Evolution of test particle orbits, taken from the P9 simulation, in ω−a plane. Only particles surviving at least 3 Gyr are taken into account. The evolutionary tracks of the particles are shown in the last Gyr of the simulation every time their orbits met the criteria: i< 50 deg, q< 80 au. The tracks below a = 200 au are not shown as these are just a forest of full-width horizontal lines. The X symbols indicate the positions of potentially unstable particles, which are discarded at some time between t = 3 and 4 Gyr, at the time of their destruction. The plus signs indicate positions of long-living particles at t = 4 Gyr. The known ETNOs with q> 35 au (circles) and q< 35 au (triangles) are plotted. TNO 2003 SS₄₂₂ is denoted as a square and its large uncertainty in a is indicated by the error bar. Shaded regions indicate the observed clustering regions for a> 250 au ETNOs.