In Europe a crossbow known as the "gastraphetes" was described by Heron of Alexandria in the 1st century AD. He believed it was the forerunner of the catapult, which places its appearance sometime prior to the 4th century BC. Other than the gastraphetes, the only other evidence of crossbows in ancient Europe are two stone relief carvings from a Roman grave in Gaul and some vague references by Vegetius. Pictish imagery dated between the 6th and 9th centuries AD do show what appear to be crossbows, but only for hunting, and not military usage. It's not clear how widespread crossbows were in Europe prior to the medieval period or if they were even used for warfare. The small body of evidence and the context they provide point to the fact that the ancient European crossbow was primarily a hunting tool or minor siege weapon. An assortment of other ancient European bolt throwers exist such as the ballista, but these were torsion engines and are not considered crossbows. Crossbows are not mentioned in European sources again until 947 as a French weapon during the siege of Senlis. From the 11th century onward, crossbows and crossbowmen occupied a position of high status in European militaries, with the exception of the English. During the 16th century military crossbows in Europe were superseded by cannons and muskets. Hunters continued to carry crossbows for another 150 years due to its silence.