New olenelline trilobites from the Northwest Territories, Canada, and the phylogenetic placement of Judomia absita Fritz, 1973

Abstract

The Early Cambrian olenelline trilobites are a diverse clade and have been the subject of several phylogenetic analyses. Here, three new species of Bradyfallotaspis Fritz, 1972 (B. coriae, B. nicolascagei, and B. sekwiensis) and one new species of Nevadia Walcott, 1910 (N. saupeae) are described from the Sekwi Formation of the Mackenzie Mountains, Northwest Territories, Canada. In addition, new specimens potentially referable to Nevadia ovalis McMenamin, 1987 were recovered that may expand that species’ geographic range, which was thought to be restricted to Sonora, Mexico. The results of a phylogenetic analysis incorporating several olenelline taxa, including Judomia absita Fritz, 1973 from the Sekwi Formation, are also presented herein. This species has been assigned to various olenelline genera, including Judomia Lermontova, 1951 and Paranevadella Palmer & Repina, 1993. Phylogenetic analysis suggests this species is closely related to Judomia tera Lazarenko, 1960 from Siberia. This phylogenetic relationship provides further support for the hypothesis that a close biogeographic relationship existed between Laurentia and Siberia during the Cambrian.

OnCallavia(Trilobita) from the Cambrian Series 2 of Iberia with systematic status of the genus

“…lotzei' = Callavia choffati) to the genus Judomia by Sdzuy ( 2001) is here rejected. After comparison with figured material from Siberia (Khomentovskii and Repina, 1965;Repina et al, 1974;Korobov, 1989;Pegel, 2000;Ponomarenko, 2005;Rozanov and Varlamov, 2008) and Laurentia (Fritz, 1973;McMenamin, 1987;Gapp et al, 2011), we do not agree that Callavia choffati mainly differs from Judomia in ocular structure. The ocular lobes in Judomia are located very close to the glabella, thus the interocular area is almost absent.…”

New olenelloid trilobites from the Northwest Territories, Canada

“…The new material comes from the Sekwi Formation, Mackenzie Mountains, Northwest Territories, Canada. This formation has yielded a diverse array of early Cambrian trilobites (Fritz 1972;Abe et al 2010;Gapp et al 2011) as well as a well-preserved chancelloriid fauna (Randell et al 2005). The unit is relatively thick, consisting of 715 to 750 m of interbedded carbonate, shale, and sandstone, comprising mainly weathered limestone and dolostone, deposited during the Fallotaspis, Nevadella, and Olenellus trilobite zones (Fritz 1972(Fritz , 1973Randell et al 2005;Dilliard et al 2007Dilliard et al , 2010.…”

“…Casts were made of external moulds using latex for figuring (these are noted in figure descriptions). Sections given for the Sekwi Formation under "occurrences" refer to those used in Dilliard et al (2007), Abe et al (2010), and Gapp et al (2011).…”