The Mesozoic Era
Periods: Triassic Period
245 mya – 208 mya
Jurassic Period
208 mya – 144 mya
Cretaceous Period 144 mya - 66 mya
Mesozoic Tectonics
The Pangea that had been forming throughout the Paleozoic Era is now
beginning to break up. In North America, the focus shifts from the Eastern
Appalachian Orogeny to the “Newer” Western Cordilleran (Rocky Mts.
Orogenies). If you remember, the Antler Orogeny of the Paleozoic actually
began the very first uplift of what would one day become the Rockies.
Beginning in the Triassic, the Cordilleran Orogenies (notice that they’re
plural) began the series of uplifts that would one day become the modern
Rockies. The Cordilleran Orogeny is divided into several smaller orogenies:
Triassic – Sonoman Orogeny
Jurassic – Nevadan Orogeny
Cretaceous – Servier Orogeny
K-T Boundary – Laramide Orogeny
These all came about from a continued, but punctuated subduction of parts
of the Pacific plate being overridden by the westward, counterclockwise
movement of the North American continent. Gold found in the Rockies of
today was at one time dissolved in seawater. As the subduction continued,
seawater bearing seafloor sediments became incorporated into the
upwelling of magmas that were forming the mountains, resulting in gold and
other precious metals forming in parts of the Rockies.
The Eastern Appalachia of the Paleozoic is now, during the Mesozoic, a
passive, eroding, trailing edge of the continent with the Rocky Mountains of
the west becoming the primary tectonic focus all the way until today.
The Craton during the Mesozoic: was for the most part “Emergent”.
Epeiric Seas are diminishing worldwide and in North America are found only
on a very small portion of the western coast. This restricted most Triassic
and Jurassic sedimentation to this western area of the continent.
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Evidences of the existence of Pangea from the Late Paleozoic through
the Late Triassic:
1. The good “fit” of the continental boundaries: i.e. eastern South
America fits into western Africa.
2. The distribution of land fossils common on continents now
separated by 100’s or 1000’s of miles of ocean water. ( i.e. Glossopteris
sp. seed ferns and early reptiles like Lystrosaurus sp. (a Cotylosaur) found
on both the African and South American continents.
3. Paleomagnetic data show unwavering evidence of the existence of
Pangea.
4. Common lithologies found on continents that are today separated
by oceans: specifically the sequence of rock called the “Gondwana Rock
Succession”:
Gondwana Rock Succession
1. At the base is Carboniferous Tillites, striated pebbles, other glacial
evidence, etc.
2. On top of this (#1) is Permian age continental depositions: Swamps
drying up, deltaic sediments.
3. On top of (#2) is Permian and Triassic “Red Beds” (drying marine
sediments, aeolian terrestrial sediments indicating very arid conditions.
4. At the very top is Late Triassic and Early Jurassic Basalt flows formed
from the initiation of the break-up of Pangea.
The Atlantic Ocean: The Atlantic Ocean began as a rift that formed at first
between North America and Africa, then later between South America and
Africa. As the continents continued to rift apart, the Atlantic Ocean’s M.O.R.
(Mid-Oceanic Ridge) continues to separate North and South America from
Africa and Europe even up until today.
No part of the Atlantic seafloor dates older that about 240 mya. The
youngest is at the M.O.R., and it gets progressively older on either side of
the M.O.R.
Mesozoic Life
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Zoologically speaking, the Mesozoic is called the “Age of Reptiles” or the
“Age of Dinosaurs”. Botanically speaking, it is called the “Age of
Cycads” or the “Age of Gymnosperms”.
Triassic Period:
Marine Life: Early Triassic invertebrates are not well known. Ammonites
and Bivalves were the most common invertebrate. Many Ammonites
became extinct during the Triassic but a few groups managed to survive
until the end of the Cretaceous. With the Rugosa Horn Coral and the
Tabulata corals of the Paleozoic now extinct, their successor of the
Mesozoic was the Scleractinian (Hard) corals. This abundance of
Scleractinian reef building corals began to set up the marine reef
ecosystems seen today. Epeiric seas are all but gone from Earth, so the
Scleractinians play a vital role in sustaining life in lagoons formed by reefs.
Terrestrial Life: Remember that in the Devonian the first reptile (the
Cotylosaur) evolved, This Cotylosaur group branched out into two major
groups by the Permian: the Pelycosaurs (reptilian/Dinosaur stock group)
and the Therapsids (mammalian stock group). Thecodont dentition began
to replace the old fish-like Acrodont dentition became common in both of
these groups because of the strength and usefulness this brought to the
“bite”. So, that in the Triassic, these thecodont groups were well
established. One thecodont group is the ancestor of the Dinosaurs.
Another is the ancestor of the modern reptiles. And a third is the ancestor
of the mammals. (Refer to the stock group chart) The first dinosaur and the
first mammal are both found in the Triassic. Since the reptilian-like stocks
sort of had a head start over the mammalian groups, they (the reptilians)
took over the major diurnal niches and attained formidable body sizes rather
quickly. The mammals during the entire Mesozoic were small shrew-like,
nocturnal organisms. The high amount of Haversian canals in their bones
indicated endothermy and the large orbital sockets indicated their being
nocturnal. The early mammal’s small size, nocturnal behavior, and
endothermic physiologies were “chosen for” on the part of the mammalian
populations because of the apparent threat by the larger, more powerful
diurnal Dinosaurs. This was to be the fate all mammals would face until the
extinction of the Dinosaurs at the end of the Mesozoic.
Plants of this time include the “leftovers” of the Primitive Vasculars
(Pterophytes and allies) of the Paleozoic. But, they were quickly being
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replaced/displaced by the much more common “Seed Plants”
(Gymnosperms: Conifers, Cycads, Ginkos, etc. See your notes on plant
evolution. Be familiar with the Euameric and Glossopteran Floras of the
Paleozoic and what happened to them to give rise to the Mesozoic
Gymnosperms). Cycads especially flourished well and became the fodder
of the herbivorous dinosaurs.
Marine Reptiles: Ichthyosaurs, Mosasaurs , and Plesiosaurs were the
dominant marine reptiles.
Flying Reptiles: Pterosaurs such as Pteranodon sp. exploited the aerial
niche. Recent fossils of these show that they may have been covered with
hair, indicating that they were “warm-blooded” (endothermic)
Terrestrial animals: Thecodont groups give rise to early dinosaur groups,
modern reptile groups, and early mammals. The Dinosauria evolved into
two basic groups based on the bones of the hip. If the bones of the hip are
fused like modern birds, the dinosaur is classified as “Ornithischian” (birdhip). If the hip is more lizard-like, the dinosaur is classified as “Saurischian”
(lizard- hip).
Jurassic Life
Invertebrates: Ammonites and Bivalves undergo rapid diversification and
evolution. Ammonites show a marked increase in complexity of the suture
patterns. All Jurassic marine strata are indexed using ammonite index
fossils.
Terrestrial life: The first bird was Archeopteryx sp. of the Jurassic. This
1st bird came from a group of Ornithischian dinosaurs called the
ornithopods. This chicken-sized Archeopteryx sp. was first found in the
lithographic Solnhofen limestone of Germany. This fine-grained limestone
preserved even the imprints of the feathers. In a sense, at least some
dinosaurs never became extinct, but are represented by their modern-day
descendants: the birds of today.
Dinosaurs: The word means “Terrible Lizard” and is a group of terrestrial
organisms that were highly successful for over 150 million years (approx.
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215 mya – 66 mya). They possessed reptilian characteristics (jaw structure,
pelvic structure, undifferentiated teeth, shelled eggs, etc.) But many also
showed mammalian characteristics such as endothermy and indications of
hair coverings.
Saurischian Dinosaurs: Pelvic structure similar to modern reptiles. These
are divided into the Theropods and the Sauropods. Theropods were
bipedal carnivores such as Tyrannosaurus rex or Deinonychus sp. The
Sauropods were herbivorous quadrupeds that arose in the early Jurassic
such as Brontosaurus sp. or Apatosaurus sp. Sauropods may have
lived in herd-like groups and carried their massive tails in the air for balance.
Ornithischian Dinosaurs: Pelvic structure similar to birds. All were
herbivores. There were bipedal and quadrupedal forms. The Ornithopods
were characterized by the “duck-billed” bipedal dinosaurs such as
Hadrosaurus sp. Some line of Ornithopods gave rise to the three major
groups of quadrupedal forms of Ornithischians: the Anklosaurus sp.,
Stegosaurus sp., and the Ceratopsians such as Triceratops sp. Many
Ornithischian groups show evidence of endothermy and a highly developed
social order.
Warm-blooded or Cold-blooded Dinosaurs? Evidences for endothermy
include:
1. Some lived in cold climates. I.e. Alaska, some fossils found associated
with glacial tillites.
2. Bone cross-sections show mammalian or bird-like Haversian canal
arrangements.
3. Bipedalism of the Theropods and some Ornithopods is not really seen in
modern reptiles.
4. Brain/body ratio is high in many dinosaur groups (mammalian-like)
5. Some show heterodonty (different teeth for different chewing functions
indicating greater food diversity and endothermy)
6. Some had such a large body mass that they were able to store body
heat (homeothermy)
7. Many show complex social behavior such as communal nesting and
parental care of the young, both indicating high metabolisms and
mammalian-like behavior.
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Life of the Cretaceous
The Rise of Angiosperms (Flowering Plants). The first flower dates to the
Late Jurassic/Early Cretaceous, and is a fossil of the Magnolia family.
Rapid diversification of flowering/fruiting plants took over the plant world and
started replacing the Gymnosperms, causing a decline in the amounts of
Cycads (the food of the herbivorous Dinosaurs). This contributed to the
demise of the dinosaurs. Today, about 95% of the plants on earth are
Angiosperms. Insects showed a rapid and close evolutionary relationship
with the flowering plants. New pollens may have contributed to the demise
of the dinosaurs by causing respiratory diseases, or by poisoning the
dinosaurs that attempted to eat these new flowers. Angiosperms provided
hiding places for the early mammals and as the mammals proliferated; they
may have preyed upon dinosaur eggs for food, causing further harm to the
dinosaur populations.
The K-T Mass Extinction: 66 mya 25% of the families of life on earth
became extinct.
By the end of the Cretaceous, extinct organisms included:
The Dinosaurs (except for the bird-forms)
Marine reptiles, Flying reptiles,
Many invertebrates such as ammonites, many Forams, many bivalves,
some corals
Some organisms went unscathed such as most fish, amphibians, and
modern reptiles such as crocodilians, turtles, snakes, and lizards.
Reasons for the K-T Mass Extinction:
1. Tectonics- Pangea continuing to break up contributed to instability of
ecosystems.
2. Climatic changes associated with tectonic repositioning of continents and
mountain ranges.
3. Abundant Phytoplankton in the seas fixed a great deal of CO2 into
limestone. The result was a reduced CO2 content in the atmosphere so
there was a cooling of the earth’s temperature. This was the opposite of the
greenhouse effect. Temperature dependent sex determination was
probably seen in dinosaurs, reducing the amount of females, reducing the
reproductive success.
4. Nemesis Dark Star Theory of extinctions.
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5. Asteroid or meteor impact near the Yucatan Peninsula shows a high
Iridium content as is seen in many places in the world at the K-T boundary.
The mass extinction at the K-T was probably a combination of these
causes.
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The Cenozoic Era
Characteristics:
I. Cenozoic Timeframe - (66MYA - Today) The Cenozoic Era is divided
into 2 Periods:
 The Tertiary Period ((66MYA - about 2MYA (it is
really closer to 1.8MYA))
 The Quaternary Period (approximately 2MYA Today)
In some countries of Europe, as well as other parts of the world, the
Cenozoic ERA is divided into the Paleogene Period (66mya - 24MYA), and
the Neogene Period (24MYA-Today). We will use the Quaternary &
Tertiary Periods.
The Cenozoic Periods are divided into smaller time units called Epochs.
These are time divisions based upon changes in cratonic sequences, glacial
events, or events such as major faunal and floral (animal & plant)
extinctions/proliferations.
The Epochs of the Quaternary Period are:
 Holocene (10,000 years - today)
 Pleistocene (2MYA - 10,000 years ago)
The Epochs of the Tertiary Period are:
 Pliocene (5.3MYA - 2MYA)
 Miocene (24MYA - 5.3MYA)
 Oligocene (37MYA - 24MYA)
 Eocene (58MYA - 37MYA)
 Paleocene (66MYA - 58MYA)
II. Cenozoic Tectonics:
 The North American continent continued to rotated counterclockwise and
northward as it approached its present day position. Pangea continued
the break up that had begun in the Triassic.
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 The Atlantic Ocean (MOR) continued to expand while the Pacific
Ocean (Continental/Oceanic Subduction) continued to shrink.
 Most of the Craton was exposed with much erosion occurring. There
was much alluvial and other terrestrial deposition. The continents were
"Emergent".
 The eastern margin of the Appalachians continued to erode down,
developing into a fully passive trailing margin. This developed the broad
continental shelf, slope and rise on the eastern margin of the continent
that still exists today.
 On the western margin, the Farallon Plate subducted completely leaving
the Juan de Fuco Plate to the north, and the Cocos Plate to the south.
This contributed to the surges of uplifts of parts of the Rocky Mountains,
but more effectively began forming the Cascade Mountain Range.
These mountains are the westernmost mountains of the West Coast of
North America from northern California to Oregon, Washington, and into
Canada. These mountains include Mt. St. Helens, Mt. Hood, Mt.
Ranier, Mt. Lassen, Mt.Baker etc. (all active volcanoes up until today)
 In the Rockies, the Laramide Orogeny of the K-T Boundary
(Cretaceous/Tertiary) contributed to the last major uplift of the Rocky
Mountains forming the Front Range (the Tetons, etc., the easternmost
Rockies)
 Because of the large amounts of subduction on the west coast of North
America in this area, vast basalt flows called the Colombia Flood
Basalts covered much of Washington, Oregon, Idaho, Montana, & British
Colombia under 2500 meters of basalt flows, each flow layer about 5 - 10
meters thick.
 Lake Missoula, an extremely large 300-meter deep freshwater lake
formed north of the Colombia Flood Basalts on the borders of Canada
and Washington/Oregon areas. It formed as a result of glacial erosion
and melt-water. It was larger than the present day Great Lakes
combined. As the natural levee dam to the south eroded quickly, it
caused an enormous flood, quickly draining this giant lake southward
over the Colombia Flood Basalts in a matter of a couple of weeks. This
tremendous amount of erosion formed the Channeled Scablands of the
eastern Washington/Oregon/Idaho, & western Montana regions, also
forming the famous rich volcanic soils famous for growing potatoes.
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 Because of the uneven movement of the North American Plate, the San
Andreas Fault system developed as a Shear Plate boundary in and
around what would one day be California/Baja.
 The "Four-Corners" area (the broad area around the boundaries of New
Mexico, Arizona, Colorado, & Utah) known as the Colorado Plateau
began to be uplifted around 50 - 60 MYA. Since rivers draining this area
had reached a base level, they were low energy & meandering. Because
of this uplift, they began downward and lateral erosion, maintaining their
meandering, forming the vast "Canyonlands" we see today.
 The Grand Canyon 1st began to form then (50MYA or so), but the
Grand Canyon as we know it today formed about 5 - 10 MYA.
 Because of the uneven stresses caused by the tectonics in the west, the
area from eastern Washington, Oregon, through Idaho, and southward to
eastern California and western Arizona experienced sufficient extensional
stresses to form huge Horst and Graben fault zones forming the Basin
and Range Province.
 Worldwide, there were transgressions and regressions of the sea,
but only the coastal fringes were effected. The Tejas Cratonic
Sequence started about 60 MYA, peaked about Mid-Cenozoic, and
continues to regress today.
 Subduction and collision of the Pacific Oceanic plates with North America
caused a "kink" in the plates of the Mid-Pacific forming a "Hotspot" (a
large. somewhat stationary, Hot body of magma close to the surface)
under what will become the Hawaiian Island Chain.
 India broke away from Gondwanaland and moved quickly northward,
slamming into Asia forming the Himalayan Mountains, while at the same
time Africa broadsided Europe and the Middle East forming the Alps and
the Ural Mountains. Collectively, this massive Continental/Continental
Convergence is known as the Alpine/Himalayan Mountain Chain,
stretching from Europe to China.
III. Glaciation and Cenozoic Climate
During the Cenozoic there were widespread episodes of massive
glaciation. With the asteroid impact of 66MYA near the present day
Yucatan Pennensula, there had been an immediate cooling trend causing
the growth of the polar ice caps, resulting in the almost immediate
(geologically speaking) regression of the Zuni Cratonic sequence near
the K-T boundary time. This resulted in a general cooling trend of the
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earth changing climatic patterns worldwide. As the earth warmed
somewhat, there began the Tejas Cratonic Transgression covering only
the low coastal areas. Around 35-40MYA,during the Oligocene Epoch, a
cooling trend started resulting in the beginning of the regression of the
Tejas Cratonic sequence. We have experienced a continual regression of
the Tejas even up until today. This general cooling trend culminated in 4
recognized very massive glacial episodes during the Pleistocene Epoch on
the North American Continent:
Glacial/Interglacial Episodes of the Pleistocene
Glacial Episode
Interglacial Episode
 The Wisconsin Glaciation 150,000 years ago
Sangomon
Interglaciation
 The Illinoian Glaciation 0.7 MYA (700,000 years ago)
Yarmouth
Interglaciation
 The Kansan Glaciation 1.3 MYA
Aftonian Interglaciation
 The Nebraskan Glaciation 2MYA
These glacial periods are punctuated by "Interglacial Periods" where
there were regressions of the ice sheets, allowing for vast amounts of
erosion. These Interglacial Periods represent warming trends resulting in
"Eustatic" (worldwide) changes in sea level. "Isostacy" is the up and
down movement of the continents due to the great weight of ice sheets
(some ice sheets were 2 miles thick!!!) literally pushing the continental
lithospheric material downward. This is followed by the continent "springing
back up" during an interglacial period. This isostatic movement of the
continents coupled by massive glacial erosion created many major
landforms on the North American continent:
 The Great Lakes
 The Finger Lake district of New York
 The changes of the major river drainage patterns of
the continent
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 "U-shaped" valleys, moraine depositions, erratics,
accumulation of glacial "tillites", striated bedrock and
pebbles, boulders, etc.
 These glacial changes played a major role in the
evolution of life, including humans.
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IV. Life in the Cenozoic:
Characteristics:
 In the oceans, invertebrates were restricted to the shallow
marine shelf areas.
 Modern marine ecosystems developed.
 Marine invertebrate and vertebrate life was more or less the
same as today.
 Epieric Seas are Gone Forever!!! The only "incubator" of
marine life was and continues to be the fringing Scleractinian
coral reefs that began in the Triassic Period.
 On land, the Cenozoic Era saw an adaptive radiation
explosion of mammalian life and is known then as the "Age
of Mammals".
The Age of Mammals: The first mammals date back to the Triassic Period
of the Mesozoic Era. These were descendants of the Therapsid early
mammal stock of the Permian Period. Since the Cotylosaur sp. (1st
reptilian group of the Devonian Period) had given rise to the Reptiles and
Dinosaurs of the Mesozoic Era somewhat faster than the Therapsid
mammals lineage developed. Therefore, small size, "warm-bloodedness"
(endothermy), the body covered with hair, and nocturnal behavior were the
rule for the mammal stocks of the Mesozoic Era. If any of the mammals
attained large size or attempted to become diurnal (coming out during the
daytime), they were quickly eliminated by the dominant reptilian and
dinosaur groups of the time. Because of the mass extinctions at the end of
the Mesozoic, the strong environmental pressures placed upon the
mammalian groups by the large reptilian and dinosaur groups during the
Mesozoic were lifted. The cooler climate and changes in vegetation proved
to be a very favorable environment for an explosive adaptive radiation of
mammal groups. The mammals took over the "niches and habitats" left
behind by the dinosaurs.
Reptiles: took a beating at the K-T boundary, reducing them in numbers,
but the modern representatives (crocodilians, snakes, lizards, & turtles)
survived.
The Mammalian Lineage: The first group of Cenozoic mammals was the
"Insectivores" of the Mesozoic. These small, shrew-like mammals
diversified by the early Paleocene into the (1) Marsupial Stock, (2)
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Monotreme Stock, and the (3) Insectivore Stock. Remember that the
plant life of the world was now dominated by the Angiosperms, the
"flowering and fruiting" plants of today. These plant groups were also
diversifying and developing modern forests and grasslands. Forests
provide both a food supply and hiding places, while grasslands provide an
enormous food supply but few hiding places. Mammals adapted to survive
and exploit both of these habitats and food supplies. As herbivorous
mammals developed, so did carnivorous mammals, setting up a
predator/prey relationship as seen in the Mesozoic reptiles and dinosaurs.
(1)Marsupials are the "pouched " mammal of Australia today. During the
Paleocene, these non-placental mammals proliferated and competed with
the insectivores. In Marsupial mammals, fertilization is internal and the
fetus develops in the uterus like other mammals. The marsupial fetus
DOES NOT form a placenta with the uterus. The fetus at about 6 weeks of
age must exit the female's cloaca and crawl on the belly of the female up
and into the "marsupium" (pouch) in order to complete gestation. If the
female at this time is scared by a predator and has to run away, chances
are that the little blind (at this time) fetus will drop off of the belly of the
mother and die.
(2)Monotremes are egg-laying mammals such as the spiny echidna and
the duck-billed platypus. These are true mammals, but the females make a
nest of sorts and deposit eggs. The nest is guarded and the young hatch
within a few days. This is not the rule of mammals today because of the
time and energy expenditures needed in this type of reproduction. The
Monotremes were never very successful. Only two or three survive today.
(3)Insectivores These were a diverse group of small Cretaceous mammals
that soon diversified into the major lineages of mammals of today. One of
the earliest Cenozoic groups of these was the:
Condylarths. These early shrew-like mammals evolved into a large
group called the Ungulates. These 1st ungulates of the Paleocene had
developed keratinized hoof/claw structures on their appendages, allowing
for a relatively quick radiation into a variety of mammal stock groups such
as:
A. The Herbivorous mammals such as The "Modern Ungulates"
(Beginning in the Paleocene were grazing mammals such as deer-like
organisms; prey animals) including Artiodactyls = "even-toed" ungulates
such as cattle, deer, sheep, hippos, camels, etc. and Perissodactyls = the
"odd-toed" ungulates such as the horse lineage, rhinos, & tapirs. These
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herbivorous mammals were exploiting the vast food supply of the
grasslands. In the early Cenozoic, a 5 toed ungulate developed called
Hyracotherium sp.. This was the first in the lineage of the horse. Direct
fossil evidence is seen from Hyracotherium sp. through to the modern
horse Equus sp.
B. The Carnivores Beginning in the Eocene, these were dog and catlike mammals that created a strong predator lineage, feeding upon the
herbivorous mammals of the grasslands.
C. The Primates Beginning in the Paleocene, these were small tree
shrew-like organisms that soon evolved to fill the arboreal habitats of the
forests. Adaptations seen in the Primates as they developed specializations
for an arboreal life include:
 Stereoscopic vision for depth perception
 An opposable thumb for grasping
 Larger brain to body size
 Mobile digits with nails instead of claws
 Some developed an opposable tail for support
 "Brachiation" ability developed. This is the free
movement of the ball and socket joints
especially on the pectoral girdles that allows for
swinging movement suited for tree life; a
mobile, flexible shoulder arrangement
 Changes in the attachment of the spine and hip
allowed for a more upright sitting position
 Longer Gestation Period (in womb fetal
development)
 Other adaptations in the skeleton allowed for a
more flexible body
V. Tectonics and Mammalian Distribution worldwide.
In Laurasia (North America & Eurasia) and Africa, modern
predator/prey (lion/deer) ecosystems soon replaced the primitive
insectivore, Monotreme, & marsupial groups. In South America, there were
as many marsupials as in Australia today. But, because of the formation of
the Isthmus of Panama in the early Cenozoic, the ferocious carnivores of
North America swept down into South America, feasting on the relatively
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defenseless marsupial groups. The only marsupials in South America to
survive were the arboreal forms such as the modern opossum.
Australia never had a land bridge connecting it to Eurasia so it still
retains its primitive assortment of early Cenozoic mammals it has had since
the Paleocene. As eustatic sea level changes occurred, some areas were
opened to cross migrations of mammals for a while, followed by being
isolated by water whenever the sea level would rise. This periodic mixing of
mammals helped to create the zones or ecosystems of mammals today.
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Rise of the Primates
Primates are divided into groupings based upon advancements seen in
anatomy and behavior:
 The Prosimians (Lower Primates) include the tree shrews, lemurs,
slender lorises, and tarsiers. These exhibit all of the physical
characteristics of primates, but lack some of the social and intellectual
attributes of other "higher" primates.
 The Anthropoids (Higher Primates) These primates from least
advanced to most advanced include:
New World: i.e. Howler, Capuchin, and Spider
monkeys
Old World: i.e. baboons, mandrills, macaques, etc.
Pongids: Members of the Pongidae Family include the
Orangutan, Chimpanzees, Gorillas, etc.
Hominids: Members of the Hominidae Family. This is
the Family of man. Today we are the only member of
this family, but not so in the past.
The Rise of Humans: About 4 to 5 million years ago, conditions changed
so as to cause a worldwide reduction in the forested areas of earth. It is
unclear as to why this happened, but what this did was to place very strong
environmental pressures upon the groups of arboreal primates. Punctuated
equilibrium shows us that the peripheral isolates of any group are under the
greatest amount of environmental pressure. Those primate groups that
were best suited genetically for an arboreal life won the struggle and
remained in the forested areas. Those that could not compete either
became extinct or were forced to leave the arboreal existence. Those that
left were mankind's ancestors.
As this early group of primates made their way out onto the grasslands
and plains, some adaptations were quickly chosen for in the group:
 Upright Stance and Bipedalism. This allowed for the individuals to
better see off in the distance to become more wary of predators or
possible dangers lurking in the tall grasses yet still retaining the dexterity
and mobility of an arboreal organism.
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 Intelligence was chosen for in the bipedal hominids - learning to cope
and adjust to new hazards, new food supplies, encounters with new
animals, new climates, etc., etc. Now, not only is it survival of the
strongest, but also survival of the smartest.
At some point, around 4 to 5 MYA, as these early hominids were
leaving their arboreal habitat, there must have been some groups that were
attacked by some ferocious predator with its large fang-like teeth and sharp
claws. Many groups were probably easily killed and eaten, but somewhere,
at some time, one of these early hominids picked up a tree branch or a
sharp stone and fought off the predator. That individual (or individuals)
"invented" technology. Those that had the mental capacity to fend off
predators were successful and survived; those that lacked these new
thought processes became food for the predators.
So, this set the stage for environmental pressures to select for
intelligence in these early hominids. The clubs and sharp stones became
our "technological fangs and claws". Those that were able to produce the
best intellectual strategies to overcome attacks from predators, or later
could produce the best weapons to kill not only the predator at hand, but
also provide game meat for the group, survived and proliferated and began
to migrate all over the planet.
The Hominidae Family Tree:
The beginning site of Hominids seems to be located in the eastern
African Rift Valleys of Kenya and Ethiopia.
Australopithecus afarensis - 3.5 MYA Found in Ethiopia named
"Lucy" by paleontologist/anthropologist Donald Johanson in 1972. The
skeleton shows that Lucy was bipedal, but still had a relatively small
sized brain case. Australopithecus afarensis is thought to have given
rise to:
Australopithecus africanus - 2.5MYA They were taller and had more
robust bones, especially in the jaws that had thick, massive molars.
These hominids spread out geographically into Europe and possibly
eastward into Asia. They gave rise to:
Australopithecus robustus 2MYA, and Australopithecus boisei
2MYA. All three of these offshoots of Australopithecus afarensis
(Lucy) became extinct around 1.25 MYA. Glacial episodes may have
played a role in their extinction.
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Australopithecus afarensis (Lucy) is thought to have been the
ancestor of another line of hominids. These are:
Homo habilus 2.0MYA "handy man" dubbed so because this is the
FIRST hominid to possess an extensive line of stone tools. The
size of the brain case shows considerable increase over all hominids to
this point.
Homo erectus 1.5 to 1.0 MYA - As H. habilus spread out into the
world and ultimately became extinct, on of its descendants, Homo
erectus adapted wonderfully to most environments of the world. This
is the first hominid to have used fire, and also walked erect, utilized
sophisticated stone tools, and was a good hunter. Homo erectus is
thought to have been the ancestor of:
The Homo sapiens line of Modern Man 1.0 MYA until today.
During the Late Pleistocene, these Homo sapiens stock groups
flourished and spread out into the accessible parts of the world. The
Homo sapiens neanderthalensis and the Homo sapiens cromagnon probably coexisted for several hundred thousand years. The
Homo sapiens neanderthalensis were good hunters, artists (cave
paintings), cared for their injured evidenced by the skeletal evidence of
severely injured individuals, probably had some religion because of
their burying their dead with artifacts, flowers, etc. indicating burial
rites. Skeletal evidence shows that Homo sapiens neanderthalensis
probably did not possess good language skills because the hyoid
bone in the throat was extremely high in position. This would have
resulted in a larynx (voice box) to be placed very high in the throat.
They may have had a rudimentary language.
Communication skills and vocabulary development is a very
important aspect of survival even today. Skeletal evidence of Homo
sapiens cro-magnon indicated that they had a larynx similar to us and
probably possessed good communication skills. Being so closely
related genetically, Homo sapiens neanderthalensis extinction
around 100,000 - 50,000 years ago may have been the result of them
being absorbed into the population of Homo sapiens cro-magnon .
Maybe Homo sapiens cro-magnon killed all of them, or maybe Homo
sapiens neanderthalensis became extinct of its own doings. No
matter what, Homo sapiens cro-magnon of around 50,000 years ago
is the direct ancestor of us, Homo sapiens sapiens.
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As Homo sapiens sapiens traveled around the accessible locals
in the world, the fluctuation of sea levels from the glacial episodes of
the Pleistocene caused land bridges to open temporarily, allowing for
human (and animal) migrations to occur, then rising sea levels or
advancing glaciers would close the migratory route. About 12,000
years ago, the Bering Straits between Alaska and Asia opened
allowing humans (& some animal groups) to migrate into and out of the
North American continent. A similar situation occurred with Australia
allowing humans to enter. Soon humans had populated all habitable
environments of the world. With changing climatic factors and the
"invention" of agriculture about 10,000 years ago, we see the
development of settled family units, then villages, then communities,
then cities, all the while the minds of humans inventing and creating
new ways to cope with the ever changing environment.
So, here we are...but,…Where are we going???
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