Typical rodent dental formula
1/1, 0/0, 0/0, 3/3 = 16
- Left = sciurognathus lower jaw = angular process of dentary is aligned with the jaw
- Right = hystricognathus lower jaw = angular process of dentary is inflected
What type of skull is this?
Protrogomorphous (primitive)
Small infraorbital foramen, flat zygomatic arch
Mountain beaver
What type of skull is this?
Sciuromorphous (squirrel-like)
Tiny/absent infraorbital foramen, zygomatic plate for lateral masseter attachment
Beaver skull
What type of skull is this?
Myomorphous (mouse-like)
Larger infraorbital foramen with lateral plate
Muskrat
What type of skull is this?
Hystricomorphous (porcupine-like)
Huge infraorbital foramen for masseter to pass through
New-world porcupine
What type of feet do perissodactyls have? What about artiodactyls?
- Perissodactyla = mesaxonic feet (odd-toed)
- Artiodactyla = paraxonic feet (even-toed)
- Have different weight distributions
- Paraxonic weight bearing is mainly divided between 3rd and 4th digits
- Mesaxonic bear weight on 3rd digit only
Describe pronghorn horns
- Horns are composed of bony layer with deciduous keratinous sheath underneath
- New layer grows underneath and old layer is shed each year
Describe Cervidae antlers
- Bony antlers grow and are shed each year
- Branched
- Growing antlers are covered in velvet - highly vascularized skin that supplies growing bone tissue with nutrients
- After mating season, bones weaken and distal portion of antler is shed
- Fastest growing tissue other than cancer
Describe Bovidae horns
- Surface of keratin
- Inner core of dermal bone (derived from frontal bone of skull) covered by keratinized sheath (derived from epidermis)
- Grow continuously and are never shed
What is baleen?
- Composed of keratin
- Plates of keratin hang in comb-like fashion from upper jaw only
- Continuously grows
What does rorqual refer to?
- Large mysticetes
- Have longitudinal grooves or pleats on throat and chest that allow for greater expansion of oral cavity as throat fills with water during gulping
What are the similarities between cetaceans and artiodactyls?
- Paraxonic limbs
- Extensive lacrimals
- Three bronchi
Four ways to estimate age from dentition
- Cementum annuli
- Tooth eruption
- Fluting (muskrats)
- Tooth wear
Other ways to determine age
- Epiphyseal sutures
- Saggital crest development
- Cranial suture closures
- Horn annuli
- Eye lens weight
- Baculum length
- Embryonic development
- Molt patterns
Locomotion patterns, ground contact, and fused vs. unfused metapodials in suiformes, ruminata, and tylopoda
- Suiformes
- Ambulatory locomotion, plantigrade foot posture, unfused metapodials
- Ruminata
- Cursorial locomotion, unguligrade foot posture, fused metapodials (cannon bone)
- Tylopoda
- Pacing locomotion, digitigrade foot posture, fused metapodials (cannon bone)
