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
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and Acanthostega had now been replaced by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.
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.
Life in the Seas |
Tetrapods and Other Life on Land
Mississippian Tectonics and Climate
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