Выпуск: 1 , Том: 19 , Год издания: 1989

The comparative study of fossil and modern elphidiids of Arctic and Boreal regions shows that characteristics of wall structure, of canal systems and of interseptal and septal bridges are key characters for classifying members of the family Elphidiidae and for recognizing within it the genera Elphidium, Canalifera, Retroelphidium, Cribroelphidium, Haynesina, Toddinella, and EIphidielIa, among others. Wall structure is used as a superspecific taxonomic criterion. For dividing genera into species it is important to recngnize micro- and megalospheric generations, which display heteromorphic test construction. The greatest species diversity among the genera we studied occurs in Retroelphidium. During the Quaternary this genus developed into two morphologically distinct groups: 1) One group (Retroelphidium subclavatum, R. provisum, R. hyalinum, R . propinquum, R . elavatum) maintained, among other characteristics, an umbilical plug (a single knob, or several of them) on the tests of both generations; 2) the other group (R. obesum, R . atlanticum, R . boreale, R . anabarense) has a plug only on megalospheric tests. Each species belonging to these two groups has a different ecology and stratigraphic range, which are important to recognize when interpreting biostratigraphy and reconstructing paleoenvironments. The diagnosis of the genus Haynesina is partly corrected herein: its aperture can be either slit-like or a row of basal openings.