to all others
Throughout most of the Mesozoic was mammal diversity high or low?
Mammal diversity remained low throughout the Mesozoic
What major vertebrate groups were extinct by the end of the Mesozoic?
Extinct by end of Mesozoic
�Flying reptiles
�Marine reptiles
�Many marine invertebrates (e.g., ammonites)
�Dinosaurs (may have already been on their way out..)
What is the primary hypothesis for the cause of the dinosaur extinction? What is the
evidence? Are there other hypotheses?
�Climatic change (cooler and more seasonal)
�Intensive volcanism
�Retreat of epeiric seas
�Mammals out-competed dinosaurs (not likely)..
�Meteorite impact
�Overhunted by Martians..Cretaceous-Tertiary
extinction meteorite impact theory is favored, but not
When did the Cenozoic begin?
Cenozoic began ~ 65 mya
and continues until the
present. It is known as "the
Age of Mammals"
- rocks are more easily
accessible and less deformed
than older rocks
- divided into the Tertiary and
Quaternary Periods with epochs
During what time frame (epoch) does the Gray Fossil Site date to?
Cenozoic Earth History (1.4%)
Paleocene to Pleistocene
The Cordilleran continues into the Cenozoic. Its final orogenic episode is the Laramide
Orogeny which builds the Rocky Mountains. Know this...
Laramide Orogeny
Centered in the middle and southern
rockies in Wyoming and Colorado, Cenozoic Cordillera Volcanism
Columbia Plateau and Snake River Plain.
- massive amounts of late Cenozoic basalts, Cordillera - Colorado Plateau
A region uplifted during
Pleistocene Glaciation
The Pleistocene began
~1.6-2 mya and ended
about 10,000 years ago
- several intervals of
widespread glaciation
separated by warmer
intervals
- Currently think 20 major
warm-cold cycles
- Earth cooling actually
began as early as the
EoceneEvidence for late
The Appalachians that we see today are an expression of what?
Passive margin
(since late Triassic)
Cenozoic uplift and
erosion produced the
Eroded to a plain by end of Mesozoic
present topography
of the Appalachians