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Fossil of a recently discovered reptile in P.E.I.

A pair of Canadian fossil discoveries is offering two very different but intriguing snapshots this week of animal evolution.

The first is a sea scorpion, one of several that have turned up over the past 20 years in a 430-million-year-old rock formation around Ontario's Bruce Peninsula. A study published on Wednesday in the journal Biology Letters reveals that the outside segments of the scorpions' walking limbs could have served as feet, allowing the marine creatures to walk while supporting their own weight.

The authors speculate that the well-preserved specimens – the oldest scorpions ever found in North America – are exoskeletons, left by creatures that ventured briefly into the terrestrial realm while moulting in order to be less vulnerable to aquatic predators.

At a time when all animals were still restricted to the sea, it's not exactly migrating onto land, says Dave Rudkin, an invertebrate paleontologist at the Royal Ontario Museum, but "it's a step in that direction."

One thousand kilometres to the east and about 130 million years later, a small lizard-like creature was making a living, probably by eating insects, in what is now Prince Edward Island. Spotted fifteen years ago in rocks eroding from the island's western shore, the creature has turned out to be the oldest known example of a parareptile, a branch of reptiles that emerged long before dinosaurs and which some researchers argue could be distant ancestors to turtles.

Described this week in the Proceedings of the Royal Society B, the find has researchers pondering what else may lie hidden in the Island's iconic red stone, much of which has yet to be systematically explored for fossils.

"Hopefully this isn't a one-off," says Sean Modesto, an associate professor at Cape Breton University, who was part of the team that worked on the find. "Maybe there's an incredibly rich locality to look into there."