Morphological characters in equatorial sections of planispirally enrolled larger benthic foraminifera were quantified using growth-independent and growth-invariant characters. While the embryonal apparatus (nepiont) is growth-independent, the subsequent chambers change size and shape during growth. Using specific growth stages for grouping (classification) of specimens hinders comparison between species with different growth modes. Here, constants of mathematical functions developed to describe the growth of specific characters are used as growth-invariant attributes. Time, the independent variable, is measured in these functions either by chamber number or revolution angle as a proxy for growth. The complete chamber sequence is not necessary for fitting growth functions: a representative number of chambers enables the equations to be defined. Incompletely preserved tests can thus be used and compared. In addition to former growth-invariant characters previously developed for larger benthic foraminifera, equations describing chamberlets and their change during growth provide a general solution for geometrical reconstruction of tests in equatorial sections. This relieves the need to sort specimens into morphologically-based classes for comparison, which can aid in phylogenetic and paleobiogeographic understanding.

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