I was reminded by David deSilva of another piece of evidence that should be weighed when considering the type of implement used to execute Jesus. He points out that the Alexamenos Graffito adds some support to the traditional depiction of the cross.
The Alexamenos Graffito is a crudely drawn and misspelled piece of graffiti carved into a wall of the Palatine Palace at Rome. It shows a man with the head of an ass hanging from a cross. At the top appears either the Greek letter upsilon or a tau cross. To the left is man raising one hand in a gesture that suggests worship. Beneath the cross there is a caption written in Greek:
Alecamenoj sebete qeon
Alexamamenos worshipping God.
This is the earliest known depiction of the crucified Jesus Christ. Obviously the sketch is mocking Jesus and those who worship him. Jews had been accused of worshipping an ass and this seems to have been transferred to Christians (Tacitus, Hist 5.3-4; Josephus, Against Apion 2.80).
The graffiti was discovered in 1857, but it dates anywhere from the late first to the early third centuries CE, although it seems that the later date is to be preferred.
The picture would seem to lend some authority to the common depiction of the implement on which Jesus died as a being a crossbeam rather than just a pole.
Since Samuelsson’s dissertation is not yet available to be read, I don’t know what if any consideration he has given to this evidence. But I think this along with the points made by Hurtado adds weight to the tradition that Jesus died on a cross rather than a pole. The abstract to Samuelsson’s dissertation notes that he investigates the philological aspects and concludes that language used in the New Testament is not clear. It may be that Samuelsson has invested too much in language without giving consideration to other artifacts that might help fill out the picture for us. I hope he plans to publish an article length summary of his conclusions soon.