The tapetum is a reflective layer at the back of the eye, thought to increase sensitivity in low light levels.

Research from the late 1990s onwards suggests that this feature has evolved more than once, possibly as many as five times,[1] so that the original Lycosoidea is paraphyletic.

[5] The "classical" circumscription of the Lycosoidea was based on the possession of a grate-shaped tapetum in some or all of the indirect eyes.

[6] Later studies have recovered a version of Lycosoidea as a monophyletic group, although with varying compositions and placements within clades.

[1][7] Ramírez, as part of a study primarily directed at dionychans, suggested that a reduced Lycosoidea, consisting of only five families, was monophyletic.