Morphology of encrusting and free living acervulinid Foraminifera: Acervulina, Gypsina, and Solenomeris, Palaeontology
Résumé
The generic identification of acervulinids is especially difficult due to a confused systematics. However, this family is of major interest because it comprises the main encrusting reef Foraminifera. Their close dependency on the substratum to which they are attached and their ability to develop various growth forms result in an irregular morphology and arrangement of the chambers. The ability of the Eocene acervulinid Solenomeris to build monospecific, kilometre-sized reefs has misled most previous workers to consider it as a red alga. The geometrical characteristics of the test of the main acervulinid general (Acervulina, Borodinia, Gypsina, Solenomeris) are analysed and discussed, based on previous descriptions and personal observations. This leads to some reliable and easily usable criteria for genera and species identification. Solenomeris is very close to Acervulina but can be distinguished by the form of the juvenile.