The Vlastimirović (, Vlastimirovići / Властимировићи) was the first Serbian royal dynasty, named after Prince Vlastimir (ruled c. 831–851), who was recognized by the Byzantine Empire. The dynasty was established with the Unknown Archont, who ruled during the reign of Emperor Heraclius (610–641). The Vlastimirović dynasty ruled in Serbia until the 960s, when some of the Serbian lands were annexed by the Byzantine Empire. History One of the fundamental sources for the early Serbian history is the work of Byzantine Emperor Constantine VII Porphyrogenitos (913–959), De Administrando Imperio. In eight chapters, the settlement of Serbs and their early history is described up until the reign of the author. The 32nd chapter, with the sub-chapter On the Serbs and the lands that they currently inhabit, gives a short note on the origin of the Serbs, their homeland, and continues with the history of members of the oldest ruling family of the Serbs. Early rulers The progenitor, according to Porphyrogenitos, was the prince (unnamed in sources and this designated as the Unknown Archon) that led the Serbs to Southeastern Europe during the reign of Heraclius (610–641). The author gives the early genealogy: "As the Serb Prince who fled to Emperor Heraclius" in the time "when Bulgaria was under the Rhōmaíōn" (thus, before the establishment of Bulgaria in 680), "by succession, his son, and then grandson, and so on, of his family rules as princes. After some years, Višeslav is born, and from him Radoslav, and from him Prosigoj, and from him Vlastimir". The time and circumstances of the first three rulers are almost unknown. It is supposed that Višeslav ruled in 780, but it is unclear when Radoslav and Prosigoj would have ruled. When the Serbs were mentioned in 822 in the Royal Frankish Annals ("the Serbs, which is said to be holding the great part of Dalmatia"; ad Sorabos, quae natio magnam Dalmatiae partem obtinere dicitur) one of those two must have ruled Serbia. According to John (Jr.) Fine, it was hard to find Serbs in this area since the Byzantine sources were limited to the southern coast, also it is possible that among other tribes exists tribe of group of small tribes of Serbs. Dalmatia, in the antique period, stretched from modern-day Dalmatia far into the hinterland, northwards close to the Sava river, and eastwards to the Ibar river. Višeslav's great-grandson Vlastimir began his rule in 830, and he is