Chapter 9 Part 1: Appendicular Skeleton

Question 1

Pterygiophores (basal and radial):

Answer 1

skeletal elements that suppirt fin rays; basal is larger bones while radial are consistent, long thin bones

Question 2

Fin rays

Answer 2

2 types: Ceratotrichia and Lepidotrichia

Question 3

Ceratotrichia fin rays

Answer 3

composition made up of keratin, example is shark; very thin rays

Question 4

Lepidotrichia

Answer 4

composition made up of bone, example in bowfin

Question 5

Stylopodium

Answer 5

skeletal part of forelimb upper arm and/or hindlimb thigh

Question 6

Zeugopodium

Answer 6

skeletal parts of forelimb forearm and/or hindlimb shank(crus)(lower part of limb)

Question 7

Autopodium

Answer 7

skeletal parts of forelimb manus(wrist-palm-fingers) and/or hindlimb Pes(ankle-sole-toes); what could be known as foot/hand

Question 8

What is the primary function of paired pectoral and pelvic fins?

Answer 8

o They are used to control: steering
- use Yaw, Roll, and Pitch

Question 9

Yaw

Answer 9

side-to-side motion (primarily dorsal and anal fins)

Question 10

Roll

Answer 10

rotation around the long axis of the body

Question 11

Pitch

Answer 11

dorsal/ventral (up/down) deviation from level

Question 12

Define the difference between an archipterygial fin and a metapterygial fin.

Answer 12

2 types of fins, difference seen in images; arch. has skeletal system down middle, while meta does not

Archipterygial fin: has preaxial and postaxial radials
Metapterygial fin: only preaxial radials

Question 13

Name the 2 hypotheses for the origin of paired appendages

Answer 13

Gill-arch hypothesis and Fin-fold hypothesis

Question 14

Gill-arch hypothesis

Answer 14

Paired appendages arose from modified gill arches; Archipterygial fin derived from gill rays

Question 15

What is not explained by the Gill-arch hypothesis?

Answer 15

 The appearance of a posterior pelvic girdle distantly placed from the gill arches
 The presence of dermal bone in the pectoral girdle
 The different embryologies of pectoral girdle and gill arches

Question 16

Fin-fold hypothesis

Answer 16

Pectoral and pelvic fins develop from pair of elongate ventral fold

Question 17

How might the expression of the genes Tbx, Engrailed-1, and Shh be able to explain the development of fins under the fin-fold hypothesis?

Answer 17

Hypothetical ancestor with lateral fin-folds

T-box gene (Tbx) expressed within the domain of the patterning gene Engrailed-1
Duplication of Tbx = anterior fin development (Tbx5), posterior fin development (Tbx4)

Between the two, the flank is undifferentiated

The acquisition of Shh promotes the outward growth of the fins from the body wall, a feature carried into tetrapods.

Question 18

How does the postaxial component of the zeugopodium contribute to the developing limb under the fin-fold hypothesis?

Answer 18

The postaxial element (ulna/fibula) branches to form the carpals or tarsals and the digital arch, which yields the fingers and toes

Question 19

How is the fin-fold hypothesis related to the metapterygial stem of the metapterygial fin?

Answer 19

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