20 



ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 500 



Discussion . — The two fragmentary specimens found in the Spencer 

 Farm Flora are 7 and 8 mm long. This fragmentary state has "been typical 

 of the specimens found in Europe, too. The Illinois specimens are simi- 

 lar to but smaller than the specimens from the Netherlands and Belgium. 

 Considering the normal variability of plants, the size does not consti- 

 tute a taxonomic difference (table 5). Stockmans and Williere (1953) 

 could show on detached pinnules that the pinnules are relatively broadly 

 attached and have as many as eleven lobes. In lateral view (if the pin- 

 nules are attached to an axis), only about five lobes can be seen. 



Gothan and Jongmans ( in : Jongmans , 1927) described Gulpenia 

 limburgensis , but did not include a figure. In 1928 (in: Jongmans, 

 1928), they described it again without giving a generic diagnosis. In 

 1955 9 Stockmans and Williere (in.: Leckwijck, Stockmans, and Williere, 

 1955) described the genus Thonia from beds of the Namurian A. They men- 

 tioned the similarity between the two genera. The only difference is 

 that the pinnules of Gulpenia are deeply lacerated whereas those of Thonia 

 have only short teeth. Considering the fragmentary character of the 

 specimen and the small amount of information available, this difference 

 does not warrant the establishment of a new genus. It would probably 

 be more appropriate to transfer the only species of Thonia, T m dentata, 

 to the genus Gulpenia. 



In Europe, Gulpenia is known only from the Namurian A. The oc- 

 currence in Illinois constitutes the extension of its range into the 

 Namurian B. Gulpenia has been found in Limburg (The Netherlands ), near 

 Argenteau and Thon-Mosseroux (Belgium), and in Brown County, -Illinois 

 (U.S.A.). Gulpenia has always been found above an unconformity in the 

 basal beds of a sedimentary sequence with an unusual flora. In Belgium 

 it was found in sinkhole fillings at the base of the Silesian (European 

 Upper Carboniferous) section in a position very similar to that of the 

 Spencer Farm Flora. This position might indicate that Gulpenia was an 

 upland plant. 



The natural relationship of the genus Gulpenia is uncertain. It 

 has been placed with the Noeggerathiales in this paper because the few 

 morphological features known do occur only in that group. The pinnules 



TABLE 5— MEASUREMENTS OF GULPENIA AND THONIA 



Name of plant: 



Thonia dentata 



Gulpenia 





Gulpenia 



Gulpenia 









limburgensis 



limburgensis 



1. 



imburgensis 



Locality: 



Be 



lgium 



Belgium 





Illinois 



Ill 



inois 



Author: 



St 



ockmans and 



Stockmans 



and 



This report 



This report 



Year: 



Wi 



lli(>re, 1955 



Williere , 



1953 



ISM A16A98 



ISM 



A16A99 



Width of whole plant 





A nun 



5-8 



mm 





5 mm 





A mm 



Thickness of axis 





. A mm 



1 



mm 





. 7 mm 





. mm 



Distance of pinnules 





2 . 3 mm 



5 



mm 





2 . 3 nun 





2 . nun 



Length oi pinnules 





2 . 3 mm 



7 



mm 





3.5-3.8 mm 





3 . mm 



Numher oi Lobes 





4-5 (?) 



7-11 



(?) 





A (?) 





5 (?) 



Lengl hoi l obes 





. 5 mm 



1. 5-5.0 



mm 





L.8-2.0 mm 





1 . 5 mm 



Widl h oi Lobea 





0.2 mm 



0.25 



mm 





0. 3 nun 





0.2 mm 



