D.C. Fontana, the pioneering TV writer who significantly shaped the "Star Trek" universe, in particular the character of Spock and his home planet, Vulcan, has died at 80.

Fontana died Monday night after a brief illness, the American Film Institute, where Fontana was a senior lecturer, said in a statement. CBS Studios and the "Star Trek" production company confirmed the announcement.

D.C. Fontana at a celebration of 'Star Trek: The Motion Picture' in Hollywood, California, in September 2016. Albert L. Ortega / Getty Images file

No further details were made public.

Dorothy Catherine Fontana — she used her initials, "D.C.," so producers during the 1960s wouldn't know she was a woman — was perhaps second only to Gene Roddenberry, the series' creator, in molding the sprawling "Star Trek" story-telling empire.

Fontana, the first female writer on the show, wrote or co-wrote some of the most notable episodes of the original series, which ran from 1966 to 1969, and, with Roddenberry, co-wrote the pilot for its revival as "Star Trek: The Next Generation" in 1987.

"The galaxy will miss you," Dan and Kevin Hageman, the developers of a CBS/Nickelodeon animated "Star Trek" series scheduled to debut next year, said on Twitter.

So sad to lose D.C. Fontana. She will always be a huge voice in the Star Trek universe. The galaxy will miss you. pic.twitter.com/cFlx0fOMku — Dan & Kevin Hageman (@brothershageman) December 3, 2019

Michael Okuda, a graphic designer on several of the "Star Trek" properties beginning in the 1980s, said he was "heartbroken."

"Dorothy Fontana brought humanity to the world of Star Trek," Okuda said Tuesday on Twitter, adding: "Star Trek's universe just got a little bit smaller with the passing of D.C. Fontana."

Fontana started as Roddenberry's secretary when he created the TV series "The Lieutenant," which ran for one season. When he created "Star Trek," he assigned her to write the teleplay for the series' second episode, "Charlie X," about a teenage boy with special powers who creates chaos aboard the USS Enterprise after he is rescued from a crashed cargo ship.

Fontana was especially significant in developing the character of Mr. Spock, the half-Vulcan, half-human science officer who struggles to repress his emotions.

"Spock kind of spoke to me because of his problematic interior," she said in a 2016 interview with the SyFy network. "'How do I be a Vulcan? How do I be a human?'"

Fontana further fleshed out Spock in the episode "Journey to Babel," which introduced the characters of his Vulcan father and his human mother, who would appear throughout the "Star Trek" stories personifying the warring halves of their son's interior life.

"I began to speculate what kind of Vulcan would marry a human, what kind of relationship did they have to each other and to their son," she said in an interview during the early 2000s with the comic book historian Marv Wolfman.

Leonard Nimoy as Mr. Spock and Joanne Linville as a Romulan commander in the 1968 'Star Trek' episode 'The Enterprise Incident,' which was written by D.C. Fontana, who died Monday, Dec. 2, 2019. CBS via Getty Images file

When, after almost 20 years, Roddenberry revived "Star Trek" on the small screen under the name "The Next Generation," he personally assigned Fontana to develop the teleplay for the pilot, "Encounter at Farpoint."

In a 2007 interview with Entertainment Weekly, she said she chose to include an unannounced appearance by DeForest Kelley as Dr. McCoy from the original series "because I thought we should have a connection with the old show."

Fontana wrote two more episodes of "The Next Generation," along with episodes or stories for another "Star Trek" spinoff, "Deep Space Nine," as well as "Star Trek" video games and animated series.

Her other credits included dozens of episodes of other series, like "Bonanza," "The High Chaparral," "Kung Fu," "The Waltons" and "Dallas." But her primary work was in science fiction.

In addition to the "Star Trek" franchise, she was credited with writing or co-writing numerous episodes of "The Six Million Dollar Man," "The Fantastic Journey," "Buck Rogers in the 25th Century," "The War of the Worlds," "Babylon 5," "Earth: Final Conflict" and, notably, "Logan's Run," for which she was the story editor.

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Her last writing credit was for "To Serve All My Days," a 2006 episode of the web series "Star Trek: New Voyages," in which Walter Koenig reprised his role as Chekhov from the original "Star Trek" series and movies.

In recent years, Fontana had been a senior lecturer at the American Film Institute. She was twice awarded lifetime honors by the Writers Guild of America, in 1997 and 2002.

She is survived by her husband, the Academy Award-winning visual effects cinematographer Dennis Skotak.