At 10.5 metres wide, four centuries old and twice the size of its nearest cousin, an “exceptionally large” coral has been discovered on the Great Barrier Reef – the widest known in the area.

The coral is 5.3 metres tall, “hemispherical in shape” and 2.4 metres wider than the next widest specimen. It is roughly the length and height of a modern double-decker bus.

It is thought to have spawned on the reef between 421 and 438 years ago and its age means it not only predates the arrival of James Cook and the advent of colonisation in Australia, but the birth of Charles Darwin, the founding of the United States and the invention of the term “biology”.

While it isn’t the largest coral in the world, the James Cook University adjunct associate professor and managing director of Reef Ecologic, Adam Smith, said it was significant to the ecosystem.

“It’s like a block of apartments,” Smith said. “It attracts other species. There’s other corals, there’s fish, there’s other animals around that use it for shelter or for feeding, so it’s pretty important for them.”

The coral was discovered off the coast of Goolboodi – the Indigenous name for Orpheus Island, part of the Palm Island group in Queensland – by a group of scientists and community members participating in a marine citizen science course.

Smith said local fishers and researchers had known about the coral for some time but until that moment no one had looked closer.

“It’s a bit like finding a giant redwood tree in the middle of a botanic gardens,” Smith said. “James Cook University has a research station at Orpheus Island and there’s been 600 scientific papers written on corals, fish and seaweed in the area.

“Over the last 20 or 30 years, no one has noticed, or observed, or thought it newsworthy enough to share photos, or document, or do research on this giant coral.”

The exact species of the coral is unknown as genetic testing has not been done to confirm, but it belongs to the genus Porites sp.

The traditional custodians of Palm Island, the Manbarra people, have named the coral Muga dhambi. The name translates to “Big coral”.

Muga dhambi has been described in the journal Scientific Reports this week with co-authors that included 17-year-old Kailash Cook, who helped measure the coral during the dive, and the “godfather of coral”, 76-year-old Dr Charlie Veron, who helped identify it.

The authors have called for the coral to be monitored and the Great Barrier Reef to be protected given the “increasing” threats from climate change, declining water quality, overfishing and coastal development.

Smith said “technically” there was nothing stopping the coral species living for 1,000 years, but noted most of its species on the Great Barrier Reef only lived to 450 or 460 years.

“It’s lived through lots of cyclones, quite a few reefs and coral bleaching events – who knows? It’s a very diverse, hard environment on the Great Barrier Reef. It’s obviously an old resilient coral,” he said.

“Whether that’s because it’s tough or lucky, I don’t know.”