The species name katalepsis is a Greek word for "seizing", "gasping" or "holding".

[1] Tokummia has a cylindrical body, with the anterior half covered by a 8.78 cm (3.46 in) long bivalved carapace.

At the front of the animal, there are a pair of antennae, possible eyes, mouthparts (mandibles, maxillule and maxilla) and prominent pincer-like maxillipeds.

[1] Tokummia is suggested to be a bottom feeder, being able to walk on the sea floor, and to occasionally swim, and used its pincers to catch prey.

[2] According to the original description of Tokummia, hymenocarines like Tokummia, Branchiocaris, Canadaspis and Odaraia are stem group Mandibulata, the group includes myriapods, hexapods and crustaceans,[1] and this theory is supported in multiple subsequent studies.