Hadley cell
Prehistoric members of "Anhinga" were presumably distributed in similar climates as today, ranging into Europe in the hotter and wetter Miocene. With their considerable stamina and continent-wide distribution abilities (as evidenced by the anhinga and the Old World superspecies), the smaller lineage has survived for over 20 Ma. As evidenced by the fossil species' biogeography centered around the equator, with the younger species ranging eastwards out of the Americas, the Hadley cell seems to have been the main driver of the genus' success and survival: