The first joint of the hind foot is clearly longer than the groove in the tip of the calf (tibia).

The antennae are brownish black, the fourth part with fine short hairs and some long bristles at the tip.

The third joint is bare (naked), without the short adjacent hairs (requires magnification to view).

Platynus assimilis is fairly common, living under bark from trees, moss and withered leaves.

They belong to the group Holometabola, who undergo metamorphosis The larvae are radically different from the adults in lifestyle and in physique.