Tenucephalus marginellus DeLong

(Figs. 10, 71)

Tenucephalus marginellus DeLong, 1944: 236 [original description, illustration, morphology]; Linnavuori, 1957: 141–142 [description, illustration]; Linnavuori & DeLong, 1976: 30 [illustrated]; Linnavuori & DeLong, 1978: 196, 211–212 [diagnostic characters; morphology; illustrated]; Zanol, 2006: 100 [catalogue]; Zahniser, 2007 [online catalogue]; Freytag & Gaiani, 2017 [online catalogue]

Diagnosis. T. marginellus can be distinguished from other Tenucephalus species by a combination of the typical col- or pattern, male pygofer processes with distinct medial tooth near midlength and with minute marginal teeth at apex, subgenital plates short, broadly rounded at apex, style apophysis apex widened apically, not foot-like, and aedeagus in lateral view very narrow, long, and evenly curved throughout length. Male, 4.2 mm; female, 4.25–5.0 mm.

Material examined. 5♀, MEXICO: Guerrero, Iguala, 25-X-1941, DeLong, Caldwell & Plummer [OSUC] .

Distribution. The species is known from the type locality of Iguala, GRO, Mexico, which is the northernmost record for any species in the genus (Fig. 10).

Remarks. T. marginellus is the type species of the genus and it was described and illustrated by DeLong (1944). Linnavuori & DeLong (1976) provided more detailed illustrations of the male genitalia. Linnavuori & DeLong (1978) provided additional illustrations of the female sternite VII.