The earliest Ordnance Survey name books, compiled as part of the meticulous mapping of Ireland in the nineteenth century, recorded it plainly: a very large irregular shaped stone erected upon five lesser ones. That description points to a dolmen, or portal tomb, the type of megalithic monument in which a massive capstone is raised on several upright supports to form a chamber, typically associated with Neolithic burial practice. The structure at Killaneer, however, has left no visible surface trace. The field it once stood in is given over to tillage, and the monument, whatever its original scale, has been swallowed entirely by centuries of agriculture.

The Ordnance Survey name books were produced alongside the first edition of the six-inch maps of Ireland, a project that ran from the 1820s onward and represents one of the most thorough documentary exercises ever carried out on the Irish landscape. Local correspondents and surveyors noted townland names, ruins, and curiosities, preserving descriptions of things that were already disappearing or difficult to interpret. The entry for Killaneer is a small example of that work: a snapshot of a monument that was apparently still recognisable when the surveyor passed through, and that has since vanished. Whether it was dismantled for building material, buried beneath accumulated soil, or simply broken up during land clearance is not recorded.