Thaleops can be told apart from other illaenids because of the cheek spines that many species possess under their eyes.

Thaleops had a large distribution range, With some species being found in parts of Canada to some U.S states including Oklahoma, Wisconsin, and New York.

[1] It is thought to have lived in shallow water, as a study published in Oklahoma found that deposits that contained Thaleops and the asaphid trilobite Bumastides contained 4 times as many trilobite genera, where associated with shallow water areas.

[2] Classification of Thaleops, Illaenus, and Nanillaenus by Amati & Westrop, 2004.

[1] Raymondaspis I. roemeri I. fallax I. praecurrens I. crassicauda I. sarsi I. aduncus I. planifrons I. oscitatus I. marginalis I. utahensis I. lacertus I. viator T. mobydicki I. conradi T. laurentiana Nanillaenus mackenziensis Nanillaenus aduncus T. anusacerbissima I. fieldi I. latiaxiatus I. depressicapitatus T. jaanussoni T. raymondi I. angusticollis T. ovata I. conifrons T. longispina Thaleops