CERAMBYCID BEETLE FAUNA 301 



EVIDENCE FROM THE PALEONTOLOGICAL RECORD 



In North America, fossil Cerambycidae have been found only in 

 the Florissant beds of Colorado. The lacustrine deposits at this 

 site contain abundant plant remains and the richest modern-type 

 insect fauna yet discovered on this continent. MacGinitie (1953) 

 made a critical taxonomic and ecological study of the fiora, which he 

 regards as of Lower Oligocene age but, based upon vertebrate 

 evidence, R. A. Stirton (w litt.) treats the beds as middle Oligocene. 

 In any event, by comparing the fossil plant community with 

 living plant communities and considering the chemical and physical 

 aspects of the sediments, MacGinitie has reconstructed the en- 

 vironment as follows: 



The Oligocene forest occupied streamside and lakeside habitats in a 

 piedmont of low relief and moderate elevation which bordered the Rocky 

 Mountain uplift on the east. The drainage was disorganized and partly 

 ponded by successive volcanic outbursts which covered the area with 

 dust, pumice, and mudflows. 



The fossil fauna and flora were deposited in the resulting shallow and 

 ephemeral lakes. The climate was subhumid and warm temperate, not 

 unlike the present climate of Monterrey, in the state of Nuevo Leon, 

 Mexico. Warm winters and hot summers prevailed, and abundant sun- 

 shine is indicated. The vegetation on the high ground, away from the 

 stream and lake borders, was characterized by pines and evergreen oaks 

 and was most probably of an open, scrub-forest type, with grass and 

 microphyll shrubs in the drier areas. 



MacGinitie has provided a useful table of the fossil gymnosperms 

 and angiosperms together with the modern occurrence of the most 

 similar living species. Of these last, 57.1 per cent are found in 

 habitats encompassed by a circle of radius 400 miles, centered in 

 southwestern Coahuila, Mexico, especially in the southern Rockies 

 of San Luis Postosi and Texas and northeastern Mexico. The west 

 Mexican and southern Arizona area now contains only three or 

 four additional species. The Ozark-southern Appalachian area and 

 the Asiatic area have nearly equal representation and together 

 comprise 57.1 per cent of the list. These living forms are very 

 largely mesic, streamside types of warm-temperature aspect, and 

 many of their fossil equivalents were found by MacGinitie to be 

 relatively abundant forms. However, nineteen of the Ozark species 

 are also found elsewhere; only six are unique to the region. The 

 species now living in California he regards as having no particular 



