<a href="https://en.wikipedia.org/wiki/Concretion" class="extiw" title="en:Concretion">Concretion</a> from the <a href="https://en.wikipedia.org/wiki/Cretaceous" class="extiw" title="en:Cretaceous">Cretaceous</a> of western South Dakota.
<a href="//commons.wikimedia.org/wiki/User:Wilson44691" title="User:Wilson44691">Wilson44691</a>.
<span class="int-own-work" lang="en">Own work</span>