What is now the Waitaki Valley must have been a rich feeding or breeding ground in a vast sheltered embayment, he said, given the treasure trove of fossils preserved in its rocks.
The area offers a window to an era 24 to 30 million years ago, almost halfway back to the age of the dinosaurs, and is considered by scientists as one of the most important sites in the world for understanding the evolution of marine life today.
Professor Fordyce and his team are finding new creatures all the time - some whose fossils are nearly intact - and work only just completed has produced three dolphin specimens yet to be described.
"There are a couple of articles that we've submitted to journals recently, and that is going to mean two new species."
His first find was part of the skeleton of a huge baleen whale, around 28 or 29 million years old, which was the first of its kind ever found in New Zealand.
"It was very primitive, so I was pretty excited," he said.
"I realised it was quite a significant spot, so I wrote an application for a grant to do field work that went to the National Geographic Society in Washington DC, and they funded it."
Another 10 baleen whale skulls, ranging between 23 and 29 million years in age, have since been unearthed around the valley.
Some are presently being studied by his students, while others are still sitting in the university, encased in plaster jackets weighing hundreds of kilograms.
"There have been a few remains of small dolphins, which are geologically young-ish and right at the 23 or 24 million year level, so they are really quite significant little guys, and some other material belongs to a group we call the shark-tooth dolphins."
Unlike anything living today, the shark-like dolphins had a metre-long skull and shark-like teeth that were found to be worn down, probably from chomping penguins or bony fish.
"These things can be so rare that there might only be one animal known anywhere in the world."
After the discovery of what was named the Waipatia dolphin, the valley yielded another similar species whose spiky teeth protruded out and around its beak.
Among the more impressive penguin samples were the giant Kairuku, which were found to have stood around 1.2m when the reconstruction of a long-kept fossil was finally completed in 2012.
The Kairuku was described as an elegant bird by penguin standards, with a slender body and long flippers, but short, thick legs and feet.
Less handsome was a massive shark, whose remains Professor Fordyce recovered from the Awamoko valley near the small town of Duntroon in the early 1990s.
"It really was a monster. It reached an estimated length of 9m. There were bigger sharks around, but that was the biggest one we ever collected."
The Carcharodon angustidens, which would have dwarfed a person, had left Professor Fordyce a cluster of 150 large teeth to work from.
On trips to the valley, his team will walk through riverbeds and past cliffs, searching for tell-tale pieces of bone poking out of rocks.
Of the 40 or so hunting spots in the area, lime quarries in the Hakataramea Valley have offered up some of the greatest finds.
The researchers have sometimes dug holes big enough to drive a car into to retrieve bulky slabs of fossil, later fitted with splints of heavy timber plastered into place and trucked into Dunedin.
"Many of our fossils can be related to species that are still living today, and can be used to basically produce a tide-point for genetic finger printing," he said.
"It's quite an important part of understanding relationships between living species."
Some existing marine species, like the right whale which can often be seen cruising through Otago Harbour, may also have ancestors buried in the valley.
"The fossils do show us that ancient ecosystems were quite complex - about as complex as today - but they were often structured in different ways.
"They had different mixes of species, maybe different lifestyles - so that's a constant reminder to us that life has evolved pretty fast through geological time."
Giants of the Valley
• Great White Grandfather: The Carcharodon angustidens, which lived around 25 million years ago, reached a length of 9m and dwafted its descendant, the great white shark. Fossils of its large teeth were found in the Awamoko Valley, near Duntroon, in the early 1990s.
• Prehistoric penguin: Kairuku were giant, elegant penguins that stood about 1.2m, with a slender body and long flippers, but short, thick legs and feet. Remains of these creatures, about 26-27 million years old, have been found in the Waitaki valley.
• Jaws meets Flipper: Shark-tooth dolphins had a metre-long skull and shark-like teeth that were found to be worn down, probably from chomping penguins or bony fish.
• Whale of a find: One of Professor Fordyce's first major finds in the Waitaki Valley was the skull and part skeleton of a huge, early baleen whale, probably 28 million years old. It's presently on display at Otago Museum.
