Three wolf pups, resembling extinct dire wolves, have been trotting, sleeping and howling in an undisclosed secure location in the United States iformore than 10,000 years.

These genetically engineered wolves, which are believed to be three to six months old, have long white hair, muscular jaws and already weigh in at around 80 pounds — on track to reach 140 pounds at maturity, the Associated Press quoted researchers at Dallas-based biotech company Colossal Biosciences as saying.

According to the Colossal Biosciences, two of the wolves have been named after twin brothers Romulus and Remus, while the third one was called Khaleesi, named after the popular species that featured in the Game of Thrones series.

The company said Romulus and Remus were born on October 1, 2024, while Khaleesi was born on January 31, 2025.

Dire wolves, which went extinct more than 10,000 years ago, were much larger than grey wolves, their closest living relatives today.

Colossal scientists learned about specific traits that dire wolves possessed by examining ancient DNA from fossils, the Associated Press reported.

The researchers studied a 13,000 year-old dire wolf tooth unearthed in Ohio and a 72,000 year-old skull fragment found in Idaho, both part of natural history museum collections.

Then the scientists took blood cells from a living gray wolf and used CRISPR to genetically modify them in 20 different sites, Colossal’s chief scientist Beth Shapiro was quoted as saying.

They transferred that genetic material to an egg cell from a domestic dog. When ready, embryos were transferred to surrogates, also domestic dogs, and 62 days late,r the genetically engineered pups were born.

Colossal had previously announced similar projects to genetically alter cells from living species to create animals resembling extinct woolly mammoths, dodos and others.