PLATE 12. 1–12, 17. Tesselacauda morrisoni n in Revision of the Early Ordovician (late Tremadocian; Stairsian) cheirurid trilobite Tesselacauda Ross, with species from the Great Basin, western USA

PLATE 12. 1–12, 17. Tesselacauda morrisoni n. sp., from Section MME 49.8 m, Fillmore Formation (upper Tremadocian; Stairsian; Rossaspis leboni Zone), Middle Mountain, Ibex area, Millard County, western Utah, USA. 1, 4, 6, 11. Thoracic segment, SUI 147584, dorsal, anterior, posterior, and left lateral views, x10. 2, 3, 5, 7, 9. Thoracic segment, SUI 147585, right lateral, dorsal, ventral, anterior, and posterior views, x8. 8, 10, 12, 17. Thoracic segment, SUI 147586, dorsal, posterior, anterior, and left lateral views, x10. 13–16, 18–29. Tesselacauda n. sp. A, from Section MME 36.4 m, Fillmore Formation (upper Tremadocian; Stairsian; Rossaspis leboni Zone), Middle Mountain, Ibex area, Millard County, western Utah, USA. 13. Cranidial fragment (probably from same individual as fig. 14), SUI 147587, dorsal view, x7.5. 14. Cranidial fragment (probably from same individual as fig. 13), SUI 147588, dorsal view, x7.5. 15. Pygidium, SUI 147589, dorsal view, x15. 16, 20, 21. Pygidium, SUI 147590, dorsal, right lateral, and posterior views, x12. 18. Pygidium, SUI 147591, dorsal view, x12. 19, 23, 24. Pygidium, SUI 147592, dorsal, posterior, and right lateral views, x15. 22, 28, 29. Pygidium, SUI 147593, dorsal, posterior, and left lateral views, x12. 25–27. Pygidium, SUI 147594, posterior, right lateral, and dorsal views, x12.