A few weeks after the publication of the original book Fantastic Beasts and Where to Find Them (March 2001), a man named Howard Brayton, inspired by his profession as educational consultant, wrote a letter to J.K. Rowling (addressing her as Professor Scamander). In his letter, Brayton points out that the mythical Wyvern has been ommited from the book and that it should be included in the next edition. He also notes that the English poet Robert Browning makes references to the Wyvern.
J.K. Rowling decided to reply to the letter in the following way (the response was received on May 29, 2001):
Ah yes, the fabled “wyvern”. Well, naturally I had heard the rumours ~the poet Browning’s allusion had not escaped me~ and so I set out to investigate. Extensive research however, has convinced me that the beast in question was a Common Welsh Green whose legs were counted by a Muggle with a very shaky grasp of numeracy. You know how that is, you’re an educational consultant.
It is always a blow to have a chesired part of one’s life dismissed as a figment of the imagination, so I tender my apologies to yourself and your alma mater – but we wizards have to deal with that every day.
Both letters (the original letter by Brayton and J.K. Rowling’s response) were auctioned in 2014.