Classification of the Animal Kingdom

Classification of the — ANIMAL KINGDOM Richard E. Blackwelder Classification of the Animal Kingdom CLASSIFICATION OF THE ANIMAL KINGDOM Richard E. Blackwelder SOUTHERN ILLINOIS UNIVERSITY PRESS Carbondale, Illinois COPYRIGHT © 1963 by Southern Illinois University Press All rights reserved LIBRARY OF CONGRESS CATALOG CARD NUMBER 62-17618 PRINTED IN THE UNITED STATES OF AMERICA DESIGNED BY ANDOR BRAUN CONTENTS INTRODUCTION 1 Simplified List of Recent Phyla 6 Simplified List of Recent Classes and Orders, with Common Names 9 Notes on the Taxa 26 Complete List of Phyla 36 Complete List of Classes and Orders, with Synonyms, Subgroups, and Geologic Range 39 BIBLIOGRAPHY 72 INDEX TO COMMON NAMES 75 INDEX TO LATIN NAMES 80 INTRODUCTION THE CLASSIFICATION OF ANIMALS is Still Very much a field in which discovery and revision are continuing, even after two hundred years of study. The importance of classification in biology increases every year, because the experimental and practical fields find increasing need for accurate identification of animals and for understanding of comparative relationships. At least one outstanding biologist has opposed pubUcation of this new classification on the ground that it would be accepted as final, the classification, and would tend to make students think that all higher classification is finished. The intention of the compiler is just the op- posite. Just as this classification is different in detail from all previous ones, so will future editions be still different, as we learn more about the comparative features of animals. It is anticipated that every new edition will spur students of the individual groups to propose improvements. It is therefore planned to issue corrected editions whenever appropriate. The very appearance of these subsequent editions will emphasize the growth of understanding of animal groups. Only one ostensibly complete classification of animals, living and fossil, has been published in recent years. That classification, by A. S. Pearse of Duke University, is a good one, based on the views of many specialists. Certain mechanical faults make it less usable than it should be, and the need for revision gave the original impetus to preparation of the present classification. Because Pearse did not usually indicate the source of his arrangements, he is not here cited as an authority. Never- theless, the two classifications are basically very similar. No other single classification has been found that agrees so closely with the conclusions of the present study. It should be emphasized that, within certain limits, this classification is not a simple compilation of the views of specific workers. In nearly all details, choices have been made between conflicting schemes CLASSIFICATION OF THE ANIMAL KINGDOM 2 of various authors, not on the basis of the reputation of those authors but on my judgment of the soundness of their supporting arguments or on my analysis of the data they present. In none of the larger groups has the work of any single author been accepted without modification. Several considerations have influenced the decisions embodied in this classification. First, a false picture is given by a simplified classification, because the existing diversity is one of the principal features of the animal kingdom. Therefore, no groups should be combined merely for the sake of sim- plicity. Second, although the previous item would seem to require coverage of the groupings at all possible levels, to show the extreme range of division and subdivision, this is not in fact possible. Not only are there many conflicting groupings at certain levels, such as of phyla or orders, but there is no practical way to show these groupings in a general classification. It is a compromise that is believed to be effective to subdivide the phyla only into classes, subclasses, and orders. Other possible groupings, such as subphyla and superorders are referred to in the notes. Third, two groups which are so distinct at any level that they cannot be described in common terms must be separated at that level. (For example, Pterobranchia and Enteropneusta; see the Notes on the Taxa.) Fourth, groups which cannot be distinguished at any particular level by the type of characters used for their neighbors must be combined at that level. (For example, the sometime classes of Nematoda.) Fifth, the discovery of groupings within a class, for example, does not justify the creation of new classes for each of the subgroups. The proper level for the new groups can only be determined by comparison with neighboring parts of the classification. Sixth, although uniformity in the form (endings) of names at each level would unquestionably be helpful, it cannot now be attained without adding greatly to the total of name forms and synonyms. The systems so far proposed are so diverse as to introduce further confusion of their own. None of the systems has been widely enough accepted to be entitled to adoption throughout the Animal Kingdom. None has been so widely accepted on a world basis, even in one group, as to indicate Introduction 3 universal acceptance in the near future. Indeed, even the ordinal endings in -iformes adopted by American ichthyologists and ornithologists are almost entirely unused in the rest of the world. The resulting names are unnecessarily long and cumbersome. The system does not relieve any- one from learning the shorter forms also. The latter are used here, with the uniform-ending forms listed as synonyms. In other groups, usage of the source of the classification is followed as to spelling, in most cases. There are a variety of systems in use and no obvious trend to- ward adoption of any single system. This classification attempts to show the various spellings as well as the various synonyms. Each zoologist will choose which one he wishes to use in each case. Seventh, no single rule will suffice for choice of names where several apply to a single taxon. Reasons for each decision are given in the text in many cases, but in general it has been the goal to retain the best known names, at the most appropriate level, regardless of homonymy. Priority is considered to be of secondary importance at these levels. Eighth, although considerable homonymy exists at all levels, even up to that of phylum names, there is almost no real confusion caused thereby. Until there are direct rules to govern the decisions, there seems to be nothing gained by replacing well known names, such as Decapoda (either in the Cephalopoda or in the Crustacea). This classification is in three parts, the purposes of which are quite different. In order of preparation, these are: 1] the complete classification, including lists of the phyla and of the classes and orders, of all animals, living and fossil; 2] the justification for unusual features in this classification; and 3] a simplified classification of Recent animals for student use, with common names, again including lists of the phyla and of the classes and orders. The arrangement of these parts in the book is just the reverse of this. In both lists, the phyla are first arranged in four subkingdoms, and one of these is divided into four series. Many other groupings of these phyla are possible, and several are shown in the footnotes of the section Complete List of Phyla. It is not here believed that these supra-phylum groupings are of much significance at this phase of the knowledge of animals. In both lists of orders, these orders are arranged in the appropriate classes and subclasses. No other levels, such as superorder, are rec- CLASSIFICATION OF THE ANIMAL KINGDOM 4 ognized. They may be of use in some circumstances but seem to be of little value in showing the arrangement of the orders on a practical basis. Throughout, rejected synonyms are printed in itaUcs, the accepted class names are in capital letters, and the subclass names and the order names are both set in capitals and lower case letters. In the footnotes, names that also appear in the classification above are printed in small capitals. The other names in the footnotes are somewhat in the nature of rejected synonyms, but as most of them are really the names of non- accepted groupings, they appear in capitals and lower case roman letters. To the variety of spellings there is no end. No attempt is made to list all forms, but such spellings as would appear at a separate place in an alphabetical index are listed, along with those variations that are used for distinct levels; e.g., Echiuroidea (phylum), Echiurida (class), and Echiuroina (order). In the Complete List of Orders the geologic range of each group is shown by symbols at the right margin. The meaning of these symbols is shown in the following table. REC Recent JUR Jurassic QUA Quaternary mes Mesozoic PLE Pleistocene per Permian PLI Pliocene pen Pennsylvanian OLI Oligocene mis Mississippian Mio Miocene car Carboniferous EOC Eocene (+ Paleocene) dev Devonian ter Tertiary sil Silurian CEN Cenozoic ord Ordovician CRE Cretaceous cam Cambrian TRI Triassic pal Paleozoic There are a few points of discrepancy between the Simplified List and the Complete List. These are intentional, to make the simplified list more useful to students. The Complete List shows the definitive classification that is here being proposed. The names included under the footnote heading "Includes" may be suborders, synonyms, rejected groups, or names of questionable ap- plication. They are all names which have at some time been used for orders or more inclusive groups and are included merely to indicate their approximate position in the scheme. 5 Introduction Several recent schemes of classification in particular groups are known to the compiler but are not followed herein. Some were received too late for study (e.g., part W of the Treatise of Invertebrate Paleon- tology).

Load more