Vertebrates 8 - Appendicular skeleton

Question 2

Parts of appendicular skeleton

Answer 2

Pectoral and pelvic girdles, attached limb

Question 3

Parts of fin

Answer 3

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

Question 4

Fins in extinct lobe finned fish

Answer 4

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

Question 5

Evolution of tetrapods theories

Answer 5

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

Question 6

Fish to tetrapod transitional fossils

Answer 6

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.

Question 7

Gene expression in fish vs tetrapods

Answer 7

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.

Question 8

Early tetrapod limb skeleton (Acanthostega)

Answer 8

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

Question 9

Phalangeal formula in most lizards.

Answer 9

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

Question 10

Primate forelimb

Answer 10

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

Question 11

Ungulate limbs

Answer 11

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

Question 12

Therapod limbs

Answer 12

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.

Question 13

Reading: Difficulty with whale evolution

Answer 13

Lack of transitional fossils. Hard to determine the ancestors

Question 14

Reading: possible ancestors of whales

Answer 14

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

Question 15

Reading: Ankle bones and cetaceans

Answer 15

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

Question 16

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

Answer 16

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

Question 17

Reading: Whale evolutionary forms

Answer 17

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

Question 18

Reading: Whale evolution progressive steps: Pakicetus and ambulocetus

Answer 18

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

Question 19

Reading: Whale evolution progressive steps: Rodhocetus, dorudan

Answer 19

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;

Question 20

Reading: Whale evolution progressive steps: basilosaurus and modern whales

Answer 20

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

Question 21

Evolution of wings

Answer 21

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

Question 22

What is a wing?

Answer 22

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

Question 23

Wings in reptilia

Answer 23

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

Question 24

Wings in birds

Answer 24

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

Question 25

Wings in mammals

Answer 25

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

Question 26

Pterosaur

Answer 26

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

Question 27

Girdles

Answer 27

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

Question 28

Pelvic girdle features

Answer 28

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.

Question 29

Pelvic girdle in mammals vs reptiles

Answer 29

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

Question 30

Pelvic girdle groups in dinosaurs

Answer 30

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

Question 31

Confusion with dino groups

Answer 31

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