Marine Invertebrates Ebook
Concealed with this buried tropical forest were the remains of aquatic invertebrates. From his early studies on the Downs, Gideon Mantell was an expert on the marine invertebrates of the chalk deposits. The invertebrates of the Weald were different. He could not see the familiar whorls of the ammonite or snake-stone, of belemnites, nautilus or other shelled creatures which once swarmed in the primitive seas that formed the chalk. Instead there were the casts of shells that he did not recognise impressions sometimes so faint that they left just the barest trace of their external forms the hinge of two joined shells, as in certain types of clam and pearl mussel, or the fragmentary pieces of a species of snail, perhaps. It was indeed tantalising fragments both familiar and unfamiliar, never quite forming a complete fossil or displaying a clear marking. Uncertain what they could be, Mantell wrote to his usual correspondents such as James Sowerby, an expert on fossil shells, hoping he...
Say that the early Paleozoic was the age of trilobites, even though their remains dominate the fossil record of that period. We now know that a surprising richness of other marine invertebrates constituted only of soft parts did coexist with the trilobites and that trilobites represented only a small fraction of a major proliferation of arthopods.
The first paper suggesting this cause appeared only after the turn of the millennium, in 2001. This is the most journalist friendly of the various scenarios and is a scientific descendant of the Alvarez Impact Hypothesis of 1980, which had been formulated for the end-Cretaceous catastrophe. The major proponents of impact as the cause of the Permian extinction are Luann Becker of the University of California at Santa Barbara and Robert Poreda of the State University of New York, who in the first part of this century announced that Bucky Balls claimed to have been found at Permian-Triassic boundaries at several locales around the globe are evidence of large-body impact some 251 million years ago. About a year after this initial report, which was published in the prestigious journal Science and accompanied by worldwide publicity, they announced that they had found the crater as well, a structure named Bedout located near Australia. At that time newly...
The oxygen high of the Carboniferous-early Permian. Just such a finding has recently been made. In 2005, paleontologist Matthew Powell of Johns Hopkins University compiled voluminous data on the fates of various marine invertebrates during this oxygen high. He discovered very low rates of both origination and extinction. In other words, few new taxa appeared, and those that were already present rarely went extinct. The marine world was composed of an assemblage of virtual living fossils, which are characterized by long ranges (they existed for long periods of time) and produced very few new species.
Suspension feeders may be epifaunal, infaunal or pelagic. They include sedentary animals like corals, bryozoans, brachiopods, many bivalves and the crinoids, all of which have well-developed hard parts and are thus common as fossils. Their main food supply is probably diatoms and other protists which rely on photosynthesis, and which can thus only develop in abundance very near the surface of the sea (Ryther, 1963). The pelagic larval stages of many marine invertebrates also feed on these protists and live with them near the surface of the oceans. These larvae are also an important part of the marine food chain. Much more of this (protist and larval) food supply is thus available on the sea floor in shallow water areas these are the areas, both today and in the Palaeozoic, where the majority of suspension feeders live.
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