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Mammalian characteristics: Cranial (skull) features.

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Presentation on theme: "Mammalian characteristics: Cranial (skull) features."— Presentation transcript:

1 Mammalian characteristics: Cranial (skull) features

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

3 -apsid conditions AnapsidSynapsidDiapsid Pelycosaur Modern mammal

4 Double occipital condyle: greater range of motion

5 Pelycosaur Therapsids Single bone in mandible: dentary

6 post-dentary bones Dentary-squamosal articulation

7 Reptile: Mammal: stapes (incus) incus malleus (malleus) (stapes) (incus) (malleus) 3 inner ear ossicles

8 Tympanic bone (="annulus" or "tympanic ring") tenrec skull; no auditory bulla

9 Mammalian characteristics: Dental features

10 Heterodont dentition

11 Diphyodonty (vs. polyphyodonty)

12 Matched shear surface on upper & lower teeth

13 Complex occlusal surface on cheeckteeth

14 Secondary palate

15 Mammalian characteristics: Postcranial (skeletal) features

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

17 Indeterminite growth vs. Determinite growth Long-bone epiphyses

18 Stabilized and regionally specialized vertebral column

19 Atlas Axis Dorsal-ventral flexion Rotation

20 Simplified skeleton

21 Mammalian characteristics: Soft anatomy, sensory, and physiological features

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23 Hair (=fur or pelage)

24 Mammal hair: invagination Bird feather: evagination

25 cuticle cortex: pigment medulla: dead cells containing air; variably present. Hair structure

26 New PNAS article on origin of hair: PNAS November 25, 2008 vol. 105 no

27 Hair function: tactile perception (vibrissae)

28 Hair function: locomotory specializations

29 Hair function: defense

30 Hair function: aggression and display

31 Hair function: communication

32 Mammary glands (=mammae), structural variation Monotreme Nipples (most mammals) Teat (e.g., cows) Skin glands

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34 4-chambered heart Mammal Crocodyle

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36 Enucleated blood cells Muscular diaphragm

37 Improved olfaction

38 Endothermy---Body temperature regulated internally. Homeothermy---Body temperature maintained within a narrow range.

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

40

41 Did these all appear simultaneously???? How do we know???

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?

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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