Until 2000, it was thought that rock sequences spanning the Permian–Triassic boundary were too few and contained too many gaps for scientists to reliably determine its details.
Ata 2000 pensábase que as secuencias de rochas do límite Permiano-Triásico eran demasiado poucas e tiñan demasiados baleiros para que os científicos puidese determinar fiablemente os seus detalles.