radiation of the ray-finned fishes

Question 1

Actinopterygii (Gnathostomata class)

Answer 1

• 26,891 living spp
• sister group to sarcopterygii
• monophyletic but not strong derived characters
  
  • scales :ganoid , cycloid , ctenoid or absent
  • spiracle absent
  • gular plate absent

Question 2

Actinopterygii subclasses

Answer 2

3 subclasses :
1. Cladistia (16 spp)
2. Chondrostei (27 spp)
3. Neopterygii

Question 3

Neopterygii (Actinopterygii subclass)

Answer 3

equal numbers of fin rays as supports in dorsal and anal fins
3 orders:
1. Lepisosteiformes (Gars): 7 spp
2. Amiiformes (Bowfin) : 1 spp
3. Teleostei : 26,840 spp

Question 4

Teleostei (Neopterygii division)

Answer 4

• mobile premaxilla
• neural arches on dorsal side of tail base -> uroneural bones
• ventral pharyngeal tooth plates unpaired
• particular arrangement of skull bones

Question 5

lower Teleostei skeletal feature and scales

Answer 5

• 60-80 ossified vertebrae
• many vertebral accessories
• many bones in skull
• many bones/rays in tail
• six or more fin rays in paired fins
• cycloid (heavy) scales

Question 6

higher Teleostei skeletal feature and scales

Answer 6

• 20-30 ossified vertebrae
• few vertebral accessories
• few bone sin skull
• six or fewer fin rays in paired fins
• ctenoid (light) scales

Question 7

soft rays

Answer 7

• usually soft and not pointed
• segmented
• usually branched
• bilateral, left and right halves

Question 8

Spines

Answer 8

• usually hard and pointed
• unsegmented
• unbranched
• solid

Question 9

gas bladder

Answer 9

arose either as breathing or buoyancy device
- living preteleosts (e.g gar) and basal teleosts (e.g herring) are physostomous: gas released through pneumatic duct
- derived teleosts (e.g seabass) are physoclistous : gas excn=hanged across rete mirable

Question 10

trends in teleostean phylogeny

Answer 10

• Reduction in bony elements
• Shifts in position / use of the dorsal fin
• Shifts in placement and function of paired fins
• Caudal fin and gas bladder modifications
• Modifications to feeding apparatus

A suite of interrelated trends:
* Increased speed, manoeuvrability and feeding capability
* No significant loss of defensive structures
* Diversity of swimming types and morphology

Similar (independent) trends in other groups of fish