In the analysis of planktonic Foraminifera, true phylogenetic lineages are difficult to assess because of the small number of morphologic characters and convergence due to similar ecologic stress. However, the development of the planispirally coiled genus Pseudohastigerina is well documented in Paleocene strata from California. The origin of Pseudohastigerina has been traced in the type Lodo Formation section at Lodo Gulch. In the lowermost Lodo Formation (Heliolithus riedeli Zone), Globorotalia chapmani gives rise to a form transitional with typical Pseudohastigerina in the overlying strata (Discoaster multiradiatus Zone). This lineage transition involves the migration of the extraumbilical-umbilical aperture onto the spiral side of the test with further development of b lateral symmetry. A similar lineage transition has been observed in the upper Santa Susana Formation of the Poison Oak Canyon section from Simi Valley. Typical Pseudohastigerina wilcoxensis specimens, which show a more perfect planispirality and a more nearly equatorial aperture, occur in the middle of the Lodo Formation (lower Discoaster tribrachiatus Zone).

In the Paleogene, other genera of the Hantkenininae evolved from Pseudohastigerina, all serving as important biostratigraphic indicators. The first occurrence of Pseudohastigerina, the so-called Pseudohastigerina (or Globanomalina) datum, is a useful criterion for distinguishing lower Eocene from upper Paleocene in strata from California and throughout the world.

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