!(, 



ILLINOIS STATE GEOLOGICAL SURVEY 



in the Rock Island (No. 1) Coal (macera- 

 tion 929) , McDonough County, Illinois. 



Triletes praetextus Zerndt, 1934 

 Plate 5, figures 9, 10 



1934 Triletes praetextus Zerndt, p. 24, fig. 10; pi. 

 26, figs. 1-6; pi. 27, figs. 1-7. 



1944 Triletes praetextus Zerndt, in Schopf, Wil- 

 son, and Bentall, p. 24. 



1946 Triletes praetextus Zerndt, in Dijkstra, p. 43- 

 44; pi. 7, figs. 66, 67; pi. 8, figs. 68, 69. 



1955 Setosisporites praetextus (Zerndt) Potoni£ 

 and Kremp, p. 124-125; pi. 5, figs. 30-32. 



Description. — Megaspores trilete, gener- 

 ally compressed obliquely; compressional 

 forms circular to rounded subtriangular in 

 body outline, probably originally spheroi- 

 dal oblate in shape; spore body 1160/x and 

 1025 /x in diameter. Trilete rays strongly 

 developed, two-thirds the radius of the 

 spore body in length. Lips increasing in 

 height gradually, more rapidly near apex to 

 form an apical prominence up to 170 fx in 

 height. Spores in many specimens com- 

 pressed so that strong folds develop on the 

 contact areas on each side of and parallel 

 to each ray (pi. 5, fig. 9a) . Spores charac- 

 terized by single and branching spines that 

 are restricted to a zone (pi. 5, fig. 9b) ex- 

 tending from the arcuate ridges to a point 

 slightly distal to the geometrical equator. 

 Spines up to 170 /x long, branching and sin- 

 gle (pi. 5, fig. 10) . Remainder of spore coat 

 appearing granulose, about 50 ^ in thick- 

 ness, black by reflected light. 



Discussion. — The few complete mega- 

 spores and fragments from the Battery 

 Rock Coal, described above, are not well 

 preserved, but as yet are the only spores of 

 this species to be found in Illinois coals. 

 Even though badly preserved, the branched 

 type of spine, the spinose equatorial zone, 

 and the strong development of trilete rays 

 are unmistakably identical to those features 

 on previously described megaspores of Tri- 

 letes praetextus. 



Abundant megaspores of Triletes prae- 

 textus, also not well preserved, were found 

 in the Pratt Coal from the Warrior Basin 

 of Alabama. These range from 750 to 

 1080 ^ in diameter (mean 920 ^ for 13 spec- 

 imens) ; their apical prominence ranges 

 from 70 to 170 ^ in height. Only two (750 H . 



and 755 [x in diameter) possess apical prom- 

 inences less than 100 ^ in height. The other 

 spores are more than 1000 ^ in diameter 

 and possess apical prominences of about 

 170 xi in height. Whether or not any of the 

 smaller megaspores are comparable with 

 those described by Dijkstra (1952a, p. 103) 

 as T. praetextus forma minor is not known. 

 These smaller forms were found by Dijkstra 

 only in the Namurian A-C of Turkey, 

 whereas the more typical large forms were 

 found in the Westphalian. 



Many beautifully preserved spores of 

 Triletes praetextus were found in the shale 

 above the Pinnick Coal (maceration 163), 

 Orange County, Indiana. These mega- 

 spores, some still in tetradic association, are 

 generally obliquely compressed and range 

 from 685 to 1200 ^ in diameter (mean 

 1065 jx for 19 specimens). In the same 

 tetrad spores differ from one another in 

 diameter by as much as 104 ^. The smallest 

 spore observed, probably immature, is 

 strongly triangular, as are the immature 

 spores of Triletes mamillarius illustrated by 

 Dijkstra (1946, pi. 3, figs. 14, 15) rather 

 than circular in outline, but possess the 

 characteristic high (170 p) apical prom- 

 inence. 



The range in apical prominence height 

 on these spores is from 100 to 240 ^ (mean 

 1 90 fi) . The ray length ranges from less 

 than two-thirds to more than three-fourths 

 of the body radius, whereas the diameter of 

 the contact area as a whole is about three- 

 fourths that of the spore body. The upper 

 margins of the lips are membranous and 

 frilled or notched to a depth of about 10 ^. 

 The rays are generally bordered on each 

 side by secondary folds of the spore coat. 

 The distinctive ornamentation is confined 

 to a zone extending distally from the junc- 

 ture of the ray and the arcuate ridge about 

 410^ towards the distal pole, extending 

 about half as far distally interradially. The 

 spines are usually branched, 13 to 46 /x wide 

 basally, and have a maximum length rang- 

 ing from 140 to 275^. Distal to the equa- 

 torial spinose zone the spore coat is orna- 

 mented with low (5 /x) flattened-hemispher- 

 ical tubercles about 15 /x in diameter. These 

 tubercles probably cause the more or less 



