At Bryntwppa in Mid Wales there is a possible single stone row measuring 4.8m long, including one medium and two large stones situated on level ground. The stones are orientated east to west and stand at the northern end of a long mound. Whilst they may represent a structural element of the long mound the possibility that this is a stone row cannot be wholly dismissed. Further details are available here.
The standing stones (red) at Bryntwppa protrude from the northern end of a long mound (Source: survey from Google Earth and fieldwork).
Plan of the stones at Bryntwppa (Source: survey by Sandy Gerrard at 1:100)