Another trait introduced from Middle America was that of placing the burials of important people, such as chiefs, priests, and family members of the ruling class, in shaft graves, sunk into mounds or special cemetery areas. Some of the more important early Caddo tombs are quite large, as much as fifteen to twenty feet in length and eight to sixteen feet in depth. Many had special sands or pigments on the pit floor, numerous offerings, and indications that retainers or servants were sacrificed to accompany the revered person in the afterlife. Shaft tombs in mounds and pyramids occurred in the Maya areas of Guatemala and Yucatan, and also in the Mexican Highlands, before and during the time of the early Caddos. Other Mexican traits were the concepts of the long-nosed god and the feathered serpent. These symbols are seen in the Caddo area in sheet copper masks, on carved stone pipes, and on carved conch shells. In Middle America, the long-nosed god symbol relates to the worship of the rain god, Chaac, and the feathered serpent is the symbol of Quetzalcoatl (Kukulcan in Maya). Signs of elaborate ceremonialism have been found in large Caddoan mound groups or centers in each of the four states: Davis, Sanders, and Sam Kaufman sites in Texas; Spiro and Harlan in Oklahoma; Crenshaw, Mineral Springs, Ozan, and East mounds in Arkansas. Along Red River in northwestern Louisiana, the well-known early Caddo centers are Gahagan and Mounds Plantation. The Gahagan site is on the west side of Red River, almost equidistant between Natchitoches and Shreveport. Formerly it was situated on an old channel but much of the channel and site have been destroyed by river caving. A village area, a conical burial mound, and a small flat-topped mound surrounded a large plaza at Gahagan. Another small mound is about a quarter mile distant. The burial mound was excavated by Clarence B. Moore in 1912, and by Webb and Dodd (1939). Moore described a central shaft, eleven feet in depth and thirteen by eight feet in dimensions, with five burials and more than 200 offerings. Webb and Dodd found two additional pits along the slopes, both starting at the mound surface and terminating near the base. They were nineteen by fifteen and twelve by eleven feet in dimensions, and contained six and three burials, respectively. Between 250 and 400 offerings were preserved in each pit.