[1] Hantkenina is highly distinctive from other planktonic foraminifers as they are characterized by planispiral coiling and their hollow, slender extensions of each chamber known as tubulospines.

[3] The first hantkenids (Hantkenina mexicana) lived in deep planktonic environments with minimum oxygen levels.

A consequence of this global cooling was that bacterial metabolic rates at the upper water column slowed down and allowed sinking organic matter to descend further to deeper environments in the ocean.

New niches for deep-dwelling zooplankton that were able to tolerate low levels of oxygen opened up.

Pearson and Coxall (2013) speculate that the evolution of Clavigerinella and Hantkenina was related to this global cooling,[3] as well as pulses of deep-water anoxia [5]