Estimated to be about 560 million years old, H. quadriformis is identified as a cnidarian polyp, and represents the earliest known evidence for muscle tissue in an animal.

Structural examination of the muscles and morphology indicate that the animal is a cnidarian, though, which class H. quadriformis belongs to was undetermined[2][3] until a 2024 study found it to be a staurozoan.

The actual fossil specimen, or holotype, remains on the north shore of Back Cove, roughly 1.8 km NNW of Melrose town.

The specific name quadriformis is said to be derived from Latin quadri, meaning "fourfold", and formis, for "form", relating to the quadrilateral symmetry of the body.

It indicates it is a soft-bodied animal having an appearance of a smooth discoidal structure connected by a relatively short stem to a quadrate body comprising numerous and regularly aligned linear fibres.