cockerell: lower cretaceous flora 109 



PALEOBOTANY. — A Lower Cretaceous flora in Colorado. T. 

 D. A. Cockerell, University of Colorado. 



During the past summer Mr. Terry Duce, working for the 

 Geological Survey of Colorado, was so fortunate as to find a 

 new locality for Mesozoic plants, with fairly abundant remains. 

 The locality is on the high point between Cutthroat Gulch and 

 Hovenweep Canyon, Lat. 37°, 53' N., Long. 108°, 57' W. The 

 greater part of the section there exposed is assigned to the 

 McElmo, presumed to be Jurassic. Above the McElmo black 

 shales alternate with massive sandstone, the two combined in- 

 cluding the uppermost 131 feet of the whole exposure, which 

 measures some 410 feet. The plants are preserved in hard white 

 quartzose sandstone, with occasional iron concretions, about 

 10 feet below the top of the section. This flora is of peculiar 

 interest, not only for the light it throws on the age of the strata, 

 but especially because it belongs to the period when angiosper- 

 mous plants were just beginning to appear. One of the greatest 

 puzzles in evolution is the apparently sudden arrival of the an- 

 giosperms during the Mesozoic ; at first represented by few species, 

 but presently developing a remarkable series of broad-leafed 

 trees, including generic types apparently identical with those 

 now living. Any plant material from the period which saw the 

 dawn of the higher plants in North America is therefore of par- 

 ticular value, although we must doubtless go to some very differ- 

 ent part of the globe to find, if they ever are found, the immediate 

 ancestors of the Cretaceous angiosperms. 1 



At the beginning of my studies of Mr. Duce's material I sent 

 photographs of the best specimens to Dr. A. C. Seward and Dr. 

 Edward W. Berry, both of whom very kindly reviewed and 

 criticised my preliminary determinations. There is in the col- 

 lection only one species which can claim to be an angiosperm. 

 Elongate-lanceolate willow-like leaves, at first rather suggesting 

 some Podozamites, 2 are seen on closer inspection to have lateral 



1 For a most interesting discussion of this problem, see Weiland, G. R. : Amer. 

 Journ. Sci. 38: 541-460. 1914. 



2 See, Seward, A. C, Jurassic Plants from Caucasia and Turkestan: Mem. d. 

 Comite-Geolog. (St. Petersbourg), N. S., 38: pi. 8, fig. 68. 1907. 



