The Uffington White Horse has been caught up in an identity battle after it was suggested it could be a dog.
Retired vet Olaf Swarbrick has said the ancient carving in the Oxfordshire hillside is not anatomically correct and has more canine-like features.
But the National Trust, which said soil samples indicated that the figure dated back 3,000 years to the Bronze Age, has rejected Mr Swarbrick's ideas.
However it admitted there were many theories about the carving.
Written records date back to the 12th Century but do not give proof of its exact age or why it was created.
It used to be thought that the figure was constructed by the Saxons to celebrate a victorious battle of King Alfred's. This view is now mainly discredited.
Mr Swarbrick wrote a letter to scientific journal the Veterinary Record appealing for his fellow professionals to cast their opinion on his claim.
He said he believed the figure looked like a hunting hound at full stretch.
"Anatomically it's not a horse at all," Mr Swarbrick said.
"It's too long and too lean and it has a long tail - horses don't have a tail the length of that stylised creature at Uffington."
Mr Swarbrick joked that its name might have to be changed.
"If I'm correct, it needs to have its horse removed - maybe the wolf hound of Uffington.
"The other thing about short-carved figures is that over the years they have had to be cleaned and refurbished and they do change in their shape over periods."
Keith Blaxhall, from the National Trust, said he thought its shape suggested the figure was supposed to be a horse.
"What you have to remember it's a stylised horse, almost like a stencil on the hillside, so it's not a complete figure of a horse, it's a suggestion.
"I would like to think it's frozen in perpetual canter across the downs.
"Visibility wise you can't see the entire figure, my theory is it's meant to be revered by the living and by the gods and the ancestors - a view from above and below."