Stone Sour is an American rock band formed in Des Moines, Iowa, in 1992, performing for five years, before disbanding in 1997. They reunited in 2000 and since 2006, the group has consisted of Corey Taylor (lead vocals, guitar), Josh Rand (guitar) and Roy Mayorga (drums). Longtime members Joel Ekman (drums, percussion), Shawn Economaki (bass guitar), and Jim Root (guitar) left the group in 2006, 2011, and 2014 respectively. To date, Stone Sour have released six studio albums Stone Sour (2002); Come What(ever)

The band released a song called "The Pessimist" as a free download on their Facebook page on March 27, 2012. The song was previously only available on the iTunes deluxe version of the soundtrack to Transformers: Dark of the Moon. They also released their first DVD Live at Brighton in the same year, capturing their performance on November 7, 2010.  It was announced via Instagram on May 3, 2012 that bassist Shawn Economaki had parted ways with the band on amicable terms. He was replaced in the studio by current Skid Row bassist Rachel Bolan. Stone Sour started recording their fourth studio album in early 2012. Corey Taylor stated that the album would end up being a double album or concept album, and described the album's sound as "Pink Floyd's The Wall meets Alice in Chains's Dirt". It was later announced that the new material would be released as two separate albums. The first album, House of Gold & Bones - Part 1 was released worldwide on October 23, 2012, and the second album House of Gold & Bones - Part 2 was released worldwide on April 9, 2013. The project also has a 4-part graphic novel series that accompanies the albums, telling the linear storyline featured in the twin albums' lyrics.  The first two songs from Part 1, "Gone Sovereign" and the first official single, "Absolute Zero" were released for radio airplay in mid/late August 2012. The first single from House of Gold & Bones Part 2 was "Do Me a Favor". It was released digitally on February 12. Guitarist Josh Rand stated in an interview with O2 Academy that there was a song recorded for Part 1, an instrumental which was deemed 'not up to par' by the band. The song will likely be released in the future once James Root and Josh Rand do 'some stuff to it guitar-wise'.  On October 5, 2012, Johny Chow of Fireball Ministry and Cavalera Conspiracy was announced as the bassist for the band on the House of Gold & Bones tour cycle. Stone Sour subsequently played Soundwave Festival 2013 in Australia and on the Sunday at Download Festival 2013. Guitarist James Root did not tour with Stone Sour in the winter of 2013, as he had to take a brief hiatus from the group to work on .5: The Gray Chapter with Slipknot, although it was later revealed that he was fired from the band due to musical differences. He claimed that the band wanted to focus on "radio play and money," in which Root fought against, and that led to a split. Christian Martucci filled in for Root during that period.

Using a quote from the above article, answer the following question: Who replaced him?
He was replaced in the studio by current Skid Row bassist Rachel Bolan.