 The Caddoan communities were not as large as other eastern and southern Mississippian communities, they were not fortified, and they did not establish large, complex chiefdoms; with the possible exception of the Spiro Mounds on the Arkansas River.As complex religious and social ideas developed, some people and family lineages gained prominence over others.This hierarchical structure is marked in the archaeological record by the appearance of large tombs with exotic grave offerings of obvious symbols of authority and prestige, such as those found in the "Great Mortuary" at Spiro.