Dimorphodon macronyx has had the misfortune of being represented as a puffin in almost every recent artwork depicting it. This is due to an apparently large and robust-looking head on which artists simply add puffin coloration in a popular new trend of adding modern animal color schemes to extinct creatures.
The meme of a fish-hunting Dimorphodon probably began with paleontologist Bob Bakker illustrating a fishing individual in 1986. From here on, artists have drawn the creature as a fish-hunter, more so because the Early Jurassic Lias beds in which it was found, contain marine fossils.
Also, the majority of pterosaurs were once assumed to have been exclusively fish-eaters. This theory is being discarded primarily because the jaws of the puffin and the pterosaur are so different. For one, the big skull of Dimorphodon is a proper bony head. A puffin's beak size is due mostly to soft tissue. Also, Dimorphodon, with its broad wings, probably could not lead a puffin-like lifestyle of "flying" underwater and diving deep to catch fish.
Instead, studies of its limbs show that they were very well-developed for a pterosaur as early as 195 million years old. It had powerful musculature for walking, running and even climbing. This additionally falsifies the idea that early non-pterodactyloid pterosaurs were not good walkers. Instead, Dimorphodon was probably incredibly good on land instead of in the air, probably almost as good as some pterodactyloids. There have been alternatives in the past though. Harry Govier Seeley assumed rightly that pterosaurs must be active and warm-blooded. Thus is 1901, he released an image of a Dimorphodon walking on two legs. This was rejected as the years would go by.
So instead of fishing, Dimorphodon macronyx (the species name means "big claws") was more adept on land. It probably fed on small vertebrates and insects, using its famous "two types of teeth" to render its prey helpless. The long upper jaw teeth have cutting surfaces while the lower jaws bear shorter teeth. Broad-winged Dimorphodon was not the most graceful flyer though, given its short and broad wings roughly 1.45 meters across.
Fossils of the animal were first discovered by famed pioneer in paleontology, Mary Anning. The remains were collected from Lyme Regis in Dorset in the year 1828. This area also revealed numerous other fossils from the Early Jurassic, from a World Heritage Site called Jurassic Coast. The specimen was only properly named and described by Sir Richard Owen in 1859, on the basis of two other fossils from the same locality. Earlier it had been tossed into the genus Pterodactylus as Pterodactylus macronyx by William Buckland.