Xiphactinus was one of the largest bony fish of the late Cretaceous period. (National Geographic)

The fossilized remains of a massive predatory fish that lived 80 million years ago is being dug out of an ancient seabed in southern Manitoba.

The discovery of the six-metre long xiphactinus was made by staff of the Canadian Fossil Discovery Centre (CFDC) in late 2009 but it wasn't confirmed until the bones were being cleaned during the winter.

The exact location of the find is being kept a secret. The CFDC, located in the town of Morden, about 110 kilometres southwest of Winnipeg, has several active dig sites in that Pembina Valley region.

Canadian Fossil Discovery Centre staff work at the dig site where a six-metre-long ancient sea creature known as xiphactinus was uncovered. (Canadian Fossil Discovery Centre)

Paleontologists cleaning the specimens gathered from one of the sites found a set of massive xiphactinus jawbones locked on piece of flipper belonging to a mosasaur — a marine reptile.

The CFDC fossil crew is now back at the site for a major excavation. More than six metres of earth has been removed, exposing more and more pieces belonging to the xiphactinus and its prehistoric prey, said CFDC general manager Tyler Schroeder.

"The site is proving to be a fantastic find, with both xiphactinus and mosasaur fossils present, as well as other specimens," he said.

"We'll likely be excavating at this fossil-rich spot throughout this year and possibly into next year."

The xiphactinus was one of the largest bony fish of the late Cretaceous period and was one of the fiercest creatures in the Western Interior Seaway at the time.

'It's quite remarkable to have the opportunity to find one fossil, and absolutely incredible when that one fossil leads to the discovery of an ancient sea monster skeleton.'—CFDC museum curator Anita Janzic

The seaway passed across the middle of what is now North America, stretching from the Rocky Mountains in the west to the Appalachians in the east and was some 1,000 kilometres wide.

"It's quite remarkable to have the opportunity to find one fossil, and absolutely incredible when that one fossil leads to the discovery of an ancient sea monster skeleton," said CFDC museum curator Anita Janzic.

The Canadian Fossil Discovery Centre houses the largest collection of marine reptile fossils in Canada, including a 13-metre long mosasaur named Bruce, the largest mosasaur in the country.

Currently housed in the Morden Community Centre, the CFDC has been working on raising funds to build a new state-of-the-art facility in the Manitoba escarpment.

"It's finds like this that continue to push the CFDC into a leading role for the collection of marine reptile fossils across the country," said CFDC board president Henry Penner.

"Now we need a facility that's better up to the task of presenting these spectacular finds to the public, as well as supporting our paleontologists in their scientific research."