These illustrations are from Domenico Gnoli's 1968 title Bestiario Moderno (Modern Bestiary), an "incredible collection of pen and ink illustrations that are intricately detailed and nothing short of amazing." The book appears to be out-of-print, which is a damned shame.
Domenico Gnoli (1933-1970) is one of the most neglected illustrators of the 20th century. Born in Rome, Italy, he was an Italian artist, writer and stage designer. Gnoli was an imaginative, intense and technically gifted artist. He is best known for his books Orestes (The Art of Smiling), 1961 and Bestiario Moderno (Modern Bestiary), 1968.
In Modern Bestiary, Gnoli produced an incredible collection of pen and ink illustrations that are intricately detailed and nothing short of amazing. Looking like 'pop art', his animal creations look like strange but lovable household pets. Who wouldn't want a flying cat or rhino-chicken?
Modern Bestiary [Curious History]
(via Neil Gaiman)