2 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 463 



INTRODUCTION 



Pennsylvanian plant flossils from the Mazon Creek area are better known 

 than any other compression flora of Illinois. Fertile specimens from the flora 

 have been described by Lesquereux (1866-1884), Sellards (1902, 1903), Darrah 

 (1936, 1937, 1938, 1970), Arnold (1938), Schopf (1948), Andrews and Mamay 

 (1948), Kosanke (1955), Chaloner (1956), Langford (1958, 1963), Delevoryas 

 (1964), Taylor (1967), and Taylor and Eggert (1969a, b) . The following fructifi- 

 cation genera of ferns and pteridosperms have been reported from Mazon Creek: 

 Asterotheca Presl, Codonotheca Sellards, Corynepteris Bailey, Crossotheca Zeiller, 

 Hymenotheca Potonii, Myriotheca Zeiller, Oligocarpia Goeppert, Ptychocarpus 

 Weiss, Radstockia Kidston, Renaultia Stur, Schopfitheca Delevoryas, Senften- 

 bergia Corda, Wittleseya Newberry, and Zeilleria Kidston. 



In addition to the above miospore fructifications, two rather poorly de- 

 fined genera, Sorocladus and Staphylopteris , were reported by Lesquereux (1880). 

 Inferences of the occurrences of other fertile genera from Mazon Creek are based 

 only on sterile foliage (Langford, 1958, 1963). In formal descriptions the prac- 

 tice of applying generic names of fructifications to sterile foliage is as misleading 

 as using sterile foliage names for fructifications. 



There are two nomenclatural systems for foliage fossils: one is a system 

 of form-species and form-genera of foliage; the other recognizes organ-species 

 and genera of fructifications, which can often be related to a family. One species 

 of fertile foliage may belong to two genera, one in each system, and geologically 

 oriented paleobotanists consider it helpful to express both genera. In certain 

 cases one form-species can be the foliage of either of two organ genera; for ex- 

 ample, Pecopteris miltoni can be the foliage of Asterotheca miltoni or Mokrawia 

 alberti (Knopp, 1933). Of the many nomenclatural practices in use we regard that 

 one used by Remy and Remy (1968) in, for example, Asterotheca (ex form-genus 

 Pecopteris) lamuriana as one of the clearest means of the generic designation of a 

 specimen of fertile foliage. A shorter version is adopted for fertile fronds, where 

 possible, in this study, for example, Asterotheca (ex Pecopteris) lamuriana . This 

 kind of designation should be applicable in any case where the form-genus is de- 

 terminable and well known. We suggest that only the form-genus and species be 

 used for specimens of sterile fronds even if fructifications are known from other 

 apparently identical foliage specimens. 



The spores found in situ in fructifications may be compared to genera 

 and species of dispersed spores but not assigned to them, because a separate 

 binomial system has been adopted for dispersed spores, which are found in rock 

 macerations without direct evidence of their natural affinities. 



This study was undertaken to gain more data about the correlation of spores 

 and megafossils. Only those fructification specimens which promised to yield 

 new data were selected. These include the genus Stellatheca, previously not 

 reported from North America; a new species, Myriotheca arnoldi ; and other species 

 of the genera Myriotheca , Corynepteris , Asterotheca , and ? Scolecopteris . 

 Spores isolated from these fructifications have been examined by light and 

 scanning electron microscopy and compared with Punctatisporites , Calamospora, 

 Cyclogranisporites , Apiculatasporites , Apiculatisporis , Micro re ticulatisporites , 

 Camptotriletes, and Laeviqatosporites. 



Information obtained from this study supports the conclusion that differences 

 exist between the flora of the No. 2 Coal and the flora represented by the Mazon 

 Creek compression fossils from the overlying Francis Creek Shale (Peppers and 

 Pfefferkorn, 1970). 



