In the Late Rust Age, there was a shift from the creation of ceremonial objects to more purely aesthetic ones. An example is this oddly modernistic piece, highlighting the natural sculptural properties of bones,feathers, and plant matter.
More info at zymoglyphic.org/rustage.html

The Lizard-Headed Mud Cart

This artifact hints at an era even earlier than the Rust Age, tentatively known as the Mud Age. The cart is believed to be a magic vehicle for navigating the spirit-infested landscape, guided by a reptilian brain and harnessing the generative power of mud.

The museum's Rust Age exhibit contains artifacts from a time lost to memory. The Rust Age is so named because many of the ceremonial artifacts were made of decaying metal, which was thought to have a sublime quality of character and texture of age.

See zymoglyphic.org/rustage.html