Blountina eleanora Lochman, in Lochman & Duncan, 1944

Westrop, Madison Armstrong Stephen R. & Eoff, Jennifer D., 2020, Systematics of a survivor: the Cambrian kingstoniid trilobite Blountia Walcott, 1916 across the Marjuman-Steptoean (Guzhangian-Paibian) extinction interval in Laurentian North America, Zootaxa 4804 (1), pp. 1-79 : 24

Blountina eleanora Lochman, in Lochman & Duncan, 1944

Plates 26, 27

1944 Blountina eleanora Lochman, in Lochman & Duncan , p. 56, pl. 8, figs 35–40.

non 2000 Blountia eleanora Lochman, in Lochman & Duncan ; Stitt & Perfetta, p. 213, figs 11.8–11.13 [= Blountia ? sp. indet].

Diagnosis. Frontal area 24% (23–24) of cranidial length (sag.) with steeply sloping preglabellar field. Cranidium is slightly wider than long with evenly rounded anterior margin. Strongly convex glabella with nearly parallel sides, well-rounded front, and shallow occipital furrow expressed on the exoskeleton. Posterolateral projections long, extend to a narrow, tapered point. Semielliptical pygidium has distinct axial furrows that shallow at the terminal piece; pleural and interpleural furrows expressed only on internal mould. Border furrow nearly effaced on external surface, but inner edge of border marked on mould by termination of pleural and interpleural furrows (Pl. 27, fig. 4); border flexed steeply downward. Internal mould with pitted surface.

Material. Figured specimens include the holotype cranidium ( USNM 127156 , Pl. 26, figs 1–3), two paratype cranidia ( USNM 127158 , Pl. 26, figs 4–6; USNM 127158 , Pl. 26, figs 7–9), one paratype librigena ( USNM 127157 a, Pl. 26, fig. 10), and seven paratype pygidia ( USNM 127157 b, Pl. 27, figs 1–3; USNM 127157 c, Pl. 27, figs 6, 7; USNM 127158 , Pl. 27, fig. 4; USNM 127158 , Pl. 27, fig. 5; USNM 127158 , Pl. 27, figs 8, 9; USNM 127158 , Pl. 27, fig. 10; USNM 127158 , Pl. 27, fig. 11) from the Pilgrim Formation, Half Moon Pass section ( Lochman & Duncan 1944), Big Snowy Mountains , Montana .

Occurrence. Crepicephalus Zone, Pilgrim Formation, Half Moon Pass section, Lochman and Duncan’s (1944) horizon 9.2, Big Snowy Mountains , Montana.

Discussion. Blountina eleanora was reported from the Deadwood Formation of South Dakota by Stitt & Perfetta (2000, figs 11.8–11.13), but comparison with the types (Pls 26, 27) shows that their specimens are misidentified. As far can be determined from their very small images, the cranidia have very short frontal areas that lack preglabellar fields. The palpebral lobes are located farther forward than in B. eleanora , and the posterior branches of the facial sutures are less divergent, so that the posterolateral projections tapers (exsag., tr.) more rapidly. The associated pygidia ( Stitt & Perfetta, 2000, figs 11.11–11.13) are relatively longer and narrower than both small (Pl. 27, fig. 5) and larger (Pl. 27, fig. 1) specimens from Lochman & Duncan’s (1944) types.