Maryvillia Walcott, 1916

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 : 21

Genus Maryvillia Walcott, 1916

Type species. Maryvillia arion Walcott, 1916 , from the Nolichucky Formation , eastern Tennessee (by original designation) .

Diagnosis. Short, evenly tapered glabella with nearly straight sides, a concave anterior crandial border, and a pygidial axis that extends back beyond the anterior edge of the border.

Discussion. As noted above, under the discussion of Blountia , four synapomorphies support monophyly of Maryvillia in the phylogenetic analysis ( Fig. 2 ). In addition to the type species, M. arion Walcott , the genus also includes M. triangularis (Lochman, in Lochman & Duncan, 1944) .

Figures

FIGURE 2. Phylogenetic analysis of Blountia and related taxa. 1. Strict consensus of six trees of length 30 (CI, 0.50; RI, 0.62; RC, 0.31). Names of species from Steptoean strata are identified by bold font. 2. Optimized character distribution plotted on one of the most parsimonious trees. Only unambiguous transformations (i.e., optimize to the same nodes under the assumptions of ACCTRAN and DELTRAN) are shown; open circles indicate characters that are homoplastic. Numbers above the circles refer to characters and those below identify particular states (Table 2).