Question: Yvonne Mounsey, the South African-American ballet dancer was known for the important roles she created in the works of which choreographer who co-founded the New York City Ballet?
Context: Troy Schumacher is an American choreographer, dancer, and director based in New York City.  He is a soloist in the New York City Ballet and has choreographed for the company since 2014; before being promoted to soloist, he danced in NYCB's corps de ballet starting in 2005.  He is the founder of BalletCollective, an arts collective that has created new ballet-based works since its inception in 2010.  His work has been presented by New York City Ballet, Performa, Danspace Project, Guggenheim Works and Process, the Joyce Theater, and NYU Skirball Center.  In addition to live performances, Schumacher has choreographed numerous fashion and commercial shoots, including works for Sony PlayStation, Capezio featuring Maddie Ziegler, HP, Aritzia, CR Fashion Book, Tom Ford, and The New York Times. Holly Hynes is an accomplished costume designer with over 250 ballets to her credit, including more than 70 at the New York City Ballet.  Ms. Hynes' designs are also on view in companies around the world, including American Ballet Theatre, San Francisco Ballet, Bolshoi Ballet, National Ballet of Canada, Kirov Ballet, Royal Ballet, Paris Opera Ballet, Royal Danish Ballet, La Scala Theatre Ballet, Koninklijk Ballet van Vlaanderen, Houston Ballet, BalletMet, Pennsylvania Ballet, Ballet Vancouver, Les Grands Ballets Canadiens, American Repertory Ballet, Pacific Northwest Ballet, Atlanta Ballet, Richmond Ballet, Nashville Ballet, Miami City Ballet, Alberta Ballet, Joffrey Ballet, Kansas City Ballet , and the Suzanne Farrell Ballet at The John F. Kennedy Center for the Performing Arts, where she serves as the resident costume designer. George Balanchine (born Giorgi Melitonovich Balanchivadze; January 22, 1904April 30, 1983) was a choreographer.  Styled as the father of American ballet, he co-founded the New York City Ballet and remained its Artistic Director for more than 35 years. Robert Weiss is an American ballet dancer, choreographer, and Artistic Director of Carolina Ballet.  He began his professional career at age 17 joining the New York City Ballet under George Balanchine, eventually becoming a Principal Dancer.  Balanchine created several roles for him, including Ballo della Regina.  Weiss remained with the New York City Ballet for 16 years.  He later served as Artistic Director of the Pennsylvania Ballet from 1982 to 1990.  Weiss then became the founding Artistic Director of Carolina Ballet in 1997 where he has remained to this day. Igor Zelensky (also Igor Zelenski) is a Russian ballet dancer.  He was born in Labinsk.  He was a principal at the Mariinsky Ballet from 1991 until 2013.  He graduated from the Tbilisi School of Ballet (class of Vakhtang Chabukiani) and trained at the Vaganova academy (class of Gennady Selutsky).  He was a principal for five years at the New York City Ballet.  He has a wide repertoire including Romeo in Romeo and Juliet and Siegfried in Swan Lake.  He has performed around the world, including with the Royal Ballet in London, at La Scala in Milan, at the Bayerische Staatsoper in Munich and with the New York City Ballet.  He has danced with many professional ballerinas during his career. Heather Watts (born September 27, 1953), was a principal ballerina with New York City Ballet.  A native of California, Ms. Watts was born as Linda Heather Watts in Long Beach on September 27, 1953.  As a little girl, she was a troublemaking child.  She had always wanted to be an actress.  An acting coach advised her taking ballet classes, seeing as she was incredibly dramatic (and clumsy).  She started dancing at the age of 10, came to New York at the age of 13 on a Ford Foundation summer scholarship to attend the School of American Ballet, the official school of the New York City Ballet.  She moved permanently to New York at age 15, again on a Ford Foundation scholarship to the School of American Ballet.  Watts joined the New York City Ballet in 1970 and was promoted to principal dancer by company founder George Balanchine in 1979.  George Balanchine took Watts into his companies "because he would not let such a talent disappear."  During Ms. Watts's tenure with the company, she had numerous principal roles created for her by George Balanchine, Jerome Robbins, and Peter Martins among others.  Mr. Balanchine gave Ms. Watts the principal roles in many of his existing masterpieces, including "Agon", Concerto Barocco, "Apollo", Symphony in C, "Theme and Variations" and "Serenade".  Ms. Watts performed around the world and starred in numerous "Dance in America" television programs, and she performed opposite frequent partner Mikhail Baryshnikov at the White House in a national televised performance of Balanchine's "Rubies" for President and Mrs. Carter.  Ms. Watts retired from the stage in a gala performance at Lincoln Center in 1995. Yvonne Mounsey (2 September 1919 – 29 September 2012) was a South African-American ballet dancer and teacher.  Described as "a dancer of glamour, wit, and striking presence," she spent ten years with the New York City Ballet (1949-1959), where she created important roles in the works of George Balanchine and Jerome Robbins. Debra Austin (born July 25, 1955) is an American ballet dancer who rose to prominence in 1982 as the first African-American female principal dancer of a major American ballet company.  She was also the first African-American female dancer at the New York City Ballet.  She currently serves as the ballet mistress for the Carolina Ballet. John Meehan (born 1950) is an Australian ballet director, choreographer, professor, and retired ballet dancer.  He was educated at the Anglican Church Grammar School in Brisbane and studied at the Australian Ballet School.  Meehan joined the Australian Ballet in 1970 and was promoted to principal dancer in 1974, creating roles in several works, including Ronald Hynd's "The Merry Widow".  He danced also with American Ballet Theatre from 1977 to 1980 and later was a guest artist with National Ballet of Canada and the New York City Ballet. Mary Helen Bowers (born 1979) is an American celebrity fitness guru, entrepreneur and former New York City Ballet dancer originally from Charlotte, North Carolina.  She attended Alexander Graham Middle School in Charlotte, North Carolina before leaving for New York.  She was a full scholarship student at the School of American Ballet in Manhattan at fifteen years old.  One year later she was invited to join the New York City Ballet.  She graduated with a Bachelor of Arts degree in English Literature from Columbia University in New York City.  She danced with the New York City Ballet for a decade.
Answer: George Balanchine