LEC4: The Mammalian Skeleton and Locomotion

Vocabulary flashcards covering mammalian skeletal anatomy, bone growth structures, divisions of the skeleton, and various evolutionary locomotion styles.

Axial Skeleton

The main division of the mammalian skeleton that includes the skull, vertebral column, sternum, and ribs.

Appendicular Skeleton

The division of the mammalian skeleton that includes the limbs (or fins) and the pectoral and pelvic girdles.

Vertebral Column Regions

The five regions of the backbone: Cervical (neck), Thoracic (chest), Lumbar (back), Sacral (pelvic), and Caudal/Coccygeal (tail) vertebrae.

Atlas and Axis

The first two cervical vertebrae, which are modified to support the skull and permit pivotal movements.

Thoracic Basket

The structure formed by the ribs that surrounds and protects vital internal organs, such as the heart and lungs.

Pectoral Girdle

The shoulder girdle, consisting of the clavicle (collar bone) and scapula (shoulder blade), which attaches forelimbs to the axial skeleton.

Pelvic Girdle

The hip girdle, comprised of three main bones (illium, ischium, pubis), which supports weight transfer, allows live birth, and forms the floor of support for abdominal organs.

Ossacrum

The structure formed in most mammals by the fusion of the sacral vertebrae, to which the pelvic girdle is attached.

Articular Surfaces

Well-defined places on mammalian bones where bones fit together.

Metaphysis

The cartilaginous growth plate located between the end of the bone (epiphysis) and the main bone shaft (diaphysis) that allows lengthening.

Epiphysis

The end of a bone.

Diaphysis

The main shaft of a bone.

Epiphyseal Line

The line formed after the growth plate hardens (ossifies), used to estimate age in some species with well-defined age-based growth patterns.

Cursorial

Locomotion style adapted for running.

Plantigrade

Foot posture where the animal walks on the soles of its feet, as seen in bears and humans.

Digitigrade

Foot posture where the animal walks on its toes, as seen in cats.

Unguligrade

Foot posture where the animal walks on the tips of its toes on keratinized hooves, as seen in horses.

Terrestrial Foot Postures

Diagram illustrating plantigrade (e.g., squirrel), digitigrade (e.g., dog), and unguligrade (e.g., deer) limb postures.

Saltatorial

Leaping locomotion primarily powered by the hind legs, though the front legs are usually involved, as seen in hares.

Richochetal

Leaping locomotion powered by hind legs only, using the tail as a counterbalance, as seen in kangaroos and jumping mice.

Graviportal

Lumbering locomotion characterized by a weight-oriented columnar structure often with padding, as seen in elephants.

Fossorial

Locomotion adapted for living almost exclusively underground, featuring compact bodies, reduced tails, short necks, vestigial eyes/pinnae, and powerful pectoral muscles/girdle for digging (e.g., moles).

Semi-Fossorial

Locomotion adapted for spending time living in ground burrows and procuring food on the surface, as seen in lagomorphs, many rodents, and mustelids.

Aerial (Volant)

True flight with skin membranes between digits to form wings, as seen in bats.

Scansorial

Climbing locomotion in tree-dwelling animals that are structurally built for the ground but have sharp claws and long tails to aid in climbing, such as tree squirrels.

Brachiating

Swinging through trees, usually involving long hands and opposable thumbs.

Gliding

Gliding through trees using an extended flap of skin between front and rear limbs, as seen in flying squirrels and flying lemurs.

Nictitating Eye Membrane

A 3rd eyelid found in semi-aquatic mammals used to seal out water.

Flukes

Tail structures in aquatic mammals that assist with propulsion via vertical undulation.

Cannon Bone

A single long bone formed on each limb by fusing or losing metacarpal and metatarsal bones to add strength for digitigrade locomotion.

Perissodactyls

"Odd-toed" ungulates (e.g., horses, tapirs, rhinoceroses) whose main weight-bearing axis passes through the enlarged third digit and possess a "single pulley system" at the ankle.

Artiodactyls

"Even-toed" ungulates (e.g., pigs, hippos, deer, cattle, antelope) whose main weight-bearing axis passes through the third and fourth digits and possess a "double pulley system" at the ankle.