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Epilogue: Diving in the Cincinnatian Sea

Richard Arnold Davis Indiana University Press ePub

 

Many paleontologists, ourselves included, became fascinated with fossils and embarked on scientific careers long before we ever encountered living marine animals. For many of us, the greatest thrill has been our first encounters with living representatives of the animal groups we knew first only as grey, lifeless forms encased in rock. Both of us have been privileged to examine firsthand living relatives of animals of our favorite groups of fossils—crinoids for Meyer and nautiloid cephalopods for Davis. Our experiences have fueled a curiosity that affects practically anyone who contemplates the fossil richness of the Cincinnatian or other comparable fossiliferous strata. Many times, in the field, we stand on a Cincinnatian outcrop where fossils are abundant in almost every rock, and we wonder: what did the Cincinnatian sea actually look like? How did these creatures behave when alive? If we could travel back in time to dive into the Cincinnatian sea, what would we see?

In his book The Crucible of Creation, the paleontologist Simon Conway Morris (1998) takes the reader on a journey through time in an imaginary time machine that lands on the shores of the Cambrian sea in western Canada of 520 million years ago. The time machine then descends into the sea and enables time traveling scientists to view the varied and bizarre animals found as fossils in the famous Burgess Shale. Conway Morris recreated the environment of the Cambrian sea and the life within it from the evidence of the fossils and rocks, but he embellished the scenario with a measure of speculation and fantasy.

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Appendix 2. Individuals and Institutions Associated with the type-cincinnatian

Richard Arnold Davis Indiana University Press ePub

 

The following is a list of the names of individuals and institutions associated with the Cincinnati region, and, especially, its geology and paleontology. Some of the individuals listed were members of the Cincinnati School; most were not.

There are some potential problems with this list. In some instances, there are two people with similar, but different names, but who may not be different people. For example, different sources refer to a J. H. Hall and a John W. Hall associated with the Cincinnati Society of Natural History, and there is I. Harris, I. H. Harris, and I. M. Harris, all of Waynesville, Ohio. George Vallandingham and George Vallandigham are almost certainly the same person, and the latter probably is the correct spelling, but maybe not.

In this volume, we present photographs of some of the people discussed. Many of the individuals portrayed are sufficiently well known that there is little question of identification. In some instances, however, a photograph is the only one of which we are aware that is supposed to represent the person in question. The identification may be based on a hand written notation on the photograph or on the album page that bears the photograph, with no independent verification. We hope that such identifications are correct.

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8 Brachiopods: The Other Bivalves

Richard Arnold Davis Indiana University Press ePub

Figure 8.1. Comparison of a brachiopod with a pelecypod. A and B, pelecypod. C and D, Platystrophia ponderosa showing sulcus and fold. Drawings from Meek (1873), courtesy of the Ohio Department of Natural Resources Division of Geological Survey.

 

Brachiopods are among the most common fossils in the Ordovician rocks of the Cincinnati area. Only fossils of bryozoans are more numerous to the naked eye. In a study of type-Cincinnatian limestones, Martin (1975) reported that brachiopods and bryozoans together constitute about 60 percent of the fossil fragments comprising the limestones. There even are some layers, for example, in the Bellevue Limestone, in which the rock is a veritable coquina, in this case consisting of complete and nearly complete shells of large, flat brachiopods of a single genus. These aptly named “shingled Rafinesquina beds” commonly are thought of as remains of very shallow water deposits reminiscent of the shingled beaches of today. Although they have been living on Earth since the Cambrian Period, brachiopods are not well-known animals to most of us. In fact, many folks confuse them with that group of molluscs that includes the clams. Members of the phylum Brachiopoda and those of the molluscan class Pelecypoda are bivalved animals, that is, each has a shell that consists of two valves. But there the resemblance ends. The brachiopods and pelecypods are otherwise strikingly different animals.

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11 Arthropods: Trilobites and Other Legged Creatures

Richard Arnold Davis Indiana University Press ePub

Figure 11.1. The Ordovician trilobite Triarthrus. Left, dorsal view, right, ventral view. Drawings by Kevina Vulinec.

 

In terms of sheer abundance, species diversity, and exploitation of habitats, arthropods rank as the most successful of all living animals. More than 750,000 species (mostly insects) inhabit a vast range of environments on land, in the sea, and in fresh water. Living arthropods include the insects, crustaceans, horseshoe crabs, arachnids, centipedes, and millipedes. During the Ordovician, arthropods had not yet invaded the land, but trilobites were abundant and diverse in the sea, along with the eurypterids, ostracodes, and a few other minor groups.

Despite their bewildering variety of form, all arthropods share certain basic features. Like their close relatives, the annelid worms, arthropods have a segmented body. Unlike the annelids, the body and its appendages are encased in an exoskeleton composed of the protein chitin. The exoskeleton is much like a suit of armor in having rigid components articulated by flexible joints. (The name arthropod means “jointed legs.”) Not only does the exoskeleton shield the internal organs from predation and some environmental hazards, but it also provides rigid points for muscle attachment. Consequently, arthropods are capable of rapid locomotion by walking, swimming, or flying. The nature of the exoskeleton has two important implications for the fossilization potential of arthropods. First, because the chitinous exoskeleton decomposes after death, many arthropods are poor candidates for fossil preservation. However, arthropods that have thicker exoskeletons or incorporation of calcium carbonate into their skeletons (such as some crustaceans and trilobites) will have enhanced potential for preservation. Second, all arthropods grow by periodically shedding the exoskeleton and forming a new skin that accommodates growth. Each individual arthropod can contribute numerous shed exoskeletons (molts) as potential fossils during its lifetime. Molting may thus explain in part the abundance of some arthropod fossils.

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12 Echinoderms: A World Unto Themselves

Richard Arnold Davis Indiana University Press ePub

Figure 12.1. One skeletal element of a modern crinoid, showing the porous microstructure (stereom) typical of all echinoderms. The arm of a crinoid is composed of a series of these elements, connected by muscles and ligaments. Comactinia sp., Caribbean. Scanning electron micrograph,×79.

Figure 12.2. Arm of modern crinoid (dark) with pinnules (light branches) bearing fine tube feet in feeding posture. Pinnule length about 1 cm. Aquarium photo, comasterid crinoid, Curaçao, Netherlands Antilles

 

Echinoderms are among the rarest and most sought-after fossils in the Cincinnatian rocks. Not only are they complex in form and structure, but they also possess a certain beauty and mystery that never fail to attract interest. Anyone who has visited the seashore is familiar with living echinoderms such as sea stars or starfish (asteroids), sea urchins, and sand dollars (both echinoids) (Plate 9). Other living echinoderms found in deeper marine waters are the sea lilies and feather stars (crinoids), brittle stars (ophiuroids), and sea cucumbers (holothuroids) (Plate 9). There are about 6650 living species of echinoderms, and over 3500 genera and 13,000 described fossil species.

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