Mastigopsis hjorti is similar to Idioteuthis cordiformis in that it has large fins, skin tubercles, no pocket between the bridles and the large dividing, protective membranes on the tentacular clubs but the main difference is that this species has photophores on its eyes.

The suckers on the tentacular club are all of similar size, except for those nearest the tip.

The funnel has a locking-apparatus which has an oval, slightly curved depression and towards the posterior its sides protrude having no cartilaginous fleshy projections.

The mantle, head, funnel and the aboral surface of the arms in subadults are covered in large tubercles.

[4] Mastigopsis hjorti has a wide distribution and is possibly a tropical-subtropical circumglobal species which ranges north as far as 40°N although the southern limits have yet to be determined.