He is mentioned in the bishop-list of the later medieval historian Walter Bower as the successor of Bishop Máel Dúin.
[1] Túathal's name, like his immediate predecessor Máel Dúin's, is known from other sources.
A charter preserved in the Registrum of the Priory of St. Andrews, although probably translated into Latin from Gaelic at a later date,[2] records a grant of the lands and church of Scoonie by Bishop Túathal (Tuadal) of St. Andrews to the Céli Dé of Loch Leven.
[3] Bower says that Túathal ruled as bishop for four years; as his successor Máel Dúin is known to have died in 1055, this would put his episcopate at roughly between the years 1055/6 and 1059/60.
Túathal's immediate successor was the famous Bishop Fothad II.