Vertebrates 8 - Appendicular skeleton Flashcards Preview

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Flashcards in Vertebrates 8 - Appendicular skeleton Deck (30)
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Parts of appendicular skeleton

Pectoral and pelvic girdles, attached limb


Parts of fin

Basals, radials, and fin rays (majority of surface area). Most of these formed of cartilage in chondrichts. and bone in bony fish


Fins in extinct lobe finned fish

Fin rays, radials, basals still present. Radials branch on basals. A humerus is present which connects to pectoral girdle. Some have large basals and humerus


Evolution of tetrapods theories

Lobe-fin fish walk onto land, or amphibian with legs leaves water. Arose in devonian period about 400-375mya


Fish to tetrapod transitional fossils

tiktaalik (most like a fish with an amphibian head = fishapod) and acanthostega (more amphibian like = tetrapod). Both found in the arctic (Canada and Greenland). Both had moveable heads (opercular bones more like separate shoulder). Fossilized tetrapod tracks in Poland.


Gene expression in fish vs tetrapods

Hox genes. Fish express certain hox genes to form fin, only one time. Amphibians and mammals express these genes two times, contributing to extension of limb and digits.


Early tetrapod limb skeleton (Acanthostega)

Same bones for the most part. Humerus attaches to girdle, radius, ulna, carpals, metacarpals. Hindlimb is also similar. Acanthostega had 8 digits.


Phalangeal formula in most lizards.

1 is most medial. 2-3-4-5-3


Primate forelimb

Opposable thumb, rotation and flexibility, doesn’t bear any weight. 2-3-3-3-3.


Ungulate limbs

Bear weight on end of last digit (only one in horse, Phalangeal = 00300). Long limb, extra joints for flexibility speed


Therapod limbs

Hindlimb is robust, thick. To decrease this weight, they have more spongy bone in whole skeleton. Hindlimb 2-3-4-4-0, hallux (thumb) in rear), 3-4-0-0-0 forelimb, not sure what used for.


Reading: Difficulty with whale evolution

Lack of transitional fossils. Hard to determine the ancestors


Reading: possible ancestors of whales

Artiodactyl (ungulates) or mesonychian (hoofed wolf-like animal)


Reading: Ankle bones and cetaceans

Transitional forms had remnants of legs and ankles. Astralagus has two “pulleys” where it articulates. This is found in artiodactyls and whale transitional forms but not mesonychian


Video which had to do with reading: Evidence of whale evolution (not bones)

The way their spine undulates is just like otters or even dogs as they run


Reading: Whale evolutionary forms

Pakicetus, ambulocetus, rodhocetus, dorudan, basilosaurus, modern whale


Reading: Whale evolution progressive steps: Pakicetus and ambulocetus

Pakicetus inner ear was removed from skull, would help hear better in water; Ambulocetus more streamline, flat feet, smaller limbs;


Reading: Whale evolution progressive steps: Rodhocetus, dorudan

Rodhocetus totally aquatic, long digits as tho webbed, large spines for swimming, reduced sacrum, nares move back, more dorsal; Dorudon has no pelvic girdle but still small hindlimb, more lumbar vertebrae, muscular articulating tail, forelimb couldn’t support body but could steer, fused cervical vertebrae;


Reading: Whale evolution progressive steps: basilosaurus and modern whales

basilosaurus has minimized sternum, hindlimb almost nonexistent, nares further back; modern whales nares very far back, dolphins (toothed) and baleen whales which still have pelvis and hindlimb (most dolphins don’t), baleen don’t have teeth


Evolution of wings

First in Reptilia (pterosaurs), then birds, then mammals. Convergent evolution, totally unrelated.


What is a wing?

A modified forelimb. Generally long, a large surface area, with a specific shape.


Wings in reptilia

Pterosaur. In Cretaceous. Skin membrane stretched across the elongated arm and digit four down to the hindlimb. Had 3 free claws, climb to heights to take off possibly. 23440


Wings in birds

In Jurassic. Wing on arm and digit 3 is biggest. Surface area increased by feathers. No free digit, less friction. Feathers are an advantage because you don’t need blood etc, so it is much lighter


Wings in mammals

Bats. In Tertiary period. Arm and 4 digits used to support the skin membrane. One free grasping digit normally



Is not a dinosaur!! Just a reptile (different skull)



Pectoral and pelvic girdles. Pelvic is more often connected to the axial skeleton at the sacrum, bears more weight.


Pelvic girdle features

Ilium, ischium, pubis (clockwise). Acetabulum is ball and socket joint, bears weight and provides flexibility. Fused at pubic (pelvis) symphysis. Obturator foramen is the window in the pelvis.


Pelvic girdle in mammals vs reptiles

Rotated underneath more which is better for running. Reptile limbs are more splayed out.


Pelvic girdle groups in dinosaurs

Saurischian “lizard hip”, large pubis; and Ornithischian “bird hip”, ischium is long.


Confusion with dino groups

Ornithischian means bird hip, but birds evolved from therapods which were saurishcians. Their pelvic girdle today has evolved to look like ornitischian’s.