Evolutionary trends in the larger foraminifer Halkyardia maxima Cimerman: a biometrical approach
Biometric analysis of megalospheric Halkyardia maxima specimens reveals evolutionary trends that are yet undescribed for the genus. Despite the low number of centered specimens in thin section sampled from a Rupelian sedimentary succession from northern Sicily, the increase in the embryo size and the tendency of the test to become flattened are not confirmed as taxonomic characters of phylogenetic relevance, but their fluctuations may depend on environmental factors. In addition, a new index introduced, i.e., the central angle, seems to be more suitable for evolutionary interpretations with respect to the umbilical angle routinely employed as taxonomic character for the recognition of different species of Halkyardia.
Keywords: Evolution; Halkyardia; Larger Foraminifera; Oligocene; Sicily
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