The status of foraminiferal knowledge is reviewed in the light of some common misconceptions, as erroneous results have come from some misapplied facts. The quantity of foraminiferal publications has been exaggerated by a high degree of bibliographic documentation, although less than half of the publications cited concern foraminifera themselves, their morphology, taxonomy or occurrence, and less than 17 per cent are dominantly taxonomic; the remainder concern their stratigraphic application.
Classification and taxonomic subdivision in foraminifera is compared to that in other invertebrates and other groups of Protozoa. In a graphic representation of the rate of proposal of foraminiferal genera, the cumulative totals for the past 200 years follow a straight line on a semilog graph, with no indication of the discontinuity to be expected from a supposed taxonomic surge coincident with and resulting from foraminiferal economic application. The taxonomic expansion of the fresh- water uneconomic “thecamoebians” has followed a similar pattern. Proposal of new foraminiferal genera has resulted from new methods of study, additional morphologic criteria, study of micro-structures, emphasis on the living animal and life cycles, and work in previously neglected strata and regions.
Certain concepts and ideas require an understanding of foraminiferal biology for correct application. The apparent geographic subspecies, differentiated by size, result from temperature-controlled delay or acceleration of the reproductive cycle, larger shells occurring in less favorable environments (colder water, decreased salinity, etc.). Robust foraminiferal specimens associated with depauperate invertebrate faunas are not an anomalous occurrence, but an indication of adverse conditions.
Migration time required for planktonic species is regarded as negligible. Their current-borne rate of dispersal is discussed on the basis of data from modern current studies. The present emergent continents are seen to be a more formidable though not complete barrier to planktonic migrations than was present during the Cretaceous and Tertiary time of broad epicontinental seas. The rate of evolutionary change in Protozoa is compared to that of higher invertebrates and vertebrates, and shown to be theoretically rapid, because of short life span, rapid production of new generations, and great abundance of progeny. Causes of mutations and extinctions of pelagic organisms are discussed.
The importance of the aragonite shell in foraminiferal taxonomy is regarded as unaffected by geologic age, the aragonite test being preserved as such or completely removed by solution. No specimen referrable to the superfamily Robertinacea has been found to have the test converted to calcite.
Suggested lines of future study include stratigraphic and taxonomic studies in additional strata and regions, correlation of benthonic facies with planktonic zones, detailed morphologic studies of the test (gross morphology, wall microstructure and lamellar character, ultrastructures, apertural features, internal partitions and toothplates, test mineralogy, etc.,), and life cycles, morphology, physiology, genetics, and ecology of the living animal.