Holmiella domackae, Gapp, I. Wesley & Lieberman, Bruce S., 2014

Gapp, I. Wesley & Lieberman, Bruce S., 2014, New olenelloid trilobites from the Northwest Territories, Canada, Zootaxa 3866 (4), pp. 479-498 : 489-492

Holmiella domackae sp. nov.

Fig. 7

Type material. Holotype: PWNHC-2013.23.23; paratype: KUMIP 355548-355549, PWNHC-2013.23.24–25.

Etymology. In honour of Hamilton College paleontologist Cindy Domack, who had an important influence on the professional development of IWG.

Diagnosis. Cephalic border between intergenal spine and genal spine diverges anteriorly; genal spines have a sinuous shape; the posterolateral margins of LA diverge anteriorly.

Description. Anterior border abaxial of sagittal line at an angle approximately 25 degrees to transverse line; length (sag.) anterior cephalic border directly anterior LA approximately 0.5 length of L3, developed as a flattened shelf; anterior portion of genal spines attached to cephalon at point directly abaxial to midpoint of LA along a sagittal line; genal spine deflected back rapidly and slightly outward creating an S-shape; length (sag.) LA approximately equal to length (sag.) of LO and L1; lateral margins of LA abaxial to lateral margins of LO; S3 convex anteriorly; ocular lobe separated from glabella by furrow; line between antero- and posteromedial tips of ocular lobe creates an angle with sagittal line of approximately 0-10 degrees; posterior ends of ocular lobes extend back to adaxial part of L1; width of ocular lobe at adaxial point about 60-70% length (sag.) of L1; width (tr.) of extraocular area opposite L1 approximately 55–65% interocular area; S3 gently convex and does not conjoin adaxially; S2 gently convex and not conjoined adaxially; S1 gently convex and not conjoined adaxially; L1, L2, and L3 are approximately equal in length (sag.); lateral margins of L2, L3, and LA constricted posteriorly; width (tr.) of LO approximately equal to width of L3, length (sag.) approximately 1.5 times length (sag.) of L1; small spine on posterior margin of LO; intergenal spines positioned directly abaxial of occipital spine; posterior border between LO and intergenal spine directed back posteriorly abaxially.

Discussion. This species can be distinguished from H. falcuta and H. preancora by its much wider genal spines, which are directed abaxially before being directed posteriorly (similarly to H. falx ), and have a slightly sinuous shape. The posterior cephalic border between the intergenal spine and the genal spine diverges anteriorly in H. domackae unlike in most other species of Holmiella (though see Fritz 1972, pl. 7, figs. 7, 12), which are parallel to subparallel. Lastly, the posterolateral margin of LA diverges anteriorly unlike H. taurus sp. nov. This species may be biostratigraphically significant as it appears to represent the only species of holmiid that survives into the Olenellus zone or Dyeran stage and thus crosses the Montezuman-Dyeran stage boundary sensu Webster (2011a, b) and Webster et al. (2011) (M. Webster, pers. comm.).

Occurrence. Olenellus zone or Waucoban Series, Dyeran stage, sensu Webster (2011a, b) and Webster et al. (2011), early Cambrian, Sekwi Formation, Mackenzie Mountains, Northwest Territories, Canada, Section 2, in float, Section 3, 700– 800 m above the base of section, Section 14 in float.

Figures

FIGURE 7. Holmiella domackae sp. nov. 1, holotype PWNHC- 2013.23.23, x 3.2; 2, PWNHC 2013.23. 24 (latex cast), x 1.1; 3, KUMIP 355548, x 1.9.