A unicornate sea-pegasus is an SCA-only heraldic monster which appears on the arms of the Shire of Trinovantia Nova. A unicornate sea-pegasus is a winged horse with the tail of a fish and a unicorn's horn. Two appear on the arms of Trinovantia Nova, facing outwards, their tails within a laurel wreath. This charge is no longer allowed in SCA heraldry, however any person or branch who has registered it may register a unicornate sea-pegasus again under the heraldic Grandfather Clause.
The unicornate sea-pegasi are affectionately known to the people of Trinovantia Nova as the "A.T.U.s" -- for "All-Terrain Unicorns", a term also applied to the local newsletter, "The Unicorn's Tale."