B2 Vertebrates

Question 1

Jawed species remaining

Answer 1

108

Question 2

What did jaws bring?

Answer 2

Diversification of prey, biting and catching larger prey. Deemphasis of reliance on armour. More niches.

Question 3

3 subphyla

Answer 3

Urochordata, Cephalochordata, Craniata

Question 4

3 extant superclasses of craniata

Answer 4

Myxinomorphi, Petromyzontomorphi, Gnathostomata

Question 5

5 extinct superclasses of craniata

Answer 5

Conodonta, pteraspidomorphi, anaspida, thelodonti, osteostracomorphi

Question 6

Gnathostome ancestors

Answer 6

Most common theory: Osteostracomorphs. Ossified bones around the eye and internal cellular bone. Could have been starting point of jaw development.

Question 7

Hypocercal tails

Answer 7

Don’t create lift, bottom swimmers. Looks large and vertical.

Question 9

Epicercal tails

Answer 9

Do create lift, more horizontal and flat.

Question 10

3 extant classes of Gnathostomata

Answer 10

Chondrichthyes, Sarcopterygii, Actinopterygii

Question 11

Gnathostome class Placodermi

Answer 11

Bony with ornamented plates over 30-50% of body. Big jaws, teeth and mouth gape. 200 genera. Antiarchs (pectoral fins enclosed in bone-like arms, reduced body armour over time). Limitations (can’t replace teeth, no suction). First Gnathostomes in fossil records, dominated in Devonian.

Question 11

2 extinct species of Gnathostomata

Answer 11

Placodermi, Acanthodii

Question 12

Gnathostome class Chondrichthyes

Answer 12

970 living species (highest diversity of living fish). Prismatically calcified cartilage skeleton. Males have pelvic claspers used for reproduction. very specialised marine predators (sharks).

Question 13

Gnathostome class Acanthodii

Answer 13

Small and stout with bony spine which they had before fins. cartilaginous skeleton and small scales (like modern sharks). Pelagic fish, large head and eyes (water column feeder), reduced armour (evolutionary trend).

Question 14

Gnathostome class Sarcopterygii

Answer 14

Fleshy and lobed fins with enamelled teeth. Cosmoid scales. Only 8 extant species of fish (26,742 other extant species in this class that aren’t fish).

Question 15

Gnathostome class Actinopterygii

Answer 15

26,891 extant species (35% of fish species live in this class). Monophyletic. Scales (ganoid, cycloid ctenoid or absent). Spiracle and lunar plate absent.

Question 16

Different Scales

Answer 16

Placoid scales (sharp looking, chondrichthyan), cosmoid scales (rounded, sarcopterygian). Ganoid/cycloid/ctenoid scales (Actinopterygian).

Question 17

Fish labels (start at anterior, then dorsal, posterior and ventral, then back to anterior)

Answer 17

Mouth, pectoral fin, dorsal fin(s), caudal fin, anal fin, pelvic fin, gill flap (and then back to mouth).

Question 17

Ossification

Answer 17

Of endoskeleton or jaw is to strengthen. Came through Placoderms, transferred to Actionopterygii and Sarcopterygii.