The taxonomic position of Penichrus blapstinoidesChampion, 1885 (type species of PenichrusChampion, 1885) within Tenebrionidae is discussed based on the analysis of both type material and comprehensive internal and external morphology. The species was formerly classified within Opatrini (subfamily Blaptinae); however, this hypothesis is hereby rejected as this species does not share any of the diagnostic characteristics proposed for that tribe. A detailed analysis of other phylogenetically crucial features (including male and female terminalia, defensive glands, antennae, and abdominal ventrites) places Penichrus within Tenebrioninae. However, a more detailed assignment is not currently possible given the present circumscriptions of tenebrionine tribes. The genus is hereby placed as incertae sedis within Tenebrioninae. A morphological analysis and discussion of current tribal concepts is presented, which exposes the weakness of the currently accepted classification system, and highlights a need for extensive comparative morphological studies within Tenebrioninae and related subfamilies. A lectotype for Penichrus blapstinoides is designated. Distolinus impressicollisFairmaire, 1892 is reinstated as a junior synonym of Penichrus blapstinoides. A revised checklist and key to the genera of Opatrini known from mainland North America are provided.