INTRODUCTION TO LIFE OF THE CENOZOIC ERA

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1 BACKGROUND INTRODUCTION TO LIFE OF THE CENOZOIC ERA This set contains 16 specimens of Cenozoic fossils selected to show representative fossil forms collected from rocks of Tertiary and Quaternary ages. The fossils in this set provide a broad overview of the paleontological record in the rocks from each period of the Cenozoic Era. Fossil (fos -sil): Any remains, trace, or imprint of a plant or animal that has been naturally preserved in the Earth s crust since some past geologic time; any evidence of past life. Geologic column: A composite diagram that depicts in a single column the subdivisions of part or all of geologic time or the sequence of stratigraphic units of a given locality or region. The oldest rock units appear at the bottom and the youngest at the top. Each unit is arranged vertically to indicate their relative positions to each other and to the subdivisions of geologic time. e The accompanying activities effectively cover the basic concepts necessary for the student to identify and understand certain typical Cenozoic fossils. THE GEOLOGIC TIME SCALE In order to understand the significance of fossils and their role in geologic history, we must have some knowledge of geologic time. An understanding of the geologic time scale and the geologic column is important for the earth scientist who must be able to associate fossils, and the rocks that contain them, with specific chapters in earth history. The earth scientist, like the social scientist dealing with the development of civilization, must have some method of relating important events to one another. Consequently, earth scientists have developed a special time scale consisting of major divisions and subdivisions of geologic time. These divisions are arranged in sequence on a time scale in the order of their age. Therefore, a geologist might speak of an animal that lived during the Cenozoic Era in much the same manner that a historian might speak of a general who served during the Civil War. Each of these terms gives us an idea as to when an animal lived or a general served, but in terms of relative time rather than in a specific dated time. The geologic time scale is a geologic calendar consisting of named units of time during which various rock strata were formed. Geologists use these time units to date geologic events that took place in the past. The largest time units are eras. The eras are divided into periods, and these may be further subdivided into smaller time units called epochs. When arranged in their proper historical sequence, these time units provide a standard by which the age of rocks can be discussed. Thus, the geologic time scale might be roughly compared to the calendar in which the year is divided into months, months into weeks, and weeks into days. Unlike years, however, geologic time units are somewhat arbitrary in length and of differing duration. The geologist cannot be positive about the exact length of time spanned by each unit. The time scale does, however, provide an internationally recognized standard by which we can discuss the ages of rocks and their incorporated fossils. Geologic time has been divided into six eras. Each has been given a name of Greek derivation that is descriptive of the sequential position of that era on the geologic time scale. 1

2 1. Cenozoic (SEE-no-zo-ic) recent-life - from present to 65 million years ago. 2. Mesozoic (MES-o-zo-ic) middle-life from 65 million to 248 million years ago. 3. Paleozoic (PAY-lee-o-zo-ic) ancient-life from 248 million to 544 million years ago. 4. Proterozoic (PRO-ter-o-zo-ic) fore-life from 544 million to 2.5 billion years ago. 5. Archaean (ar-kay-en) beginning-life from 2.5 billion to 3.8 billion years ago. 6. Hadean (HAD-e-an) from 3.8 billion to 4.5 billion years ago. GEOLOGIC TIME SCALE ERA PERIOD/(EPOCH) MILLIONS OF YEARS BEFORE PRESENT Cenozoic Quaternary (Holocene Epoch) (Pleistocene Epoch) Tertiary (Pliocene Epoch) (Miocene Epoch) (Oligocene Epoch) (Eocene Epoch) (Paleocene Epoch) 1.8 to present.008 to present 1.8 to to to to to to to 55.5 If you were to begin counting at the rate of one number per second and continued nonstop for 24 hours a day, 7 days a week, it would take nearly 150 years to count to 4.5 billion! Mesozoic Cretaceous Jurassic Triassic 145 to to to 213 Paleozoic Permian Pennsylvanian Mississippian Devonian Silurian Ordovician Cambrian 286 to to to to to to to 505 Proterozoic Vendian 2,500 to to 650 Archaean 3,800 to 2,500 Hadean Time 4,500 to 3, WARD S Natural Science Establishment, Inc. All Rights Reserved

3 The Law of Superposition was first derived and used by Nicholas Steno, a 17th century Italian physician and naturalist who later became a theologian. From his geological studies in northern Italy, Steno observed that in an undisturbed sequence of sedimentary rocks, the topmost layer is always the youngest, and the bottommost layer is always the oldest. The earliest era is at the bottom of the scale. Customarily, the geologic time scale is read from the bottom of the chart upward. Placing the earliest era at the bottom of the time scale, with successively younger eras above it, allows the time scale to be compared directly with the rock record (in which, according to the Law of Superposition, the oldest rock is at the bottom, with successively younger rocks above). As mentioned before, each era has been divided into periods. Most of these periods derive their names from the regions in which the rocks of each were first studied. For example the Pennsylvanian rocks of North America were first studied in the State of Pennsylvania. The Cenozoic Era has been divided into two periods of geologic time. With the earliest at the bottom of the list, these periods and the sources of their names are: 1. Quaternary (kwah-tur-nuh-ri) meaning fourth derivation; from present day to 1.8 million years ago. 2. Tertiary (TUR-shi-ri) meaning third derivation; from 1.8 to 65 million years ago. The Cenozoic periods derived their names from an old European system of classification, which divided all of the earth s rocks into four groups, according to supposed age. (The Primary and Secondary Periods have been replaced by era names.) The Tertiary Period has been divided into five smaller divisions of time known as epochs. The Quaternary Period has been divided into two epochs. These epochs, a guide to their pronunciation, and an explanation of their names is listed below: The Precambrian time (Proterozoic, Archaean, and Hadean) accounts for nearly 88% of earth history, and yet is the least understood span of geologic time. Surface outcrops of Precambrian rocks are relatively rare and consist largely of deformed metamorphic rocks devoid of fossils. Some early life existed during the Precambrian, but consisted mainly of primitive soft bodied forms not easily fossilized. 1. Quaternary Period: a. Holocene (HO-low-seen) or Recent the latest time division; from 8,000 years ago to the present time. b. Pleistocene (PLICE-toe-seen) most recent ; from 8,000 to 1.8 million years ago. 2. Tertiary Period: a. Pliocene (PLY-o-seen) more recent ; from 1.8 to 5.3 million years ago. b. Miocene (MY-o-seen) less recent ; from 5.3 to 23.8 million years ago. c. Oligocene (OLL-I-go-seen) little recent ; from 23.8 to 33.7 million years ago. d. Eocene (EE-o-seen) dawn of recent ; from 33.7 to 55.5 million years ago. e. Paleocene (PAY-lee-o-seen) ancient recent ; from 55.5 to 65 million years ago. The above epochs are based on the relationships between the life forms of those times and the present forms of life. 3

4 THE GEOLOGIC COLUMN Unlike the geologic time scale, which consists of units of time, the geologic column is composed of the total succession of rocks, from the oldest to the most recent, in a given area. Thus, the geologic column of Texas, California, or New York consists of all rock divisions known to be present in those states. By referring to the geologic column previously worked out for a given area, the geologist can determine what types of rocks he might expect to find there, and at what levels. In using the geologic column, geologists usually work with units of rock strata called formations. In geology, a formation is identified and established on the basis of distinctive physical and chemical characteristics of its rock, and sometimes its fossil content. Formations are usually given geographic names, which are combined with the type of rock that makes up the bulk of the formation. For example, the Beaumont Clay was named for Beaumont, Texas. Formations of this kind of clay found in other localities and of the same age as the clay near Beaumont, are also called Beaumont Clay. In the specimen identification list on the inside cover of the topic set box, you may note a number of geologic terms used in abbreviated form. They are: 1. Formation (Fm.) may consist of several layers called beds. 2. Group (Grp.) two or more formations. 3. Series (Ser.) two or more groups. Abbreviations for the kinds of rocks are: 1. Ls. limestone 2. Sh. shale 3. Ss. sandstone THE CENOZOIC ERA THE AGE OF MAMMALS A glance at the geologic time scale shows that we are now living in the Cenozoic Era. As its name suggests, the plants and animals of this era are characterized by the presence of large numbers of modern looking species. Although many types of present-day invertebrates appeared during the Cenozoic Era, the major biological event was the phenomenal expansion of the mammals. These warmblooded creatures were so numerous and diverse that the Cenozoic Era has been called the Age of Mammals. Mammals had remained small, rare, and inconspicuous until the extinction of the great reptiles at the end of the Mesozoic. With the dawn of a new era, mammals began to emerge and evolve into a host of types, many of which are still with us to this day. The fossil record indicates many great changes in the molluscan fauna of the Cenozoic. The subdivision of the Tertiary into several epochs was a convenient method of documenting, comparing, and evaluating these changes WARD S Natural Science Establishment, Inc. All Rights Reserved

Life of the Tertiary Period. Plants of the Tertiary closely resembled forms that are now living, and the forests must have had a decidedly modern appearance.

In addition to composing much of the limestone used to build the pyramids of Egypt, the discshaped foram (Nummulites) was also once regarded by the Greek historian, Herodotus, to be the remains of

Foraminifera had an essentially modern look from the beginning of the Cenozoic, but early in the era one group, the nummulites, developed several giant species, such as #139.

5 Life of the Tertiary Period. Plants of the Tertiary closely resembled forms that are now living, and the forests must have had a decidedly modern appearance. Hardwood trees, flowering plants, and grasses became common and probably encouraged the development of the various mammal populations. In addition to composing much of the limestone used to build the pyramids of Egypt, the discshaped foram (Nummulites) was also once regarded by the Greek historian, Herodotus, to be the remains of petrified lentils. Herodotus believed these fossils were the remnants of food that the Egyptians provided for their slaves. Foraminifera had an essentially modern look from the beginning of the Cenozoic, but early in the era one group, the nummulites, developed several giant species, such as #139. Some limestones are composed almost entirely of these large protozoans; the pyramids at Gizeh in Egypt were built of this kind of rock. Foraminiferal Limestone: Nummulites - Eocene Today, much of the ocean bottom is covered with sand and small bits of organic debris, along with the tests (shells) of foraminifera. Specimen #134 is typical of sea bottom sand throughout much of the Cenozoic. The hexacorals (#130), appearing in the Mesozoic, built great reefs in tropical waters all around the world. These massive reef structures provided protection for thousands of species of marine organisms. Mollusks especially clams (#145), oysters (#140), and snails (#131 and 135) were abundant in the sea. Specimen #144 is a trace fossil: clam borings in silicified wood. Gastropod: Vasum - Pliocene The ammonites that had been so numerous during the Mesozoic were now extinct; only a few species of shelled cephalopods, like the modern Nautilus, remained. True sharks appeared in Jurassic seas and spread rapidly worldwide. They were generally moderate in size, but began to grow and dominate the seas when many marine reptiles died out at the close of the Mesozoic. Many species, including the giant Carcharodon, had dozens or hundreds of serrate triangular teeth in their jaws. These teeth were shed over time and replaced by new ones. Many such shed teeth were preserved and fossilized in sea bottom sediments. Among the echinoderms, echinoids (#133) were prominent members of the shallow water marine community, as they are today. Many Cenozoic species are difficult to distinguish from living species. In certain Middle and Upper Cenozoic formations, shark teeth are extremely abundant, and most of them look like modern shark teeth (#141), except for mineral stains. Some giant sharks lived in the Eocene and Miocene Epochs, one species having teeth about 20 centimeters long. A notable development among marine vertebrates was the appearance of whales, at first of modest size and with well-developed, shark-like teeth. As they Shark Tooth: Carcharodon - Miocene 5

evolved, successively larger species appeared; the largest species exist in modern times (Holocene Epoch). Birds were common during Tertiary time and resembled many of our modern species.

6 evolved, successively larger species appeared; the largest species exist in modern times (Holocene Epoch). Birds were common during Tertiary time and resembled many of our modern species. Their fossils are always rare, however, for the fragile nature of their remains normally prevents fossilization. A few species of birds attained very great size; some lost the ability to fly. Unlike Mesozoic species, the Cenozoic birds had modern avian features hollow bones, beaks, and short tails. The extinction of the dinosaurs at the end of the Mesozoic was followed by the almost explosive development of the mammals in the Early Tertiary Period. Horses appeared very early in the Cenozoic and were about the size of a small dog. Through the Middle Cenozoic, several species of horses were larger and more modern looking in appearance. Certain Tertiary mammals were every bit as gigantic and bizarre as the reptilian hordes of the Mesozoic. There was, for example, the uintathere, a great six-horned, rhinoceros-like beast that weighed many tons and stood over two meters tall at the shoulder. Another giant mammal was the Brontotherium. Its elephant-like body and horned skull gave it a most grotesque appearance. Largest of all was the Baluchitherium, which stood 6 meters high at the shoulder. Also present were giant pigs and unusual early camels and deer. Brontotherium belonged to a group of rhinoceros-like mammals known as titanotheres. This 4-ton animal was a plant eater and had a brain no larger than a human fist. They pulled leaves from shrubs and low trees, but their teeth were not well suited for grinding coarse, gritty grasses. This inability to chew grass and their small brain size is the reason some scientists believe the titanotheres died out at the end of the early Oligocene epoch. Brontotherium jaw with molars Oligocene Changes in the earth s landscape and climate, brought about by tectonic activity at the close of the Mesozoic Era, also had an impact on the emergence of Cenozoic plant life. Land plants responded even more rapidly to these events than animals. Where Jurassic dinosaurs roamed among forests of ginkgos or cycads and flowering plants were rare, the Cenozoic saw an explosion of many new angiosperms and gymnosperms (#132). Many of these included modern flowering trees such as maples, oaks, willows, poplars, magnolias, and elms. Life of the Quaternary Period. The most recent chapter in earth history, this period has been divided into two smaller units of time called the Pleistocene and Holocene (or Recent) Epochs. Angiosperm (an -gi-o-sperm): A plant with true flowers, in which the seeds, resulting from double fertilization, are enclosed in an ovary, comprising the fruit. Such plants originated in the early Cretaceous or possibly before, and flourished during the Cenozoic. The Pleistocene Epoch was characterized by great continental glaciers that blanketed much of Canada and the northern United States, northern Europe and parts of Siberia. At one time during this great WARD S Natural Science Establishment, Inc. All Rights Reserved

Ice Age, approximately one-third of the earth s land surface was buried beneath glacial ice.

Just the opposite was true in the Paleozoic Era.

Much of the marine fauna of the Pleistocene is found in sands and gravels, largely beach deposits and terraces marking old shorelines, bordering the continents.

7 Ice Age, approximately one-third of the earth s land surface was buried beneath glacial ice. Comparing the bivalved animals, it is interesting to note that the pelecypods (#136 and #143) are very common in Pleistocene formations, and brachiopods (#137) are relatively rare. Just the opposite was true in the Paleozoic Era. Although fresh water and land snails (air breathers) appeared in the late Paleozoic, they increased in prominence through the Cenozoic (#142) and are flourishing today. Much of the marine fauna of the Pleistocene is found in sands and gravels, largely beach deposits and terraces marking old shorelines, bordering the continents. In all probability, the marine habitat along the shore is little changed since the Pleistocene; the species are essentially the same as those living today. Mastodon Teeth - Pleistocene Mammoth Tooth - Pleistocene PALEONTOLOGIST Paleontologists study fossils to learn more about the kinds of life and conditions that existed on earth in the geologic past. They use this information to better understand the nature and evolution of life on our planet, and also use fossil evidence to help locate deposits of strategically important resources, like oil, coal, and natural gas. During the Pleistocene, the colder temperatures of the middle latitudes had a profound effect on terrestrial life. Some forms which had been abundant during the Tertiary evidently could not adjust to the frigid glacial climate and, failing to adapt or migrate to warmer areas, they became extinct. But more hardy creatures such as the mastodon, woolly mammoth, musk ox, and woolly rhinoceros were adapted to the chilly climate and ranged far and wide along the edge of the ice sheet. Among other well-known Pleistocene mammals (#138) are the saber-toothed cat, giant dire wolf, huge ground sloths, and the thickshelled glyptodonts; large armadillo-like mammals which were almost the size of a small car. At the end of the Pleistocene Epoch, approximately 8,000 years ago, scores of species of these animals became Glyptodon - Pleistocene extinct. However, the major biological event of Pleistocene time was the appearance of humans. Although hominids (human-like animals) developed much earlier, the modern genus Homo probably appeared some 600,000 years ago. Considering the great age of the earth and how long life has been present on it, human beings are very new additions to the geologic scene. The most recent part of the Quaternary Period is the Holocene, or Recent Epoch. This, the latest chapter in earth s history, began a little over 8,000 years ago and continues through this very moment. Its beginning is generally considered to be marked by the disappearance of the most recent continental glacier in North America, Europe, and Asia. 7

Mesozoic Era 251 m.y.a 65.5 m.y.a

Mesozoic Era 251 m.y.a 65.5 m.y.a Mesozoic Cenozoic notes.notebook Mesozoic & Cenozoic 251 m.y.a Present at the end of the Permian, 90% of marine organisms and more than 70% of land organisms died. because resources and space were readily