Some entitys disappear

In a radius of 8 Chunks,  all entities like villagers, animals and named animals disappeared and reset to deafult.  Three iron golems, about 30 villagers and 50 animals,1 of which was named, are gone, replaced with the random animals straying planes biome. A minecart disapeared,too. 
All chests on the other hand are unharmd and function normally. Monsters do behave normal, too.