Foraminifera Aperture Types

Planktic foraminifera exhibit various aperture types. A supplementary sutural aperture is an additional opening found along the suture line between chambers, distinct from the primary primary aperture.

Analysis of Genera

• (P) Globigerina: Typically possesses a single primary umbilical aperture. It lacks supplementary sutural apertures.
• (Q) Globorotalia: Generally characterized by a single primary aperture, often interiomarginal or umbilical-extraumbilical. It does not have supplementary sutural apertures.
• (R) Globigerinoides: This genus is well-known for having multiple small supplementary sutural apertures located along the sutures, in addition to the primary umbilical aperture.
• (S) Orbulina: The final chamber is spherical, but derived forms often retain or develop supplementary apertures, characteristic of their lineage which includes Globigerinoides. Thus, Orbulina species possess supplementary sutural apertures.

Identifying the Correct Pair

Based on the analysis:

• Globigerina (P) - No supplementary apertures.
• Globorotalia (Q) - No supplementary apertures.
• Globigerinoides (R) - Has supplementary apertures.
• Orbulina (S) - Has supplementary apertures.

Therefore, the pair having a supplementary sutural aperture is (R) Globigerinoides and (S) Orbulina.