AN ANNOTATED SYNOPSIS OF PALEOZOIC FOSSIL SPORES 



AND 



THE DEFINITION OF GENERIC GROUPS 



BY 



J. M. ScHOPF, L. R. Wilson, and Ray Bentall 



INTRODUCTION 



The literature on fossil spores is scat- 

 tered, and in addition there has been much 

 diversity in methods of classification. The 

 objects of the present article are to bring 

 this material together in summary form 

 for convenient taxonomic reference and to 

 evaluate the genera which have been pre- 

 viously proposed. After a study of these 

 microfossils in America and a thorough 

 study of the literature it seems essential 

 also to describe some new genera. It is 

 hoped that a fundamentally sound basis 

 has been provided for studies now in 

 progress in the three laboratories repre- 

 sented by the authors and for future 

 studies. 



Guiding principles which relate to the 

 treatment of this material are given below. 



1. Only adherence to the systematic 

 principles embodied in the International 

 Rules will give satisfactory results in the 

 study of these microfossils (as in other 

 fields of paleontologic study). Therefore, 

 the International Rules of Botanical 

 Nomenclature, 3rd edition (Briquet), re- 

 vised by the International Botanical Con- 

 gress of Cambridge, 1930, and published 

 in 1935,^ have been used as a basis for 

 taxonomic treatment. 



2. Species classified within the same 

 genus or under the same generic name 

 must possess significant characteristics in 

 common. There can be little positive proof 

 of generic identity unless substantial 

 homologous comparisons can be drawn be- 

 tween respective biocharacters of each 

 congeneric species and the type species of 

 the genus. For example many isolated 

 lycopsid megaspores must be classified 

 separately from the microspores found in 



^ Gustav Fischer, Jena. 



association with them because there is no 

 adequate basis for close comparison of 

 biocharacters exhibited by these diversified 

 organs. 



When affinities become better known 

 so that the difficulty due to uncomparable 

 features may be partially overcome, it 

 then may be possible to relate the forms 

 more naturally in classification within 

 suprageneric groups such as tribe, family, 

 and subfamily depending on how closely 

 information may be correlated. Indeed, 

 assignment to the same genus, or even 

 species, is theoretically possible and may 

 eventually be achieved in some few in- 

 stances, but in general this implies a much 

 more precise and detailed historical knowl- 

 edge of interrelationships than is likely to 

 be fully established. 



For satisfactory nomenclature it is most 

 convenient that those fossils which possess 

 numerous demonstrably comparable fea- 

 tures shall be placed under the same ge- 

 neric name. However, it* is unsatisfactory 

 to classify fossils under the same generic 

 name simply because a few arbitrary fea- 

 tures are held in common. The essential 

 validity of any classification depends on 

 the relative significance that attaches to the 

 various biocharacters. In fact it is by 

 virtue of such interpretive discrimination 

 that taxonomy is to be distinguished from 

 a cataloging procedure. Interpretations 

 nevertheless must be based on evidence and 

 not on supposition ; difficulties are multi- 

 plied whenever interpretation exceeds fac- 

 tual bounds. 



3. In paleobotanical practice there has 

 been much divergence with regard to the 

 significance and proper interpretation of 

 unusually complete specimens in which 

 parts usually found separated, and there- 

 fore generally classified separately, are 



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