Compare the pictorial format above with the descriptive narrative below:
Introduction: Recently split from the Ptychopariida (Ebach & McNamara 2002), advanced members (Harpetidae) easily distinguished by marginal sutures and lack of rostral plate, as well as the presence of the "harpetid brim."
Cephalon: semicircular to ovate; fringe inclined, consisting of vaulted inner genal roll, which is convex or flat, and an outer bilaminar brim, either flat, convex or concave, extending posteriorly to long, flat genal prolongations; facial sutures marginal, in Entomaspididae involving the eyes, but with anterior and posterior sections running close together toward otherwise marginal sutures; glabella convex, narrowing forwards, with 1 to 3 pairs of furrows, posterior pair isolating triangular basal lobes; occipital ring convex; alae typically present; preglabellar field broad, sloping down to flat or upwardly concave border; eyes commonly reduced to prominent tubercles, centrally located on genae, strong eye ridges present; external surface of cephalon may be tuberculose or granulose.
Thorax: with 12 or (frequently) more segments, pleurae flattened, with broad axial furrows.
Pygidium: subtriangular, elongate to short.
Families: Entomaspididae, Harpetidae, Harpididae (=Loganopeltidae).
Occurrence: Upper Cambrian to Late Devonian (Frasnian).
Representative Genera: Bohemoharpes, Brachyhipposiderus, Dolichoharpes, Dubhglasina, Entomaspis, Eoharpes, Harpes, Harpides, Kielania, Lioharpes, Loganopeltis, Hibbertia (formerly Paraharpes), Scotoharpes (formerly Aristoharpes)
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