If those polygons are already attached, then you can select a line segment or a loop and click Remove, hold CTRL while clicking Remove and it will also remove the vertices that the edge was attached to rather than leaving a vertex on a line.
If those polygons are already attached, then you can select a line segment or a loop and click Remove, hold CTRL while clicking Remove and it will also remove the vertices that the edge was attached to rather than leaving a vertex on a line.