CH. 15 - 17
Change during the Cenozoic
As a result of the change in climate and vegetation, adaptive radiation occurred among the Old World primates. During the late Miocene, primates appeared that gave rise to the pongids (orangutan, chimpanzee, and gorilla) and the hominids (human family).
"Lucy" - Australopithecus afarensis
Australopithecus afarensis was discovered by Donald Johanson in 1974 and nicknamed "Lucy". Lucy was an erect-walking hominid in East Africa about 3.5 million years ago. Posture is determined from analysis of pelvic and leg bones. Further evidence of bipedalism (walking upright on two feet) of australopithecines is the discovery of footprints and a trackway in 3.2 million years volcanic ash layers (tuff) at Laetoli, eastern Africa. (Pliocene). Australopithicine dentition (tooth structure) was essentially human. Cranial (brain) capacity was less than that of modern humans. (600 cm³ vs. 1400-1600³ in modern humans).
Old World monkeys or Cercopithecoidea
Baboons, mandrills, macaques, rhesus monkeys, Barbary ape. Nostrils close together and directed downward, as in humans. Tail not prehensile.
Antarctica has been covered by glaciers for at least the past -- million years. The Antarctic ice sheet began to form in the Eocene, and glacial conditions were well established by the Miocene. The East Antarctic ice cap has been in place since the middle Miocene. In the latest Miocene (about 5 m.y. ago), ice volumes in Antarctica were greater than those today.
15
Name "Cenozoic"
"new life" or "recent life"
Little People of the South Pacific
A new species of human was discovered on the Indonesian island of Flores in 2004, Homo floresiensis. An excavation produced the remains of seven small individuals. The adults were only 3 ft (1 m) tall. The ancestry of this species is uncertain, however, Homo erectus probably reached the island about 800,000 years ago, and evolved into a smaller species as a result of living on an island with limited food and few large predators. Homo floresiensis lived as recently as 13,000 years ago, at the same time as both the Neandertals and modern humans. They hunted, used fire, and made stone tools.
The Paleogene is dominated by:
The deposition of marine sediments in eastern and southeastern North America The presence of mountains and lakes in western North America.
Meat-eaters
The earliest meat-eating placental mammals are Late Cretaceous in age. Creodonts - Extinct small-brained animals with short limbs and claws. Dominant meat-eating mammals in the Paleocene. Carnivores - Cats, hyenas, dogs, wolves, raccoons, bears, and weasels. Aquatic carnivores include the seals, sea lions, and walruses. Larger brains than the creodonts. They replaced the creodonts by the Miocene.
As a result of the Ice Age:
Climatic zones in the Northern Hemisphere were shifted southward. Arctic conditions prevailed across Europe and the U.S. Sea level dropped as much as 75 m (225 ft) and the shoreline shifted seaward, exposing the continental shelves as dry land. Streams cut deep canyons into the continental shelves and on land. Land bridges existed and led to migrations of mammals, including humans Across the Bering Sea between Siberia and Alaska Between Australia and Indonesia British Isles were attached to Europe The land was sculpted by glaciers in Europe and North America. Rainfall increased at lower latitudes. Large lakes formed in the Basin and Range Province.
About 15,000 -10,000 years ago, humans began to:
Domesticate animals Cultivate plants Produce more highly developed tools Make utensils of fired clay Develop permanent settlements Use language Develop writing With the development of writing, the era of recorded history began.
Neandertal skeletons were somewhat more robust than human skeletons. The Neandertals can be divided into three groups.
Early Neanderthals, that lived approximately 250,000 to 130,000 years ago Neanderthals that existed during the transition to the Upper Paleolithic, approximately 130,000 to 45,000 years ago Late-surviving Neanderthals after 45,000 years ago, up until about 28,000 years ago.
Volcanic Activity during the Little Ice Age
Earth also experienced heightened volcanic activity during the Little Ice Age. Volcanic ash and aerosols in the atmosphere cause temperatures to drop by blocking out incoming solar radiation. The eruption of Mount Tambora in Indonesia in 1815 was followed by the Year Without A Summer in 1816. Frost and snow were reported during June and July of 1816 in New England and Northern Europe.
In the Miocene (which lasted from 23 to 5 million years ago), plate tectonics affected primate evolution. Africa and Arabia drifted northward and eventually collided with -------. This changed the circulation in the Tethys Sea and the climate in East Africa became cooler and drier.
Eurasia
Hominidae
Humans
Pongidae
Orangutans, chimpanzees, bonobos, and gorillas
Evidence for the earlier arrival of humans in the Americas includes:
Pre-Clovis remains in South America near Monte Verde, Chile dated at 12,500 years old include hut foundations and building materials, hearths with burned animal remains, and stone tools. Charred human remains from Washington State dated at 11,500 to 13,000 years old. Stone weapon points and tools in the Meadowcroft Rockshelter in western Pennsylvania that appear to be 14,250 to 19,600 years old. A human skull unearthed near Laguna Beach, California dated to between 15,680 and 18,620 years old. Stone tools in soils dated at 16,000 years old or more in Allendale County, SC along the Savannah River. Artifacts in a sand dune along the Nottoway River at Cactus Hill, Virginia at least 15,000 years old. An obsidian blade found under a 23,000 year old log in Mexico. Fire pits in Nevada, dated at 24,000 years old. Cooked mammoth bones in a campfire on Santa Rosa Island off the coast of California, dated at 28,000 years ago. Crude stone tools in California that may be around 30,000 years old.
Anthropoidea
monkeys, apes, and humans
Principle adaptations of the primates include:
rogressive enlargement of the brain Shortening and flattening of the face (reduction of snout) Modifications of the hand - opposable thumb Mobility of the forearm, allowing rotation of the ulna and radius, so that the hand can be turned Modifications of the thorax allowing upright posture Forelimbs and hind limbs diverged in form and function Eyes are close-set and positioned toward front of face, allowing binocular stereoscopic vision and the ability to judge distance These adaptations may have been beneficial to an arboreal (tree-dwelling) existence, or to catching prey.
Hominoidea or anthropoid ape
tail-less primates.
The Neogene Period is divided into...
the Miocene, Pliocene, Pleistocene, and Holocene epochs.
The lizards and snakes belong to an order of reptiles called...
the squamates. In fact, the lizards are the ancestors of snakes. Fossil snakes are found in rocks as old as Early Cretaceous.
During the Cenozoic, the Atlantic and Indian Oceans did what?
widened, and the continents moved to their current positions. Half of the present ocean crust has formed at the mid-ocean ridges since the beginning of the Cenozoic.
Genus Homo
The genus Homo arose nearly 2.5 million years ago when australopithecines evolved into the ancestors of humans, Homo ergaster, also called Homo habilis. Homo rudolfensis and Homo ergaster/Homo habilis lived in Africa around 2 million years ago. The evolutionary transition may have been stimulated by the change to a cooler, drier climate about 2.7 million years ago. Rainforests were replaced by grasslands. In this environment, selective pressures may have led to bipedalism, greater intelligence, and the ability to make stone tools. Stone tools are found with fossils of Homo. Genus Homo has a larger cranial capacity and some smaller teeth, but no striking anatomical differences.
Proconsul
discovered by the Leakeys in 1948 in Kenya, was a dryomorph or a dryomorph ancestor. It had ape-like skull, jaws, and teeth. It had monkey-like long trunk, arms and finger bones. Middle Miocene descendants of Proconsul are probably ancestral to modern African apes and the first hominids, the australopithecines.
Australopithecus africanus
discovered in 1924 by Raymond Dart in South Africa. Since then, many specimens have been discovered in East Africa, particularly in Olduvai Gorge by Mary and Louis Leakey. East African fossil sites have yielded hundreds of hominid bones, documenting human evolution over the past 4 million years.
Milankovitch cycles correspond well to what?
glaciation
The Paris Basin
is the type area for most of the epochs of the Cenozoic. There is a major unconformity in the basin, and it is chosen as the boundary between the Paleogene and the Neogene.
The animals which traveled northward were dominantly ---------. The animals which traveled southward were dominantly --------.
marsupials placentals
Age of Oldest hominid fossils
6-7 million years old
Homo erectus fossils include
A 1.8 million years jaw in the Caucasus Mountains of Georgia A 1.5 million years complete skeleton from east Africa near Lake Turkana (long-limbed, tall and slender with a remarkably modern skeleton) A 750,000 year old skull cap from Olduvai Gorge Homo erectus lived in the Early to Middle Pleistocene.
Australopithecus anamensis lived from -.- to -.- million years ago. It appears to be an evolutionary intermediate between Ardipithecus ramidus and Australopithecus afarensis or "Lucy."
4.2 - 3.9
Cro-Magnon
About 34,000 years ago during a glacial advance, humans closely resembling modern Europeans moved into the area occupied by the Neandertals, and eventually replaced them. They are Homo sapiens, and are called Cro-Magnon. Characteristics of Cro-Magnon: Mostly taller than Neandertals More vertical forehead Jutting chin Continued cultural traditions of the Neandertals - manufactured a greater variety of stone tools, painted pictures of animals in caves, carved and sculpted images of women and animals from bone or ivory, made and wore jewelry, elaborately buried their dead (such as burying hunters with their weapons). Developed art and complex rituals. Hunted and gathered edible plants.
Early Anthropoids
Anthropoids are the higher primates - monkeys, apes, and humans. Early anthropoid fossils are found in the Oligocene (33-34 million years old) of Fayum, Egypt. Aegyptopithecus. These are robust arboreal primates with a monkey-like tail and limbs, and eyes on the front of the skull. The prosimian-anthropoid transition had occurred by the Oligocene. At that time, Egypt was covered by tropical forests and streams.
Neandertal skull characteristics:
Brain size equal to or larger than that of modern humans Heavy supraorbital ridge (brow ridge) Prognathous (face extends forward at toothline) - but not as much as Homo erectus No chin - but lower jaw not as receding as that of Homo erectus Enlarged nasal cavity (for warming cold inhaled air)
Human Origins Prosimian Vanguard
Earliest fossil record for primates is Purgatorius, known from the Late Cretaceous Hell Creek Formation at Purgatory Hill, Montana. The earliest primates lived during the time of the last of the dinosaurs. The Paleocene Plesiadapis is the only primate genus other than Homo to inhabit both the Old World and the New World. This suggests that the continents were not fully separated by the Paleocene.
The Appearance of Homo sapiens The Earliest Humans
Fossil evidence from along the Omo River in southern Ethiopia shows that modern humans, Homo sapiens sapiens, with the large brain case, forehead, and prominent chin, lived in Africa as much as 195,000 years ago, according to an article published in February 2005. Previously, modern humans were thought to have appeared in Africa about 160,000 years ago. Humans appeared in Africa many thousands of years before our species appeared on any other continent. There appears to have been a time gap between the appearance of the modern human skeleton and modern types of behavior resulting in cultural artifacts. Stone knife blades appeared between 50,000 and 200,000 years ago. Other types of cultural artifacts, however, appeared just 50,000 years ago. Humans left Africa between about 40,000 and 50,000 years ago, and appear to have taken culture with them, including things such as bone carving, tools such as harpoons, jewelry and ornamentation, artwork, and arrowheads.
Two types of australopithicines have been distinguished
Gracile - Smaller, lighter-bodied with smaller teeth. Includes Australopithecus afarensis (Lucy). This group is transitional to genus Homo. Robust - Larger, heavy-bodied with larger teeth. Includes Australopithecus boisei (sometimes called Paranthropus boisei) and Australopithecus robustus (sometimes called Paranthropus robustus). Both are evolutionary side branches.
The Homo erectus Stage
Homo erectus (formerly known as Pithecanthropus erectus from Java and Sinanthropus pekinensis from China) is the first hominid known to have moved from Africa into Eurasia.
Central Europe Neandertals
In central Europe, Neandertals coexisted with early modern humans for thousands of years. As a result, interbreeding occurred. Bones discovered in 2002 show a mix of human and Neandertal traits, suggesting interbreeding.
When did Humans enter America?
It is not definitely known when the first human set foot in America. The traditional view is that humans arrived in the Americas from Asia, crossing the Bering Land Bridge between Asia and Alaska between 10,000 and 25,000 years ago (to perhaps 30,000 years or more), during a glaciation which lowered sea levels. Humans may have followed migrating herds of mammals. Opinion is divided over whether the migrating groups of Paleoindians would have traveled on foot or by boat. If traveling by boat, they may have followed the coastline, or crossed the open Pacific. Stone tools of the Clovis culture, about 12,000 years old, are known from Alaska to South America. Pre-Clovis dates are viewed with skepticism by some, but there are a number of reports of human activity dated at several thousand years earlier.
The Neandertals
Late Pleistocene hominids are called Neandertals (sometimes spelled Neanderthals). Neandertals may be a subspecies of Homo sapiens, designated as Homo sapiens neandertalensis. DNA analysis suggests that they were a separate species of genus Homo - Homo neanderthalensis. If so, they represent a dead end in human evolution.
A new group, the dryomorphs (formerly dryopithecines) appeared in the -----
Miocene
Other evidence for early arrival:
Mitochondrial DNA studies of Native Americans relating molecular divergence and population splits suggesting 20,000 to 36,000 years Linguistic analysis of Native American language diversity suggesting an arrival time of 35,000 years ago. Much of the pre-Clovis evidence is still somewhat controversial.
Neandertal Lifestyle
Neandertals hunted cold-tolerant mammals including cave bears, mammoths, wooly rhinos, reindeer, bison, and aurochs (a type of cattle). Neandertals manufactured a variety of stone tools, and used fire, which provided light in caves, gave warmth, allowed the thawing and cooking of food, and provided protection from predators. They constructed shelters or houses of skins, sticks and bones. They cared for the sick and buried artifacts with the dead, suggesting a belief in an afterlife. Musical instruments have also been found in association with Neandertal remains, such as a flute made from a bone, dating to between 82,000 and 43,000 years ago.
Humans in the Americas are called
Paleoindians
Monotremes
Primitive egg-laying mammals,
Hylobatidae - Gibbons
The most primitive branch of the tail-less apes.
Types of modern primates:
Tree shrews and lemurs have long snouts and eyes on the sides of the head. Most digits have claws. Tarsiers have relatively flat face, close-set eyes for stereoscopic vision, and fingers and toes have nails rather than claws.
Homo erectus
arose from Homo ergaster/Homo habilis. The opening at the base of the skull, where the spinal cord joins the brain, called the foramen magnum, is in a more forward position in Homo erectus, indicating that it had a more erect posture.
During the Eocene, primates underwent:
eduction in length of face Increase in brain size Movement of eyes to more forward position Development of a grasping big toe Tarsiers and lemurs were abundant and widely distributed on Northern Hemisphere continents during the Eocene. When the climate cooled in the Oligocene, the primates virtually disappeared from North America. They were forced southward into Asia, Africa, and the East Indies.
New World monkeys or Ceboidea
not involved in evolution of humans. Includes spider monkey, capuchin, and marmoset. Most are small. Prehensile tails.
The Cenozoic is the time of what?
of the adaptive radiation of the mammals, a dramatic cooling of the Earth's climate resulting in the Ice Ages, and the evolution of humans.
One particular species of foraminifera, Globorotalia truncatulinoides, is known to coil:
to the right in warmer waters, and to the left in colder waters. By examining the percentage of right- and left-coiled specimens, a cyclic pattern representing glacial advances and retreats can be determined.
During the Cenozoic Grass-covered plains replaced what?
tropical forrests
The Columbia Plateau was built by...
volcanic activity The Columbia Plateau province is one of the largest volcanic regions on Earth. During the Miocene, about 15 m.y. ago, basaltic lava poured out of deep fissures and buried more than 500,000 km2 of land in Washington, Oregon, and parts of Idaho. Lava flows are 2800 m (more than 1.5 miles) thick.
Homo erectus lifestyle
was a toolmaker and hunter. It is unclear whether they had language, wore clothes, built dwellings or used fire
The Diversity of Life in the Cenozoic
The Cenozoic dawned with the aftermath of the extinction at the end of the Cretaceous Period of the Mesozoic Era. The extinction had affected vertebrates and invertebrates, on land and in the sea, causing the disappearance of many groups of organisms including: Dinosaurs Ammonoids Large marine reptiles (plesiosaurs and mosasaurs) Rudists (reef-forming bivalves) There were also drastic reductions in the number and diversity of groups of organisms such as: Coccolithophores Planktonic foraminifera Radiolarians Belemnoids
At the beginning of the Cenozoic Era, ------- (as indicated by the number of genera) was much lower than it had been in the Cretaceous, as a result of the extinctions. Recovery from the extinctions was rapid (explosive), and diversity quickly climbed to a level much higher than had ever existed previously.
diversity
The Cenozoic Era is sometimes called what?
the Age of Mammals. During the Cenozoic, mammals came to dominate the Earth, much as reptiles had done during the Mesozoic.
Until 2003, the two periods in the Cenozoic Era were what?
the Tertiary and Quaternary Periods. You may see these terms on maps and in other publications, particularly older ones. In 2003, the International Commission on Stratigraphy revised the nomenclature, dropping the terms Tertiary and Quaternary. The two periods of the Cenozoic Era are officially recognized as the Paleogene and the Neogene.
The Cenozoic Era followed what?
the extinction of the dinosaurs (and many other organisms).
The end of the Pleistocene and beginning of the Holocene is generally considered to be the time when what occurred?
the ice sheets melted to approximately their current extent. This coincides with the rise of sea level. The boundary is placed between about 12,000 and 11,000 years ago, at the midpoint of the warming of the oceans.
The Cenozoic Era consists of what two periods?
the older Paleogene Period and the younger Neogene Period.
As the North American plate moved westward (accompanying the widening of the Atlantic Ocean), subduction of ocean crust and accretion of exotic terranes occurred along its ------- edge.
western
Following the terminal Cretaceous extinction, diversity of marine and terrestrial organisms increased sharply, and rose to present levels. A slight drop in diversity in the Paleogene, shown in the graph above, marks an extinction event at the Eocene-Oligocene boundary, which was associated with dramatic --------- -------. Many species of marine molluscs, foraminifera, and ostracodes were affected. Marine organisms were affected more severely by the extinction than were terrestrial organisms.
worldwide cooling
Cenozoic Events Basin and Range Province
The Basin and Range Province occupies a broad area in Nevada and western Utah, extending southward into Mexico. The province is dominated by up-faulted mountain ranges and down-faulted basins.
Dominant invertebrates of the Cenozoic include:
Sponges Scleractinian corals - modern reef corals (Phylum Cnidaria) Bryozoans Brachiopods (both articulates and inarticulates) Molluscs Bivalves Gastropods Cephalopods Arthropods Crustaceans Insects (on land) Echinoderms Starfish Echinoids (sea urchins sand dollars, and sea biscuits)
Rocky Mountains and High Plains During the Paleogene
Structural features of the Cordillera were created by Late Cretaceous and Paleogene deformation. Sediments eroded from the mountains were trapped in low areas between the mountains, or intermontane basins. Sediment from erosion of Rockies was spread over the plains to the east. Oligocene through Pliocene sands, shales, and lignites were deposited on western high plains. Beds of volcanic ash are interlayered with these sediments, indicating volcanic activity, and providing radiometric dates for correlation. Paleocene Fort Union Formation contains gray sandstones and siltstones, carbonaceous shales, lignites, and low sulfur coals, deposited in swamps in the intermontane basins. These coals are used for electricity generation and produce very little pollution. Eocene Green River Formation is a lake deposit with fossil fish, insects, plants, varves, laminated oil shale, and limestone. White River Formation contains well-preserved skeletons of Oligocene mammals. Also makes up the Badlands of South Dakota. Well preserved fossil insects and leaves are found at Florissant Fossil Beds National Monument in Colorado. They were buried when Oligocene volcanic ash settled into a lake. Large petrified stumps of sequoia trees are also present. Fluvial and lacustrine sedimentation continued in intermontane basins and on plains to east into the Miocene epoch. Climates had cooled by Miocene time. As the climate cooled, the grasslands expanded and were populated by Miocene camels, horses, rhinos, deer, and other grazing mammals. Volcanic activity occurred during the Miocene in the central and southern Rockies. Gold deposits at Cripple Creek, Colorado formed in association with a Miocene volcano. Regional uplift of Rockies began in Miocene. Increased erosion rates. Sediment spread eastward, helping to build the Great Plains. Fossils in Pliocene sediments indicate cooler and drier conditions. Normal faulting and volcanism accompanied Cenozoic uplifts and produced spectacular scenery.
Humans, Homo sapiens
meaning "thinking man" or "intelligent human", appeared during the latter part of the Cenozoic Era, in the Pleistocene Epoch. Homo sapiens share many characteristics with the other members of the Order Primates, including basic body structure and biochemistry, but humans are quite distinct from the other primates in many important ways, as follows: Larger, more complex brain Stand and walk erect as result of structural modifications to vertebral column, legs and pelvis Flatter face Teeth less robust Greater manual dexterity, leading to ability to manufacture and use sophisticated tools Greater intelligence, leading to language and culture
Interestingly, several large --------- impacts occurred in the late Eocene (Chesapeake Bay area and Siberia), but they had no obvious effect on life, and appear to have caused no extinctions of significance.
meteorite
Cenozoic rocks contain what?
modern types of plants and animals, more advanced than those in the Paleozoic and Mesozoic.
Snakes of the Cenozoic
modified from lizards by the loss of limbs, the change of the skull to become more flexible to engulf prey, and there are more vertebrae and ribs. Some primitive snakes retain vestigal rear limb and pelvic bones, attesting to their tetrapod ancestry. Snakes began to diversify during the Miocene. Poisonous snakes evolved with specialized teeth for injecting venom into their prey. The diversification of snakes may be linked to the diversification of mammals, which serve as their prey.
Eastern and Southeastern North America During the Paleogene
Cross-section of Cenozoic sedimentary deposits in the mid-Atlantic region. Note the seaward thickening of sediments. Carbonate sediments accumulated in Florida where less terrigenous clastic sediment was available. Eight marine transgressions and regressions are recorded in Cenozoic sediments on the Atlantic and Gulf Coastal Plains. On the Gulf Coastal Plain, transgressions brought Gulf of Mexico waters inland as far as southern Illinois. During regressions, deltaic sands were deposited over offshore shales. These sediments provided ideal conditions for formation and entrapment of oil and gas in the Gulf of Mexico region. Much of the oil was trapped around salt domes. A clastic wedge of sediments thickens seaward in the Gulf of Mexico region. Paleogene sediments in the Gulf of Mexico region appear to be more than 10,000 m thick. The Gulf of Mexico region has been subsiding rapidly.
Most of these large land mammals began to become extinct around 8000 years ago. Why? There are two hypotheses.
Human hunting and predation Climate change associated with global warming at the end of the last Ice Age.
Little Ice Age and Humans
Human-induced warming may be the reason for the end of the Little Ice Age. Greenhouse gases associated with the Industrial Revolution are the major factor influencing global warming and climate change today.
The meanings of the root words for the epochs of the Cenozoic are in the table below. They refer to the proportions of fossil species that are still alive. Pleist = Pleion = Meion = Oligos = Eos = Paleo =
Pleist = most Pleion = more Meion = less Oligos = few Eos = dawn Paleo = ancient
Most extensive glaciation began when?
1 million years ago
Cenozoic Era
65.5 million years ago to the present.
Antartica and Australia split
Before Antarctica separated from Australia, it was warmed by currents moving southward from more equatorial latitudes. After Australia separated from Antarctica, circumpolar currents developed around Antarctica, cutting it off from equatorial currents. This resulted in temperature decrease and culminated in glacial conditions over Antarctica. Australia began to drift northward and separate from Antarctica in the early Eocene, about 55 m.y. ago. Eocene paleogeography compared with the world today. Note that in the Eocene, Antarctica and Australia were still connected. After they separated, circumpolar currents developed which led to cooling. Highlights on globes show areas of major tectonic changes.
Changes during the Cenozoic
Biologic changes in the Cenozoic can be tied to changes in the environment and geographic change. Changes in climate to cooler and dried conditions, led to the expansion of the grasslands, which influenced the evolution of herbivorous mammals. Continental breakup as a result of plate tectonics, stimulated biological diversity. This resulted in distinct faunal radiations on separate landmasses, and in isolated marine basins.
Birds of the Cenozoic
Bird fossils are rarely preserved, so the Cenozoic fossil record of birds is rather poor. Characteristics of birds include: Lightweight skeleton with thin and hollow bones More neck vertebrae than most other animals (13 to 25) Jaws form a toothless horny beak Keeled breastbone or sternum for attachment of the large flight muscles leading from the breast to the wing Fused collarbone (wishbone) Pelvic girdle and vertebrae are fused together to provide rigidity during flight Fusion of bones of the "hand" to help support the wing Four-chambered heart Constant body temperature Birds have undergone extraordinary adaptive radiation to produce songbirds, forest birds, seagoing birds, wading birds, flightless aquatic birds, and flightless land birds.
Amphibians of the Cenozoic
Cenozoic amphibians resembled modern forms. All are relatively small with smooth skin (unlike the large Paleozoic amphibians). Cenozoic amphibians include: Frogs Toads Salamanders
What have recurred periodically into the Holocene?The period between 1540 and 1890 is known as the "Little Ice Age", when temperatures were several degrees cooler than today. Cold conditions resulted in loss of harvests, famine, food riots, and warfare in Europe. Cold conditions generally correlate with periods of low sunspot activity. The period of 1645 to 1715, in the heart of the Little Ice Age, had extremely low sunspot activity, and some years having no sunspots at all. This period of low sunspot activity is known as the Maunder Minimum.
Cold spells
Most dramatic Cenozoic tectonic event =
Collision of Africa and India with Eurasia, forming the Alps and Himalayas. Tethys Sea deposits were deformed into mountain ranges.
The New West Coast Tectonics
During most of the Cenozoic, subduction continued along the west coast. The Farallon plate was almost completely subducted under North America. Only the small Juan de Fuca plate remains as a corner of the once much larger Farallon plate. In addition, part of the East Pacific rise spreading center was also subducted under North America. Once the Pacific plate came into contact with the North American plate, the direction of movement changed. Instead of being subducted, the Pacific plate slid laterally along the edge of the North American plate. This formed the San Andreas fault with its strike-slip motion, and ended subduction in this area.
WHen did angiosperms appear?
During the Cretaceous
Marine Phytoplankton
Entire families of phytoplankton became extinct at the end of the Mesozoic Era. Only a few species in each major group survived into the Cenozoic Era. Surviving species of phytoplankton diversified rapidly in the Paleogene due to decreased competition. Cenozoic phytoplankton include: Diatoms Dinoflagellates Coccolithophorids
Volcanoes of the Cascade Range include:
Mt. St. Helens - erupted in 1980 and 2004 Mt. Rainier - major eruption about 2000 years ago, and minor eruptions in 1800's. It is considered to be the most dangerous volcano in the range. Mt. Adams Mt. Hood Mt. Jefferson Mt. Lassen - erupted in 1914 and 1915 Mt. Shasta Crater Lake, Oregon formed from the eruption and collapse of Mt. Mazama in the Cascade Range about 6000 years ago.
This dramatic worldwide cooling resulted in:
First Cenozoic widespread growth of glaciers in Antarctica about 38-22 m.y. ago, although the ice cap did not form until the middle Miocene about 11-14 m.y. ago. Global drop in sea level by about 50 m in the Early Oligocene as glaciers formed. Cold, dense polar water flowing across ocean bottom. Decrease in diversity and extinction of many marine mollusc species. Decrease in diversity and extinction of many planktonic and benthonic foraminifera and ostracodes. Extinctions were earlier and more severe at higher latitudes. Reefs shifted toward the equator. Calcarous biogenic deep sea sediments (foraminiferal ooze) shifted toward the equator and were replaced by siliceous biogenic sediments (diatom and/or radiolarian ooze) at higher latitudes. Upwelling of cold bottom waters, which affected world climate. Changes in pollen indicate long term cooling and drying. As a result: Temperate and tropical forests shifted toward lower latitudes. Grasslands expanded. Rainforests became confined to tropical, equatorial areas.
Cenozoic vertebrates include:
Fishes Amphibians Reptiles Birds Mammals
Bats
Flying mammals, the bats evolved during the Cenozoic; their teeth have been discovered in Paleocene strata. The wings are developed on elongated fingerbones.
Land Bridges effect on animals
For a while, the animals flourished in their new locations. Eventually, the marsupials began to decline, and all of the hoofed marsupials became extinct. Ground sloths and glyptodonts also became extinct. The land bridge caused many species of South American marsupial mammals to go extinct, because of migrants from the north. Other land bridges also existed. The Bering land bridge existed between North America and Eurasia during the Pleistocene (now occupied by the Bering Sea). Camels, horses, mammoths, and a wide variety of other land mammals migrated across the Bering land bridge during the Pleistocene. The land bridge was also used by early humans to enter North America at least 14,000 years ago.
Evidence of glacial conditions
Glacial till - unsorted mixture of clay- to boulder-sized particles. The amount of weathering of glacial deposits or soils, and the amount of dissection by streams may help with relative dating. Bedrock with glacial striations Stratified drift - glacial deposits which have been washed and sorted by meltwater Varved clays - seasonal laminations deposited in glacial lakes. Counting varves may reveal the number of years during which they clay was deposited. Plant remains Pollen grains - types of plants indicate climate
Insectivores
Insect-eating mammals such as the moles.
Foraminifera in the Cenozoic
Large benthic foraminifera resembling coins in size and shape, called nummulitic foraminifera, lived in the Tethys seaway and other areas. Their remains accumulated to form thick beds of nummulitic limestone, which were used to build the Great Pyramids and Sphinx in Egypt. Foraminifera are useful in correlating rocks of Cenozoic age, particularly in oil fields around the world. Benthonic forams can be used as water depth indicators.
Cenozoic Vertebrates Mammals
Mammals dominated the Cenozoic, much as the dinosaurs dominated the Mesozoic. Mammals have the following characteristics: Warm-blooded Hair (insulating body cover) Mammary glands Differentiated teeth (incisors, canines, molars) Jaw bone is a single bone on either side (reptiles and birds have several bones in their jaw) Ear bone structure (3 ossicles; incus and malleus were derived from bones of the reptilian jaw) Presence of 7 vertebrae in neck of most mammals (including giraffes). The only exceptions are the manatee and the sloth, animals with exceptionally low metabolic rates. Large braincase compared to other vertebrates Secondary palate separating mouth cavity from nasal passages, allowing simultaneous breathing and feeding (needed for infants to nurse)
More on mammals in the Cenozoic
Mammals originated from an advanced group of synapsids called therapsids (sometimes called mammal-like reptiles) that lived in the Permian and Triassic. Both mammals and dinosaurs appeared about the same time, in the Late Triassic. After the extinction of the dinosaurs, mammals expanded into habitats vacated by the dinosaurs, as well as additional ones. The first mammals were small. Since small animals lose heat rapidly, the insulation of hair would have been beneficial to survival. Mammary glands are modified sweat glands. If the young were kept warm by snuggling up to the female, the young may have been nourished by secretions from glands that preceded the development of true mammary glands. Fossils provide few clues. Tooth patterns indicate that the earliest mammals ate insects. Evidence from their braincases indicates that the senses of smell and hearing were well developed, suggesting that they were nocturnal.
Proboscidians
Mammals with a proboscis or trunk, including elephants and the extinct mastodons and wooly mammoths.
Ungulates
Mammals with hoofs, including horses, cattle, sheep, goats, deer, antelopes, camels, tapirs, rhinos, and other animals. This group also includes the descendants of mammals with hoofs, including whales, manatees and dugongs, elephants and other animals with trunks (called proboscideans), such as the extinct mastodons and wooly mammoths.
Marsupials
Mammals with pouches in which they keep their young
Stratigraphy of Pleistocene Deposits
Pleistocene deposits are difficult to date and correlate. Pleistocene sedimentary deposits, however, may show evidence of fluctuating climatic conditions, which can be used to mark times of glacial advance and retreat.
A sea level drop in the ------- associated with glaciation, resulted in the isolation of the Mediterranean basin. Deep canyons were cut by rivers feeding the Mediterranean, and the sea ultimately dried up producing thick (1000-2000 m) evaporite deposits, 5-6 m.y. ago.
Miocene
Important continental breakups:
North Atlantic rift separated Greenland from Scandinavia, and severed the land connection between Europe and North America. Australia separated from Antarctica by the Oligocene, about 30 m.y. ago. Circumpolar currents isolated Antarctica from warmer waters. Led to cooling of Antarctica. Cold, dense ocean waters around Antarctica drifted northward along ocean floor, contributing to global cooling and eventually the Ice Age. Rifting occurred between Africa and Arabia, associated with a branch of the Indian Ocean. This formed the Red Sea and the Gulf of Aden. Continental interiors were well above sea level and not flooded by epicontinental seas during the Cenozoic. Marine transgressions were limited. Overall cooling trend during the Cenozoic. Tropical and subtropical plants were replaced by temperate plants, such as grasses. Tropical plants retreated toward the equator.
Position of the continents during the Eocene, about 50 million years ago.
Note that Antarctica and Australia are still connected. India has not yet collided with Asia. North and South America are not yet connected. South America is connected or nearly connected with Antarctica.
Tectonic and Paleographic Changes and Their Effects on Climate
Orogenic and volcanic activity were intense along the western edge of the North and South American plates, and caused the formation of the Isthmus of Panama, a land bridge linking North and South America. This land bridge blocked the westward flow of the North Atlantic Current. The current was deflected to the north (turning to the right, as a result of the Coriolis Effect), and formed the Gulf Stream. The Gulf Stream transported warm water northward and resulted in bringing warmer climates to northwestern Europe. (It also supplied warm, moist air toward the North Pole, which would ultimately result in precipitation which helped build the glacial ice sheets.) The land bridge between North and South America provided a path for plant, animal, and human migration between the Americas. Several major tectonic changes occurred. The changes involving Antarctica affected climate.
The Paleogene Period is divided into what three epochs?
Paleocene, Eocene, and Oligocene.
Nomadic Tribes during the Pleistocene
Parts of northern and eastern Africa that are currently arid, had abundant water, were fertile and populated by nomadic tribes. Nomadic tribes hunted along the edges of the continental glaciers. Wild game was abundant, furs provided warm clothing, and there was less problem with spoiled meat in the cold temperatures.
Placentals
Placental mammals appeared during the Cretaceous as small insect eaters.
The cyclic climatic changes result from changes in the distance and angular relationships between the Earth and Sun due to periodic fluctuations in Earth's orbit.
Precession - Earth's axis wobbles or moves in a circle like a spinning top over 26,000 years, affecting the amount of solar radiation received at the poles. Orbital eccentricity - Earth's orbit around the Sun changes from more circular to more elliptical by about 2% over about 100,000 years, moving the Earth closer to or farther from the Sun, and varying the amount of solar radiation received by the Earth. Angle of tilt of the Earth's axis - currently about 23.5o, this tilt angle causes the seasons. Tilt angle varies from about 21.5o - 24.5o over about 41,000 years, changing length of days and amount of solar radiation received at the poles.
Order Primates
Primates are a group of placental mammals. They have five digits, which is a primitive, non-specialized characteristic. They have not developed hoofs, horns, antlers, or trunks, unlike some other groups of placental mammals, and so they remain structurally generalized compared with other mammalian groups.
Primates
Prosimians (lemurs and tarsiers), monkeys, apes, and humans.
Rabbits
Rabbits are not rodents. Their teeth are similar, but the rabbits have two upper pairs of incisors, and one lower pair. The tail is reduced and the hindlegs are strengthened for hopping.
Oxygen isotope ratios in shells of foraminifera from cores can be used to determine the volume of water stored in glacial ice
Ratio of oxygen-18 to oxygen-16 The atomic number of oxygen is 8. This means that oxygen has 8 protons. The numbers 16 and 18 refer to the atomic mass, which is the sum total of the protons plus the neutrons in the oxygen atom. Since oxygen has 8 protons, then: Oxygen-16 has 8 neutrons, and Oxygen-18 has 10 neutrons. An atom of oxygen with 10 neutrons is heaver than an atom of oxygen with 8 neutrons. Oxygen is an integral part of water (H2O). Oxygen is also present in certain minerals, such as calcite or aragonite (CaCO3), which make up the shells of foraminifera. The ratio of oxygen-18 to oxygen-16 in the water (and also in the shells that form in that water) depends on the temperature. Lighter oxygen isotopes (oxygen-16) accumulate in glacial ICE. The reason for this is that during evaporation, lighter isotopes are concentrated in the water vapor in the air. Water with light-weight oxygen (oxygen-16) is easier to evaporate than water with heavier oxygen (oxygen-18).The water moves through the hydrologic cycle (water cycle) and later falls as rain or SNOW. The snow accumulates to form glaciers under certain conditions. As a result, the oxygen-16 becomes trapped in glacial ice. Oxygen-18 remains in the oceans, because water with O-18 did not evaporate as readily. Hence, as temperatures drop, air becomes drier, and the percentage of oxygen-18 in seawater (and in foram shells) INCREASES. Foram shells rich in O-18 = COLD & DRY. Glacial conditions. Foram shells richer in O-16 = WARM & WET. Interglacial conditions.
Colorado Plateau Uplift
The Colorado Plateau is centered in the four-corners region where Utah, Colorado, Arizona and New Mexico meet. The rocks in this area are relatively flat-lying. The rocks were not deformed during the Mesozoic orogenies. The Colorado Plateau has been subject to uplift and erosion. Uplift occurred during the Pliocene. Faults formed locally, providing conduits for volcanic rocks. Example: San Francisco Peaks near Flagstaff, Arizona. The best-known feature in the Colorado Plateau is the Grand Canyon, eroded by the Colorado River to a depth of more than 1.6 miles. The river has eroded through Phanerozoic strata and into the Precambrian basement rocks.
Columbia Plateau and Cascade Range Volcanism
The Columbia Plateau is named for the Columbia River, which forms the boundary between Washington and Oregon.
The Pleistocene Ice Age
The Pleistocene is significant as the time in which humans evolved. During the Pleistocene Ice Age, more than 40 million cubic kilometers of snow and ice covered about a third of the Earth's land area. Continental glaciers covered much of North America and Europe. Alpine glaciers also covered parts of the Cordilleran Mountain range in western North America, and the Alps and other mountain ranges of Europe.
Sierra Nevada and California
The Sierra Nevada mountains lie to the south of the Cascade Range. The mountains belong to a large granite body called the Sierra Nevada batholith. The batholith formed as the Farallon plate was being subducted under the western edge of the North American continental plate during the Mesozoic. Erosion during the Paleogene removed the overlying rocks and caused the granite batholith to be exposed at the surface. During the Pliocene and Pleistocene, the Sierra Nevada batholith was raised up along normal faults to a height of 4000 m (more than 2 miles) above the California trough to the west. Streams and glaciers carved the landscape we see today. In the Paleogene, the region west of the Sierra Nevada was affected by subduction, but in the Miocene, it changed to strike-slip movement. Fault movements created islands and sedimentary basins. Marine clastic sediments, diatomites, and bedded cherts were deposited in the basins. Folding and uplift led to regression.
Reptiles of the Ceozoic
The beginning of the Cenozoic was marked by the absence of the large reptiles that had existed in the Mesozoic. Gone were the dinosaurs, large marine reptiles and flying reptiles. Surviving reptiles included the following: Turtles Crocodilians Lizards Snakes The tuatara, the only surviving rhynchocephalian, which resembles a large lizard, and is found on islands near New Zealand. The turtle lineage dates back to the Late Permian. Turtles have no teeth. Their jaws are covered by a beak that is used to slice through plants or animal flesh.
Fishes of the Cenozoic
The bony fishes or teleost fishes thrived during the Cenozoic in marine and freshwater environments. Sharks were also common in the Cenozoic. Sharks have skeletons of cartilage rather than of bone, and hence the skeletons are rarely preserved. The teeth of the sharks are well preserved in Cenozoic sedimentary rocks.
Antartica waters
The cold waters around Antarctica were dense, and sank to the ocean floor around Antarctica. (Cold water is denser than warmer water.) These cold, dense ocean-floor waters moved northward (downward and outward) away from Antarctica. The northward movement of cold dense waters contributed to cool conditions during the late Eocene and early Oligocene, and ultimately led to the Pleistocene Ice Age.
Invertebrates of the Cenozoic
The invertebrate faunas of the Cenozoic have a modern appearance. Once-successful groups of invertebrates such as the ammonites and rudist bivalves went extinct at the end of the Cretaceous. No new major invertebrate groups appeared in the Cenozoic.
Magnetic stratigraphy
The record of magnetic reversals in cores of deep sea sediments can be correlated to magnetic reversals documented in volcanic rocks. The volcanic rocks can be dated radiometrically, and the dates can be applied to the sediments with the same magnetic characteristics.
The Basin and Range formed as follows:
The region was up-arched in the Mesozoic Era. Subsidence occurred along normal faults beginning in the Miocene. Upfaulted crustal blocks formed linear mountains that shed sediment into the adjacent down-dropped basins. Faults opened conduits for igneous rock, producing lava flows and volcanism. Erosion followed the volcanism. Sediments eroded from the mountains filled the down-faulted basins, clogged rivers, and caused closed-basin (no outlet) lakes to form. Evaporite minerals (gypsum and salt) were deposited as the lakes evaporated.
Changes in animals due to grasslands
The resistant enamel of the chewing teeth became infolded. As the teeth wore down, a complex pattern of enamel ridges became apparent on the grinding surface of the teeth. The incisors (front teeth) gradually aligned into a curved arc, which served for biting the grasses. The length of the face in front of the eyes increased in the grazing mammals to provide space for these teeth (for example, in the horses). The digestive system of the grazing mammals also evolved for life in the grasslands. A four-chambered stomach evolved, which served as an improved mechanism for digesting tough grasses. The limbs of the grazing mammals also changed to become better adapted to life on the grasslands. Because grasslands provide few places to hide from predators, the grazing herbivores developed modifications that permitted them to run more quickly. The bones of the limbs and feet were lengthened, strengthened, and modified by natural selection to permit rapid fore-and-aft motion, and to prevent rotation. The ankle was elevated, and the grazing mammals ran on their toes like sprinters. Many grazing mammals gradually developed hoofs as an adaptation to protect the bones of the toes as they ran across the hard prairie sod. Mammals with hoofs are called ungulates. These grazing mammals also lost some of their side toes.
Rodents
The rodents probably outnumber all other mammals; they have adapted to a remarkable range of habitats. This group includes partially aquatic mammals such as the beaver and muskrat, desert-dwelling jerboas and kangaroo rats, and tree-dwelling mammals such as the squirrel. Others are the hamsters, gerbils, guinea pigs and chipmunks. The rodents have teeth specialized for gnawing and nibbling. They lack canine teeth and have two upper and two lower pairs of prominent, continuously-growing incisors.
Cenozoic Migrations
The southern continents (South America, Australia, and Antarctica) were separated from North America and Eurasia during most of the Cenozoic. As a result, distinctive assemblages of mammals developed on the southern continents, showing convergent evolution with northern hemisphere species. The development of the Panamanian land bridge about 3 million years ago (during the Late Pliocene) led to the migration of mammals between North and South America.
Cenozoic Paleoclimates Global Surface Cooling
There was a 10o C (18o F) temperature drop at end of Cretaceous Period. Several warming trends occurred in the late Paleocene and Eocene, as indicated by: Fossils of palm trees and crocodiles in Minnesota, Germany, and near London. Fossils of trees from temperate zones in Alaska, Norway and Greenland. Coral reefs in latitudes 10-20o closer to the poles than their present habitat. The climate was semitropical and mild in Antarctica during the Paleogene, despite the fact that it sat on the South Pole. The evidence for a mild climate includes Paleogene fossil spores and pollen.
Why Did Earth's Surface Cool?
There was both a long-term decline in temperatures, as well as an oscillation of glacial and interglacial stages. Any hypothesis for the cooling must consider both of these factors. A widely accepted hypothesis for the temperature fluctuations is related to Earth's orbital oscillations. This hypothesis was developed by Yugoslavian mathemetician Milutin Milankovitch, and it is referred to as the Milankovitch cycles.
Odd-toed ungulates - Also called perissodactyls.
These ungulates have an odd number of toes (either 1 or 3 toes) on each foot. Reduction of lateral toes. Includes modern horses, rhinos, and tapirs, as well as extinct chalicotheres, brontotheres, and other groups. The modern horse is an odd-toed ungulate that evolved from small (about 40 cm tall) Eocene browsing horses with 4 toes on the front feet and 3 toes on the rear feet. The horse changed from a small animal with a short skull and low-crowned teeth to a larger animal with fewer toes, longer skull, larger brain, and complexly-ridged high-crowned teeth for chewing grasses.
Cetaceans
This group includes mammals that have adapted fully to life in the sea, such as the whales, porpoises, and dolphins. They are descended from hoof-bearing land dwellers related to the hippo.
Edentates
Toothless mammals. This group includes the living armadillos, tree sloths, and South American anteaters. Extinct fossil edentates include the glyptodonts and giant ground sloths.
Even-toed ungulates - Also called artiodactyls.
Ungulates or hoofed mammals with an even number of toes (2 or 4 toes) on each foot. Those with two toes are said to have cloven hoofs. The even-toed ungulates include cattle, pigs, deer, hippos, goats, sheep, camels, llamas, giraffes, and antelope. This group of animals is important to humans because it provides meat, milk, and wool.
What era do we know the most about?
We know more about the life of the Cenozoic Era than we know about life of any other time. This is because the fossils are better preserved and have had less time to be destroyed, they are stratigraphically uppermost, and more accessible for study. In addition, Cenozoic fossils more closely resemble life today.
Marine Zooplankton
Zooplankton diversified in the Cenozoic, and became abundant in the seas. Cenozoic zooplankton include: Benthonic and planktonic foraminifera
Diatryma
a large flightless bird from the Eocene of North America, was about 2 m tall and weighted about 300 pounds. It had massive legs, clawed feet, and a huge beak, suggesting that it was a predator. Others interpret it as a scavenger or browsing herbivore.
A spectacular -------- -------- of mammals near the beginning of the Cenozoic resulted in the appearance of mammals as diverse as bats and whales, descending from shrew-like mammalian ancestors in as little as 12 million years.
adaptive radiation
Crocodilians
began their evolution during the Triassic, and coexisted with the dinosaurs. Modern crocodilians include the alligator (with a broad snout), the crocodile (with a narrow snout), and the gavial (with a very narrow snout).
Grasses, a flowering plant commonly eaten by grazing mammals, became widespread when?
during the Miocene. The expansion of the grasslands across the plains of North America and other continents was related to cooling and drying of the global climate. Mammals evolved in conjunction with the spread of the grasslands. Many grasses contain siliceous secretions, and because they grow close to the ground, grasses are often coated with fine particles of soil. As a result, grasses are abrasive to the teeth of grazing mammals. To compensate for the tooth abrasion resulting from chewing grasses, the major groups of herbivorous mammals evolved high-crowned cheek teeth that continue to grow at the roots during part of the animals' lives.
Ridges and valleys of the Appalachian Mountains were carved by what?
erosion. As erosion proceeded, gentle isostatic uplift occurred. This stimulated more erosion, as streams cut downward. Uplift in the eroding Appalachians was coupled with downward tilting and deposition of sediments on the Atlantic Coastal Plain and continental shelf. Sediments thicken seaward forming a clastic wedge.
The appearance and evolution of primates led to the ancestors of what?
humans by the Neogene. Homo sapiens appeared in the Pleistocene Epoch.