Date of Award

1980

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

The objective of this investigation is to describe the Ostracoda of the Paria-Trinidad-Orinoco shelf, and to determine if the observed distribution patterns can be related to measured environmental factors. The study is based on specimens recovered from washed residues and picked slides from 147 stations sampled during the Orinoco Shelf Expedition in 1953. The described fauna includes 133 species in 66 genera, 6 molt groups, and 5 species of uncertain taxonomic designation. Of the species, 48 could not be related to previously described forms, and are considered to be new. An analysis of variance was conducted at the specific and generic levels based on a model containing two discrete factors: lithology and transect, and two continuous factors: water depth and distance from shore. As water depth has previously played an important role in defining depositional environments, this factor was evaluated for the linear, quadratic, and cubic responses. Due to the unequal sample size, analyses were conducted using binomial data (presence/absence). Although a number of the taxa yield significant test results, no single environmental effect appears to be the controlling factor over the observed distributions. The bathymetric distributions of the taxa are presented in detail to enable comparison to past studies. In general, the following taxa appear to be more widespread in their bathymetric range than has been previously reported (van den Bold, 1971b, 1974b): Bradleya, Bythoceratina, Cativella, and some species of Krithe. In addition, Parakrithella does not appear, in the present study, to belong to the deepwater fauna, as has been suggested (van den Bold, 1969b). The variation in the bathymetric range and other preferences of the species of some of the studied genera suggests that care should be taken when drawing conclusions based on individual genera.

Pages

557

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