CENOZOIC LIFE

I. Evolution of Mammals During Mesozoic

(evolved in Tr, diversified in K, radiated in Cz)

http://www.museums.org.za/sam/resource/palaeo/cluver/destiny.htm

1. Mammal-like reptiles (synapsids)

-upright posture, bulky bodies, may have been early endotherms (evid. from skull/palate characteristics).

-Examples include PZ Cynodonts and sail-back reptiles

http://www.museums.org.za/sam/resource/palaeo/cluver/index.html

http://www.ucmp.berkeley.edu/synapsids/synapsida.html

2. General characteristics of mammals

-hair, warm-blooded (endothermic),

-milk-producing gland in females (nursing young important), mammary gland

-live birth, better vision, hearing and overall sensory perception due to presence of 3 inner ear,

-differentiated teeth molars and canines and diet (omnivores)

-jaws have single large bone for better articulation

http://www.museums.org.za/sam/resource/palaeo/cluver/mamlike.htm

3. Main groups

a. monotremes (Australia & So. Amer.)

-egg-laying mammals, living fossils

-anteaters, platypus

b. marsupials, pouched mammals (mostly see in Australia

-koalas, kangaroos, oppossums,

-young born at immature state and must be suckled in pouch to maturity

-Most diverse in Australia due to isolation and lack of competition. Marsupial wolves and cats also known, convergent evolution

c. placentals

-largest, most diverse group of mammals and are characterized by live birth after long period of internal embryonic development (due to nourishment by placental gland in females)

-may have evolved in Cretaceous (K) but did not diversify until early Tertiary (Cz)

II. Importance of Cenozoic Plant Communities

1. Angiosperm diversification

-Flowering plants evol. in Cret.

-most diverse plants in Cz (see pp. 220-231 in Ch, 14).

-Insect-pollinated so important co-evolution

2. Development of grasslands:

-grasses are a type of flowering plant that diversify along with the cooling and drying trends in the Cz

-hoofed mammals (diverse group of herbivores in Cz) diversify along with flowering plants and grasses. Includes horses, cattle and other grazers that show distinctive changes in teeth and hooves

3. Co-evolution with animal populations

Insects, birds and mammals all radiate in the Cz partly in response to changing/evol. of plant communities in response to climate