Olenelloides armatus has been collected from the Fucoid Beds, Northern slopes of the Meall a'Ghiubhais, County Ross and Cromarty, Scotland, UK.

Like all other members of the Olenelloidea superfamily, the eye-ridges spring from the back of the frontal lobe (L4) of the central area of the cephalon, that is called glabella.

The exoskeleton of Olenelloides armatus is small (up to 1 cm (0.39 in)) and narrow (less than 1⁄2 as wide as long, measured between the base of the outermost spines).

The front side of the cephalon is slightly bulging out forward to accommodate the frontal lobe (L4) of the raised central area called glabella.

McNamara[2] argued that O. armatus developed from Olenellus ancestry through retention of juvenile features (paedomorphosis), and regarded the original ranking more appropriate.

More recent scholars however suggest to treat Olenelloides as a peculiar but valid genus within the Olenellidae, and assign it provisionally to the subfamily Laudoniinae.