A plate-backed reptile and a flying giant with the wingspan of a small aircraft: this souvenir Mayotte set of 2019 pairs Stegosaurus with Quetzalcoatlus.

It contains two «Un franc» tokens from the «Dinosaurs» series sharing one obverse — a coat of arms and «MAYOTTE»; the reverses read «Stegosaurus 2019» and «Quetzalcoatlus 2019». Numista lists them as fantasy coins: Mayotte is a French department using the euro, and these «francs» have no state issuer.

Othniel Marsh named Stegosaurus in 1877 — the «roof lizard» — believing its plates lay flat on the back like roof tiles. In fact its 17 to 22 plates stood in a staggered double row, and the brain of this animal of more than four tonnes was no bigger than a dog’s. Palaeontologists jokingly call its tail spikes a «thagomizer», a word borrowed from Gary Larson’s cartoons.

Despite the series title, Quetzalcoatlus was not a dinosaur but a pterosaur, a flying reptile of 67 to 66 million years ago. Student Douglas Lawson found the first bones in Texas’s Big Bend National Park in 1971 and in 1975 named it after the Aztec god Quetzalcoatl, with the species honouring aircraft designer Jack Northrop. Its wingspan is estimated at 10 to 11 metres, one of the largest flying animals ever.

Uncirculated: neither token has been in circulation. A pair for a themed collection that puts Mesozoic life on land and in the sky side by side.

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