GREENWICH — Two hundred million years ago. land that is now in central Connecticut and Massachusetts was along the edge of the Atlantic plate and subject to a completely different climate pattern than today.

“Imagine yourself on the shores of an east African lake where there’s a dry season and a wet season,” said Nicholas McDonald, a retired geology instructor. “What’s going to happen in the dry season? The lake will get shallower and some fish might get caught in the shallow water.”

Those fish would die and settle into the sediment, or become an easy meal for opportunistic predators of the time — dinosaurs, which would leave their tracks on the shoreline.

McDonald spent his career studying fossil evidence of that ancient food chain, preserved in Connecticut’s deep rift valley.

Recently retired from his position as a teacher and chairman emeritus of the Science Department at Westminster School in Simsbury — the institution McDonald credits for fostering and supporting much of his research for 37 years — he is donating his entire collection of fossils to Greenwich’s Bruce Musuem in hopes of inspiring young people, adults and budding scientists to go outside and explore.

“Fossils are abundant in central Connecticut,” McDonald said. “The process of finding and collecting them is a challenge, but it’s also an aesthetic experience. It’s the thrill of discovery. When I split a rock and find a fossil, to know that that’s the first time sunlight has hit that fish in 200 million years is just amazing.”

Since finding his first fossils growing up in Mystic, McDonald has dedicated his life to leaving no stone unturned.

His passion led him to his undergraduate and graduate theses on ancient fish — discovering in 1970 that no research had been published on the subject since the late 1800s, and the most recent work on fossils in Connecticut had been done in 1911. He spent extensive time tapping black and red shale open to find almost perfectly preserved specimens in the sediment.

McDonald’s fossil collection includes dinosaur footprints and teeth, fish, plants, invertebrates, rock samples and even coprolites — the preserved droppings of ancient creatures.

“There are so many interesting specimens in this collection,” said Daniel Ksepka, Bruce Museum curator of science. “Everything from the skull of a giant coelacanth fish to ancient logs infused with copper.

“This donation will transform the Bruce Museum fossil collection, making it an important resource for researchers studying the prehistory of our region,” he said. “One of the exciting things about the collection is that some of the fossils are still hidden beneath a thin layer of rock. We’re going to get to work preparing these fish right away — we may even find new species lurking in some of these blocks.”

McDonald is the author of two books and has donated numerous specimens to other museums already — the American Museum of Natural History in New York, the Museum of the Earth in Ithaca, N.Y., Yale’s Peabody Museum and Connecticut’s Dinosaur State Park.

But this donation is different, he said.

“The quality of the collection going to the Bruce is exceptional,” said McDonald. “The fossils are an archive of immense scientific value, and many are unstudied.”

McDonald will be recognized for his donation at the reception for the Bruce Museum’s upcoming “Wild Bees” exhibition from 3:30 to 5 p.m. April 13. Exhibition supporters and friends will get to see many of the specimens up close and the fossil expert will on hand to sign copies of his recent book, “Window into the Jurassic World.”

“I hope that this will be a legacy passed on from this 68-year-old to everybody else,” he said. “It was a little difficult to part with them, but I’m looking toward the future and realizing that my time with them is getting shorter and shorter, and you know, passing the torch. But to new generations with new ideas and greater energy and so on. And they’re still available to me even tough they’re not in my basement anymore.”; T: @jturianoGT; IG@greenwichgreen