Ubaydallah ibn Abdallah ibn Tahir was the last major Tahirid to hold high office in what dynasty?
Tahirid dynasty The Tahirid dynasty (Persian: طاهریان‎ ‎ , "Tâhereyân") was a dynasty, of Persian dihqan origin, that governed the Abbasid province of Khorasan from 821 to 873 and the city of Baghdad from 820 until 891. The dynasty was founded by Tahir ibn Husayn, a leading general in the service of the Abbasid caliph al-Ma'mun. Their capital in Khorasan was initially located at Merv but was later moved to Nishapur. The Tahirids enjoyed a high degree of autonomy in their governance of Khorasan, but they remained subject to the Abbasid caliphate and were not independent rulers.
Numayrid dynasty The Numayrids were an Arab dynasty based in Diyar Mudar (western Upper Mesopotamia). They were emirs (princes) of their namesake tribe, the Banu Numayr. The senior branch of the dynasty, founded by Waththab ibn Sabiq in 990, more or less continuously ruled the Euphrates cities of Harran, Saruj and Raqqa until the late 11th century. In the early part of Waththab's reign (990–1019), the Numayrids also seized Edessa, until the Byzantines conquered it in the early 1030s. In 1062, the Numayrids lost Raqqa to their distant kinsmen and erstwhile allies, the Mirdasids, while by 1081, their capital Harran and nearby Saruj were conquered by the Turkish Seljuks and their Arab Uqaylid allies. Numayrid emirs continued to hold isolated fortresses in Upper Mesopotamia, such as Qal'at an-Najm and Sinn Ibn Utayr near Samosata until the early 12th century, but nothing is heard of them after 1120.