Abstract A short stratigraphic interval near Bulin in western Hunan (China) yields multiple specimens of the ~514-Myr-old oryctocarine trilobite Oryctocarella duyunensis . Size data obtained from these indicate that, meraspid degree 1 onward, degrees represent successive instars. Meraspid growth persisted until a terminal stage was reached, providing first example determinate trilobites and, no...