18 



ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 500 



twice. Basal anadromic pinnule on each pinna longer and narrower than 

 normal pinnules. Only one vein enters each pinnule, but it may appear 

 as if there were two. The dentation of the outer margin of the pinnules 

 is very delicate and is not visible in some types of preservation. The 

 frond is twice pinnate as far as can be judged from the largest preserved 

 specimens. There are no intercalary pinnules ( "Zwischenfiedern," or 

 rachial pinnules) known. Other data are found in table k. 



Discussion . — The pinnules of Palaeopteridium reussii show dis- 

 tinct differences according to their position in the leaf or branch sys- 

 tem (text fig. 7A-C). The pinnules that are narrower and smaller occur 

 near the tip of the frond. They have a somewhat Tingi a-like appearance. 

 The pinnules of more mature parts become wider and attain a diamond 

 shape ( rhomb ohedr al ) . The adaxial margin thus becomes more and more 

 parallel to the axis. In the widest pinnules, the margin rests on the 

 axis or even overlaps it. The wider pinnules overlap one another also. 



TABLE U— COMPARISON OF MEASUREMENTS OF PALAEOPTERIDIUM SPECIMENS 

 FROM THE SPENCER FARM FLORA AND OTHER LOCALITIES 











Palaeopteridium reussii 













C~) 









E 



M 00 

 Dl CN 



a 



TJ •■-] 



E oj 

 B 



• 0) 

 Oh Z 



P. sessilis 

 Leggewie, 1966 

 pi. 1, pi. 2 



On • 



— i 4-1 



-a vo 



t— 1 CNJ 



o 

 c • 



CN CO 



<tn oo 



—t -rH 



c - 



O LT> 



.u m 



CO 



TJ • 

 •H iH 



t4 a 



> 



•H 



e 



cfl 



•H CN 



'O 1 



C !=> 

 1— 1 1— 1 



Spencer Farm 

 specimens 



Rushville, 



Ohio, 

 specimens 



Pinnules 

















Length L (mm) 



17 



4-5.5 



7 



10,8,5 



9 



9,9,9,7,9,10,7,8 



9,6.5,8 



Width W (mm) 



9 



2.5-3 



4.5 



6,3,5 



4 



7,6,2.5,3.5,5,6 



3,2,2.5 



L : W 



1.9 



1.8 



1.5 



1.7 



2.2 



1.3-3.6 (2.0) 



3.2 



Distance between 

















centers of 

















pinnules (mm) 



10 



4 



4 



8,4,4,5 



5 





2.5 



Angle of 

















attachment 



35°-60° 



40° 



40° 



40°, 30°, 

 40°, 60° 



35° 



30°-55° (42°) 



30°-40° 



Pinna 

















Width (mm) 







11 







11,12 



10 



Distance between 

















pinna axes (mm) 



20 



9 



- 







12, 7 



10 



Angle of 

















attachment 













50°-55° 



55°-60° 



