Jawless Fishes & Gnathostomes: Chondrichthyes

Question 1

Identify the diagnostic features, explain adaptations of hagfish and lamprey

Answer 1

hagfish/ lamprey- jawless, no paired appendages, monophyletic (from same origin)

Question 2

Explain the evolution of “jaws” and importance in feeding ecology

Answer 2

Expanded realm by moving into water column, away from bottom dwelling; jaws were originally a gill arch

Question 3

Discuss Gnathostomes and two main groups of modern fish

Answer 3

Gnathostomes- Fish with jaws.
Two main groups (modern)- Cartilaginous fish (Chondrichthyes)- sharks, rays, skates, & chimaeras
Bony fish (Euteleostomi)- replaced ostichthyes

Question 4

Explain phylogeny and identify different families & representative species in Class Chondrichthyes

Answer 4

Chimaeras, sharks, & rays

Question 5

Discuss differences between stingrays and skates

Answer 5

Stingrays- viviparity, large, thinner tails, barb on dorsal, have spiracles, pectoral fins, & pelvic fin.

Skates- oviparity, smaller, thicker tails, spiracle, pelvic, & dorsal fin.

Question 6

Order Myxiniformes (Hagfishes)

Answer 6

simple, cartilagenous skeleton; 1 semicircular canal in inner ear; rudimentary eyes; 1-16 pairs on external gill aperatures; ventolateral surface: glands produce slime (protects while feeding on carcasses); marine only; developed from large meroblastic egg

Question 7

Order Petromyzontiformes (Lampreys)

Answer 7

Cartiligenous skeleton;
2 semicircular canals (inner ear);
eel-like body;
7 pairs lateral gill openings;
2 types (parasites, non- feeding forms)

Question 7

Extinct Ostracoderms

Answer 7

Mineralized tissue in dermis- hard exoskeleton

Question 8

Gnathostomes

Answer 8

Fishes with Jaws

Question 9

Subclass Holocephali (Order Chimaeriformes)

Answer 9

Single gill cover;
no spiracle;
upper jaw fused to cranium;
no scales;
2 dorsal (1st venom);
male w/ claspers;
inferior mouth;
all marine; respire through nostrils; hylostylic jaw (primitive jaw, mandible fused to cranium)

Question 10

Subclass Elasmobranchii (Sharks and Rays)

Answer 10

Cartilaginous endoskeletons (can be calcified);
jaw suspension hyostylic or amphistylic;
Branchial skeleton posterior to neurocranium;
dermal denticles (placoid scales (decr. drag), some no scales);
5-7 gill open. each side;
males with claspers;
no gas bladder;
can replace teeth

Question 10

Class Chondricthyes

Answer 10

Jaws & Paired appendages;
Cartilaginous vertebrae;
Some feed on plankton;
no bone; Ampullae of Lorenzini (pourous structures, detect electrical fields); no swim bladder; fatty liver; lateral line present; placoid scales;
more developed eyes/ brain

Question 11

Squalea

Answer 11

inferior mouth; Rays- venomous barb;

Question 12

Galeomorphii

Answer 12

subterminal mouth; countershading; jaw suspension; dorsal, pectoral, anal fins; appendages; lack spine; 5 gill slits; some with spiracles; many rows of teeth; Ampullae Lorenzini;
placoid scales

Question 13

Batoidea/ Squalea

Answer 13

dorsal; spiracles; depressiform; some with electric organs; some give live birth; cartilagenous endoskeleton (can be calcified); jaw suspension: hydrostylic or amphistylic; 5-7 gill slits; no gas bladder; cloaca

Question 14

Batodea

Answer 14

depressiform; electric organs; pectoral extended/ fused to head; electroplaque

Question 15

No paired appendages?

Answer 15

Agnathostomas

Question 16

Paired appendages?

Answer 16

Gnathostomata

Question 17

Lamniformes

Answer 17

Different shark species (great white shark, thresher shark, goblin sharks, mako sharks, sand tiger sharks, basking sharks)