"I can't smell anything," the youngster tells a demure little girl on his left. "Here - you try," he says, shoving the hard brown lump under her nose.
"Geroff," she says, making a face and pulling away.
She needn't have worried. After 100 million years, all scent of fresh saurian has evaporated. But the coprolite being passed round Sacred Heart Primary in Greenock would certainly smell if it could. It's the real thing.
Anne O' Brien once used replica fossils in her nature workshops, she says, since they are cheap and easy to find. But it wasn't good enough for the children. "They'd be fascinated, then they'd ask if they were real and I'd have to say `No'. Now I use genuine fossils whenever I can."
Attention to authenticity is a feature of all the Closer2Nature workshops, developed and delivered to schools as a joint venture of the Scottish Seabird Centre and Our Dynamic Earth, with Pounds 30,000 funding from the Scottish Government. "This is the second time we've had Anne here this year," says Sally Peel, acting head. "She's great with the kids. We also like the fact that the price - pound;85 a day - means we can get all our children, from the infants up, involved."
Pitching the delivery at the right level for every age group is straightforward, says Ms O'Brien, a primary teacher seconded to the Closer2Nature project. "This job has everything I'm interested in. I have an ecology degree and taught science in middle school. "
Mums and babies are an important part of the story of this workshop, whose theme is the dwindling puffin population on Craigleith, a small island in the Firth of Forth. Almost 30,000 pairs lived on Craigleith less than 10 years ago, but their numbers have dropped and only a few thousand now nest there. Hence the whodunnit.
Before getting to the heart of the mystery, the youngsters learn a thing or two about puffins in an enjoyably interactive way. "Stand up and stick out your elbows," Anne demonstrates.
"Puffins have little, stubby wings. They look like flying footballs and have to work very hard. Flap your wings as fast as you can." She demonstrates and the kids comply with enthusiasm. "Faster, faster," she tells them.
When no one leaves the ground, Anne explains why. "Your wings weren't moving as fast as a puffin's. Theirs flap 400 times a minute."
The children get the chance to be angry puffins - legs apart, mouth open, foot stamping; and "don't-mean-to-bother-you puffins" - eyes downcast and sidling along. They imitate the call of the puffin, which sounds like "a laughing cow". They catch sand-eels in beaks and gather feathers to make nests, in which they deposit a single, small white egg. Six weeks later, there's a knocking noise and a puffling pops out.
Things go well with attentive parents feeding the puffling constantly, Anne explains. "Then one morning he wakes up and he's on his own. He waits all day and night but nobody comes to feed him."
Anne and the children act out the hungry bird's first dramatic dive into the sea in search of food. Ten minutes later, with the children seated in a circle, Melissa (P3) is still concerned about a young puffin making its way in the world alone. "What happens to it when it's just a wee kid and it's scared in the water?"
"It doesn't go into the water until it's six to seven weeks old," Anne replies. "It's much bigger by then and has waterproof feathers. Puff-lings are looked after until they are big enough to go into the sea by themselves."
Craigleith Whodunnit is a multimedia show, with sounds and images of wildlife from a computer, lifelike models of puffins, seals, gannets and robins from Anne's hands, and even a chimp called Oxo from a charity shop. There's a large board-game laid out on the floor, which the class plays in teams, answering questions and acting out what they've learnt to collect tasty sand-eels.
"I liked that bit best because our team nearly won," says Sean (P2).
There are fossils in a box ready for a later show, which Anne passes around at the request of the children. "I liked the fossils," says Ryan (P2). "They were a million times older than our teachers."
But the most effective resource, as with all good teachers, is Anne. Thoroughly prepared, highly knowledgeable and colourfully clad with dangly ear-rings, she effortlessly commands the kids' attention.
So what is the solution to the Craigleith mystery? Why are its puffins struggling? There are several reasons and the children remember most of them.
"All the sand-eels are going away," says Adam (P3). "And if the puffins can't eat, they die."
Climate change and warming seas are adversely affecting the plankton on which sand-eels feed, and overfishing is further reducing their numbers, the youngsters have learnt. It's a problem for many seabird species, for which sand-eels are a staple when young.
But Craigleith puffins have a particular problem - a huge, invasive plant called a tree mallow, which has been stealing their nesting space. But there is good news. Volunteers organised by the Seabird Centre are currently helping to cut down the plant, and the puffins are slowly coming back to Craigleith.
As the young audience troops out and an even younger one gets seated for the next session, headteacher Sally Peel explains why this is Sacred Heart's second all-day Closer2Nature visit. "Our kids love them and, because the teachers sit in on the sessions, it helps raise their confidence with science," she says. "You need to be looking for good value resources in schools all the time."
Other Closer2Nature workshop themes include climate change, landscape formation and biodiversity with interactive voting for P5-S2. There are also storytelling sessions for the nursery. Anne O'Brien T: 0131 523 1233. E: firstname.lastname@example.org