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

Teeth important to be able to capture, ingest, and digest food as efficiently as possible. High energetic costs associated with higher body T; increased selective pressure for efficient food processing

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

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,....

Don’t know which tooth this IS (tusk only present in males).

Researchers at Harvard and Smithsonian cross-sectioned this tooth.

narwhal tusks have no enamel. WHY. Seems odd narwhal tusks have no enamel. WHY??? Seems odd.. Tooth has extremely sensitive surface with millions of tiny nerve endings. Can detect changes in water temp and pressure, and chemicals that enable the whales to gauge salinity---in indication of ice formation---and find fish to eat.

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!!!

Teeth Important for understanding ecology of FOSSIL mammals 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

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

Teeth Finally, FOSSILIZE well; better than any other tissue type. 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!

Published last November. Not even sure WHICH tooth this is Published last November. Not even sure WHICH tooth this is! This is a condylarth, extinct Cretaceous lineage that we believe was outcompeted and eventually replaced by artiodactyls and perissodactyls.

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.

Crown Root gumline Alveolus (pl. “alveoli”) Enamel: hardest Enamel is HEAVILY MINERALIZED, 3% organic, composed of crystals of hydroxyapatite. dentine: Same mineral composition, but 30% organic, so SOFTER Enamel: hardest tissue in mammals. 3% organic... “pre-fossilized” Crown gumline Dentine: same mineral composition, but 30% organic; softer. Pulp cavity: nerves & vessels. Remains open in rootless, ever- growing teeth (rodent incisors, some cheekteeth) Root Cementum: bony material surrounding root Alveolus (pl. “alveoli”)

Teeth grow from one of 3 bones Teeth present in most verts (birds, turtles excluded), and diverse in some groups, but in mammals TEETH RESTRICTED TO 3 BONES: MAX, PREMAX, & DENTARY Teeth grow from one of 3 bones

Tooth replacement MOST mammals (we’re an exception) are BORN with milk teeth. ACTIVE GROWN in jaw occcurs when milk dentition present, poor occlusion, but milk doesn't require CHEWING, so OK. MOLARS added after space becomes available. 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

dC1 Pregnant SUBadult Microgale! Note looseness of P2 also, as well as several anterior teeth. dC1

4 basic kinds of teeth Incisors: Anteriormost, erupt entirely from premaxillary, us. single-root. Usually used for picking or grasping, and grooming. Modified in several ways: "Chisels": mostly rodents, but some other mammals. "Tusks" of elephants "Scalpels" of vampire bats "Shovels" of hippos.

Incisors Incisors: Anteriormost, erupt entirely from premaxillary, us. single-root. Usually used for picking or grasping, and grooming. Modified in several ways: "Chisels": mostly rodents, but some other mammals. "Tusks" of elephants "Scalpels" of vampire bats "Shovels" of hippos. incisors Anteriormost teeth, grow out of premaxilla, usually single-rooted Used mainly for picking, grasping, grooming, but heavily modified in some taxa...

Incisors Dog Rodent Lemur incisors Incisors: Anteriormost, erupt entirely from premaxillary, us. single-root. Usually used for picking or grasping, and grooming. Modified in several ways: "Chisels": mostly rodents, but some other mammals. "Tusks" of elephants "Scalpels" of vampire bats "Shovels" of hippos. incisors Dog Rodent Lemur

Incisors Elephant Vampire bat incisors Elephant tusk is definitely an incisor. SEe e-mail from eRic seiffert in Sept. 2008. Use as example of how fossil evidence + phylogeny can provide insites into dental homology incisors Elephant Vampire bat

I C P M Incisors Tusk is modified 2nd incisor. How do we know??? 1 3 3 Elephant tusk is definitely an incisor. SEe e-mail from eRic seiffert in Sept. 2008. Use as example of how fossil evidence + phylogeny can provide insites into dental homology incisors I C P M 1 3 3 Tusk is modified 2nd incisor. How do we know??? Elephant

Moeritherium NEW slide in 2008.

NEW slide in 2008.

NEW slide in 2008.

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

Canine Cat Moschid deer Rodent canine First (anterior-most) tooth growing out of maxilla. May even be nested b/w maxilla and premaxilla canine Cat Moschid deer Rodent

Canine Walrus Babirusa canine Some sources say walrus tusks are modified incisors, but see notes for this lecture. canine Walrus Babirusa

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 aren’t

Premolars premolars Dog carnassial pair

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

Molars Capybara molars Shrew Elk Raccoon

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

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

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

I C P M =44 I C P M =50 Primitive dental formula 3 1 4 3 5 4 1 3 4 PRIMITIVE dental formulas for placental/eutherian mammals and marsupials known from fossil record. Differences in dental formula are the result of TOOTH LOSS since we diverged from common ancestor. Placental: I C P M =44 3 1 4 3 BUT 1st premolar (P1/p1) lost in many living placentals, so maximum often 3 premolars!!!!!!! Marsupial: I C P M =50 5 4 1 3 4

Go over order of loss. Lost from front or back. E. g 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 Esselstyn’s JM paper.

I C P M = =44 Primitive dental formula 3 1 4 3 11 Placental: Used to summarize number of different teeth on upper and lower jaw of mammals Example of how to use primitive formula to deduce that this is an incisor, not a canine. BUT we can only conclude that it’s I2 or I3. Diastema and/or non-replaced milk teeth useful from here. Placental: I C P M = =44 3 1 4 3 11 “caniniform” incisor

I C P M = =44 Primitive dental formula 3 1 4 3 11 SO, can USUALLY assume that first premolar encountered is P2. EXCEPTIONS (example in later slide). P1 absent in MOST, but not ALL, living placental mammal Placental: I C P M = =44 3 1 4 3 11

Evolution of molars cingulum 3 prominent cusps. earliest mammals: 3 main cusps in line or slightly triangular; fit b/w space b/w lowers WOULD BE HELPFUL TO TALK ABOUT HOMOLOGOUS CUSPS IN INCISORS, CANINES, AND PREMOLARS. ALSO, LABEL THESE CUSPS TO HELP THEM ORIENT THEM WITH THE NEXT. ALSO, HAVE A SIDE-BY-SIDE COMPARISON, WITH BETTER ORIENTATION, OF THIS TYPE OF TOOTH AND SIMPLIFIED TRIBOSPHENIC. cingulum 3 prominent cusps. Mammals of Triassic (early) mammals..................... “shearing” action.

“Tribosphenic” molar pattern triangle expanded, leading to tribosphenic modern mammal teeth thought to evolve from tribosphenic. BUT FEW LIVING MAMMALS RETAINED IT AS FIGURED. significance of talonid basin (mortor & pestle). INTERLOCKING of trigon/hypocone with trigonid & hypoconid of lower. WHY IMPORTANT?---chewing much more PRECISE, EFFICIENT expansion of STYLAR SHELF. stylar shelf (expanded cingulum) Upper: Lower: (compare with early mammal)

Modifications of the tribosphenic molar Addition of 4th major cusp, the Hypocone (lower: hypoconid) Quadritubercular or Quadrate or Euthemorphic tribosphenic quadritubercular

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

Dilambdodont Crests connecting two prominent outer cones IDENTIFY STYLAR SHELF ON THIS! (addition of 4th major cusp) Crests connecting two prominent outer cones with smaller cones (“-styles”) of stylar shelf form double-V or W-shape.

Zalambdodont parastyle mesostyle LOSS of metacone, metastyle. Zalamb (metacone lost or greatly reduced)& Dilamb. IDENTIFY STYLAR SHELF---THIS IS WRONG! DO A SIDE-BY-SIDE OF THE B&W ILLUSTRATION TO ILLUSTRATE THE LOSS OF METACONE, METASTYLE. parastyle mesostyle LOSS of metacone, metastyle. Zalambdodont = cusps form single V. (Stylar shelf is incorrectly labeled on this figure!)

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

Herbivores cheekteeth characterized by primary cusps elongated in an anterior-posterior direction to form crescent-shaped ridges

Brachydont vs. hypsidont brachydont (also "brachyodont"): teeth having relatively low-crowned teeth, usually found in omnivores hypsodont: teeth having relatively high-crowned teeth, usually found in herbivores

Lophodont (herbivores) lophodont: a tooth consisting of a series of lophs loph (lophid for lower teeth): a ridge formed by the elongation (and sometimes fusion) of cusps on a tooth paracone metacone hypocone protocone anterior labial

Carnassial pair (carnivores) an efficient shear for cutting meat and tendon. Found in most members of the order Carnivora, but has also evolved convergently in hedgehogs. P4 M1

Carnassial pair metacone paracone protocone anterior labial

example of how to use primitive formula for eutherians to identify loci. In some canids, “P1” present! Know this by using carnassial and canine.

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