SKINS AND BONES

The image below is a photo of the exhibit panel. Following it is a transcript of the panel.

Photo of the panel from the exhibit.

The oldest vertebrates had outer skeletons made of plates of dentine. In later vertebrates, a layer of enamel covered the plates; their external armor consisted of "teeth." On some animals, the "teeth" fused into large shield plates that covered most of the body.

Sharks: jawed vertebrates with cartilaginous skeletons, including Cladoselache , skates, and rays
New features:

  • Denticles skin-teeth have a pulp cavity surrounded by layers of dentine and enamel
  • Unique pattern of tooth replacement rows of teeth in jaws are continuously replaced
  • Claspers extend from the male's pelvic fins to transfer sperm to the female during mating

When? 380 million years ago to present

Skin-teeth in modern sharks:

  • Toughen the skin; a feature that's especially useful for bottom-dwellers that scrape along the ocean floor
  • Streamline the skin. Tiny ridges on skin-teeth speed water flow over the body.
  • Protect against predators and external parasites.

Skin-teeth in ancient vertebrates:

  • Protected against predators and external parasites
  • May have detected physical or chemical changes in the water (exposed dentine is very sensitive -- think of a toothache!)

PICTURE CAPTIONS:

  • Diagram showing common ancestry and evolution of sharks, placoderms, and lunged vertebrates from organisms with jaws and stomach.
    3-D TOUCH SAMPLES:
  • shark skin
    Notorynchus cepedianus (recent specimen)
    Pacific Ocean
  • placoderm
    Bothriolepis canadensis (cast of fossil)
    370 million years ago; Quebec

Learn more about how today's Great White Sharks are related to the earliest shark species ( White Death ).