A sedimentary basin in which the rate of subsidence exceeds the rate of sedimentation is called a starved basin. Basins can be dynamic for hundreds of millions of years as depositories of water-borne sediment. Starved of water, they quickly (in geological time, a few million years) become stranded and lose their sediments to wind and erosion. Marathon Basin in west Texas exhibits the exposed rock belt of a starved basin system. During the Eocene Era—some ﬁfty million years ago— the area of Fossil Butte in southwest Wyoming harbored palm-fringed lakes teeming with ﬁsh, crocodiles, turtles, and other animals. Changing salinity levels and variations in the amount of water ﬂowing from the Uinta Mountains caused dead plants and animals on the deep lake bottoms to be covered with ﬁne sediment. When the lakes dried up, subsidence thrust up rich worlds of fossilized sediment. These starved basins of Wyoming are unique in that they have also disclosed fossilized birds and bats.