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

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

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

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

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

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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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