A Spined body is a members-only piece of Ranged armour. To wear a spined body, the player must have at least 40 Defence, 40 Ranged, and have completed The Fremennik Trials quest. Stat-wise, it is identical to the Gilded d'hide body.
To obtain a spined body, a player can either bring 3 dagannoth hides, 1 flattened hide, and 10,000 coins to Sigli the Huntsman in Rellekka, receive it as a drop from Dagannoth Supreme, or trade with another player.
This body can be stored in the armour case of a costume room, as part of the Spined armour set. Ultimate Ironmen will be unable to retrieve individual pieces until the full set is stored.
For an exhaustive list of all known sources for this item, see here