In 1870, Seeley assigned Dimorphodon to its own family, Dimorphodontidae, with Dimorphodon as the only member.
It was suggested in 1991 by the German paleontologist Peter Wellnhofer that Dimorphodon might be descended from the earlier European pterosaur Peteinosaurus.
Later exact cladistic analyses are not in agreement.
According to Unwin, Dimorphodon was related to, though probably not a descendant of, Peteinosaurus, both forming the clade Dimorphodontidae, the most basal group of the Macronychoptera and within it the sister group of the Caelidracones.
This would mean that both dimorphodontid species would be the most basal pterosaurs known with the exception of Preondactylus.
According to Alexander Kellner, however, Dimorphodon is far less basal and not a close relative of Peteinosaurus.

The cladogram recovered by Andres and Myers in 2013 is reproduced below.
In 1870, Seeley assigned Dimorphodon to its own family, Dimorphodontidae, with Dimorphodon as the only member. It was suggested in 1991 by the German paleontologist Peter Wellnhofer that Dimorphodon might be descended from the earlier European pterosaur Peteinosaurus. Later exact cladistic analyses are not in agreement. According to Unwin, Dimorphodon was related to, though probably not a descendant of, Peteinosaurus, both forming the clade Dimorphodontidae, the most basal group of the Macronychoptera and within it the sister group of the Caelidracones. This would mean that both dimorphodontid species would be the most basal pterosaurs known with the exception of Preondactylus. According to Alexander Kellner, however, Dimorphodon is far less basal and not a close relative of Peteinosaurus.
The cladogram recovered by Andres and Myers in 2013 is reproduced below.
Dimorphodon