Havva Mustafa, 57, was taking a stroll along Hove beach with his partner Yvonne when he came across the “ghostlike” carcass.
The Brighton resident said it was “quite high up the beach” and “not close to the water’s edge”.
He said: “When we first saw the carcass, we thought it was a seal, as we approached it we realised that there were four legs and hooves.
“We thought it was a sheep. It was a strange sight and confusing, the skin was pearlescent, with no wool, if it is a sheep.
“We were shocked to see legs and feet and the absence of a head.
“We wondered how it ended up on the beach.
The mystery animal carcass on Hove beach (Image: Havva Mustafa)
“The strangest thing was the pearly sheen all over it – ghostlike, almost lit from the inside.”
Mr Mustafa said he was coming up with “all sorts of theories about how a sheep might end up drowned in the sea”.
A spokesman for Sussex Wildlife Trust said it was “really difficult” to identify the animal, which looked to have been in the water “for a while”.
He added it was “likely to be a sheep”.
Cordelia Slaughter, a passionate beachcomber from Bexhill, also made a shocking discovery during a walk along Galley Hill when she spotted a skull “high up” on the beach.
She said the skull is “one of the most unusual things I have found”.
Although she has found several dead mammals on the beach over the years, including seals, she has never found a head on its own.
She speculated that the creature, which looks either to have been a dolphin or porpoise, may have been decapitated by a boat.
The beachcomber reported her find to the Sussex Dolphin Project.