Okay. In the interim I flipped open The Cambridge History of Turkey, Volume 1 (published in 2009) and it says:
The origins of the timar system are still being disputed. Some scholars argue that it derives from the Seljuk ikta, others from the Byzantine pronoia. Whichever might prove true, the first timars were apparently hereditary, as were the appanages and estates (mülk, vakıf ) assigned to family members, allies and military commanders. 17 The principle and practice of heritability were not alien either to ikta of the Mongolian period, or to pronoia of the Palaeologan era.
(page 195-196)