Scientists have officially announced that the ancient, lizard-like reptile was a new species, which has been given the name Erpetonyx arsenaultorum, after Arsenault.
"Oh my God, it’s quite an honour, really," said Arsenault, now 28 and living in Ottawa.
It is the only reptile ever found from the five-million-year Gzhelian Age that started about 304 million years ago. As such, it helps fill a gap in the early evolutionary history of reptiles.
"That's quite possibly the most exciting part for us," Arsenault told CBC News in one of the first media interviews he has given.
Arsenault and his family kept quiet about the discovery for years, even as they faced criticism for wanting to sell the fossil instead of donating it to a museum. Arsenault said his family always felt it was his story alone to tell, and for many years he wasn't ready.
It began when he and his family were vacationing at the cottage of friends in Cape Egmont in western Prince Edward Island.
Inspired by Jurassic Park
It was just a couple of years after the the movie Jurassic Park was released, and nine-year-old Arsenault was obsessed with finding dinosaur fossils, even though none had ever been found in P.E.I.
Each day, he and his four-year-old friend Alex Lapp, whose family owned the cottage, would go down to the beach to hunt for fossils. One day, as his friend ran ahead, Arsenault slipped on some slime and fell on a sandstone slab at the edge of the water.
"In getting up, I could see the upper arch of the backbone sticking out of the rock," he recalled.
Convinced it was a dinosaur, he called Lapp, and the two boys ran excitedly back to the cottage to tell their skeptical parents.
At the boys' insistence, they went down to the beach and helped pry out a coffee-table-sized fossil-containing stone slab of with shovels and other yard tools. Then they used a hammer and chisel to cut it down to a "manageable" 30-kilogram chunk. The boys' mothers hauled the slab up a set up stairs to the cottage.
At the time, Arsenault said, much less of the fossil was exposed, so they used a plastic brittle brush to remove some of the sediments.
"I'm sure every person in the professional field is probably cringing when they hear that," he said with a laugh.
'It's not a dinosaur'
Despite their doubts that the fossil was the dinosaur, Arsenault's parents contacted the Museum of Natural History in Halifax and, a few weeks later, drove to Halifax to show it to curator Bob Grantham.
"The moment that he saw the rock it was in, his eyes lit up," Arsenault recalled. "He said to us, "It's not a dinosaur.' And so my heart sank right away.
"And then he said, 'It's older than a dinosaur.'"
Based on the grade of the sandstone, Grantham said it was likely 250 million to 300 million years old. It was also probably a new species because so few specimens had been found from that time period.
He added that the museum couldn't pay much for the fossil and wouldn't be offended if the family declined its offer. But he begged the family never to sell the fossil to a private collector.
Show and tell
After paleontologists warned the family to protect the fossil from the atmosphere and from human contact, they built a wooden box for it with Plexiglas on top, said Arsenault. He stored it in his bedroom, at times in the closet and at others under his bed. He even took it to school for show and tell.
The family declined early cash offers to buy the fossil, from the Royal Ontario Museum and the Museum of Natural History.
Arsenault said that led to some public criticism of him and his family. Some people thought they should donate the fossil to a museum instead of selling it.
But he said he was a child when he found it, and judged the fossil as a priceless treasure that had a lot of sentimental value to him.
"People don't just necessarily give it away."
He also wanted to be able to negotiate to get two replicas and to have the fossil named after him.
Finally, a family friend named Bette Sheen negotiated with the Royal Ontario Museum on his behalf and the fossil was sold into the museum's collection in 2004.
While Arsenault wanted the money from the sale to go toward his education, he said it didn't come close to covering the cost of his education in engineering, and later, training to become an elevator technician.
"It did assist me with my first year of university, but that's as far as it went."
However, it was important to him to sell the fossil to an institution that could store it properly and study it, he said.
"In the end, I certainly believe we did the right thing."
While he thinks the fossil was worth far more than he was paid, he says it named after him was a priceless honour in itself.
"I'll always have this," he said. "It's something I can present to my future children and grandchildren and say, 'This is such a big part of history that it's named after our family.'"