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Class Mammalia: Recent Mammals

I. Characteristics of Major Mammal Taxa:

A. Subclass Prototheria

1. Order Monotremata (six species)

a. spiny anteaters (Echidna)b. duck-billed platypus

2. shared characteristics with reptiles:

a. cloaca- receives products from (3) organ systems

b. oviparous; no uterus in female

c. no scrotum; internal testes

d. no pinna = ear

3. distribution: Australia & New Guinea only

B. Subclass Theria

1. characteristics:

a. heterodont teeth

b. no cloacac. uterus present

d. viviparous

e. mammary glands with nipples -vs- milk fields

f. fleshy pinna

2. Infraclass Metatheria (pouched mammals); 250 species

a. short gestation period; tiny, feeble newborn

b. marsupium overlies mammary glands

c. restricted to Australia & new world

3. Infraclass Eutheria (placental mammals); 3800 species

1. young born in advanced state

2. no pouch3. dominate outside Australia

4. (18) orders:

1. Order Insectavora (shrews & moles)

2. Order Chiroptera (bats); 20% of all mammal species

3. Order Rodentia (rodents); 40% of all mammal species

4. Order Artiodactyla (even-toed ungulates)

5. Order Carnivora (carnivores)

6. Order Cetacea (whales & dolphins)

7. Order Primates (primates)

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II. Important characteristics of mammals:

A. integument (single largest organ of the body):

1. functions: protection from: mechanical injury, water loss/gain, germ resistant

barrier, UV radiation; synthesis of Vitamin A, communication, excretion

2. hair- functions:

a. insulationb. communication

c. sensory (nocturnal spp.)

3. skin glands:

a. apocrine glands (sweat)- secrete urea, oils, & proteins; bacterial

breakdown results in body odor

b. holocrine glands- oil glands often associated with hair follicles

c. mammary-modified for feeding, & scent

4. nails, claws, & hooves- beta keratin composition

a. functions: protection, traction, & manipulation

5. horns and antlers

a. functions: protection, display, & mineral storage6. melanin- color

7. structure: epidermis, dermis, hypodermis

B. skeleton:

1. skull:

a. (2) occipital condyles

b. single dentary fused as mandible

c. teeth: thecodont, heterodont, & diphyodont

d. increased fusions

e. second, hard palate

2. vertebrae: cervical, thoracic, lumbar, sacral, & caudal

3. limbs/girdles:a. (2) pair of limbs; digits on all toes

b. plantigrade, digitigrade, & unguligrade locomotion

c. fused pelvic elements

C. upper & lower eyelids movable

D. respiration: lungs; vocalizing larynx; diaphragm

E. circulatory system:

1. four chambered heart (double circulation); right = pulmonarycircuit; left =

systemic

2. non-nucleated red blood cells

3. hepatic portal system present; renal portal system absent

F. endothermicG. excretion: metanepric kidney & urinary bladder; urea

H. digestion: manipulatory tongue & movable lips; oral glands & saliva; compartmentalized

GI tract

I. reproduction:

1. internal fertilization

2. scrotum

3. single copulatory organ

4. microscopic amniotic eggs no shell & little yolk

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