Halicryptus is the sole genus of its class of priapulid worms, [1] and has an important effect on the structure of soft-sediment communities.

Halicryptus spinulosus is a species of priapulid worm found in marine environments.

Known for its distinctive spiny appearance, this worm plays a role in the benthic ecosystem, often inhabiting sandy or muddy substrates.

Like other priapulids, it has a relatively simple body structure and is considered a predator, feeding on small invertebrates.

[4] Its presence provides insights into the evolutionary history and ecological roles of priapulids, linking modern forms to ancient lineages.