The term "Shetland pony" is a breed name, not a species name. It's like saying "Golden Retriever" - it's a breed within the species Canis familiaris (dog).
What is the scientific name for a shetland pony?
There isn't a separate scientific name for a Shetland pony. They are classified as Equus caballus, the same scientific name as all other domestic horses.