Appendicular

What are girdles and what do they do?

internal skeletal braces that anchor appendages.

What are the two major girdles?

Pectoral girdle (shoulder, supports forelimbs/fins)

Pelvic girdle (hip, supports hindlimbs/fins)

What supports fins?

Rays or spars at the dermis-epidermis interface

What are ceratotrichia and where are they found?

Keratinized rods that support fins in elasmobranchs (e.g., sharks).

What are lepidotrichia and actinotrichia?

Lepidotrichia: Bony fin rays in bony fish

Actinotrichia: Keratinized rays

What are pterygiophores?

internal fin support elements, made of:

Basals (most proximal)

Radials (more distal)

What is a chiridium?

A muscular limb with joints and digits (found in tetrapods).

What are the three regions of a limb (chiridium)?

Stylopodium: Proximal (single bone, humerus or femur)

Zeugopodium: Middle (two bones, radius/ulna or tibia/fibula)

Autopodium: Distal (manus or pes, includes carpals/tarsals and digits)

What is the stylopodium and where does it attach?

It is the upper limb (humerus/femur) and articulates with:

Glenoid fossa (forelimb)

Acetabulum (hindlimb)

What do both gill-arch and fin-fold theories agree on?

Paired fins evolved to allow more precise control of movement in water.

What does the Gill-arch theory propose?

Paired fins and girdles evolved from gill arches.

What does the Fin-fold theory propose?

Paired fins evolved from lateral body wall folds that later gained skeletal support.

What is an archipterygial fin?

The metapterygium (main support) runs down the center of the fin

Radials project symmetrically on both sides

What is a metapterygial fin?

the metapterygium is posterior

Radials project mostly on the preaxial (anterior) side

Did ostracoderms have fins?

Yes, they had pectoral fins but no pelvic fins. Fins were supported by dermal bone, not strong internal bones.

Do modern agnathans have paired fins?

No paired fins. Just unpaired (middle) fins and a notochord for support

What limb structures did placoderms have?

Well-developed paired pectoral and pelvic fins with distinct girdles

How are fins supported in Chondrichthyes?

Fins supported by ceratotrichia (keratin rods); paired fins articulate with endochondral girdles.

Describe the pectoral girdle in Actinopterygii.

Made of both bone and cartilage. Includes cleithrum, clavicle, and other bones that help anchor the fins near the skull.

Describe the fin and girdle structure of lungfish and coelacanths.

Lungfish:
Have archipterygial fins (straight fin structure) supported by scapulocoracoid and dermal bones like the cleithrum and clavicle.

Coelacanths:
Have a crescent-shaped shoulder girdle (no interclavicle) and a single pelvic bone. Their fins help them stay stable in water.

What makes Eusthenopteron's fins important?

Their fins contain bones homologous to tetrapod limbs — with a scapulocoracoid, dermal bones (clavicle, cleithrum), and an interclavicle. Pelvic fins articulate with a single bone but don't meet at midline.

what fin/limb features define Tiktaalik?

Tiktaalik shows detached head from pectoral girdle, allowing neck movement, with a mobile shoulder and possible wrist joints, bridging fish and tetrapods.

How does Ichthyostega differ from tiki?

ichthyostega has a pelvic girdle fused to the spine, and digits replaced fin rays, showing stronger limbs for terrestrial life.

what are the two main limb postures in tetrapods?

Sprawling: limbs extend out to the sides (earliest tetrapods)

Vertical: limbs under the body (derived tetrapods)

What are the three foot postures related to running speed?

Plantigrade: whole foot (autopodium) touches ground (e.g., humans, bears)

Digitigrade: only toes (phalanges) touch ground (e.g., dogs, cats)

Unguligrade: only tips of toes (distal phalanges) touch ground (e.g., horses, deer)

What is digit reduction, and how does it relate to cursorial animals?

Many fast runners lose or reduce side toes for efficiency.

Artiodactyls (even-toed): walk on digits 3 and 4; digits 1, 2, and 5 reduced or lost.

Perissodactyls (odd-toed): walk mainly on digit 3 (horses) or digits 2, 3, 4 (rhinos, tapirs).

How have bird wings adapted for flight?

Digit reduction or loss (fewer fingers)

Hollow bones to reduce weight

Wing shape varies by flying style (soaring, flapping)

Flapping helps with breathing (ventilation)

How are bat wings different from birds?

Bats have greatly elongated digits that support their wing membrane.

What are the limb adaptations for digging animals?

Limbs are robust and strong for mechanical advantage

Broad, shovel-like hands or feet (manus/pes) to move soil effectively

Bones and muscles adapted to resist digging forces

Zeugopodium

Middle (two bones, radius/ulna or tibia/fibula)

Autopodium

Distal (manus or pes, includes carpals/tarsals and digits)