Kootenia randolphi (Robison & Babcock, 2011)


Diagnosis.—Kootenia having ovate exoskeletal outline. Glabella slightly expanding forward, indenting narrow anterior cranidial border. Occipital ring with short median spine. Genal spines short to moderately long, with tips opposite thoracic axial ring 2 to 4. Thoracic axial rings each having median spine slightly shorter than that of occipital ring. Paired pleural spines of thorax and pygidium gradually increase in length rearward. Pygidial axis containing four rings and terminal piece, border having four pairs of marginal spines. Spaces between pygidial spines progressively widen rearward.

Etymology.—After Robert L. Randolph, for initial study of trilobites from the Swasey Formation in the Drum Mountains (Randolph, 1973).

Holotype.—Exoskeleton, BPM 1004

Discussion.—Kootenia randolphi resembles K. youngorum n. sp. but differs by having 4 rather than 5 pairs of marginal spines on the pygidium. Also, the spacing and patterns of spine elongation differ. Kootenia randolphi is the only species of Kootenia known to have four pairs of marginal spines on the pygidium so far described from the Wheeler Formation or its lateral equivalents in the Great Basin.

Occurrence.—Locally common in the upper 30 m of the Wheeler Formation of the Drum Mountains, as used here, where it occurs in the lower Bolaspidella Zone. Some authors have referred these strata to the Pierson Cove Formation.