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Two small creatures are at the heart of today鈥檚 questions, sent in to curiouscases@bbc.co.uk.

The Tiniest Dinosaur
"What is the tiniest dinosaur?" asks young listener Ellie Cook, aged 11.

Our hunt takes us from the discovery of dinosaurs right up to the present day, which is being hailed as a 'golden age' for palaeontology. Currently, one new species of dinosaur is unearthed on average every single week. But what's the smallest dino? And what can size reveal about the life of extinct animals?
Hannah Fry goes underground at the Natural History Museum in London to look through their vaults in search of the tiniest dinosaur with palaeontologist Susie Maidment. Meanwhile Adam Rutherford chats to dinosaur expert Steve Brusatte from Edinburgh University about why size really does matter, especially when it comes to fossils.

The Baffled Bat
"Why don't thousands of bats in a cave get confused? How do they differentiate their own location echoes from those of other bats?" This puzzling problem was sent in by Tim Beard from Hamburg in Germany.
Since eco-location was first discovered, this question has perplexed biologists. Hannah turns bat detective to try and track down these elusive creatures at The Queen Elizabeth Olympic Park in East London. This is where zoologist Kate Jones from University College London is using a network of smart sensors to find, identify and track wild bats.
Bat researcher and impressionist John Ratcliffe from Toronto University explains how bats use sonar to find their way around, and the clever tricks they鈥檝e developed along the way. It's an unlikely tale involving gruesome early experiments, cunning electric fish and some surprising bat maths.

(Image: Dinosaurs and a meteor falling from the sky in back background. Credit: ugurhan/Getty Images)

Producer: Michelle Martin