Lecture 4a: Skull and Teeth Flashcards
1) What is the proper name for the lower jaw
2) describe what is it used for in marine mammals?
3) what bone does it articulate with?
4) what bone is it in contact with?
1) Manidible
2) to obtain food to enter the digestive tract
3) with the skull
4) maxilla (upper jaw)
What can the shape of the skull reflect? Contrast this between a cetacean with a short blunt skull vs. Long narrow skill)
Exhibit the maker of how they hunt or forage for their food becuase it acts as a organ for sound reception
Pelagic
- what two areas can you find pelagic fish and define each
- decried the 4 main pelagic zones and their more common names
Inhabit the water column (Not bottom or shore)
- coastal (up to depth 655 ft; above continental shelf)
- oceanic (below continental shelf)
Epipelagic = sunlight mesopelagic = twilight Bathypelagic = midnight Abyssophelagic = lower midnight
Demersal
On or near bottom
Benthic
In the bottom
Ie: sediment
Skull: frontal bone
Portion of the skull above the eyes and includes the forehead, roof other nasal cavity and roof of the orbits (bony socket) of the eyes
Skull: parietal bone
Protects the brain
Forms side and roof of the skull
Skull: temporal bone
Forms base and sides of skull
Skull: maxilla
Upper jaw bone
- support teeth and palate of skull.
Includes: eye sockets and lower parts and sides of the nasal cavity
Skull: orbit
Eye location
- made up of 7 bones which protects, supports, and maximize the function of the eye
Skull: Zygomatic Arch
Protects the eye
(Cheek)
- from temporal bone to maxilla
Masseter chewing muscles attaches here
Skull: Area of Turbinates
Warms and moistens air
Structure made up of mix cartilage/bone to warm and moisten air
Skull: Mandible (lower jaw)
Bone that forms the lower art of the skull (support teeth) and with maxilla the mouth
Skull:
Compare shapes and location for sea otter
have really small heads, large zygomatic arch, large area of turbinates, parietal bone is larger, small frontal bone, enlarged maxilla and mandible
They are carnivores that use their teeth in a more diverse fashion for tearing and cracking of food.
Skull:
Compare shapes and location for crab eater seal and bearded seal
Crabeater seals are carnivores that use their teeth to strain from the ocean water
Bearded sea are carnivores that use their teeth to capture small fish (flat teeth, gums are worn down; 34 teeth flat and thicker)
Skull:
Compare shapes and location for Dolphin
Dolphins are carnivores with teeth that are uniform and conical in shape and used to capture prey
- cannot identify different kinds of teeth
Skull:
Compare shapes and location for Manatee/Dugong
- use their teeth for grinding vegataration
They only have 5 -7 functional teeth
20-30 teeth/jaw in their lifetime
Teeth are replaced from the rear
1) What structures in marine mammals possibly has the widest range of adaptations and variations in comparison to terrestrial animals?
2) what is the purpose of this?
Mandibles
These adaptations and variations allows for an extensive range of prey animals that are used for food
Mandibles & Dentitation: Cetaceans
What is another unique function for the mandible?
It acts as an organ for sound reception
Mandibles & Dentition: Odontoceti Whales
How variable are the number of teeth? (In regards to shape, and numbers)
Shape of the mouth, jaw and the number of teeth may vary between families. but the shape of the teeth are similar throughout and teeth numbers are usually used to differentiate
Mandibles & Dentition: Odontoceti Whales
What does 15/18 mean?
15 teeth in upper jaw
18 teeth in lower jaw
Mandibles & Dentition: Narwhales
What is the unique structure they have? (Give the characteristics)
Long tissue that is from the LEFT canine tooth
- erupts anteriorily from the head
- may reach up to 3 m
- males may have 2 tusks
- females may ahve tusks but much shorter
- these are used for sexual display only! Not for fighting
- grows in a spiral (only species to do this)
- Recently thought to also be a sensory organ (detect salinity, etc)
- rest of ht e teeth are vestigial
Mandibles & Dentition: Phocoenidae (porpoises)
1) number of teeth
2) shape of teeth
3) diet
1) equal number of teeth ranging form 15-30
2) flat spatula like teeth
3) coastal species: small pelagic herring anchovies, caplin
Falls porp: squalid, small mesopelagic fresh when closer to surface
Mandibles & Dentition: Delphinidae (dolphins)
1) number of teeth
2) shape of teeth
3) diet
1) large range of teeth numbers (0/2 to 65/58)
2) conical in shape
3) normally Cephalopods fish
Mandibles & Dentition: Mysticetes whales
Do adults have teeth? What do they have instead
No teeth Baleen plates (2 rows) instead that extend centrally from the upper jaw
Mandibles & Dentition: Mysticetes (baleen) whales
what are baleen plates?
What is the use of them? What are they covered with?
Are strong yet flexible
Grow continuously after being worn down by the tongue and grey
Covered by a sheath of keratin filled cells
Mandibles & Dentition: Mysticetes (baleen) whales
Does the density of baleen (baleen fibres/ cm2) vary within mysticetes family? If so by how much? (Gray vs. Right whale)
There is a 10 fold difference between species
Gray whales: 155/ cm2 and 0.4=0.5 m in length
Right whales: more than 350/cm2 and longer than 3m
Mandibles & Dentition: Mysticetes (baleen) whales
What forms the filter surface?
The inner fringe becomes entangled and forms this
Mandibles & Dentition: Mysticetes (baleen) whales
What are the length differences of baleen and how does it affect feeding techniques?
Right whales have very long and dense baleen so they have narrow rostrum, which makes them have a skimmer technique
Grey whales have a gulper technique bc their mouths are wider from the not as long baleen but less dense
Mandibles & Dentition: Pinnipedia
Are their teeth all similar in shape? Give an explanation for this?
No, have different types of teeth specialized for specific task as and diets .
Ex: crab eater seals (strain like teeth) and bearded seals (flatter and thicker teeth)
Mandibles & Dentition: Pinnipedia
Describe how they are referred to?
Incisors, Canines, Post canines, Premolars, Molars
Mandibles & Dentition: Pinnipedia
Where are incisors and what are they used for
Front of ht e moth
Small gripping teeth
Mandibles & Dentition: Pinnipedia
Where are canines and what are they used for
Beside the incisors,
Powerful, puncturing teeth found in PAIRS
Mandibles & Dentition: Pinnipedia
Where are post canines and what are they used for? What are the also referred to as?
Back of the mouth
Cut, shear and crush food
Premolars or Molars
Mandibles & Dentition: Pinnipedia
What is the range of numbers they might have in total?
(Compare otariidae, phocid, and walrus)
Range between 18-38 teeth
Otariids: 34-38 teeth
Phocids: 22-26 teeth
Walrus: 18-24 teeth
Mandibles & Dentition: Pinnipedia
What is unique about the walrus?
(Characteristics, purposes, sex differences)
Both sexes have tusk
Tusks are NOT for feeding
Males: use them for display
Female: for defence
Mandibles & Dentition: Pinnipedia What are the shapes of the following teeth: (discuss their diets) 1) Bearded seals 2) Crabeater seals 3) Walrus
1) flat and thick teeth used to capture and crush their food.
Diet: shrimp, crabs, clams
2) strainer teeth
Diet: krill
3) long growing canines - disturb the bottom; thick and flat teeth for crushing shells
Diet: bottom feeders: shellfish, small fish, clams
Mandibles & Dentition: Sirenia –> Manatee
1) how many teeth in their mouth at any one time?
2) what is unique to manatee teeth and describe this
3) what is their diet consist of?
1) 5-7 functional teeth in the upper and lower jaw –> 20/30 teeth/jaw during their lifetime
2) teeth grow from the rear as they get worn down and fall out
3) Herbivores: vegetation (ie: sea grasses)
Mandibles & Dentition: Sirenia –> Dugongs
How do teeth compare to manatee?
They have a fixed number of teeth
Both sexes develop small tusks (<15 cm)
Tusks are NOT used for weapons
Also herbivores
Mandibles & Dentition: Ursidae (Polar bears)
1) how many teeth do they have?
2) how specifically do their teeth differ from other bears? Why?
1) 38-42 teeth
2) premolars/molars are sharper than other bears because more carnivorous and shows an evolutionary adaptations
Mandibles & Dentition: Mustelidae (Sea Otters)
1) how many teeth do they have?
2) What if any differences are there compared to other carnivores? Why?
3) describe their diet
1) 32 teeth
2) reduced number of lower incisors; modified molars
3) hard shelled invertebrates
