The Cenozoic

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TheCenozoic
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Tectonics
Tectonics of the Mesozoic and Cenozoic
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Major Mammal Groups

• Multituberculates - now extinct - rodent-like
  mammals who lived from Jurassic to Oligocene and
  were probably outcompeted by modern rodents
  longest lived of all groups!
• Monotremes - only three species still alive,
  duck-billed platypus and two species of echidna
  (long-nosed and short-nosed spiny anteaters), all
  found in Australia and New Guinea

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Major Mammal Groups

• Metatheria (Marsupials) - Important group of
  mammals - originated in Middle Cretaceous as
  opossum-like organisms. They give birth to live,
  immature offspring.
• Eutheria (Placental mammals) - Give birth to live
  young, often very mature functional organisms.
  Provide support for developing offspring through
  placenta connecting it to mothers blood supply.

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Echidna - a Monotreme
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Platypus - a Monotreme
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Platypus - a Monotreme
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Monotremes

• A mix of primitive, standard mammal, and advanced
  features
• They lay eggs like birds or reptiles
• They support their young with milk
• They have standard mammal skull structure
• They have very specialized parts (e.g. nose
  parts, webbed feet)
• Platypuses are even venomous!

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Monotremes

• Monotremes have no teeth as adults (some have
  teeth as young)
• Eggs are small (1/2 to 3/4 inch in diameter) and
  leathery in platypus only the left ovary works
• Probably split from other mammals sometime in
  Mesozoic - the earliest fossil is from the
  Cretaceous
• Some possible monotreme fossils found in
  Argentina - could they have been widespread at
  one time?

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Kangaroo - a Marsupial
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Tasmanian Wolf - a Marsupial
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Marsupials

• Originated in North America around Middle
  Cretaceous
• Rapidly spread to South America and then to other
  parts of the world (scattered fossils found in
  Europe, Asia, the Americas), but faded away from
  North America by the Miocene when placental
  mammals entered the scene
• Marsupials recolonized the Americas during the
  Pliocene.

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Marsupials

• Young are born after only 8-40 days of gestation
• What is the problem they are trying to solve?
• Rejection by mothers immune system
• Whats better, marsupial reproduction or
  placental?
• Not clear, but placentals have outcompeted
  marsupials most places where they have been in
  conflict

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Marsupials

• Lots of forms of marsupials which are parallel to
  placental forms have existed at various times
• There have been big marsupial grazers, marsupial
  dogs, cats, rodents, even a lion-like marsupial
  with retractable claws
• Kangaroos and their relatives are an exception -
  no known parallel among other mammals. Theyve
  been more diverse in the past too - one ten-foot
  high species existed.

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Placental Mammals

• Includes most mammals we think about - whales,
  bats, elephants, shrews, and armadillos
• All give birth to live offspring after extended
  gestation
• Sometimes offspring are fairly helpless for long
  periods after birth other times offspring are
  fairly mobile
• All require mothers milk for support for at
  least a while (like other mammals)

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Placental Mammals

• First showed up no later than Upper Cretaceous,
  possibly earlier (early fossils havent been
  definitively split between marsupials and
  eutherians)
• Eutherians were widespread in Asia by the K-T
• Many modern groups were around at or near the
  start of the Cenozoic, and all modern groups were
  in place by the end of the Miocene.

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Early Cenozoic Mammals

• Paleocene
• Mammals diversify, spread
• Insectivores and rodents common
• Some grazers, but not huge ones yet
• Many are primitive and lack the specializations
  they will later evolve i.e., they are
  generalists.

Info and images from M. Jehle, Paleocene Mammals
of the World, http//www.paleocene-mammals.de
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Paleocene Mammals
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Multituberculates
Paleocene multituberculate Ptilodus, about 50 cm
in length
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Paleocene Mammals
Ectoconus Paleocene herbivore size of goat or
sheep
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Paleocene Mammals
Purgatorius, possible ancestor to later primates
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Paleocene Mammals
Ectoganus and two Pantolambda digging for food
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Paleocene Mammals
Plesiadapis, anoter possible ancestor to later
primates
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Paleocene Mammals
Carpolestes, from late Paleocene
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Paleocene to Eocene
Chriacus larger, more mobile
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Paleocene to Eocene
Phenacodus sheep-sized herbivore note the feet
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Eocene
Oxyaena - predator
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Eocene
Pachyaene attack Diatryma (8 feet tall)
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Big guys
Elephant-sized Titanotheres
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Big guys
Uintathere and early horse ancestors in the Eocene
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Indricotherium (was baluchitherium)Oligocene-Mioc
ene
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Ungulates
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Andrewsarchus Eocene ungulate predator
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Andrewsarchus
Sarkastodon (member of creodonts dominant
predators from 55-35 Ma) 6 at shoulder could
kill a modern elephant
Brontothere rhino sized herbivore
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Big guys
Irish Elk largest deer variety ever from
Pleistocene not restricted to Ireland, but good
fossils found there
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Big guys
Mastodon Pliocene to end of Pleistocene ate
leaves
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Big guys
Mammoth Pliocene to 1500 BCE (dwarf species
survived on Wrangel Island, Russia) ate grasses