FROM FINS TO LIMBS

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.

Land animals with legs evolved from aquatic animals with fins.

Four strong fins supported and propelled Eusthenopteron along the bottom of streams and ponds. Fossil trackways suggest that this lobefin could crawl across muddy ground, probably in search of deeper water.

Ichtyostega had sturdy legs and feet (with toes!) for walking. This lobefin had scales, a tailfin, and a lateral line system for detecting underwater mechanical impulses.

lobefins: limbed vertebrates including Eusthenopteron , Ichtyostega , and tetrapods (four-legged land animals)

New features:

  • new joint in skull increases power of bite, drives fangs on palate into prey
  • enamel covers dentine in teeth
  • ring of four or more bones supports eyeball
  • new outer layers cover body scales

When? 380 million years ago to present

PICTURE CAPTIONS:

  • Icthyostega (ik-thee-o- STAY -gah)
    This tetrapod relative had limbs with fingers and toes that improved traction on the muddy bottom of streams and ponds. Hips connected its limbs to the backbone for walking -- even on land.
    360 to 345 million years ago; Greenland
  • Eusthenopteron (you-sthen- OP -ter-on)
    This early lobefin prowled the bottoms of freshwater swamps. Although not a strong swimmer, it probably lunged short distances to catch or ambush its prey
    360 to 345 million years ago; Europe and North America
  • Diagram showing common ancestry and evolution of Eushtenopteron, Ichthyostega , and amphibians/amniotes from organisms with a nose that opens into mouth. Evolution of Ichthyostega and amphibians/amniotes is where fingers and toes and hip bones attached to backbone branch off.