You are in the shallow lagoons of China, Asia, 244 million years ago.

The water of the Triassic Tethys Sea was warm and murky, filled with suspended green algae. You kept your eyes fixed on the seabed about nine feet down, where a 9-foot-long Atopodentatus was doing something truly bizarre. Its head, remarkably shaped like a T-square or hammerhead, was angled sideways against the limestone seafloor.

As you watched, it used the chisel-like teeth running along the edge of its wide, blunt snout to scrape thick mats of algae and plant matter from the rock. The creature seemed slow and methodical, focusing entirely on dredging the sediment rather than attacking fish. Its body was surprisingly long, tapering into a slender tail, with specialized, shorter limbs that seemed perfectly adapted for navigating the murky bottom.

Suddenly, the animal shifted its posture, opening its mouth to create a vacuum effect, sucking up the loosened, cloud-like plant matter. It then closed its jaws, forcing the water out through a dense row of needle-shaped teeth—a natural filter-feeding sieve. It was a jarring, yet efficient, sight—a prehistoric "vacuum cleaner" navigating the ocean floor.