Anapsida
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Transcript of Anapsida
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Anapsida Diapsida
SynapsidaSaurapsida
Turtles
Lizards & snakesCrocodilesDinosaurs & birds
Mammals &reptile-like mammals
Amniota -evolution of cleidoic (shelled) egg; ca. 350 mya (late Paleozoic)
Amphibians
-ca. 320 mya
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-apsid conditions
Anapsid Synapsid Diapsid
PelycosaurModern mammal
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Double occipitalcondyle:
greater range of motion
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Pelycosaur
Therapsid
s
Single bone in mandible: dentary
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post-dentary bones
Dentary-squamosal articulation
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Reptile:
Mammal:
stapes
stapes
stapes
(incus)
incusmalleus
(malleus)
(stapes)(incus)
(malleus)
3 inner ear ossicles
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Tympanic bone (="annulus" or "tympanic ring")
tenrec skull; no auditory bulla
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Heterodont dentition
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Diphyodonty (vs. polyphyodont)
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Matched shear surface on upper & lower teeth
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Complex occlusal surface on cheeckteeth
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Secondary palate
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Modified limbs and pelvic girdle
Reptile-like Mammal-like
Sprawling posture Upright postureLateral gait Fore-aft gaitPoorly developed calcaneus Well-developed calcaneus
calcaneus
fibula
femur
tibia
pelvicgirdle
calcaneus
fibulatibia
femur
astragalusastragalus
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Indeterminite growth vs. Determinite growth
Long-bone epiphyses
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Stabilized and regionally specialized vertebral column
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AtlasAtlas Axis
Dorsal-ventralflexion Rotation
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Simplified skeleton
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Hair (=fur or pelage)
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Mammal hair:invagination Bird feather: evagination
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cuticle
cortex: pigment
medulla: dead cells containing air; variably present.
Hair structure
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Hair function: tactile perception (vibrissae)
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Hair function: locomotory specializations
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Mammary glands (=mammae), structural variation
Monotreme Nipples(most mammals)
Teat(e.g., cows)
Skin glands
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4-chambered heart
Mammal
Crocodyle
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Enucleated blood cells
Muscular diaphragm
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Improved olfaction
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Endothermy---Body temperature regulated internally.
Homeothermy---Body temperature maintained within a narrow range.
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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
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Occipital condylesDentary, ear ossiclesDentitionUpright postureDeterminite growth/ephiphysesSimplification of skeletonVertebral columnMammary glands4-chambered heartEnucleated red blood cellsDiaphragmEndothermy/homeothermyOlfactionHair
Fossil evidence?