Unit 3 Notes
13: Mammals 1
• Permian
o 300-250mya
o Formation of Pangaea dries landscape
o Amniotes and gymnosperms dominate
§ Amniotic egg was big advance
• Amnion protects embryo from dessication
• Yolk sac provides nourishment
• Allantoic sac holds waste produced by embryo
• Allows colonization of dry habitats
§ Amniote Radiations
• Mesozoic was Age of Reptiles
• Amniote ancestor Hylonomus developed into
• Diapsid
• Anapsid, or turtles
• Synapsid, or mammals
o Major Phyla
§ Deuterostomes
• Chordata
o Vertebrata
§ Gnathostomes
• Tetrapods
• Amniotes
§ Synapsids radiate and dominate
• Dimetrodon was a Pelycosaur
§ Gorgonopsides
• Radiate as top-predator niche in Permian
§ Jaw development
• Dentury à mandible
• Other bones become the middle-ear bones
o Cochlea and tympani
• Radiations of Mammals
o Diversify during Mesozoic
o Modern groups radiate and dominate in Cenozoic
o From Therapsid ancestors that dominated Permian and Early Triassic
§ Triassic Takeover
§ Dominance of dinosaurs drove some therapsids to nocturnal,
insectivorous lifestyle
§ Selection for hair and endothermy
, • Led to first mammals (Morganucodontids)
§ Lactation evolved initially to keep eggs moist
• Monotremes still do this
o Mammal transition from cynodont reptiles
§ First fossils with all mammalian features 200mya
• Had jaw, ear, dentition, fur
• Morganucodontids
o Jurassic and Creataceous radiations of small, nocturnal mammals
§ Largest discovered Repanomamus giganticus about the size of an otter
• 1m, 30lbs.
• Ate vertebrates, including young dinosaurs
§ Creataceous also wiped out a lot of mammals
o Mammalian Phylogeny
§ 5400 living species
§ 50% rodents
§ 20% bats
§ Atlantogenata includes Afrotheria and Xenartha
§ Boreoeutheria includes Euarchontoglires and Laurasiatheria
§ Extinction of dinosaurs at K-T boundary
• K-T boundary high concentrations of meteorites
o Extinction of dinosaurs
• Correlates with radiation of most major Cenozoic mammal groups
o Primates, Afrotheres, Xenarthans began radiation before
K-T boundary
• Correlates with Pangaea breakup
o Pangaea à Gondwana and Laurasia
o Gondwana à South America and Africa
§ Great American Interchange
• 2.7mya
• Laurasians and Afrotheres to Africa
o Notably carnivores, camels, horses, rodents
§ From Africa
• 40mya
• Rodents and primates
§ Marsupials and Xenarthans to North America
• Extant Mammals
o Only ones that survived Cretaceous
o Monotremes
§ One opening/cloaca for urine, feces, and reproduction
• Like reptiles and birds
§ Leathery egg
• Genes for egg proteins
• Like reptiles in birds
, • Egg-laying mammal
§Extra clavicle bones
• Like reptiles
§ Gait like reptiles
§ Sweat milk for feeding young
• No nipples
§ Energetic pathway
• Food à digestion à nutrients in mother’s bloodstream à milk
production in mammary glands à food for offspring à digestion
à nutrients in bloodstream of offspring
o Energy transformations < 100% efficient
§ In Australia and Papua New Guinea
§ 1 species of platypus, 2 species of echidna
o Marsupials
§ Live birth to embryo
• Embryo attaches to nipple to complete development
§ Mother does not abandon nest/young to feed
§ Energetic pathway
• Food à digestion à nutrients in mother’s bloodstream à milk
production in mammary glands à food for offspring à digestion
à nutrients in bloodstream of offspring
o Energy transformations < 100% efficient
• Eat everything
o Fruits, leaves, insects, small vertebrates like rodents and
birds, eggs, dead animals
o Large species immune to rattlesnake venom and eat them
§ Arms race/arms reversal
• Predators have ways of subduing prey, so
select for those who survive
• Then selection for predators who catch the
most elusive prey
§ Arose in North America
• Oldest fossils here
• Migrated to South America and across Gondwana as continents
break up
• Didelphids radiate in South America
o Xenarthrans evolve in South America
• Australian radiation of families
o Longer isolations from placentals
• 110 species in North America
o Virginia opossum is only one north of Mexico
§ Ranges south through Nicaragua
§ Introduced out west in depression as food stuff
, § 3ft long
§ Lives 2-3 years
§ Omnivorous
• Eats insects, ticks, carrion, eggs, fruits,
birds, lizards, etc.
o Others in Mexico, Central America, 8 species radiated in
South America
§ 1 species in Chile and Argentina
§ 110 species in South America today
§ 334 extant species in Australia, PNG, and surrounding islands
• 70% of marsupials
• Diprotodon is largest marsupial ever
o Rhino sized
• Thylacoleo is marsupial lion
§ Pygmy possum from Australia, kangaroo
o Placentals
§ Longer internal development
§ Precocial behavior
• Independence on birth
§ Placental direct, energy-efficient transfer of nutrients
• Between blood systems of mother and offspring
§ Energetic pathway
• Food à digestion à nutrients in mother’s bloodstream à
placenta à nutrients in bloodstream of offspring
§ Includes Afrotheria
• From Atlantogenata
• Radiate in early Cenozoic, when Africa was island continent
• Aardvark
o Only living member of Tubilidentata
o Eats ants, termites, and “aardvark cucumber”
o Large
§ 130-180lbs
o Abandoned burrows used by a variety of animals
§ Hyena, wild dogs, pythons, warthods
o Aardvark cucumber is vine only eaten by aardvarks
§ Flowers and fruits above ground but pushes fruit
underground 6-12in
§ Aardvarks rely on it for water
§ Defecate seeds closer to soil surface
• Germinate in soft soil around burrows
• Elephant shrews
o Sengis
o 20 species distributed across Africa
13: Mammals 1
• Permian
o 300-250mya
o Formation of Pangaea dries landscape
o Amniotes and gymnosperms dominate
§ Amniotic egg was big advance
• Amnion protects embryo from dessication
• Yolk sac provides nourishment
• Allantoic sac holds waste produced by embryo
• Allows colonization of dry habitats
§ Amniote Radiations
• Mesozoic was Age of Reptiles
• Amniote ancestor Hylonomus developed into
• Diapsid
• Anapsid, or turtles
• Synapsid, or mammals
o Major Phyla
§ Deuterostomes
• Chordata
o Vertebrata
§ Gnathostomes
• Tetrapods
• Amniotes
§ Synapsids radiate and dominate
• Dimetrodon was a Pelycosaur
§ Gorgonopsides
• Radiate as top-predator niche in Permian
§ Jaw development
• Dentury à mandible
• Other bones become the middle-ear bones
o Cochlea and tympani
• Radiations of Mammals
o Diversify during Mesozoic
o Modern groups radiate and dominate in Cenozoic
o From Therapsid ancestors that dominated Permian and Early Triassic
§ Triassic Takeover
§ Dominance of dinosaurs drove some therapsids to nocturnal,
insectivorous lifestyle
§ Selection for hair and endothermy
, • Led to first mammals (Morganucodontids)
§ Lactation evolved initially to keep eggs moist
• Monotremes still do this
o Mammal transition from cynodont reptiles
§ First fossils with all mammalian features 200mya
• Had jaw, ear, dentition, fur
• Morganucodontids
o Jurassic and Creataceous radiations of small, nocturnal mammals
§ Largest discovered Repanomamus giganticus about the size of an otter
• 1m, 30lbs.
• Ate vertebrates, including young dinosaurs
§ Creataceous also wiped out a lot of mammals
o Mammalian Phylogeny
§ 5400 living species
§ 50% rodents
§ 20% bats
§ Atlantogenata includes Afrotheria and Xenartha
§ Boreoeutheria includes Euarchontoglires and Laurasiatheria
§ Extinction of dinosaurs at K-T boundary
• K-T boundary high concentrations of meteorites
o Extinction of dinosaurs
• Correlates with radiation of most major Cenozoic mammal groups
o Primates, Afrotheres, Xenarthans began radiation before
K-T boundary
• Correlates with Pangaea breakup
o Pangaea à Gondwana and Laurasia
o Gondwana à South America and Africa
§ Great American Interchange
• 2.7mya
• Laurasians and Afrotheres to Africa
o Notably carnivores, camels, horses, rodents
§ From Africa
• 40mya
• Rodents and primates
§ Marsupials and Xenarthans to North America
• Extant Mammals
o Only ones that survived Cretaceous
o Monotremes
§ One opening/cloaca for urine, feces, and reproduction
• Like reptiles and birds
§ Leathery egg
• Genes for egg proteins
• Like reptiles in birds
, • Egg-laying mammal
§Extra clavicle bones
• Like reptiles
§ Gait like reptiles
§ Sweat milk for feeding young
• No nipples
§ Energetic pathway
• Food à digestion à nutrients in mother’s bloodstream à milk
production in mammary glands à food for offspring à digestion
à nutrients in bloodstream of offspring
o Energy transformations < 100% efficient
§ In Australia and Papua New Guinea
§ 1 species of platypus, 2 species of echidna
o Marsupials
§ Live birth to embryo
• Embryo attaches to nipple to complete development
§ Mother does not abandon nest/young to feed
§ Energetic pathway
• Food à digestion à nutrients in mother’s bloodstream à milk
production in mammary glands à food for offspring à digestion
à nutrients in bloodstream of offspring
o Energy transformations < 100% efficient
• Eat everything
o Fruits, leaves, insects, small vertebrates like rodents and
birds, eggs, dead animals
o Large species immune to rattlesnake venom and eat them
§ Arms race/arms reversal
• Predators have ways of subduing prey, so
select for those who survive
• Then selection for predators who catch the
most elusive prey
§ Arose in North America
• Oldest fossils here
• Migrated to South America and across Gondwana as continents
break up
• Didelphids radiate in South America
o Xenarthrans evolve in South America
• Australian radiation of families
o Longer isolations from placentals
• 110 species in North America
o Virginia opossum is only one north of Mexico
§ Ranges south through Nicaragua
§ Introduced out west in depression as food stuff
, § 3ft long
§ Lives 2-3 years
§ Omnivorous
• Eats insects, ticks, carrion, eggs, fruits,
birds, lizards, etc.
o Others in Mexico, Central America, 8 species radiated in
South America
§ 1 species in Chile and Argentina
§ 110 species in South America today
§ 334 extant species in Australia, PNG, and surrounding islands
• 70% of marsupials
• Diprotodon is largest marsupial ever
o Rhino sized
• Thylacoleo is marsupial lion
§ Pygmy possum from Australia, kangaroo
o Placentals
§ Longer internal development
§ Precocial behavior
• Independence on birth
§ Placental direct, energy-efficient transfer of nutrients
• Between blood systems of mother and offspring
§ Energetic pathway
• Food à digestion à nutrients in mother’s bloodstream à
placenta à nutrients in bloodstream of offspring
§ Includes Afrotheria
• From Atlantogenata
• Radiate in early Cenozoic, when Africa was island continent
• Aardvark
o Only living member of Tubilidentata
o Eats ants, termites, and “aardvark cucumber”
o Large
§ 130-180lbs
o Abandoned burrows used by a variety of animals
§ Hyena, wild dogs, pythons, warthods
o Aardvark cucumber is vine only eaten by aardvarks
§ Flowers and fruits above ground but pushes fruit
underground 6-12in
§ Aardvarks rely on it for water
§ Defecate seeds closer to soil surface
• Germinate in soft soil around burrows
• Elephant shrews
o Sengis
o 20 species distributed across Africa
