Transcript KINGDOM ANIMALIA

KINGDOM ANIMALIA
Phylum Chordata
Subphylum Vertebrata
Class Chondrichthyes
Class Chondrichthyes
846 species of sharks and rays
Date to over 400 mya
Cartilaginous endoskeleton
Jawed
Well-developed pectoral/pelvic fins,
powerful tail fin
Skin is rough due to numerous
placoid scales (constantly worn
out/replaced)
Class Chondrichthyes
Teeth = enlarged
placoid scales
Teeth form in actively
growing skin areas in
mouth just behind
upper/lower jaws; skin
grows, teeth pushed
over edge of jaw and
increase in size
Teeth worn =
reabsorbed or lost
In rays, teeth fuse to
form bony plates
Class Chondrichthyes
Internal fertilization facilitated via
unique pelvic claspers on males
Anamniote eggs encapsulated in
leathery case or retained in body until
birth of living young
Class Chondrichthyes
2 informal groups: differ
in body plan and dentition
1. Sharks (359 species)
– powerful swimmers
– mid-water dwelling
– solitary predators
2. Rays (456 species)
– dorsoventrally flattened,
enlarged pectoral fins-subject to waves of
muscular contraction
– bottom-dwelling
– eat shelled inverts (crush)
Class Chondrichthyes
Most marine, some taxa are
estuarine or freshwater (28
species)
Range in size (from 20 cm to
over 12 m)
Commercially important in
food, cosmetic, pharmaceutical,
and medical products
Estimated 771,400 tons of
sharks/rays harvested each
year by humans (while only 30
humans-2.6 tons harvested by
sharks)