Shell Morphology of the Late Cretaceous Planktonic Foraminifera and Its Value in Modern Taxonomy

Abstract

Planktonic foraminifers in the Late Cretaceous developed by the way of biological progress. Their taxonomic diversity increased, the shell morphology became more complicated, the number of individuals in the population grew, and the territorial dispersal of the group was active. This process had an intermittently-continuous pattern, as there was alternation of poly- and oligotaxic stages of development of the group. Each of these stages was characterized by the predominant morphotype of shell structure, a certain type of life strategy (k and r strategists), as well as by a certain type of evolutionary process (gradualism or punctualism). All these events are reflected in the systematics of the group, which is regularly updated.