In soil Taxonomy udolls is a suborder of

Udolls is the suborder of Mollisols in soil taxonomy. They are divided into eight suborders: Albolls, Aquolls, Rendolls, Gelolls, Cryolls, Xerolls, Ustolls and Udolls.
Mollisols are the soils of grassland ecosystems or cropland. They are characterized by a thick, dark surface horizon. Mollisols are among some of the most important and productive soils in the world.