There’s a T. rex-sized dispute raging over the writing credits for Jurassic World, the next installment of the blockbuster franchise. Universal Pictures wanted the names of one writing team to appear in the screen credits, but a WGA arbitration panel has ruled that credit should be shared by two writing teams.

Sources familiar with the dispute say the studio wanted director Colin Trevorrow and his longtime writing partner, Derek Connolly, to share a written-by screen credit, with the late Michael Crichton getting a “based on the novel by” credit. A promo for the film that aired during the Super Bowl listed the credits just that way, showing that the film had been “written by” Trevorrow & Connolly – the ampersand signifying a writing team.

A three-member arbitration panel, however, ruled last week that Trevorrow and Connolly should share writing credit with Rick Jaffa and Amanda Silver, the husband-and-wife team who’d written an earlier draft of the script. And instead of a “written by” credit, the arbiters ruled that they would all share a “screenplay by” credit. Trevorrow and Connolly have appealed, insisting they wrote an entirely new screenplay that wasn’t based on the Jaffa and Silver draft. They want their solo “written by” credit restored.

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The difference between a “written by” credit and a “screenplay by” credit might seem like a narrow distinction, but they mean tw

o entirely different things. A “written by” credit is the guild’s highest screen credit, meaning that the script was not based on any source material of a story nature. The arbiters, however, ruled that in this case the final shooting script had indeed been based on source material of a story nature – specifically, the earlier script written by Jaffa and Silver.

Jurassic World, which hits theaters in June, has been kicking around for years. In 2011, executive producer Steven Spielberg revealed at Comic-Con that a writer – it turned out to be Mark Protosevich of Thor and I Am Legend fame – was working on a treatment. In 2012, Jaffa and Silver, who wrote the two most recent Planet of The Apes films and Avatar 2, were brought in to write the next Jurassic Park sequel. For whatever reasons, it didn’t work out, and Trevorrow and Connolly, film school buddies who worked together on Safety Not Guaranteed and Gary: Under Crisis, were brought in to write their own version of Jurassic World.

The guild has set a meeting for Friday to go over the appeal, which requires proof of some sort of procedural error to overturn the arbiters’ ruling.