. Bulletins of American paleontology. Cumulative collections 1 2 Cumulative abundance (thousands) Text-figure 8.—DR collecting curves for cheilostome species of three growth forms in each of three intervals. The relative diversities of encrusting, erect, and free-living cheilostomes are maintained in about the same rank order in each of the three time in- tervals represented by the PPP collections (Text-fig. 7). However, the number of encrusting species increases from 55% of the total in the oldest interval (>6 Ma) to 65% and finally 75% in the youngest (0-3 Ma). In the younge
. Bulletins of American paleontology. Cumulative collections 1 2 Cumulative abundance (thousands) Text-figure 8.—DR collecting curves for cheilostome species of three growth forms in each of three intervals. The relative diversities of encrusting, erect, and free-living cheilostomes are maintained in about the same rank order in each of the three time in- tervals represented by the PPP collections (Text-fig. 7). However, the number of encrusting species increases from 55% of the total in the oldest interval (>6 Ma) to 65% and finally 75% in the youngest (0-3 Ma). In the youngest interval, the percent share in abundance for the encrusting species more than doubles to 33% (from 13% and 11% in the successively older inter- vals), partly but not entirely because of the 75% re- duction in abundance of free-living species. These changes are probably related to the increased number of reef-associated stratigraphic units sampled in the Late Pliocene—Pleistocene interval in the Bocas and Limon Basins. In the DR (Text-fig. 8), the relative diversities and abundances of the three growth forms are more uni- form, especially for the 6-3 Ma and 9-6 Ma intervals. The oldest (>9 Ma), however, shows a deficit of en- crusting species relative to younger intervals, possibly a sampling artifact. Erect species are dominant in abundance in all three time intervals, comprising 50% or more of the total abundance in each. Frequency distributions of numbers of species and abundance per collection for each growth form (Text- figs. 9, 10) are similar to those for the faunas as a whole (Text-fig. 5). Modal numbers of species are all one for the PPP and more than one for the DR, with abundances showing less difference between the two areas. These relationships suggest that sampling adequacy is good to fair for species of different growth forms, and that the quality of sampling is similarly good for the two younger intervals in each area, and only slightly reduced f
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