Traditional Mammal Evolution Ideas (3):
- Early mammals were small like shrews
- Persisted amongst the dominant dinosaurs without diversification into new lineages and niches
- Evolved into many diverse lineages after extinction od the dinosaurs when niches became avaliable
Modern Mammal Evolution Ideas (3):
Mammals started to diverge before the KT extinction and continued to diverge
Living Groups of Mammals (3):
- Monotremes
- Metatheria (marsupials)
- Eutheria (placentals)
Mammal Characteristics (4):
- Feed young milk secreted from mammary glands
- Extended parental care of young
- Large brain/body size ratio
- hair (integumentary derivative)
Modern Mammal Integument: Specialized Glands (2)
- Sebaceoous Glands
- Sweat glands
Modern Mammal Integument: Specialized Glands (Subaceous Glands) (3)
- Alveolar glands
- Oily/waxy secretion often with hair
- Waterproof hair and protect skin from drying
Modern Mammal Integument: Specialized Glands (Sweat Glands) (3)
- Tubular glands
- Secrete water, salts, urea
- Some important for thermoregulation
Mammary Glands (Development, location, and function):
- Develop from clumps of cells in the ectoderm during embryonic development
- Number and location of nipples varies across species
- Provide nutrition for young offspring
Sweat Glands (Development, location, and function):
- Derived from sebaceous glands, and sweat glands
- Located on integument
- Defense, sexual selection
Epidermal Derivatives in Mammals (4):
- Claws, hooves and nails at the ends of digits
- Horns (most not shed; keratin over bony cover)
- Antlers (shed; mostly bone)
- hair (thermoregulation and sensory organs)
Dermal Derivatives in Mammals:
Osteoderms (only armadillos)
What do Marsupials Do:
Give birth to tiny young who suckle until they grow much larger, often in a specialized pouch of the mother
What are Placentals (Eutheria):
- Most diverse and widespread group of mammals
- Radiated extensively after the KT extinction
- Prolonged gestation of embryo in uterus with placenta
How are Placentals (Eutheria) Distributed:
Correlate with isolation of continents as they drifted away from the earlier supercontinent (pangea)
Marsupial Diversity:
- Became isolated after continental breakup
- Through convergent evolution
Different Eutheria (Placental) Diversity (3):
- Afrotheris (aardvarks, elephants, and some shrews - Africa)
- Xenartha (armadillos, sloths, and anteaters (South America))
- Euarchontoglires (treeshrews, colugos, primates, rabbits, and rodents)
- Laruasiatheria (hedgehogs, shrews, moles, bats, dogs, cats, and hoofed animals (in all continents))
