Stephany Folsom was hired in December 2015 to do a new draft of Thor: Ragnarok before filming began, but now the screenwriter said that she's not getting credit for her work.
Marvel gave me "story by"credit on THOR RAGNAROK and the writers' guild denied me the credit due to guild regulations. Are you kidding me?— Stephany Folsom (@StephanyFolsom) September 11, 2017
The Writer's Guild of America traditionally allows for only two individuals to be given "Story By" credit, with the allowance for a defined writing team to count as one individual. That's the case currently with Thor: Ragnarok, which in Marvel Studios' marketing is credited to "Craig Kyle & Christopher Yost and Eric Pearson."
Kyle and Yost wrote the original draft of the Thor: Ragnarok script, while Pearson was brought on in early 2016 to do a draft after Folsom. In early January 2017, Marvel gave "Story by" credits to Kyle, Yost, and Folsom, but in later marketing material reverted to the Kyle, Yost, and Pearson credit.
Folsom said she intends to appeal WGA's decision, and that Marvel supportive of her goals.