In Genesis 3:1, the serpent is described as in it’s Edenic form, which is not a writhing reptile. In Genesis 3:14, God cursed the serpent by telling it: “On your belly you shall go, and you shall eat dust all the days of your life.” It seems that Genesis 3:14 describes the serpents (snakes) of today’s world. However, there are serpents in today’s world which have appendages which appear to the remnant of legs or feet. Is there any correlation between these serpents of today, which have these appendages, and the serpents of Edenic period, described in Genesis 1:26 as “….every creeping things that creeps on the earth”?
As a Bible teacher, I can only express opinions about things the Bible actually says. The Hebrew word translated serpent in Genesis 3 comes from a root meaning enchanter, or one who practices divination, so we don’t have a good idea about what he looked like before the curse. Adam and Eve don’t appear to be surprised that he could speak with them, and in Genesis 3:15 God said the Messiah (the seed of the woman) would eventually defeat him. There must have been a lot going on that we don’t know about. It may be that the Hebrew word came to mean serpent because of this incident and was originally something completely different. It’s one of those mysteries we’ll have to ask God about when we see Him.