Alfonso Thomas, the Dolphins and South Africa fast bowler, has joined Somerset as a Kolpak player subject to obtaining a work permit.
Thomas, 31, made his Twenty20 debut for South Africa against Pakistan last year, picking up 3 for 25 in his four overs.
"I watched him play twice when I was out in South Africa and was impressed with what I saw," Brian Rose, Somerset's director of cricket, told the club's website. "He is very highly rated and has a great record. Alfonso will be a great addition and will really strengthen the Somerset squad."