Cryptid Wiki
Cryptid Wiki
Giant Acorn Worm
Larvae of the planctosphaera pelagica
Type Acorn Worm
First Sighting N/A
Last Sighting N/A
Country Worlds Oceans
Habitat Oceanic mud
Possible Population Unknown

Giant Acorn Worm are an undiscovered marine invertebrate of the Eastern North Atlantic and North Pacific Oceans.


The species Planctosphaera pelagica of the phylum hemichordata is only known by its swimming larvae. Its larvae (known as tornariae larvae) is larger than other hemichordates, and if the size ratio is the same as in other species, the adults could potentially grow to 9 feet long. The larvae are large, transparent spheres with ciliated feeding bands and a U-shaped alimentary tract. This species is also unique in possessing mucus secreting glands around the ciliated band.

The Planctosphaera pelagica live at depths of 250-1,660 feet in oceanic mud.


It is possible the larvae may be an abnormally enlarged tornariae of another family of acorn worms (the Ptychoderidae family) that fail to metamorphose into adults.