Bird Egg
Oligocene
Brule Formation
White River Badlands
South Dakota

True fossil bird eggs from the Oligocene are quite rare because eggshells are fragile and usually break apart before fossilization. Most discoveries consist of partial eggshell fragments rather than complete eggs. In South Dakota, Oligocene deposits are mainly associated with formations such as the White River Group, which preserves a rich assemblage of ancient mammals, reptiles, and birds.
51mm bird egg near complete. Very rare.