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An integrated package? Natural selection favored increasingly efficient use of energy Endothermy facilitated nocturnal activity Endothermy is especially.

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Presentation on theme: "An integrated package? Natural selection favored increasingly efficient use of energy Endothermy facilitated nocturnal activity Endothermy is especially."— Presentation transcript:

1 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

2 Teeth High energetic costs associated with higher body T; increased selective pressure for efficient food processing

3 Teeth High energetic costs associated with higher body T; increased selective pressure for efficient food processing Mammal teeth---modified & specialized to far greater extent than in any other group of vertebrates

4 Teeth High energetic costs associated with higher body T; increased selective pressure for efficient food processing Mammal teeth---modified & specialized to far greater extent than in any other group of vertebrates Slice, dice, puncture, stab, grind, defend,....

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8 Teeth High energetic costs associated with higher body T; increased selective pressure for efficient food processing Mammal teeth---modified & specialized to far greater extent than in any other group of vertebrates Slice, dice, puncture, stab, grind, defend, display,.... SENSORY ORGAN!!!

9 Teeth High energetic costs associated with higher body T; increased selective pressure for efficient food processing Mammal teeth---modified & specialized to far greater extent than in any other group of vertebrates Slice, dice, puncture, stab, grind, defend, display,.... Teeth alone often indicative of diet

10 Teeth High energetic costs associated with higher body T; increased selective pressure for efficient food processing Mammal teeth---modified & specialized to far greater extent than in any other group of vertebrates Slice, dice, puncture, stab, grind, defend, display,.... Teeth alone often indicative of diet Variable BETWEEN major lineages, relatively constant WITHIN species

11 Teeth High energetic costs associated with higher body T; increased selective pressure for efficient food processing Mammal teeth---modified & specialized to far greater extent than in any other group of vertebrates Slice, dice, puncture, stab, grind, defend, display,.... Teeth alone often indicative of diet Variable BETWEEN major lineages, relatively constant WITHIN species FOSSILIZE; may fossil species described from teeth alone, often a SINGLE TOOTH!

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13 Teeth High energetic costs associated with higher body T; increased selective pressure for efficient food processing Mammal teeth---modified & specialized to far greater extent than in any other group of vertebrates Slice, dice, puncture, stab, grind, defend, display,.... Teeth alone often indicative of diet Variable BETWEEN major lineages, relatively constant WITHIN species FOSSILIZE; may fossil species described from teeth alone, often a SINGLE TOOTH! Traditionally given heavy emphasis in inferring relationships, BUT often misleading due to convergence, etc.

14 gumline Crown Root Alveolus (pl. alveoli) Enamel: hardest tissue in mammals. 3% organic... pre-fossilized Pulp cavity: nerves & vessels. Remains open in rootless, ever- growing teeth (rodent incisors, some cheekteeth) Dentine: same mineral composition, but 30% organic; softer. Cementum: bony material surrounding root

15 Teeth grow from one of 3 bones

16 Tooth replacement Living mammals DIPHYODONT (EXCEPT molars!). Ancestral condition for mammals. Most other vertebrates have POLYPHYODONT dentition. Deciduous teeth replaced by permanent teeth. Replacement timing varies (e.g., shrews) Morphology often different in deciduous teeth vs. permanent teeth Sequence of replacement constant w/in species: useful for AGING

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18 dC1

19 4 basic kinds of teeth

20 Incisors incisors Anteriormost teeth, grow out of premaxilla, usually single-rooted Used mainly for picking, grasping, grooming, but heavily modified in some taxa...

21 Incisors incisors DogRodentLemur

22 incisors Vampire bat Incisors Elephant

23 incisors Incisors Elephant IC P M Tusk is modified 2 nd incisor. How do we know???

24 Moeritherium

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27 Canine canine First tooth in maxilla or at maxillary/premaxillary suture. All mammals have AT MOST one canine per quadrant Usually single-cusped (unicuspid), single-rooted (but exceptions) Generally used for stabbing, holding prey in carnivores (but exceptions) Often absent (rodents, some artiodactyls) or heavily modified (elephants) Can be problematic to identify if absent and next tooth is caniniform

28 canine CatMoschid deerRodent Canine

29 canine Walrus Babirusa Canine

30 Premolars premolars Posterior to canines, rooted entirely in maxilla Variable: tiny, peglike in some, massive crushing tool in others Often molariform, but generally smaller, less developed than molars Premolars are replaced, molars arent

31 Premolars premolars Dog carnassial pair

32 Molars molars Posteriormost teeth in toothrow Variable, but late to erupt Erupt anterior-to-posterior NOT REPLACED!

33 Molars molars Raccoon Elk Capybara Shrew

34 Cheekteeth molars premolars cheekteeth Despite variation in I, C, much of the important functional variation is found in CHEEKTEETH, particularly MOLARS.

35 Assembly line for food processing capture, pick up puncture puncture, shear grind gulp!

36 Convergence within dental arcade: Elk Sea otter Philippine treeshrew caniniform incisor incisiform canine molariform premolar

37 Primitive dental formula Marsupial: IC P M= IC P M= Placental: BUT 1st premolar (P1/p1) lost in many living placentals, so maximum often 3 premolars!!!!!!!

38 Go over order of loss. Lost from front or back? E.g., humans have 2 premolars. Are they 3, 4? 1,2? Incisors? Etc. Also, Nancy Simmons claims that P1 retained in pteropodids...see Jake Esselstyns JM paper.

39 Primitive dental formula IC P M == Placental: caniniform incisor 11

40 Primitive dental formula IC P M == Placental: 11 P1 absent in MOST, but not ALL, living placental mammal

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42 Evolution of molars Mammals of Triassic (early) mammals shearing action. 3 prominent cusps. cingulum

43 Upper: Lower: (compare with early mammal) stylar shelf (expanded cingulum) Tribosphenic molar pattern

44 Modifications of the tribosphenic molar Quadritubercular or Quadrate or Euthemorphic tribosphenic quadritubercular

45 Modifications of the tribosphenic molar Quadritubercular or Quadrate or Euthemorphic stylar shelf (addition of 4th major cusp)

46 Dilambdodont Crests connecting two prominent outer cones with smaller cones (-styles) of stylar shelf form double-V or W-shape. (addition of 4th major cusp)

47 Zalambdodont = cusps form single V. (Stylar shelf is incorrectly labeled on this figure!) Zalambdodont parastyle mesostyle LOSS of metacone, metastyle.

48 Omnivores Quadritubercular Bunodont (ROUNDED) Brachydont (LOW-CROWNED)

49 Herbivores

50 Brachydont vs. hypsidont

51 Lophodont (herbivores) hypocone protocone paracone metacone anterior labial

52 Carnassial pair (carnivores) P4P4 M1M1

53 protocone paracone metacone anterior labial Carnassial pair

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55 Assembly line for food processing capture, pick up puncture puncture, shear grind gulp!


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