Introduction and survey of living orders

How we make sense out of the whole group?
Can we find a way of categorizing and classifying mammals that sets them apart as a distinct taxonomic group and shows the evolutionary relationships among the different kinds of mammals?

I. Early classification schemes

  1. Aristotle (384-322 BC):
    Mammals were viviparous animals with red blood.
    He recognized three categories:

  2. John Ray (1693)

  3. Carolus Linnaeus ( Systema naturae , 1758)
    1. Early editions:
      • hairy bodies
      • quadrupedal
      • viviparous
      • females made milk
    1. 10th edition: "Mammalia," Linnaeus basically adopts Ray's definition
    2. Linnaean system

      A hierarchical system
      Seven obligate categories of classification
        Kingdom
          Phylum
            Class
              Order
                Family
                  Genus
                    Species

      Can also have optional (=intermediate) categories
        "super-"
          [category]
            "sub-"
              "infra-"

      A taxon can refer to any category of classification
    3. Nomenclature
      System is used world-wide; avoids mix-ups and confusion such as occur when common names are used

      1. Latinized words
      2. Name usually means something (ex. Carnivora=flesh eaters)
      3. Endings often depend on level of classification
        "-idae" Family
        "-inae" Subfamily
      4. Specific names are 2 words: Genus species


  1. ca. 1799: An early attempt at a classification scheme for mammals based on locomotion

  1. Early 1800's: Monotremes/Marsupials/Placentals. By the late 1800's, these became known by the present-day terms: Prototheria/Metatheria/Eutheria.

  2. George Gaylord Simpson (ca. 1928-1929): Three very distinct SUBCLASSes