1. Mammalian characteristics
Soft anatomy
-tissue other than bones or teeth
-good features to use when looking at
living animals or preserved specimens
-but, don’t fossilize well
Hard anatomy
-often used by paleontologists
-bones & teeth

2. Mammalian characteristics
Soft anatomy
1. Hair
-unique feature of mammals
-whales are a special case; generally only have
hair embryonically
pangolin

3. Mammalian characteristics
Soft anatomy
2. Lactogenic (milk producing)
-also unique to mammals
Mammary glands
-special cases
cetaceans
monotremes

4. Mammalian characteristics
Soft anatomy
1. Hirsute
2. Lactogenic
3. Endothermic- internal heat production
Unique to mammals
Not unique; also birds
Special cases: -hibernating mammals essentially
ectothermic at times
-naked mole-rats

5. Mammalian characteristics
Soft anatomy
4. Viviparous- give live birth (not unique to mammals, but
characteristic of almost all mammals)
Exception: monotremes
Oviparous (egg layers)
Platypus
Echidna

7. Mammalian characteristics
Soft anatomy
5. Four-chambered heart
-also true of birds and crocodilians
(fish, amphibians, turtles, other reptiles <4 )
4 chambered heart allows for a complete separation
of oxygenated and deoxygenated blood
-more metabolically efficient
increased activity

8. Mammalian characteristics
Soft anatomy
6. Enucleated red blood cells (RBCs)
-lack nuclei
-allows rbc’s to carry more oxygen
7. Muscular Diaphragm
-aids in ventilation of the lungs

9. Mammalian characteristics
Soft anatomy
8. No Renal Portal System
-blood goes through one less capillary bed than other
vertebrates
-allows mammals to maintain a higher blood pressure
-also increases the efficiency with which oxygen can
be transferred to cells

10. Mammalian characteristics
Soft anatomy
Four-chambered heart
Enucleated red blood cells
Muscular diaphragm
No renal portal system
-all features of the soft anatomy of mammals
that permit a higher metabolism

11. Mammalian characteristics
Soft anatomy
9. Complex integumentary structures
Hair
Sweat glands
Sebaceous glands
Horns

13. Mammalian characteristics
Soft anatomy
10. Nitrogenous waste excreted as urea
-expensive to make, but less toxic and can be concentrated in urine
-also found in some adult amphibians and reptiles
uric acid
-expensive to make, but non-toxic and requires almost
no water (birds & desert reptiles)
Ammonia
-Inexpensive for an animal to produce, but it
is highly toxic and requires lots of water for dilution
and elimination. Common among aquatic vertebrates,
such as fish and tadpoles.

14. Mammalian characteristics
Soft anatomy
11. Complex facial-dermal muscles
-complex facial expressions
-control facial tactile hairs
(vibrissae)
-suckling
12. Extreme expansion of cerebral cortex
-way smarter

15. Mammalian characteristics
Hard anatomy
1. Double occipital condyles
-strengthens contact
with vertebral column
yet flexible in two
planes
-also occurs in some
amphibians

16. Mammalian characteristics
Hard anatomy
2. Epiphyseal lines on long bones
-joint remains stable while
bone is growing
Epiphyseal lines

17. Mammalian characteristics
Hard anatomy
Lower jaw made up of 2 dentary bones
-single dentary on each side
-six or more bones
(3 per side) in the reptilian
lower jaw
-reduction of bones leads
to increased strength

18. Mammalian characteristics
Hard anatomy
Dentary-squamosal articulation
(suspensorium)
squamosal
-very strong joint

19. Mammalian characteristics
Hard anatomy
5. Three middle ear (bones) ossicles
-two of these (incus & malleus) are derived from the jaw bones in reptilian ancestors
6. Tympanic bone present

20. Mammalian characteristics
Hard anatomy
7. Teeth-restricted to perimeter of jaws
8. Heterodont dentition
-individuals have different types of teeth serving different
functions (shearing, grinding, piercing, gnawing etc.)
Dolphin
Opossum
Heterodont
-some have secondarily reverted to
Homodont

21. Mammalian characteristics
Hard anatomy
9. Diphyodont dentition
-2 stages: deciduous (milk) teeth & permanent teeth
10. Thoracic ribs only (no lumbar as in reptiles)

22. Mammalian characteristics
Hard anatomy
11. Hard secondary palate
-keeps nasal cavity from collapsing when mouth is
full of food
-can eat and breath at the same time
-talk with our mouth full

23. Mammalian characteristics
Hard anatomy
12. Calcaneus (heel bone) present

24. Mammalian characteristics
Hard anatomy
13. Phalyngeal formula: 3 3 3 3 2

25. Mammalian characteristics
Hard anatomy
14. Reduced shoulder girdle
(1-2 bones)
Lizard
Hedgehog
-increased mobility, but not as strong

26. Next week -evolution & paleontology (do the reading)
-study the skeleton
-make the annotations to Lawlor before lab