A heavyweight bout between Kevin Randleman and Roger Gracie and a middleweight tilt between Joey Villasenor and Ronaldo “Jacare” Souza have been added to Strikeforce “St. Louis: Heavy Artillery” on May 15 at the Scottrade Center in St. Louis, Mo., the promotion announced on Thursday.

Strikeforce St. Louis “Heavy Artillery” will air live on Showtime.

Randleman, a former UFC heavyweight champion, is noted as one of the most explosive fighters to come out of his generation. A two-time NCAA Div. I wrestling champion for Ohio State University, the 38-year-old Randleman suffered back-to-back losses in 2009 to Mike Whitehead in Strikeforce and Bulgarian wrestler Stanislav Nedkov in Japan’s Sengoku promotion last November. Randleman is 2-4 since 2005.

Considered the brightest prospect of his famous family’s next generation, Gracie is a world-decorated Brazilian jiu-jitsu black belt. The 6-foot-4 heavyweight has ventured only twice into the cage, logging wins over UFC veteran Ron Waterman in 2006 and an under-sized Yuki Kondo in 2008.

Middleweight Joey Villasenor signed a four-fight deal with Strikeforce in January. A longtime member of the formidable Jackson Mixed Martial Arts Team, Villasenor had previously split his time between Strikeforce and the now defunct EliteXC organization. The 34-year-old middleweight striker has won five of his last six bouts, including victories against Phil Baroni and Ryan Jensen, as well as a split decision over Evangelista “Cyborg” Santos in a Strikeforce event last June.

Souza, another world-renowned black belt, touted a 10-fight win streak between 2004 and 2008, which included victories over Jason “Mayhem” Miller and Croatian striker Zelg Galesic in Japan’s Dream promotion. Jacare, which means “alligator” in Portuguese, made a strong promotional debut with a first-round submission over Olympic wrestler Matt Lindland at Strikeforce “Evolution” last December.

“Heavy Artillery” is anchored by two heavyweight bouts pairing former UFC champion Andrei Arlovski against Antonio Silva, and Strikeforce heavyweight champion Alistair Overeem making his first title defense against Brett Rogers.