section were all descended from Achaemenid Aramaic. However, some other regional dialects also continued to exist alongside these, often as simple, spoken variants of Aramaic. Early evidence for these vernacular dialects is known only through their influence on words and names in a more standard dialect. However, some of those regional dialects became written languages by the 2nd century BC. These dialects reflect a stream of Aramaic that is not directly dependent on Achaemenid Aramaic, and they also show a clear linguistic diversity between eastern and western regions. Eastern dialects of the Post-Achaemenid period In the eastern regions (from Mesopotamia to Persia), dialects like Palmyrene Aramaic and Arsacid Aramaic gradually merged with the regional vernacular dialects, thus creating languages with a foot in Achaemenid and a foot in regional Aramaic. In the Kingdom of Osroene, founded in 132 BCE and centred in Edessa (Urhay), the regional dialect became the official language: Edessan Aramaic (Urhaya), that later came to be known as Classical Syriac. On the upper reaches of the Tigris, East Mesopotamian Aramaic flourished, with evidence from the regions of Hatra (Hatran Aramaic) and Assur (Assurian Aramaic). Tatian, the author of the gospel harmony the Diatessaron came from Assyria, and perhaps wrote his work (172 AD) in East Mesopotamian rather than Syriac or Greek. In Babylonia, the regional dialect was used by the Jewish community, Jewish Old Babylonian (from c. 70 AD). This everyday language increasingly came under the influence of Biblical Aramaic and Babylonian Targumic. The written form of Mandaic, the language of the Mandaean religion, was descended from the Arsacid chancery script. Western dialects of the Post-Achaemenid period The western regional dialects of Aramaic followed a similar course to those of the east. They are quite distinct from the eastern dialects and Imperial Aramaic. Aramaic came to coexist with Canaanite dialects, eventually completely displacing Phoenician in the first century BC and Hebrew around the turn of the fourth century AD. The form of Late Old Western Aramaic used by the Jewish community is best attested, and is usually referred to as Jewish Old Palestinian. Its oldest form is Old East Jordanian, which probably comes from the region of Caesarea Philippi. This is the dialect of the oldest manuscript of the Book of Enoch (c. 170 BC). The next distinct phase of the language is called Old Judaean lasting into the second century AD. Old Judean literature can be