Biology 4429 - chapter 4

MAMMALIAN CHARACTERISTICS

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Phylum Chordata
    Subphylum Vertebrata
        Class Mammalia

Synapomorphies of extant mammals

  1. endothermy (also in Aves) aided by hair (insulation)
  2. skin glands (including mammary glands)
  3. live birth (except for monotremes)

Contrasts between ectothermic reptiles and endothermic mammals

SOME CHARACTERISTICS OF MODERN MAMMALS 

  1. Endothermy
  1. Transformation of accessory jaw bones [Fig. 4.4]
    1. mandible consists only of dentary bone
    2. dentary-squamosal jaw articulation
    3. three ear ossicles: malleus, incus, stapes [Figs. 4.5, 8.2]
      1. Stapes small relative to skull
      2. hearing highly developed
    4. tympanic bone

 

From Wikipedia: Mammalian and non-mammalian jaws. In the mammal configuration, the quadrate and articular bones are much smaller and form part of the middle ear. Note that in mammals the lower jaw consists of only the dentary bone.

From Wikipedia: A typical mammalian middle ear: sound makes the tympanum (ear-drum) vibrate; 3 small bones, the malleus, incus and stapes, transmit the vibrations to the Labyrinth (inner ear), which transforms the vibrations into nerve signals
  1. determinate growth (long bones with epiphyses) 
    1. determinate long-bone growth  
      1. epiphysis
      2. cartilage
      3. diaphysis (shaft)

 

Long bone: from Wikipedia
  1. four chambered heart (also in crocodilians, Aves)
  2.  single functional left aortic arch; reduction of the right
  3. enucleate erythrocytes (red blood cells)
  4. muscular diaphragm
  5. secondary palate (also in crocodilians) with epiglottis
  6. Skin with muscles, hair and glands [Fig. 6.2]
    1. facial muscles
    2. hair (including pelage)
      1. unique mammalian characteristic; without homologue
      2. primary function: insulation and homeostasis
      3. dead epidermal tissue strengthened by keratin 
        1. outer layer- cuticle [Fig. 6.4]
        2. middle layer-cortex;
        3. medulla-central core
      4. pelage
        1. replaced during molts [Figs. 6.5, 6.6, 8.9]
      5. secondary functions
    3. Sebaceous glands
    4. sweat glands
      1. eccrine sweat glands
      2. apocrine sweat glands
    5. mammary glands: modified apocrine glands
      1. a nipple is present in most mammals
      2. monotremes lack nipples
      3. cetacean (whales, dolphins, etc.) specializations
      4. males of the Malaysian fruit bat, Dyacopterus spadiceus, lactate
        1. more from BCI: The Incredible Milk-Producing Male Bat
        2. more from ZooGoer at the National Zoo.
    6. musk & scent glands [Fig. 8.3]
  1. Loop of Henle [Fig. 9.19]
  2. structure of brain and nervous system [Figs. 8.4, 8.5]
    1. highly developed neopallium (roof of the forebrain) 
    2. tectum (visual center in lower vertebrates) reduced to corpora quadrigemina: functions mainly as a relay center for auditory information and to control visual reflexes
    3. corpus callosum in eutherians provides additional communication
  1. smell acute except whales and higher apes
  2. eye typical of amniotes
  3. tapetum lucidum (reflective structure) well developed in nocturnal mammals
  4. touch- most have vibrissae that are controlled by facial muscles 
  5. complex, differentiated teeth (heterodont) that occlude
    6. (Fig. 4.20)
  6. two tooth generations (diphyodonty)
  7. lateral movement of jaw during mastication
  8. two occipital condyles
  9. elongate ilium

SOFT ANATOMY

FAT and ENERGY STORAGE

CIRCULATORY SYSTEM

  1. highly efficient circulation system
  2. heart rate correlates inversely to body size

REPRODUCTIVE SYSTEM

  1. Female
    1. two functional ovaries
    2. typically vagina, cervix and uterus [Fig. 10.4]
    3. monotremes: uteri to  urogenital sinus to cloaca--no vagina
    4. metatherians: lateral vaginas and two uteri
  2. Male [Fig. 9.2]
    1. penis--erectile tissue surrounded by sheath of skin
    2. os penis or baculum in most [Fig. 10.3]
    3. testes usually scrotal

SENSE ORGANS

DIGESTION

  1. salivary glands
  2. stomach-generally sac-like, but complexly divided in some [Fig. 7.2]

MUSCULAR SYSTEM

THE SKULL [Fig. 6.10]

TEETH

AXIAL SKELETON

  1. vertebrae

LIMBS and GIRDLES

  1. pectoral and pelvic girdles [Fig. 6.11]
  2. podials

LOCOMOTION

Web Resources

  1. Legs, Feet, and Cursorial Locomotion from Animal Diversity Web, University of Michigan
  2. Terrestrial Locomotion  from K. E. Peterson, Zoo 453, University of Washington.

LOCOMOTOR CATEGORIES

  1. Terrestrial Locomotion 
    1. Ambulatory 
      1. Plantigrade 
    2. Cursorial 
      1. digitigrade
      2. unguligrade 
    3. Graviportal 
    4. Saltatorial (jumpers, hoppers)
      1. richochetal (bipedal) [fig. 6.15]
    5. Fossorial
      1. Semifossorial
      2. Fossorial  [fig. 6.18]
    6. Climbing  [fig. 6.17]
      1. Scansorial
      2. Arboreal
      3. Brachiation
      4. Vertical Clinging and Leaping
    7. Glissant [Fig. 10.28]
    8. Volant [Fig. 6.19]
  2. Swimmers
    1. Amphibious or Semiaquatic [Fig. 6.12]
    2. Aquatic (mostly aquatic) 
    3. Marine (fully aquatic)

Download  this Word Document containing a list of Mammalian Locomotor and Feeding Categories that you are expected to know.

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