Sharks, skates, & rays

Question 0

What kind of scales & teeth do they have?

Answer 0

Placoid scales

Teeth are modified placoid scales

Question 1

What kind of stomach and intestines do they have?

Answer 1

J-shaped stomach & spiral valve intestines.

Intestines allow for better absorption of nutrients.

Question 2

What type of fins do they have?

Answer 2

Paired pectoral & pectoral fins

Heteroceral caudal fins

Question 3

Tell me about their endoskeleton

Answer 3

Cartilaginous endoskeleton

Brain w/ cerebellum & medulla oblengata associated w/3 pairs of semicircular canals

Question 4

What do they do to prevent water from being their bodies osmotically?

Answer 4

Elasmobranches retain nitrogenous compounds in their extracellular fluid. This raises the blood solute concentration to exceed lightly that of seawater, eliminating osmotic inequality.

(urea and trimethylamine oxide)

Question 5

What type of fish is believed to be diverged from shark lineage?

Answer 5

Chimaeras & rat fish

Question 6

Chimaeras or ratfish

Answer 6

• Diverged from sharks
• Jaws w/ large flat grinding plates
• Naked skin & diphycercal tail
• Spiral valve, NO stomach
• 4 pairs of gills covered by an operculum