10 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 463 



Lesquereux apparently was aware that his Pecopteris ornata , P. lyratifolia, 

 and _P. stellata formed a natural group (Lesquereux, 1884, p. 760), and his men- 

 tion of Pecopteris stellata in this group further suggests that the drawing and de- 

 scription of P. stellata may be incorrect and that the taxon may belong to Stella- 

 theca . However, it cannot be transferred to S.. latiloba without reinvestigation of 

 the type, whose location is unknown. Lesquereux (1880, pi. 48, figs. 5, 5a, 5b) 

 also figured a sterile foliage specimen which has some similarity to Stellatheca 

 latiloba as described here, but there is presently no basis for recognizing it as 

 the sterile frond. The lobes are longer and narrower than in S. latiloba and Les- 

 quereux compared it with Sphenopteris lyratifolia, which has been transferred to 

 Callipteris (Jongmans and Dijkstra, 195 8) and is certainly not congeneric with 

 Stellatheca. 



The major difference between the two species of Stellatheca is that the 

 pinna axis (n-3) of S_. latiloba has a wide wing while the axis (n-3) of S_. ornata 

 has no wing or only a small one. Considering the small number and small size of 

 specimens available for examination, the possibility exists that both winged and 

 unwinged pinnae could occur on the same frond. Spore data on S.. ornata are 

 lacking, thus preventing spore comparisons. 



The variation in soral position in Stellatheca is rather difficult to establish. 

 According to Danz£' s (1956) drawing and description, the sori of S.. latiloba are 

 clearly located between the midvein and. the margin; however, his photographs and 

 our specimens seem to indicate that sori are very near the margin or are marginal. 

 This discrepancy occurs because part of the lamina is often not preserved and the 

 sori or only parts of the sori form the preserved margin. This type of preserva- 

 tion led to the interpretation of a toothed margin by Langford (1958, 1963). Sori 

 are strictly confined to pinnules (n-1), although the pinnule may have the size and 

 shape of a lobe. The sori are attached near a lateral vein ending, and the number 

 of sori per pinnule (n-1) generally increases from two to six with the size of the 

 pinnule (text fig. 3). The number of sporangia per sorus is largest at the base of 

 large pinnules (n-1) and smallest at the tip of pinnules (n-1). The largest sori 

 are elliptical with the long axis parallel to the laminar margin and have three 

 sporangia in a row surrounded by 12 others. The smallest sori are circular, with 

 one sporangium surrounded by five others (text fig. 5). 



An exact correlation between spores of Stellatheca latiloba and described 

 dispersed spore taxa was not found. If found dispersed, the spores with separate 

 coni probably conform most closely to Apiculatasporites (Ibrahim) Smith and Butter- 

 worth, 1967. Spores with punctate or reticulate exines probably would be assigned 

 to Microreticulatisporites (Knox) Potonie' and Kremp, 1954, or to Foveosporites 

 Balme, 1957. 



lmm 



Text fig. 5 - Variation of sori of Stellatheca latiloba , 



