Nanda king married Chandragupta, because it was customary for Kshatriya girls to choose their husbands; thus, it implies that the Nanda king claimed to be a Kshatriya, that is, a member of the warrior class. The Puranas name the dynasty's founder as Mahapadma, and claim that he was the son of the Shaishunaga king Mahanandin. However, even these texts hint at the low birth of the Nandas, when they state that Mahapadma's mother belonged to the Shudra class, the lowest of the varnas. Since the claim of the barber ancestry of the dynasty's founder is attested by two different traditions—Greco-Roman and Jain, it appears to be more reliable than the Puranic claim of Shaishunaga ancestry. The Buddhist tradition calls the Nandas "of unknown lineage" (annata-kula). According to Mahavamsa, the dynasty's founder was Ugrasena, who was originally "a man of the frontier": he fell into the hands of a gang of robbers, and later became their leader. He later ousted the sons of the Shaishunaga king Kalashoka (or Kakavarna). K. N. Panikkar suggested that the Nandas were the sole Kshatriyas in India "at the time of the Mauryas" and M. N. Srinivas suggested that the "other Kshatriya castes have come into existence through a process of caste mobility from among the lower castes". Regnal period There is little unanimity among the ancient sources regarding the total duration of the Nanda reign or their regnal period. For example, the Matsya Purana assigns 88 years to the rule of the first Nanda king alone, while some manuscripts of the Vayu Purana state the total duration of the Nanda rule as 40 years. The 16th century Buddhist scholar Taranatha assigns 29 years to the Nandas. It is difficult to assign precise date for the Nanda and other early dynasties of Magadha. Historians Irfan Habib and Vivekanand Jha date the Nanda rule from c. 344–322 BCE, relying on the Sri Lankan Buddhist tradition which states that the Nandas ruled for 22 years. Historian Upinder Singh dates the Nanda rule from 364/345 BCE to 324 BCE, based on the assumption that Gautama Buddha died in c. 486 BCE. According to another theory, based on astronomical calculations, the first Nanda king ascended the throne in 424 BCE. Proponents of this theory also interpret the Hathigumpha inscription to mean that "Nandaraja" (the Nanda king) flourished in year 103 of the Mahavira Era, that is, in 424 BCE. The