. Bulletins of American paleontology. 300 15 10 5 Time interval (Ma) Text-figure 13.—Temporal distribution of numbers (A) and per- cent (B) of species of three growth forms in PPP and DR collections combined. Collections are "binned"' in intervals as in Text- figure 2. or fewer collections (, fewer than 2% of the 328 PPP and DR collections). Only two encrusting species, Tremogasterina mitcronata and Biflustra savartii, are among the 20 most abundant species in the combined dataset, and both are present in both the PPP and the DR collections (Table 3). In marked contrast, f
. Bulletins of American paleontology. 300 15 10 5 Time interval (Ma) Text-figure 13.—Temporal distribution of numbers (A) and per- cent (B) of species of three growth forms in PPP and DR collections combined. Collections are "binned"' in intervals as in Text- figure 2. or fewer collections (, fewer than 2% of the 328 PPP and DR collections). Only two encrusting species, Tremogasterina mitcronata and Biflustra savartii, are among the 20 most abundant species in the combined dataset, and both are present in both the PPP and the DR collections (Table 3). In marked contrast, free-liv- ing species show "flat" frequency curves, , with equal numbers of species having few and many oc- currences (Text-fig. 12). The curves for erect species are intermediate in pattern, distinctly less hollow than those for encrusting ones (Text-fig. 12). Only two erect species, Nellia tenella and Thalamoporella biperfora- ta, both present in both the PPP and DR collections, are ainong the top ten in abundance in the combined dataset (Table 3). Frequency curves for the same growth form are strikingly similar between the PPP and DR collections (Text-fig. 12), suggesting that these are inherent prop- erties of species having these growth forms rather than effects of environmental or preservational differences between the two areas. Frequency curves plotted against abundance (not shown) are very similar to those plotted against occurrences (Text-fig. 12), be- (0 c o o (1) ^ 200 o "35 o c <T3 T3 C < 100 - ? Encrusting ? Erect H Free-living. 0) u c TO •o c (D ^^ C 0) o k. w Encrusting /\a. A i -/ --'XV^^ ^A, 15 10 5 0 Time interval (Ma) Text-figure 14.—Temporal distribution of abundance (A) and per- cent abundance (B) of three growth forms in PPP and DR collections combined. Abundance is normalized to the number of collections in each interval. Collections are "binned" as in Text-figure 2. cause of the tight correlation between ab
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