CC

Appendicular Skeleton

What are the main functions of the pectoral and pelvic girdles in vertebrates? Support and anchor forelimbs (pectoral) and hindlimbs (pelvic); provide muscle attachment and facilitate locomotion.

What are the three dermal bones that support the fins in Actinopterygii? Clavicle, cleithrum, post-cleithrum.

Describe the structure of the pectoral girdle in bony fish. Includes dermal bones (clavicle, cleithrum, post-cleithrum) and scapulocoracoid; attaches dorsally to the skull.

How do the pectoral and pelvic fin supports differ in Chondrichthyes? What are these fused structures called?Supports are fused across the midline:

  • Pectoral: coracoid bar

  • Pelvic: pubioischiac bar

What are the three bones that make up the shoulder in many tetrapods? Which of these bones is lost in mammals?Scapula, procoracoid, coracoid. Procoracoid is lost in mammals (replaced by manubrium).

Describe the structure of the pectoral girdle in frogs. Includes suprascapula, scapula, clavicle (replaces procoracoid), coracoid, and a multi-part sternum.

How does the pectoral girdle of crocodilians differ from that of most lizards? Crocodilians have an enlarged scapula, coracoid, and interclavicle; lizards typically lack the interclavicle.

What bones make up the pectoral girdle of turtles? Be able to identify them. Scapula, coracoid, acromion process (procoracoid), interclavicle (entoplastron), clavicles (epiplastron).

Describe the structure of the pectoral girdle in birds. Scapula, coracoid, and furcula (fused clavicle and interclavicle). Provides strong support for flight muscles.

What is the most prominent bone in the mammalian pectoral girdle and how does this affect movement? Scapula. Its prominence allows wide range of limb movement; clavicle is reduced or absent.

Describe the structure of the pelvic girdle in frogs. Be able to label these. Composed of ilium, ischium, and pubis. Supports hindlimbs and connects to vertebral column.

What is the innominate bone, and from what bones is it formed? In birds, it’s the fused ilium, ischium, and pubis. Forms a strong pelvic structure.

Know the parts of the turtle pelvic girdle. Be able to label these. Ilium, ischium, pubis, and epipubis.

What is the sacroiliac joint, and what is its importance? Joint between sacrum and ilium. Transfers weight from spine to pelvis and hindlimbs.

What is a digit, and what is a phalanx? Define polyphalangy and polydactyly. Digit: finger or toe. Phalanx: bone segment of a digit. Polyphalangy: >3 phalanges per digit. Polydactyly: >5 digits per limb.

How are digits numbered in vertebrates? Digits are numbered I–V, from medial (thumb/big toe) to lateral. Radius aligns with digit I.

Know the fused bones in the frog fore/hindlimb and the names of their tarsal bones.

  • Forelimb: radioulna

  • Hindlimb: tibiofibula

  • Tarsals: astragalus (medial), calcaneum (lateral)

Describe the adaptations of the bird forelimb for flight, including the modifications of the bones and digits. Bones are lightweight and fused:

  • Carpometacarpus (fused metacarpals)

  • Reduced digits

  • Alula (digit I) aids in maneuvering

Know the names of the carpal and metacarpal bones in the bird. Carpal: radial and ulnar bones Metacarpal: major and minor, fused into carpometacarpus

What is the alula, and what is its function? A small digit at the carpus (digit I). Helps control airflow and maneuverability during flight.

What is the olecranon and the calcaneus in mammals?

  • Olecranon: proximal extension of ulna, forms elbow

  • Calcaneus: heel bone, attachment for gastrocnemius via calcaneal tendon

Be able to identify the common names of the bones of the horse fore and hindlimb and know what these bones are (including numbers). Which digit bears weight?

  • Forelimb:

    • Carpus = “knee”

    • Metacarpal III = cannon bone

    • Metacarpals II & IV = splint bones

    • Phalanges: P1 (long pastern), P2 (short pastern), P3 (coffin bone)

  • Hindlimb: same structure

  • Digit III bears weight

Know the bones of the bird hindlimb including the tibiotarsus and tarsometatarsus.

  • Femur

  • Patella

  • Tibiotarsus (fused tibia + tarsals)

  • Tarsometatarsus (fused metatarsals)

  • Phalanges

What is the hallux in birds? Digit I. Often reversed for perching; varies by species.

Describe the five main toe arrangements found in birds.

  • Anisodactyl: 3 forward, 1 back (most birds)

  • Zygodactyl: 2 forward, 2 back (woodpeckers)

  • Heterodactyl: 2 forward, 2 back (trogons)

  • Syndactyl: fused toes (kingfishers)

  • Pamprodactyl: all toes forward (swifts)

Define the three main stances in vertebrates: plantigrade, digitigrade, and unguligrade. Provide examples of animals that exhibit each type of stance.

  • Plantigrade: entire foot on ground (humans, bears)

  • Digitigrade: toes bear weight (dogs, cats)

  • Unguligrade: tips of toes bear weight (horses, deer)

What is the carpometacarpus and what is its role in birds? A fused structure of metacarpals. Provides rigidity and surface for feather attachment in flight.

What is the tarsometatarsus and its function in birds? Fused metatarsals in the hindlimb. Supports walking and perching.

What is the function of the furcula in birds? Acts as a spring during flight; formed by fused clavicles and interclavicle.

What is the acetabulum and which bone articulates with it? Hip socket formed by ilium, ischium, and pubis. Femur articulates with it.