Mammology Exam 1

Evolution of mammals

Tetrapod → Amniote → Synapsid →Pelycosaurs → Therapsid → Cynodont → Stem Mammals

Tetrapod → Amniote

Evolution of the amniotic egg, from the four limbed amphibian like organisms.

Amniote → Synapsid

Evolution of a single temporal fenestra from early amniotes.

Synapsid →Pelycosaurs

Heterodont dentition - Differentiation of teeth

Pelycosaurs → Therapsid

Legs positioned vertically rather than splayed to the side. More stable support allows for larger body size 

Therapsid → Cynodont

Fully developed secondary soft palate. Allows eating and breathing at the same time. 

Cynodont → Stem Mammals

Single dentary bone. Dentary-squamosal joint articulation (ball and socket)

Diagnostic characteristic for mammals in the fossil record

Fusion of all the dentary bones into a single dentary (jaw) bone. Dentary articulation in the squamosal

Mammalian characteristics 

Hair, mammary glands, single dentary bone, dentary-squamosal articulation, mostly viviparous (except monotremes), endothermic.

Order Rodentia:

1. Dispersion

2. Key characteristics

1. Cosmopolitan

2. Single pair of upper and lower ever growing incisors. Mostly herbivorous. Contains the largest family

Order Lagomorpha:

1. Dispersion

2. Key characteristics

1. Nearly cosmopolitan

2. Single pair of upper and lower incisors, and a peg like second pair of upper incisors. Hipsodont (high crowned) cheek teeth, due to obligate herbivory. 

Antlers vs horns

Antlers: Made of bone. Always shed and regrown. Typically forked. Typically only males.

Horns: Made of a bony core and keratinized sheath. Never shed, never forked. Can be in males and females. 

Types of glands. 4 kinds

1. Sebaceous 

2. eccrine

3. apocrine

4. scent

What are:

Sebaceous glands

Glands used for the nourishment of hair

Heat adaptions

1. Evaporative cooling through respiration allows for the brain to keep cool; panting

2. Urine concentration in some mammals 

3. Long, slender appendages to increase surface area and loss of heat 

4. Sweat

Heat avoidance

1. Daily torpor

2. Shade seeking 

Cold adaptions 

1. Fusiform body shade to maximize surface area to volume ratio. Less head leaving the body

2. Short, stocky appendages

3. insulation; blubber, fat, dense pelage 

4. Countercurrent heat exchange 

5. Temporal hypothermia 

6. seasonal torpor

Stages of temporal hypothermia 

1. Regional hypothermia (limbs colder than core)

2. Daily torpor

3. Shallow hibernation (5-7 C below average body temp)

4. Profound hibernation (body temp of 2-5 C, about same as the den)

Classification of hair: Growth

Angora - Grows forever

Definitive - Grows to a set length and stops 

Classification of hair: Function

1. Pelage

2. Vibrissae - Sensory hairs like whiskers 

Family Castoridae:
1. Order

2. Dispersion

3. Key characteristics

Beavers

1. Rodentia

2. North America, along waterways 

3. Webbed feet, paddle shaped tail 

Family Geomyidae:
1. Order

2. Dispersion

3. Key characteristics

Gophers

1. Rodentia

2. North America

3. Fossorial, flat shovel-like skull, powerful forelimbs with large claws 

Family Heteromyidae:
1. Order

2. Dispersion

3. Key characteristics

Kangaroo rats and mice, pocket mice

1. Rodentia

2. New world

3. Elongated hindlimbs, short neck and long tail, ricochetal locomotion 

Family Cricetidae:
1. Order

2. Dispersion

3. Key characteristics

New world rats and mice

1. Rodentia

2. Cosmopolitan

3. Second largest family of rodents

Family Muridae:
1. Order

2. Dispersion

3. Key characteristics

Old world rats and mice

1. Rodentia 

2. Cosmopolitan

3. Largest family of rodentia 

Family Erethizontidae:
1. Order

2. Dispersion

3. Key characteristics

New world porcupines

1. Rodentia

2. New world 

3. Barbed quills cover most of the body 

Family Sciuridae:
1. Order

2. Dispersion

3. Key characteristics

Squirrels, chipmunks and marmots 

1. Rodentia

2. Nearly cosmopolitan 

3. Diurnal herbivores, arched skull profile 

Family Aplodontidae:
1. Order

2. Dispersion

3. Key characteristics

Mountain beaver

1. Rodentia 

2. Pacific northwest/north america 

3. single species, many ancestral features 

Family Leporidae:
1. Order

2. Dispersion

3. Key characteristics

Rabbits and hares

1. Lagomorpha

2. Nearly cosmopolitan 

3. Hipsodont cheeck teeth (high crowned) Peg-like upper incisor. Fenestrated skull

Order Proboscidae:

1. Dispersion

2. Key characteristics

Elephants

1. Africa and Asia

2. Elongate probiscus/trunk. Enlarged skull with a short neck.

Order Hyracoidae:

1. Dispersion

2. Key characteristics

Hyraxes

1. Africa and Middle East

2. Ever growing upper and lower incisors, with a second pair of peg-like lower incisors. Meet are mesaxonic.

Order Sirenia:

1. Dispersion

2. Key characteristics

Manatees, dugongs, and sea cows

1. Topical oceans and coasts worldwide

2. Only herbivorous aquatic mammals

What are:

Eccrine glands

Sweat glands

What are:

apocrine glands

chemical glands; used for interspecific communication. Example: Skunks

What are:

scent glands

Modified glands used for intraspecific communication, like marking territory or displaying reproductive readiness.