This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Opinicus (Heraldic)
The opinicus or epimacus is another heraldic variety of griffin, which is depicted with the head of an eagle and all four legs of a lion where it occasionally has the neck and tail of a dromedary. It is sometimes wingless when born and will grow wings as it matures. The Opinicus was said to stalk the city streets of London after dark, swooping down from the blackened night sky of the British Isles, however it is not thought to harm humans.
It is described as having a long, serpentine like body, the powerful clawed paws and muscular legs of a lion, the head, neck and wings of an eagle and the short tail of a camel. The Opinicus were said to be born without wings which reportedly develop over the course of the creature's life.