It has zoological importance because, being hemichordates, they are an "evolutionary link" between invertebrates and vertebrates.

Balanoglossus specimens are deuterostomes, and resemble the chordates in that they possess branchial openings.

Johann Friedrich von Eschscholtz discovered Balanoglossus in 1825 on Mashail Island, and described it as a worm-like holothurian.

The discovery of gill slits in these animals by Alexander Kovalevsky (1865) led to the creation of the class Enteropneusta by Carl Gegenbaur (1870).

They are found in shallow waters between tide marks along the coast of warm and temperate oceans.