Did Paleozoic Corals Have Zooxanthellae? The Ph

The Phylum Cnidaria can be traced from the late Proterozoic to the Holocene. Several major geologic boundaries occur throughout that span of time. The temporal intervals are often based on biological extinction and radiation events. For example, the Paleozoic begins at the Precambrian/Cambrian boundary and ends at the Permian/Triassic boundary. Analyses of carbon-12/carbon-13 data suggest that these boundaries were characterized by major alteration of the earth's biomass. Various Paleozoic Cnidaria corals became extinct at the end of the Permian. Whether or not these extinct corals gave rise to later orders remains uncertain. Certainly there are some significant differences between the Paleozoic corals and the zooxanthellate corals.

At one time, corals, sea anemones, and jellyfish were all grouped together with the ctenophores in the Phylum Coelenterata. More recently, however, these organisms have been classified as Cnidaria. This medium-sized phylum contains a large number of both solitary and colonial invertebrates (Oliver & Coates, 1987, p. 140). Although the animals occur in most aquatic environments, their fossils have only been found in marine sedimentary rocks.

The Cnidaria typically have primary radial symmetry and are, for the most part, anatomically simple. They have no specialized cells which are grouped into organs like those found in higher animals. Rather, their different cell types occur in onl

. . .
planulae. In addition to its living species, Anthozoa also has an extensive fossil record. The corals sometimes form thick beds in the Paleozoic. Moreover, these beds--which may occur in association with stromatoporoids--have been known to form reef-like masses. The Anthozoans are divided into the following three subclasses: Ceriantpatharia, Octocorallia, and Zoantharia (Clarkson, 1986, p. 85). The corals belong to subclass Zoantharia. Recent species occur worldwide at depths ranging from 0 to 2750 meters. Perhaps the earliest corals, however, have been described from Cambrian rocks. These coral-like skeletal fossils may have eventually give rise in the Early Ordovician to the Order Tabulata. By Middle Ordovician time, these tabulate corals had become common. Often this diverse group of organisms occurred as coral-stromatoporoid reefs. The tabulata were not actually frame-builders though; they had no effective means of attachment. In fact, the smaller members of the Order Tabulata typically lived in deeper waters (Clarkson, 1986, p. 103). Yet another important Paleozoic order of Zoantharia is Rugosa. These fossils first appear in Middle Ordovician rocks of the Blackriveran in North America. The organisms subsequen
. . .

Some common words found in the essay are:
Oliver Coates, Tabulata Rugose, Phylum Cnidaria, Cretaceous/Tertiary Magaritz, Scleractinia Rugosa, According Lang, Anthozoa Anthozoa, Corals Scleractinia, Proterozoic Holocene, Middle Ordovician, clarkson 1986, oliver coates 1987, oliver coates, coates 1987, paleozoic corals, hermatypic corals, phylum cnidaria, rugose corals, zooxanthellate corals, carbon isotope, permian/triassic boundary, clarkson 1986 80, paleozoic corals zooxanthellae, 1986 pp 103-104, clarkson 1986 pp,
Approximate Word count = 2582
Approximate Pages = 10 (250 words per page)

More Essays on Did Paleozoic Corals Have Zooxanthellae? The Ph