Smithsonian National Museum of Natural History Geologic Time The Story of a Changing Earth
Presented by the Department of Paleobiology.
The Mississippian
Contents
Overview
Life in the Seas
Tetrapods and Other Life on Land
Mississippian Tectonics and Climate
Evidence
Mississippian brachiopods
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references and links
Foundational Concepts
Dating Methods
Earth Processes
Life Processes
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Tetrapods and Other Life on Land
The forests of the Early Mississippian were not like those of the preceding Devonian. The predominant tree of the Late Devonian, Archaeopteris, disappeared, and new, more diverse plants took its place. Forests in the Early Mississippian were initially dominated by short, weedy plants such as pteridosperms. There is controversy over which Late Devonian or Mississippian pteridosperms are the sister group to all other seed plants. In the stable, warm Mississippian climate, the terrestrial flora became increasingly lush. Mississippian plants were almost entirely different from those of today. Seed plants, which tended to live in better-drained habitats, were primarily pteridosperms and cordaites (closely related to modern conifers); these were accompanied by giant horsetails (calamites), tree ferns of the Marattiales (which still survive in the tropics today). Lycopsid trees preferred wetter areas. Such plants formed a lush environment and habitats for arthropods such as myriapods (millipedes and centipedes), cockroaches, and winged insects.

Terrestrial arthropods in turn became food for early tetrapods: the Mississippian was a time of great tetrapod evolutionary radiation. Many tetrapods were still semiaquatic, but a great variety of early terrestrial forms had appeared as well. Early forms such as Ichthyostega and Acanthostega had now been replaced by many new species. Most of these later Paleozoic amphibians are divided into two major groups—labyrinthodonts and lepospondyls. Labyrinthodonts include temnospondyls and anthracosaurs (or batrachosaurs), which differ from each other in skull and vertebral anatomy. Although it has been difficult to link the modern types of amphibians to these early tetrapods, paleontologists believe that they were quite similar in basic biology. Like modern amphibians, early tetrapods were probably tied to the water throughout their lives. Their eggs, which were not surrounded by any protective covering (other than a porous membrane), were probably fertilized in the water.


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Overview | Life in the Seas | Tetrapods and Other Life on Land
Mississippian Tectonics and Climate



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