Biology 4429 - chapter 2

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  [Table 4.3]

SOME CHARACTERISTICS OF MODERN MAMMALS 

1. Endothermy
2. 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 [Fig. 4.5, 7.2]
      1. Stapes small relative to skull
      2. hearing highly developed
   4. tympanic bone
3. determinate growth (long bones with epiphyses) 
   1. determinate long-bone growth  
      1. epiphysis
      2. cartilage
      3. diaphysis (shaft)
4. four chambered heart (also in crocodilians, Aves)
5.  single functional left aortic arch; reduction of the right
6. enucleate erythrocytes (red blood cells)
7. muscular diaphragm
8. secondary palate (also in crocodilians) with epiglottis
9. Skin with muscles, hair and glands [Fig. 5.2]
   9. facial muscles
   10. 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
          2. middle layer-cortex;
          3. medulla-central core
       4. pelage
          1. replaced during molts [Figs. 5.4, 5.5, 7.8]
       5. secondary functions
   11. Sebaceous glands
   12. sweat glands
       1. eccrine sweat glands
       2. apocrine sweat glands
   13. 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.
   14. musk & scent glands [Fig. 7.3]

15. Loop of Henle [Fig. 8.19]
16. structure of brain and nervous system [Figs. 7.4, 7.5]
    16. highly developed neopallium (roof of the forebrain) 
    17. tectum (visual center in lower vertebrates) reduced to corpora quadrigemina: functions mainly as a relay center for auditory information and to control visual reflexes
    18. corpus callosum in eutherians provides additional communication

19. smell acute except whales and higher apes
20. eye typical of amniotes
21. tapetum lucidum (reflective structure) well developed in nocturnal mammals
22. touch- most have vibrissae that are controlled by facial muscles 
23. complex, differentiated teeth (heterodont) that occlude
• incisors/canines/premolars/molars
24. two tooth generations (diphyodonty)
25. lateral movement of jaw during mastication
26. two occipital condyles
27. 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. 9.4]
   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. 9.3]
   3. testes usually scrotal

SENSE ORGANS

DIGESTION

1. salivary glands
2. stomach-generally sac-like, but complexly divided in some [Fig. 6.2]

MUSCULAR SYSTEM

THE SKULL [Fig. 5.8]

• the mammal skull and dentition from David Armstrong, University of Colorado

TEETH

AXIAL SKELETON

1. vertebrae

LIMBS and GIRDLES

1. pectoral and pelvic girdles [Fig. 5.10]
2. podials

LOCOMOTION

• DOWNLOAD  this Word Document or Adobe Acrobat document containing a list of Mammalian Locomotor and Feeding Categories that you are expected to know.

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
      1. Jumping
      2. richochetal 
   5. Fossorial
      1. Semifossorial
      2. Fossorial 
   6. Climbing
      1. Scansorial
      2. Arboreal
      3. Brachiation
      4. Vertical Clinging and Leaping
   7. Glissant [Fig. 10.28]
   8. Volant [Fig. 5.16]
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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