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Key to the Skulls of North Dakota Mammals


antler — a branched bony projection of the frontal bone; covered with vascularized tissue (velvet) during growth; shed annually.

auditory (tympanic) bulla — the inflated bony capsule that encases the middle and inner ear.

basal length of skull — the distance from the anterior border of the foramen magnum to the anterior margin of the premaxilla.

basilar length of skull — distance from posterior border of the tooth socket of the median incisor to mid-ventral border of foramen magnum.

basioccipital — bone that forms the ventral margin of the foramen magnum.

basisphenoid — the median ventral bone lying between the auditory bullae anterior to the basioccipital.

breadth of braincase — greatest width of skull in region where the brain is housed.

canine — the most anterior tooth in the maxilla, found just behind the incisors; often long, stout, and cone-shaped.

cheekteeth — premolars and molars.

condylobasal length — distance from anterior border of the tooth socket of the median incisor to plane of posterior border of occipital condyles.

coronoid process of lower jaw (mandible) — a dorsally projecting process anterior to the condyle (process that fits into the glenoid fossa of the squamosal bone).

crown — the portion of a tooth extending above the gumline.

cusp — a point on the crown of a tooth.

dentine lake — isolated area of dentine surrounded by enamel.

diastema — a gap separating molariform teeth from anterior ones, usually incisors.

external auditory meatus — bony canal leading into the auditory bulla.

foramen — an opening, orifice, or perforation through bone.

foramen magnum — the opening in the posterior of the skull through which the spinal cord passes.

frontal — a paired dermal bone of the dorsal part of the skull, located between the nasal and parietal bones.

greatest length of skull — greatest distance between most anterior point of skull (excluding teeth) to most posterior point of skull.

horn — permanent structure projecting from the skull of certain mammals, consisting of a bony core covered by keratin sheaths (keratin sheaths are shed annually in pronghorn).

incisive foramina — paired perforations through the anterior end of the hard palate at the point where the premaxilla and maxilla meet (also called palatine slit).

incisor — the most anterior of the four basic kinds of teeth; rooted in the premaxilla.

infraorbital opening (canal) — passage from the anterior face of the orbit to the side of the rostrum, passing through the base of the maxillary process.

interorbital breadth — least measurement across skull between orbits.

interparietal — an unpaired bone in the roof of the skull located between parietals and supraoccipital.

keratin — a protein material of which the covering of horns is composed.

lacrimal — a bone of the skull located in front of the orbit.

lacrimal fossa — a depression in the lacrimal bone anterior to the orbit.

mastoid — a process on the temporal bone posterior to the auditory meatus.

maxilla — bone that forms part of the roof of the mouth in which the upper molars, premolars and canines are rooted (found posterior to premaxilla).

maxillary breadth — the width of the skull across the maxilla.

maxillary tooth row — line of teeth in the maxilla (canines to molars).

molar — a cheektooth situated posterior to the premolars and having no deciduous precursors.

molariform — all teeth posterior to the canines; includes premolars and molars.

nasal — a paired dermal bone medial and posterior to the external nares.

occipital condyles — two knobs on the occipital bone flanking the foramen magnum.

occlusal — pertaining to the surface of contact between the upper and lower teeth.

orbit — the bony socket in which the eye is located.

palate — bony plate formed by the palatine bones and palatal branches of the maxilla and premaxilla; separates the nasal passages from the oral cavity.

parietal — a paired dermal bone of the roof of the skull, located between the frontal and occipital bones.

postorbital process — a projection of the frontal bone which marks the posterior margin of the orbit.

premaxilla — bone in which upper incisors are rooted.

premolars — teeth located anterior to the molars and posterior to the canines.

rostrum — the facial region of the skull lying anterior to a plane drawn through the anterior margin of the orbits.

sagittal crest — dorso-medial longitudinal ridges on the brain case.

tooth row — line of teeth from the incisors through the molars.

unicuspid — a tooth with a single cusp.

zygomatic arch — the arch of bone that forms the lateral border of the orbit and temporal fossa.

zygomatic breadth — the greatest width across the zygomata, measured at right angles to the long axis of the skull.

zygomatic plate — the expanded and flattened lower maxillary process.

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