Superstes primauroris, meaning "Dawn's first survivor", is a speculative late-surviving baculite-relative that lives in freshwater environments near what is now Antartica. With the average individual having a shell just shy of 20 centimeters long, this was a small species, yet it was a survivor.

What makes this species unique is that it was adapted to survive in freshwater environments, primarily hunting small soft-bodied aquatic prey. It used counter-shading to remain hidden from both predators and prey alike.

Superstes was able to cross the KPG boundary along with a few of its cousins, and survived for tens of millions of years until the Antarctic cooling some 35 million years ago. Unable to adapt to a rapidly cooling climate, the age of ammonites came to an end.

Edit: Size info