Mummaspis delgadoae, 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 : 492-494

Mummaspis delgadoae sp. nov.

Fig. 8

Type material. Holotype PWNHC-2013.23.26. Paratypes KUMIP 355525–355533 and PWNHC-2013.23.27–34.

Etymology. In honour of Alejandra Rodriguez Delgado, who helped inspire IWG throughout the course of this study.

Diagnosis. Ocular lobes separated from L3 by the S3 furrow and extending back posteriorly to LO; ocular furrow terminating posteriorly at SO; prominent anastomosing ridges present on extraocular area; lateral furrows present on LO; and posterior border of LO convex posteriorly.

Description. Anterior border narrow (sag.), approx. equal length of LO; LA contacts anterior border furrow and length (sag.) approx. length (sag.) of LO and L1; parafrontal band present; anterior margin of LA at each side of the midline deflected posteriorly at roughly 40 degree angle; ocular furrow present; preocular furrow on frontal lobe directed inward and forward from glabellar margin; ocular lobes contact frontal lobe at posterolateral margin of frontal lobe and extend posteriorly to LO, separated from extraocular area by prominent shelf; width (tr.) of interocular area approx. equal to the width (tr.) of the ocular lobe; lateral margins of LA slightly abaxial to lateral margins of LO; anterodistal margin of L3 formed by ocular lobes; course of S3 jaggedly convex and conjoined adaxially; L2 and L3 do not merge abaxially; S2 polymorphic, conjoined adaxially or not conjoined; S2 convex anteriorly; SO and S1 convex anteriorly; lateral lobes on LO present; axial part of LO with faint node present; prominent anastomosing ridges, ocular line and genal ridge present on extraocular area; width (tr.) of extraocular area from abaxial tip of ocular lobe to position of anterior border furrow opposite L1 approx. 75% width (tr.) of glabella at L1; genal spine directed posteriorly about 80-90 degrees relative to transverse line; length (sag.) of genal spines approximately equal to the length (sag.) of the first 2–3 thoracic segments (inferred based on typical relative length [sag.] of LO as compared to typical relative length [sag.] of prothoracic axial rings); genal spine angle developed opposite LO; intergenal angle not prominently developed.

Discussion. This species has been assigned to Mummaspis due to its possession of key characters such as: the anterior cephalic border between the frontal lobe and genal spine angle having a length (sag.) equal to the length (sag.) of LO; the anterior border being prominently separated from extraocular area by a furrow; the preocular furrow being directed inward and forward from the glabellar margin; S3 being jaggedly convex and conjoined adaxially; presence of lateral lobes on LO; the convex posterior margin of LO; and the intergenal angle roughly parallels a transverse line.

Mummaspis delgadoae can be distinguished from other species of Mummaspis based on characters identified by Lieberman (1999). For example, M. occidens ( Walcott, 1913) has a wider (tr.) LA with a furrow more strongly incised along the anterior border, a longer occipital spine, and glabellar furrows that are more steeply angled (especially SO and S1). Mummaspis truncatooculatus ( Fritz, 1992) has a greater constriction of the glabella at L1 and L2, more prominent intergenal ridges, L3 is conjoined with the ocular lobe, shorter ocular lobes, and a more strongly incised preocular furrow. Mummaspis oblisooculatus Fritz, 1992 possesses an anterior border that is flatter and angled further posteriorly directly abaxial of S3, L2 and L3 are conjoined abaxially, and S3 is more jaggedly convex. Mummaspis muralensis ( Fritz, 1992) appears to be most similar to M. delgadoae and they share commonalities such as prominent anastomosing ridges and they also show evidence of polygonal fracturing on some of the cephala. However, the species are specifically distinct. For example, M. muralensis has a more prominent intergenal ridge, wider (tr.) ocular lobes, and there is a greater constriction in the width of the glabella anteriorly from LO to L2.

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 1, in float, Section 2, 350– 375 m above the base of section and in float.

Figures

FIGURE 8. Mummaspis delgadoae sp. nov. 1, holotype PWNHC- 2013.23.26 (latex cast), x 4.1; 2, KUMIP 355525, x 2.0; 3, PWNHC- 2013.23.27, x 2.0; 4, KUMIP 355526, x 2.5; 5, PWNHC- 2013.23.28, x 2.5; 6, KUMIP 355527, x 2.5.