Dear Professor Williams, Course evaluations will be closing soon. Here is the information for your current course evaluation: The evaluation closes on May 1, 2016 at 11:59pm. The current response rate is: 18% (3). GEOL Historical Geology (This evaluation link is only for the course listed above. It can only be accessed by students enrolled in the course.) You may view the details and progress of your evaluations by accessing the IASystem faculty portal located at To encourage students to participate, you can copy and paste the evaluation link provided above into an or on your course website. Please contact Eva Ruiz-DuVall at if you have questions about this course Thank you. Harry Williams, Historical Geology1

2 CENOZOIC LIFE The CENOZOIC = “The Age of Mammals". The original mammals evolved from reptiles. These small, insect eating, shrew-like creatures, had the advantage of being endothermic - they produced their own heat internally by consuming great amounts of food. This gave them the advantage of being active at night, when reptiles couldn't compete because of the cold. This enabled the mammals to become dominant at the end of the Mesozoic, when the climates got colder and many of the larger reptiles died out.

Harry Williams, Historical Geology3 Another mammalian feature related to heat was the development of body hair, to help conserve the heat generated internally. Unlike reptiles, mammals also NURTURE their young using milk. Again, this helped to keep the young warm and ensured rapid growth in the vulnerable early stages of life. So, mammals had good survival skills.

Harry Williams, Historical Geology4 Animals that are transitional between the reptiles and true mammals are still around today - the duck-billed platypus and the anteater are endothernmic, have hair, nurture their young with milk, but they both lay eggs (MONOTREMES).

Harry Williams, Historical Geology5 The problem of keeping the young warm resulted in other adaptations, for example the MARSUPIALS (kangeroos, wombats, wallabies, opossums) - which nurture their young in a pouch; and the PLACENTAL MAMMALS - which carry the young inside the body for a longer period of development, feeding them nutrients from a placenta.

Harry Williams, Historical Geology6 Apart from evolutionary changes designed to keep mammals warm; other changes also occurred which were adaptations to the changing environment. Perhaps the most important of these changes was the appearance of GRASSES and vast PRAIRIES in the Miocene. This led to the evolution of grazing mammals - the UNGULATES.

Harry Williams, Historical Geology7 Ungulates are characterized by continuously-growing cheek teeth for chewing grass and multi-chambered stomachs for digesting tough grass. Due to the lack of cover on the open prairies, these mammals also developed speed or size to counter predators - long legs for running and running on toes, which became HOOVES. The ungulates are classified according to the number of toes; PERISSODACTYLS = odd-toed (if middle toe carried weight-> single hoof). Examples: zebra, horse, rhino, tapir.

Harry Williams, Historical Geology8 ARTIODACTYLS = even-toed (if middle 2 toes carried weight -> cloven hoof). Examples: bison, pig, deer, hippo.

Harry Williams, Historical Geology9 Other important orders included the carnivorous predators that preyed on the grazing mammals - ORDER CARNIVORA. Examples: Smilodon (extinct), dogs, raccoons, bears.

Harry Williams, Historical Geology10 and the mammals with trunks, forerunners of the modern elephant - ORDER PROBOSCIDEA. Examples: mastodons (extinct), mammoths (extinct), elephants.

Harry Williams, Historical Geology11 Particularly important, of course, was the evolution of the order PRIMATES, distinguished by stereoscopic vision and grasping hands - both of which probably evolved to facilitate a life in the trees. The primates evolved into the Late Cenozoic ancestors of Homo sapiens, who appeared in the Pleistocene (more next class). HISTORICAL GEOLOGY CLASS 2016

Harry Williams, Historical Geology12 The following slides show the transition from the early to late Cenozoic. Changes in environmental conditions included: cooler and drier climate; decline of woodlands; expansion of grasslands; decline in browsers, increase in grazers; evolutionary changes in mammals to adopt to vast open prairies (mainly related to running speed and a grass diet).

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Harry Williams, Historical Geology18 MIDDLE EOCENE SCENE (~45 m.y.; primitive ungulates, mainly browsers, still lots of forest)

Harry Williams, Historical Geology19 Earlier: Browsing teeth for crushing leaves, fruit, nuts, branches etc.. (mastodon) Later: Grazing teeth for grinding grass (mammoth)

Harry Williams, Historical Geology20 LATE EOCENE SCENE (~35 m.y.; more open grassy land – more long-legged grazers)

Harry Williams, Historical Geology21 EARLY MIOCENE SCENE (~20 m.y.; cooler drier climate; more advanced ungulates)

Harry Williams, Historical Geology22 EARLY PLIOCENE SCENE (~4 m.y.; prairies – woods restricted to bottom lands near rivers)

Harry Williams, Historical Geology23 LATE PLEISTOCENE SCENE (~15,000; predominately grazers)