The atlas is organized in six main sections corresponding to the geologic periods that contain the fossil record of trilobites, from their appearance at the beginning of the Cambrian to their demise at the end of the Permian. Each section is preceded by a listing of the trilobite families that are found in that particular geologic time interval, in order of appearance, following the information available in the Treatise (Moore 1959). The genuses illustrated by atlas plates are indicated in parentheses for each family. Since a time sequence translates into a depth series in the geologic column, the customary subdivisions of each geologic period into Early, Middle, and Late epochs correspond to Lower, Middle, and Upper series when referring to the stratigraphic position. Thus the latter nomenclature will be used in indicating the survival time span for each family. A number of families survived over more than one particular geologic period. Arrows pointing to the left or right of each series name indicate earlier or later presence of that particular family in the geologic column.
Unfortunately, it is not possible to maintain a chronological ordering of the first appearance of each family and at the same time preserve evolutionary continuity when a particular family is present throughout more than one period. In a few of these cases, then, related forms will appear at different locations in the atlas.
The captions accompanying the plates contain detailed taxonomic and strati-graphic information but also stress general and often nontechnical features. It should be emphasized that the vastness and diversity of the fossil record of trilobites prevents an exhaustive coverage of the material, with large format photographs. The visual impact of this choice of presentation is the trade-off of a more encyclopedic approach, beyond the scope of my atlas. The main preoccupation here has been that of presenting more vivid, real life trilobite reproductions, than, for example, those provided by the accurate drawings which adorn the professional literature. Furthermore, trilobites are generally small, and reproductions in natural size tend to become insignificant. Adequate enlargement often reveals a lot more than the unaided eye can see. In selecting the photographs to be included in each section, I have been partial to their aesthetic appeal, and I have also taken irreverent liberties in choosing mostly perfect specimens for presentation and in deliberately using nonconventional photographic techniques. Since, with rare exceptions, I have preferred to rely on my own photography, the trilobite specimens had to be available in my laboratory. Thus a large number of specimens originate from my own personal collection or were borrowed from various museums. On a few occasions, I transported my photographic equipment on location to have direct access to exceptional private collections. Although, for this revised edition, I made an effort to limit repetition and broaden the range of coverage, the atlas is still based on a very limited selection of trilobite specimens that I was able to photograph on my spare time.
One of my wishes has been to point out, with these pictures, that dinosaurs were not the only prehistoric animals that inspire awe and fascination. Trilobites tell us of an earlier world, perhaps less threatening, when life on earth could still explode into a myriad of new, unseen, uncounted forms discovering their own way to survive. They tell us of a time scale that transcends our power of imagination and how these immense spans of time allowed them to experiment and develop models and methods of biological function, vision perhaps above all, that are as awe-inspiring as the advent of giant behemoths.
Explanatory Note on Abbreviations and Nomenclature Adopted in the Adas
The following abbreviation code has been adopted in the atlas to indicate geologic column subdivision and other abbreviations used in the captions to atlas plates. This tabulation also includes the key to the word terminations used to denote taxonomic classification in invertebrate paleontology. In each legend the generic attribution (genus) is indicated first, followed by synonyms, if any, or other specifications. The combination of generic and trivial name for the species represented in the plate is indicated in italics. Whenever more than one species belonging to the same genus are presented in sequence, only the legend of the first plate of the sequence carries the generic name, author, and date. With the exceptions indicated in the captions, all photographs have been prepared by the author. Photographic techniques and specimen preparation are described in Appendix B of chapter 3. Unless a special technique is mentioned, the specimens have been photographed in air and uncoated.
Many of the specimens originate from the University of Chicago Walker Museum, now transferred to the Field Museum of Natural History in Chicago. The disposition of this material and that from other museums will be indicated in abbreviated form (see code). The names of private collectors who have either contributed photographs, loaned specimens to the author, or permitted the author to photograph specimens on location will be acknowledged in the captions. The responsibility for the classification and identification of specimens indicated by the term RLS id. rests solely with the author.
Atlas of Trilobite Photographs
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