WASHINGTON – It’s not the biggest or the most popular, but the first dinosaur has returned to the Fossil Hall at the National Museum of Natural History, marking a milestone in the five-year renovation project that is still 18 months from completion.

Exhibition project manager Siobhan Starrs practically jumped with joy as she watched workers mount a pteranodon, a flying reptile, on one of the popular gallery’s renovated walls.

“It’s so exciting. I want to open a bottle of champagne,” Starrs said.

The Fossil Hall – perhaps the most popular wing of Washington’s most-visited museum – has been closed since 2014 for a five-year, $129 million renovation. It took museum staff members about a year to move the priceless objects, and another two-plus years to renovate the 31,000-square-foot space, which is expected to reopen in 2019.

Officials will use the next 18 months to install murals, exhibition cases, mounts and – finally – the dinosaur fossils.

Highlighting the exhibit will be a Tyrannosaurus rex that was discovered in Montana in 1988. The dinosaur arrived in Washington in 2014 in crates. Some of its bones were displayed as they were being 3-D scanned, Starrs said, but the entire specimen will be on view for the first time when the gallery opens.

The renovation will return the great hall to its original grandeur, complete with stone floors, soaring ceilings and skylights and ornate molding and detail. What had been dark and closed-in has been transformed.

The pteranodon went in first because it will hang on a wall that will be covered in murals. The rest of the dinosaurs and other displays will be installed starting next summer.

Starrs described the construction project as “a process of discovery.”

“We brought it back to its architectural roots,” she said of the building, at 10th Street and Constitution Avenue on the north edge of the National Mall. “You can see the glory of the historic architecture.”

The exhibition will be installed in a new way that will connect today’s world to the stories of old, Starr said. The displays will explain how ecosystems are linked and how the planet has changed so that visitors can better understand how current issues, like climate change, are affecting the planet.

“All life on Earth is connected through all time. The architecture and narrative rhyme in a way they didn’t before,” Starrs said.

An early peek into the gallery revealed a new airy feel that is simultaneously modern and historic.

Starrs said the challenge has been to balance a new approach with the beloved objects of old. For example, two murals by Jay Matternes depicting Ice Age landscapes were preserved. The works by the well-known paleoartist were removed by hand from the wall, and prints were made of them. The prints will be installed in the new space, along with new murals commissioned by the museum.

“You’ll have the hall you knew and loved, and also the new,” Starrs said.