Description
Hantkenina is a genus of foraminifera. Hantkeninids are well-known biostratigraphic index fossils. The structure of this unique feature vary between individuals, and between species of hantkenina. All hantkeninas species retained tubulospines through their evolution. This indicates that it served a useful purpose for this particular form of foraminifera. The function of the tubulospines are unknown, however, reproduction and feeding purposes have been suggested as possible functions. == Paleoecology ==
Paleoecology
The first hantkenids (Hantkenina mexicana) lived in deep planktonic environments with minimum oxygen levels. However, isotopes suggests they migrated to fully oxygenated shallower waters at about 43.8 Ma. This climate change also affected deep-water environments. The cooling process caused gradual changes in the structure of the water column. As the water cooled, the rates of remineralization of organic matter at the near surface water altered. 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. This made the oxygen minimum zone, less intense and more spread out. 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, == References ==