Ptolemy’s use was a sort of innovation, but the Indians had been using a zero symbol to represent blanks on counting boards (which is the major innovation from the point of view of counting systems) before 400BC. We forget how subtle an idea zero originally was (and is). It took a long time for it to develop it’s modern uses and place in mathematics. I think the Indians still have it, but it may have been close. There’s a nice discussion of this at wikipedia:
The Maya were the first to use a zero, as has been taught now for many, many years. They had the first “real” zero usage of any ancient culture. Their great calendar system couldn’t be so amazing without zero.