A big dolmen with four petroglyphs that portray men with tridents and a wheel with spokes has been found at Kollur, near Tirukoilur, 35 km from Villupuram in Tamil Nadu.

The discovery was made by K.T. Gandhirajan, who specialises in art history, when he led a team to that area. Petroglyphs are engravings made with a tool. What is special about the latest find is that while two men have been shown having tridents in their hands, a third is brandishing unidentified weapons. Unusually, these figures have been chiselled on the dolmen’s capstone — that is roof-slab. While the pre-historic artist has provided a geometrical pattern to the two men with tridents and other weapons, he has chiselled the third man, with an ornament on his chest, in a free-flowing manner.

This is the second time that a dolmen with petroglyphs has been found in Tamil Nadu. The earlier discovery in the Nilgiris district was also made by Mr. Gandhirajan. But it was a circular dolmen with a petroglyph on the slab wall (The Hindu, May 24, 2009).

“The three figures belong to different periods. But the two men holding tridents are chronologically close to each other,” Mr. Gandhirajan said. He estimated that while the dolmen itself was 2,500 years old, the petroglyphs might be about 2000 years old. The tridents could have been hunting or fishing weapons. Their depiction showed that the engravings belonged to the Iron Age (circa 1000 B.C. to 300 B.C.). The engraving of a wheel was significant because the men who erected the dolmen had the knowledge of wheels.

Six more dolmens were found nearby, on the banks of a lake at Kollur. In addition, three dolmens were situated on the bed of the lake which was built at a later period. The site had been discovered earlier, but not the petroglyphs. The team that visited the site on September 13 comprised G. Chandrasekaran, retired principal of the Government College of Fine Arts, Chennai, and K. Natarajan and D. Ramesh, both academicians.

Dolmens are normally box-like structures made of granite slabs and a roof slab.

The entrance slab sometimes has a perfectly round porthole. Dolmens are found where there are no natural caverns. While in many places, they were erected over cist-burials, dolmens have also been found without cist-burials. Mr. Gandhirajan argued that it was not necessary that the dolmens be erected over cist-burials only; they had been found on rocky mounds.

Dolmens could have been used as shelters by tribals during rains or winter. Sometimes, dolmens had paintings of red ochre or white kaolin.

“Hundreds of megalithic dolmens were once found in Tamil Nadu. Urban development and extension of agricultural land led to locals smashing them up or carting away the granite slabs for use in their houses. The Tamil Nadu Archaeology Department must make a survey of the surviving dolmens, and it should fence them. For these sites are directly connected with the pre-Sangam or Sangam age culture of Tamil Nadu,” Mr. Gandhirajan said.