Lec 8 Primitive bony

Question 1

What are Actinopterygians

Answer 1

bony or ray-finned fishes
bony” because, of all the major groups of living fishes, they are, for the most part, the only taxon that has retained the ability to ossify the skeleton. Although they are exceptions like sturgeons and paddle fishes that are largely cartilaginous fishes.

Question 2

What are they called ray finned?

Answer 2

fins are fully rayed from the base as shown.

Question 3

Lobed fins

Answer 3

Fins mounted on pectoral lobes

Question 4

ganoid scale structure

Answer 4

Primitively all actinopterygians share a three-layered scale
outer lamellar layer of an enamel-like substance called ganoine, acentral layer of dentine filled with vascular canals
deep or innermost layer of spongy bone

Question 5

Ganoid scales shape

Answer 5

rhomboid in shape and arranged in sloping diagonal rows along the side of the body

Question 6

Ganoid scales are found in what kind of fishes?

Answer 6

More primitive fishes

Question 7

Most ancient lineage of fishes that has survived?

Answer 7

bichirs and reedfish

Question 8

Polypteridae, bichirs characteristics

Answer 8

Have lungs, so can inhabit lox oxygen places

Question 9

Chondrostei are known as

Answer 9

sturgeons and paddlefishes

Question 10

Acipenseridae: sturgeons

What are the characteristics?

Answer 10

anadromous and freshwater

five rows of bony scutets (ganoid scales), an inferior mouth without teeth, 4 barels, large swimbladder

Question 11

Polyodontidae: paddlefish characteristics

Answer 11

paddle-like snout, naked body (no scales), few ganoid scales on caudal peduncle, gill rakers are extremely,

Question 12

Sister group of paddlefish are

Answer 12

sturgeons, they hace similar asymmetircal caudal fin

Question 13

Difference between the American and Chinese Paddlefish?

Answer 13

American is a filter feeder, has lower jaw that drops and expand out like funnel.

Chinese paddlefish is a fish eater. Has long flatten, bony snout.

Question 14

Ginglymodi, aka gars characteristics, origin, and distribution

Answer 14

Heavily armored fishes found in shallow, weedy areas in fresh water.
Distribution is primarily USA East side.

Question 15

Gars’ snout and jaw structure.

Answer 15

Upper and lower jaws are elongate and armed with rows of strong sharp teeth Highly voracious carnivores.

Question 16

Gars’ tail structure

Answer 16

dorsal and anal fins are set back on the body and caudal fin is heterocercal.

Question 17

Opisthocoelous

Answer 17

Present in gars. They have vertebrae that is convex anteriorly and concave posteriorly.

Question 18

Amphicoelous

Answer 18

Vetebrae of most fishes that are concae on both ends.

Question 19

What family is the bowfin from?

Answer 19

Amiidae

Question 20

How are bowfins similar to derived teleosts?

Answer 20

they have single layered cycloid scales that lacks a gnoine.

Question 21

What’s the bowfin tail like?

Answer 21

caudal fin is abbreviated hetrocercal.

Question 22

What are sturgeons and paddlefishes’ tails like?

Answer 22

Strongly asymmetrical tails.

Question 23

How are teleosts characterized by having what kind of tails?

Answer 23

Symmetrical or homocercal tails.

Question 24

What is the earliest known teleost?

Answer 24

Pholidophoriforms, that originated in the late Triassic and early Jurassic times

Question 25

Pholidophoriform characteristics?

Answer 25

Large teeth, tail was symmetircal, scales had a thin layer of ganoine

Question 26

When did the teleost first appeared?

Answer 26

Appeared in the mid Triassic deposits, about 200 MYBP.

Question 27

What is the teleosts’ feeding mechanisms?

Answer 27

Upper Jaw mobility

Question 28

What did the evolution of greater upper jaw mobility lead to?

Answer 28

It opened up many feeding possibilities, and increase potential of mouth parts. This lead to successful exploitation of food resources that were unavailable to Actinopterygian.

Question 29

How does the fin change through actinopterygian evolution?

Answer 29

The change of the caudal fin would change from strongly asymmetrical, heterocercal, to abbreviated heterocercal, to less symmetrical, homocercal.

Question 30

Heterocercal shape, which fishes?

Answer 30

asymmetrical, present in sturgeons and paddlefishes

Question 31

abbreviate heterocercal shape, which type of fishes?

Answer 31

moderately asymmetrical, in gars and the bowfin

Question 32

homocercal shape

Answer 32

less symmetrical, in teleosts

Question 33

heterocercal function.

Answer 33

used to provide lift. Something a thick scaled, armored, primitive actinopterygian requires to get off the bottom

Question 34

How do fins vary with fishes with heterocercal tail?

Answer 34

Position and shape of the fins depends on shape of caudal fin. So there’s functional constraints that leads to limited maneuverability.

Question 35

How does the homocercal and heterocercal tails operate differently?

Answer 35

Homocercal tails has a vertical axic rotation. So the fish moves directly forward.
Heterocercal tail has upward and forward rotation on the rear end. Somersault effect is counteracted by large horizontally inserted pectoral fins that serves as planing devices.

Question 36

What are the advantages of having a homocercal tail?

Answer 36

1. increased efficiency in horizontal swimming
2. increased versatility for the fins, since they are free from the constraint of planing devices. The fins moved from low horizontal insertion to vertical insertion high on the body

Question 37

What evolutionary changes had to take in order for the homocercal tail to appear?

Answer 37

1. Loss of heavy bony armor and heavy scalation, it would no longer require a body plan that provides lift
2. led to the evolution of the swimbladder, so lungs acted as a hydrostatic organ