<prompt> Gadzira shanduro yakaoma zvikuru yemutsara uyu Ordovician inoratidzira nhambo yokupedzisira huru yokusiyanisa pakati pama trilobites: mienzaniso mishomanene zvikuru mitsva chose chose yesangano yakabuda pashure peOrdovician.  <response>: Zvechokwadi, shanduro yakaoma zvikuru yemutsara uyu ndeiyi The Ordovician marks the last great diversification period among the trilobites, very few entirely new patterns of organization arose post-Ordovician; later evolution in trilobites was largely a matter of variations upon the Ordovician themes. 