The first-ever discovery of dinosaur fossils in Hong Kong is a "momentous" achievement and could mark the beginning of a series of exciting finds in the wider region, a palaeontologist said on Thursday.

Officials announced on Wednesday that dinosaur fossils believed to date back to the Cretaceous period, about 145 million to 66 million years ago, have been discovered on Port Island in the northeastern waters of the SAR.

"The discovery of these bones is super exciting because we have rocks of the right age and the right environment but having looked for so many years, different people have not been able to find dinosaur bones, including myself," said Michael Pittman from the School of Life Sciences at Chinese University.

"From what I hear they seem to be from some larger dinosaurs. I've seen pictures of models that are of long-neck dinosaurs and the hadrosaur dinosaurs, so these are among the biggest."

Pittman said the find was also "very lucky" since Hong Kong isn't an ideal location for fossil preservation, given that the territory had a lot of volcanic activity in the past.

He added that finding dinosaur bones in the SAR is challenging due to the topography and landscape.

"There have been Jurassic-age fish, there have been older Devonian fish. Very interesting, but not like large volumes of fossils, and that's partly because there's not much area to look for fossils. Also, the rocks are quite hard and they don't readily erode out fossils," he said.

"When we look for fossils, we typically go to a place where you can easily access them, and we focus on places where there are lots and lots of fossils, so it's rich in fossils and makes it easier. So because of those various reasons I mentioned, Hong Kong hasn't been a focus point for looking for fossils."

He said China is one of four main countries in the world for dinosaur fossils, along with the US, Canada and Argentina, but the Guangdong area is famous only for dinosaur eggs.

Pittman also welcomed the signing of an agreement between the Development Bureau and the mainland's Institute of Vertebrate Paleontology and Paleoanthropology, to deepen exchanges and cooperation.

"Obviously, finding some fossils in Hong Kong enriches our local palaeontology heritage. But my hope is the agreement would help to further exchanges with the institute, which people like myself have been working for for more than a decade," he said.

The dinosaur fossils will be on public display at the Heritage Discovery Centre in Kowloon Park from Friday.