Superclass: Gnathostomata

Question 1

Define Gnathostomata

Answer 1

• jawed fish with 2 nostrils

Question 2

What are the main characteristics of jawed fishes (4)

Answer 2

• jaws
• paired appendages (pectoral, pelvic)
• 3 pairs of semicircular canals
• centra of vertebrae replace notochord

Question 3

What is the importance of the 3 semicircular canals?

Answer 3

• balance
• orientation
• movement

Question 4

What 3 groups of Gnathostomata are there?

Answer 4

• Placoderms
• Chondrichthyes
• Osteichthyes

Question 5

What are the main characteristics of placoderms? (2)

Answer 5

• heavily armoured
• extinct

Question 6

What are the main characteristics of Chondrichthyes? (3)

Answer 6

• cartilaginous fish (endoskeleton)
• placoid scales
• no swim bladder or lungs

Question 7

What does the urea in chondrichthyes act as?

Answer 7

• osmolyte and salt secreting rectal gland

Question 8

What are the 2 sister groups of chondrichthyes?

Answer 8

• Elasmobranchi
• Holocephali

Question 9

What do elasmobranchi consist of and how many species are there?

Answer 9

• sharks, skates and rays
• 800 species

Question 10

What is an important characteristic of elasmobranchi?

Answer 10

they have branchiophores

Question 11

What do holocephali consist of? How many species are there?

Answer 11

• chimaeras
• 30 species

Question 12

What is an important characteristic of holocephali?

Answer 12

have one sac (breathing)

Question 13

What are the main characteristics of osteichthyes? (3)

Answer 13

• bony endoskeleton(gave rise to terrestrial vertebrates)
• lung/swim bladder
• operculum covers gills

Question 14

What are the 2 main lineages of osteichthyes?

Answer 14

• Sarcopterygii
• Actinopterygii

Question 15

What are the main characteristics of sarctopterygii? (2)

Answer 15

• fleshy/lobed finned fish
• notochord retained

Question 16

What do sarcopterygii share a common ancestor with?

Answer 16

• tetrapods

Question 17

What are the main characteristics of lungfish? (3)

Answer 17

• air breathing, estivate
• 6 extant species
• paedomorphic characteristics

Question 18

What is estivation?

Answer 18

• burrow in mud and lower metabolic rate waiting for rain

Question 19

Define paedomorphic

Answer 19

• retain early traits into adulthood

Question 20

What is considered to be in the Lazarus taxon? What does it mean?

Answer 20

• coelacanths were once thought to be extinct and had “come back from the dead”

Question 21

What are major characteristics of actinopterygii? (2)

Answer 21

• fins have webs of skin supported by fin rays (ray finned fish)
• abundant

Question 22

What are the 2 subgroups of Ray-finned fish?

Answer 22

• Chondrostei
• Neopterygii

Question 23

What are the main characteristics of Chondrostei? (2)

Answer 23

• primitive bony fish with derived cartilaginous skeleton
• mix of teleost and elasmobranch-like characteristics

Question 24

What are the 2 elasmobranch-like characteristics that chondrostei have?

Answer 24

• spiracles
• heterocercal tail

Question 25

What are the 2 subgroups of Chondrosei in subclass cladistia?

Answer 25

• sturgeons
• bichirs

Question 26

What is a spiracle and what is its function?

Answer 26

• breathing hole on top of head so they can breathe as mouth is occupied

Question 27

What are the main characteristics of neopterygii? (2)

Answer 27

• new fin
• improvements to fins and jaw

Question 28

What are the 2 main groups of neopterygii?

Answer 28

• Teleostei
• holostei

Question 29

What are the main characteristics of teleostei? (3)

Answer 29

• dominant clade/group
• most successful
• vast majority of fish

Question 30

What is the main characteristic of holostei?

Answer 30

• relic: mix of teleost-elasmobranch characteristics

Question 31

what two subgroups are among holostei?

Answer 31

• gars
• bowfin