Bradyfallotaspis sekwiensis, Gapp, Wesley, Lieberman, Bruce S., Pope, Michael C. & Dilliard, Kelly A., 2011

Gapp, Wesley, Lieberman, Bruce S., Pope, Michael C. & Dilliard, Kelly A., 2011, New olenelline trilobites from the Northwest Territories, Canada, and the phylogenetic placement of Judomia absita Fritz, 1973, Zootaxa 2918, pp. 15-28 : 19-22

Bradyfallotaspis sekwiensis n. sp.

(Fig. 5.1–5.7)

? Bradyfallotaspis sp. 3 FRITZ, 1973, p. 11, pl. 6, figs. 25–27.

Type material. Holotype PWNHC-2009.20.18. Paratypes KUMIP 320708-320710 and PWNHC-2009.20.19- 2009.20.20. From Nevadella zone, Early Cambrian, Sekwi Formation, Mackenzie Mountains, Northwest Territories, Canada (Section 1, 175.6– 288 m above base of formation; Section 2 in float). There are a total of six specimens.

Etymology. Named after its occurrence in the Sekwi Formation.

Diagnosis. Anterior cephalic border (sag.) equal to length (sag.) of LO and L1; preglabellar area absent; ocular lobes not in contact with posterior border furrow.

Description. Width of cephalon (tr.) is greater than or equal to twice the cephalic length (sag.); anterior cephalic border length (sag.) is long approximately equal to length (sag.) of LO and L1; preglabellar field is absent; a pit-like structure is visible where ocular ridge contacts L3 and LA in some specimens; width (tr.) of the extraocular area varies from 0.75–2 times the width (tr.) of the interocular area; a strongly incised SO is present, often yet not always conjoined adaxially; a node is present on the posterior margin of LO in the one specimen that has a well preserved margin.

Discussion. This species differs from all other species of Bradyfallotaspis by its possession of the anterior cephalic border (sag.) equal to twice length (sag.) LO and its lack of a preglabellar area. It differs from B. fusa and B. patula by having the ocular ridges connected to the glabella at L3 and having the genal spine length (exsag.) greater than the length (sag.) of the cephalon. Finally, its ocular lobes do not contact the posterior border furrow, unlike B. coriae and B. fusa . Bradyfallotaspis sp. 3 of Fritz (1973) is questionably placed within B. sekwiensis based on its glabella with high relief, its wide (tr.) cephalon with a broad anterior cephalic border, and its posterior cephalic border that tapers to a point adaxially. However, the material of B. sp. 3 is limited, not well preserved, and some of it is based on early ontogenetic stages. Therefore, it is not possible to definitively ascertain whether it is conspecific with B. sekwiensis .