From Water to Land

Topics: Tetrapod, Vertebrate, Sarcopterygii Pages: 4 (1213 words) Published: October 8, 1999
From Water to Land (Revision)
The early tetrapods were the first vertebrates to actually walk the solid earth. They began their conquest of land in the Paleozoic era around 360 million years ago. The question many paleontologists have been asking for a long period of time is whether the anatomy for locomotion on land was developed in water for swimming purposes, or if it was adapted after the creatures became terrestrial. Recent findings of fossils indicate that the transformations of the aquatic creatures happened underwater in order to help them survive in the changing world. When looking for answers, they had to examine forearm, hip, wrist, finger, and other bones, as well as the lungs or gills of the early tetrapod fossils. This information is critical in understanding the history and the process of growth and change. It aids in learning about human evolution. Background:

Tetrapods are creatures with four limbs, hips, shoulders, fingers, and toes, which developed sometime after lobe-finned fish, and before the first fully terrestrial vertebrates. The earliest tetrapod known is Acanthostega. It is also considered the most primitive tetrapod. It is very close to its fish ancestry, but still anatomically far from its terrestrial relatives. These creatures still lived in water, but they had a lot of the terrestrial tetrapod anatomical characteristics. Introduction:

Before tetrapods existed, all vertebrates were confined to living in aquatic habitats. The only animals that lived on land were arthropods. Through natural adaptations, the fish developed into amphibians. This colossal stage of change made necessary the evolution of new ways of breathing, locomotion, and reproduction. Paleontologists needed to understand how this transition took place. If the changes in anatomy of the fish developed on land, then they served the same purposes they serve today, such as walking. But what advantages would those same body parts give to the aquatic...

References: Gardiner, David M., Torok, Maureen A., Mullen, Lina M., Bryant, Susan V. (September
1998). Evolution of vertebrate limbs: robust morphology and flexible
development. American Zoologist, v38, n4 659
McAuliffe, Kathleen. (August, 1993). Retracing the footsteps of evolution. (fossil
remains of an early tetrapod discovered in a museum) Omni v15, n10, 16
Zimmer, Carl. (June, 1995). Coming onto the land. Discover v16, n6 , 118
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