Slide 1
Mammalian characteristics: Cranial (skull) features
Slide 2
AnapsidaDiapsida SynapsidaSaurapsida Turtles Lizards &
snakes Crocodiles Dinosaurs & birds Mammals & reptile-like
mammals Amniota -evolution of cleidoic (shelled) egg; ca. 350 mya
(late Paleozoic) Amphibians -ca. 320 mya
Slide 3
-apsid conditions AnapsidSynapsidDiapsid Pelycosaur Modern
mammal
Slide 4
Double occipital condyle: greater range of motion
Slide 5
Pelycosaur Therapsids Single bone in mandible: dentary
Slide 6
post-dentary bones Dentary-squamosal articulation
Slide 7
Reptile: Mammal: stapes (incus) incus malleus (malleus)
(stapes) (incus) (malleus) 3 inner ear ossicles
Slide 8
Tympanic bone (="annulus" or "tympanic ring") tenrec skull; no
auditory bulla
Slide 9
Mammalian characteristics: Dental features
Slide 10
Heterodont dentition
Slide 11
Diphyodonty (vs. polyphyodonty)
Slide 12
Matched shear surface on upper & lower teeth
Slide 13
Complex occlusal surface on cheeckteeth
Slide 14
Secondary palate
Slide 15
Mammalian characteristics: Postcranial (skeletal) features
Slide 16
Modified limbs and pelvic girdle Reptile-likeMammal-like
Sprawling postureUpright posture Lateral gaitFore-aft gait Poorly
developed calcaneusWell-developed calcaneus calcaneus fibula femur
tibia pelvic girdle calcaneus fibula tibia femur astragalus
Slide 17
Indeterminite growth vs. Determinite growth Long-bone
epiphyses
Slide 18
Stabilized and regionally specialized vertebral column
Slide 19
Atlas Axis Dorsal-ventral flexion Rotation
Slide 20
Simplified skeleton
Slide 21
Mammalian characteristics: Soft anatomy, sensory, and
physiological features
Slide 22
Slide 23
Hair (=fur or pelage)
Slide 24
Mammal hair: invagination Bird feather: evagination
Slide 25
cuticle cortex: pigment medulla: dead cells containing air;
variably present. Hair structure
Slide 26
New PNAS article on origin of hair: PNAS November 25, 2008 vol.
105 no. 47 18419-18423
Slide 27
Hair function: tactile perception (vibrissae)
Slide 28
Hair function: locomotory specializations
Slide 29
Hair function: defense
Slide 30
Hair function: aggression and display
Slide 31
Hair function: communication
Slide 32
Mammary glands (=mammae), structural variation Monotreme
Nipples (most mammals) Teat (e.g., cows) Skin glands
Slide 33
Slide 34
4-chambered heart Mammal Crocodyle
Slide 35
Slide 36
Enucleated blood cells Muscular diaphragm
Slide 37
Improved olfaction
Slide 38
Endothermy---Body temperature regulated internally.
Homeothermy---Body temperature maintained within a narrow
range.
Slide 39
An integrated package? Natural selection favored increasingly
efficient use of energy Endothermy facilitated nocturnal activity
Endothermy is especially difficult for young Diphyodonty,
lactation, social behavior
Slide 40
Slide 41
Did these all appear simultaneously???? How do we know???
Slide 42
Occipital condyles Dentary, ear ossicles Dentition Upright
posture Determinite growth/ephiphyses Simplification of skeleton
Vertebral column Mammary glands 4-chambered heart Enucleated red
blood cells Diaphragm Endothermy/homeothermy Olfaction Hair Fossil
evidence?
Slide 43
Occipital condyles Dentary, ear ossicles Dentition Upright
posture Determinite growth/ephiphyses Simplification of skeleton
Vertebral column Mammary glands 4-chambered heart Enucleated red
blood cells Diaphragm Endothermy/homeothermy(??) Olfaction (??)
Hair Fossil evidence?
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