Omaha, Neb. ? To their surprise, officials at a Lincoln zoo are seeing double and laying claim to a new record.

The Lincoln Children’s Zoo is celebrating its first set of Matschie’s tree kangaroo twins, and an official who tracks numbers of the extremely rare species says it’s the first documented case in North America among records that go back to the 1970s.

The twins were found last month in the pouch of Milla, who had been mating with Noru, a Matschie’s tree kangaroo brought in from the Toronto Zoo. The twins make up half of the four documented Matschie’s tree kangaroo births in 2008.

“I was dumbfounded, shall I say. I was thrilled,” said John Chapo, the zoo’s executive director in recalling his response after zoo curator Randy Scheer told him what he described as “interesting news.”

Another set of twin tree kangaroos were born at the San Diego Zoo in 1994, but that was a different species, said Jacque Blessington, who coordinates plans for the survival of tree kangaroos across North America on behalf of the Association of Zoos and Aquariums.

Blessington, a zookeeper at the Kansas City Zoo, said the births are likely the only ones documented worldwide, according to others who work closely with the species.

“We’re very excited, and a little shocked,” she said.

There are only about 50 of the rare animals in North America, scattered across 23 zoos, she said. They typically see two to four births a year.

In the wild, they live in the rainforest in northeastern Papua New Guinea.

The joeys were likely the size of a lima bean at birth, she said.

“It’s a naked little thing,” she said. “It’s not even fully developed yet.”

They’ll likely remain inside their mother’s pouch for about 10 months, but should begin poking out their heads or feet as early as May. They need to continue developing since the gestation period for a Matschie’s tree kangaroo is only about 44 days, Chapo said.

Staff members are watching to ensure they stay in the pouch. If they break free, it would require nearly around-the-clock care as they continue to develop, he said.

But with each passing day, Chapo grows more confident they will thrive.

“For us to be assisting with saving this species right here in Lincoln is very exciting,” he said.