Mammal Basics

Evolution of Mammals

  • Descendants of synapsid reptiles

    • 300 MYA-190 MYA

    • Brain grew

    • Ears more complex

    • More advanced jaws

    • Differentiated teeth

  • Therapsids—line that branched to mammals

    • robust skull

    • single large canine

    • Cynognathus

      • limbs beneath trunk

      • jaws similar to modern mammals

      • endothermic? hair?

What makes a mammal and mammal?

  • Hair

  • Mammary glands

  • 3 middle ear bones

  • Deciduous and permanent teeth

  • Marrow in bones

  • Non-nucleated red blood cells

  • Muscular diaphragm

  • Heterodont dentition

    • molars, incisors, etc

  • Endothermic

Subclasses

  • Prototheria

    • lay eggs

    • Platypus, Echidna

  • Metatheria

    • marsupials

    • born very young, develop in mother’s pouch

    • Kangaroo, koala, opossum

      • live young

      • all other mammals

Mammal Diversity

  • 5000 species

  • 19-26 orders (depending who you ask)

  • DNA technology » changing classifications

  • Range in size

    • shrew and bats—as little of 3 grams

    • Blue whale—170 metric tons

  • Variety of niches, life history strategies, and modes of locomotion

    • fly, glide, swim, run, burrow, jump