QUATERNARY FAUNAS

North American Land Mammal Ages: Subdivisions of Quaternary, based on fossil assemblanges.

Definitions of Land Mammal Ages are based on Characterizing Assemblages: list of taxa that co-occur during that time interval

  Equus Mammuthus Bison
Rancholabrean
10 Ka - 0.5 Ma
  PRESENT   PRESENT   PRESENT
Irvingtonian
0.5 - 1.8 Ma
  PRESENT   PRESENT No Bison
Blancan
pre-Quaternary
  PRESENT No Mammoth No Bison

Type Localities of Land Mammal Ages: Geographic Local where assemblage first described

    Rancholabrean: Los Angeles, CA
    Irvingtonian: San Francisco Bay area
PRINCIPALS used in establishing Land Mammal Ages
  1. Superposition: younger overlies older
    Steno

  2. Stage of Evolution: long-term trends in morphologic change



  3. Dispersal: land bridges


NORTH AMERICAN LAND MAMMAL AGES
Characterizing Assemblages

RANCHOLABREAN Bison, Mammuthus, Equus, Modern taxa 10 Ka - 0.5 Ma
IRVINGTONIAN Mammuthus, Equus, Euceratherium, Smilodon, Mocrotus 0.5 - 1.8 Ma
BLANCAN Equus, Nannippus phelgon, Stegomastodon, Borophagus diversidens, Trigonictis, Nekrolagus, Procastoroides, Sigmodon. 1.8 - 4.5 Ma
HEMPHILLIAN Machairodus, Agriotherium, Plesiogulo, Osteoborus, Osbornoceros, Prosthennops, Pliohipppus, Astrohippus 4.5 - 8.2 Ma


N.Am. Land Mammal Ages & Paleomagnetic Chronology






THE MEGAFAUNAL EXTINCTIONS

Megafauna vs. Microfauna




Extinction Chronology


Global Timing of Megafaunal Extinction




Survors (Sturart et al., 2004)


Paul Martin's Overkill Hypothesis

Arrival of Humans in New World coincided with extinction of Pleistocene Megafauna
  • Extinctions earlier in north than in south, human shock-wave "blitzkreig"
  • Annual travel less than 20 km
  • Extinction event brief, killing event, so sites rare
  • Climatic change too gradual
  • Climatic change at wrong time to cause faunal extinction (cf. Haynes, 1991)
  • Earlier deglaciations did not cause extinction



Monte Alegre

Monte Verde
Monte Verde




Multiple Hypotheses

Historic Extinctions

correlating with human arrival
  • Oceanic Islands Holocene Extinction
    • Ground Sloths, West Indies, 4400 C14 yr BP (Steadman et al., 2005)
    • Pigmy Mammoths, Wrengel Island, 3730 C14 yr BP (Vartanyan et al., 1995)
        no evidence of human presence
    • Birds Pacific Islands, 2850 C14 yr BP (Steadman et al., 2002)
    • Megafauna Madagascar, 1720 C14 yr BP (Burney et al., 2003)
            gorilla-sized lemur
    • Birds New Zealand, 600 C14 yr BP (Holdaway and Jacomb, 2000)


  • Australian & Japanese Megafauna Extinction 30 - 60 Ka
    does it coincided with arrival of humans?

    MARINE OVERKILL: SERIAL EXTINCTION


    MARINE OVERKILL (background: great whale harvest)
    "We propose that decimation of the great whales by post- World War II industrial whaling caused the great whales’ foremost natural predators, killer whales, to begin feeding more intensively on the smaller marine mammals, thus"fishing-down" this element of the marine food web. The timing of these events, information on the abundance, diet, and foraging behavior of both predators and prey, and feasibility analyses based on demographic and energetic modeling are all consistent with this hypothesis."


READINGS

HOMEWORK

LINKS
CP-LUHNA
Kennewick Man
Hyperdisease Hypothesis Ross MacPhee
Pleistocene Megafauna: Disease W.K. Stevens
Great Apes
African Elephants

Webb, S.D. and Opdyke, N.D. 1995. Global climatic influence on Cenozoic land mammal faunas. National Academies Press.
www.nap.edu/books/0309051274/html/184.html