MAMMAOGY LABORATORY 1 - SKULL and SKELETON
OBJECTIVES: After this laboratory session you should be able to
a.
Identify the bones of the appendicular skeleton and axial skeleton
b.
Identify the major bones of the skull
c.
Identify the various types of vertebrae and the components of a typical vertebra.
d.
Demonstrate examples of the various features of bone
THE SKELETON
I. The Axial Skeleton
 the skull, vertebral column, and thoracic
cage (ribs & sternum)
A. The Skull (dorsal, lateral and ventral
views from Animal Diversity Web)
1. Nasal
2. Frontal
3. Parietal
4. Occipital
a. Occipital Condyle
b. Foramen magnum
5. Lacrimal
6. Squamosal (temporal in humans)
7. Jugal (malar in humans)
8. Premaxilla
9. Maxilla
a. Infraorbital foramen
10. Palatine
11. Pterygoid
12. Auditory Bulla
13. Alisphenoid
a. alisphenoid canal
14. Orbitosphenoid
15. Dentary
16. Hyoid Apparatus
B. The Vertebral Column
1. Vertebrae
a. 7 Cervical
i. Atlas
ii. Axis
b. Thoracic
c. Lumbar
d. Sacrum
e. Caudal
2. Vertebral parts
a. Centrum
b. Vertebral arch and canal
c. Neural spine
d. Transverse process
e. Prezygapothesis
f. Postzygapothesis
C. Thoracic cage
1. Ribs
2. Sternum
II. The Appendicular Skeleton [Fig. 2-15]
$ consists of the pectoral & pelvic girdles
plus fore and hind limbs
A. The Pectoral Girdle
1. Clavicle
2. Scapula
a. monotremes have precoracoids,
coracoids, & interclavicle [Fig. 5-3C]
B. Forelimb
1. humerus
2. radius
3. ulna
4. olecranon process
5. carpal bones
6. metacarpals
1. Cannon bone in artiodactyls and
perissodactyls [Fig. 20.1]
7. phalanges (singular = phalanx)
C. The Pelvic Girdle
1. Ilium
2. ischium
3. Pubis
4. epipubic bones in monotremes and
marsupials
5. baculum in most placentals
D. Hindlimb
1. femur
2. patella
3. tibia
4. fibula
5. tarsals
1. Astragalus
2. Calcaneum
6. metatarsals
1. Cannon bone in artiodactyls and
perissodactyls
7. phalanges (singular = phalanx)
FEATURES OF BONES
1. Haversian system
2. Spongy bone
3. Compact bone
4. Epiphysis
5. Diaphysis (shaft)
THE SKULL
(Taken and slightly modified from Mammalogy (BIOL 4764) at the University of Montana)
The cranium is the skull without the mandible, commonly divided into two regions: braincase and
rostrum. The braincase is the portion of the cranium containing the brain. The rostrum is the portion of
the cranium corresponding to the snout or muzzle. Use a skull of a coyote (Canis latrans) or other canid
and the white-tailed deer (Odocoileus virginianus) to identify the above bones and other features.
After identifying features on a canid and deer skull, you should be able to find the same bones or
features on skulls of other mammals.
Dorsal aspect of the Cranium
1. The nasal bones are a pair of bones roofing over the nasal passages.
2. The paired premaxillary bones are at the anterior upper jaw. They form the lower margin of the
nasal openings (nares) and the anteriormost part of the bony palate. The upper incisor teeth reside
on these bones.
3. The maxillary bones are a pair of relatively large bones that make up much of the rostrum and the
bony palate. Maxillary bones bear all upper teeth except the incisors. They also form the anterior
base of the zygomatic arch.
4. The frontal bones are a pair of bones just posterior to the maxillary bones. Frontals form the
anterior-most roof (or dorsal part) of the braincase. In many mammals, each frontal bone has a
lateral projection, the postorbital process, which marks the posterior border of the orbit, or eye
socket. Sometimes the postorbital process joins with the zygomatic arch to form a postorbital bar
as in the horse (Equus caballus) skull present in the lab.
5. The parietal bones are located posterior to the frontals and form much of the roof of the braincase.
The interparietal bone is an unpaired bone located between the parietals at the posterior end of the
braincase in some mammals.
6. Squamosal bones are located lateral and ventral to the parietal bones and form major portions of
the lateral walls of the braincase, as well as the posterior root of the zygomatic arch. The dentary
fits into the mandibular (or glenoid) fossa of the squamosal.
7. The zygomatic arches ("cheekbones") are composite structures on the sides of the cranium. The
masseter muscles attach to the bottom of the zygomatic arch. They are sometimes incomplete.
The jugal bones form the central portion of the zygomatic arch. They are located between the
zygomatic processes of the maxillary (anterior) and the squamosal (posterior). The temporal
fossae (singular, fossa) are the spaces bounded laterally by the zygomatic arch posterior to the
orbit and contain the temporal muscles.
8. The sagittal crest is a ridge extending along the dorsal midline of the braincase. It tends to rise
posteriorly, is prominent in animals with large temporal muscles, and often is a sexually dimorphic
feature that is larger in adult males. In many species the crest becomes more prominent with age.
Ventral aspect of the cranium.
9.
The occipital bone is the large bone forming the posterior part of the braincase. It is formed by the
fusion of several bones: two lateral exoccipitals, a ventral basioccipital, and a dorsal supraoccipital.
If your specimen is an older individual, sutures between these bones may be strongly fused and it
may be impossible to distinguish the components of the occipital.
10. The foramen magnum is the large opening in the occipital bone through which pass the spinal
cord and the vertebral arteries. The occipital condyles project from the occipital bone on either
side of the foramen magnum and articulate with the first cervical vertebra, the atlas.
11. The auditory bullae are swollen capsules on the anteriormost part of the occipital. They protect the
middle-ear bones and facilitate efficient transmission of sound to the inner ear. The paroccipital
processes are projections of the occipital extending laterally just posterior to the auditory bullae.
12. The secondary palate consists of a hard and soft palate. The hard palate consists of the maxillae
anteriorly and the palatines posteriorly. The palatines surround the posterior openings of the nasal
passages and ventrally reach up to contact the frontals. The soft palate extends between the
palatines and the pterygoids.
13. The internal nares are the posterior openings of the nasal passages, apparent at the posterior end
of the palate. The vomer forms parts of the walls separating the two sides of the nasal passages. It
is located anterior to the pterygoid and between the palatines and reaches deep into the nasal
passages. You will be able to see the thin, scrolllike turbinal bones, upon which the olfactory
epithelium was arrayed in the living animal in some skulls.
14. The lateral wall of the braincase consists largely of the squamosal, alisphenoid, and
orbitosphenoid bones. The internal maxillary artery passes ventral to the alisphenoid bone and is
sometimes roofed over, forming the alisphenoid canal visible on the canid skull. The
orbitosphenoid contains the orbital foramen for the optic nerve
15. The lacrimal bone contains the tear duct.
Mandible.
16. The mammalian mandible is a simple structure composed of only two bones: the left and right
dentary bones. In most mammals, dentaries are firmly fused anteriorly at the mandibular
symphysis. The horizontal ramus is the tooth-bearing portion of the dentary. The coronoid process
is the posterior, vertical part of the dentary. The masseteric fossa is the shallow depression at the
base of the coronoid process. The masseteric fossa may be more conspicuous in mammals other
than canids and sometimes penetrates the dentary to form a masseteric canal. The mandibular
condyle articulates with the mandibular fossa of the cranium. It is the pivot around which the
mandible moves. The angular process protrudes ventrally below the mandibular condyle and
provides additional attachment sites for the jaw muscles.