The Wyvern and the Jersey Devil
Some researchers believe that the traditional image of the Jersey Devil as a fierce, bat-winged demon can be traced back to an 18th century Leeds ancestor's use of their family crest. Daniel Leeds began publishing an almanac in the 1600s, and he passed his almanac practice down to his son, Titan, who added the Leeds family crest--three wyverns on a shield--to the almanac masthead in 1728. Wyverns are monsters similar to dragons, and these wyverns in particular had bat-like wings and wickedly clawed feet.
A late 17th and early 18th century feud with local Quakers led Daniel Leeds to publish a series of accusatory pamphlets about the Christian sect. In addition to his quarrel with the local Quakers, Daniel Leeds was fond of astrology, and was thought of by many as a supporter of the crown in England. These facts combined to make the Leeds family particularly unpopular in New Jersey, and scholars think that the social stigma could have contributed to such a negative legend as the Jersey Devil being born out of their legacy; with Titan's use of the monstrous wyverns giving a convenient form off of which the stories could base the Devil's appearance. Deborah Leeds, who was alive at this time, could have said something regrettable about the devil taking a 13th child, or she could have merely been a convenient character upon which to rest the foundations of the legend. Incomplete records mean that the precise truth of this legend's origin will quite possibly be lost for all time.
According to those that believe the Jersey Devil exists only in folklore, the family's crest and its devilish wyverns played an important role in shaping its appearance in the popular imagination. This explanation doesn't account for the myriad modern sightings beginning in the 20th century, of course, and could simply represent an attempt to explain away the phenomenon. If sightings of the Jersey Devil do represent something unexplained, then certainly no amount of coincidental familial imagery would influence its appearance; although perhaps it could color the perception of a witness's encounter, especially in its remembrance. It's possible that there's a middle ground, and sightings of the Jersey Devil do represent some mysterious phenomenon, but those who witness it are more likely to remember it in appearance closer to the devilish image, due to an unconscious bias created through folklore. It's certainly something worth considering.