Age of the Dinosaurs

Dinosaurs had bones in their eyes. You don’t, and nor does any other mammal, from dogs to whales to elephants. We’re the odd ones out. Birds, lizards, turtles and fish all have a ring of thin bony plates sitting in the white of the eye, holding a big eyeball steady so it can focus. Because it’s bone, it sometimes fossilises, and that matters, because the age of the dinosaurs lasted around 160 million years and roughly half of it happened in the dark. This week’s word is sclerotic ring. Sclerotic comes from a Greek word meaning hard, and the ring is usually made of 10 to 15 overlapping plates, arranged like the stones in an archway. Measure the hole in the middle, like the hole in a Polo mint, and compare it with living animals. A big hole lets in lots of light, which suits an animal that was up at night. A small hole means a daytime animal. It works just like a camera. Lauren and Cassius Morrison hear from Dr Stephan Lautenschlager, a palaeontologist at the University of Birmingham who uses computer models to work out how dinosaurs looked, lived and behaved. Bigger eyes mean bigger lenses and room for more light-sensing cells, so bigger eyes see better. The middle of a Jurassic night was probably busy, with some dinosaurs out in the day, some at night and some at dawn and dusk, which may have been ideal hunting conditions for meat-eaters. He explains why owls hear so well (one ear sits higher than the other), what the optic lobes in a dinosaur’s brain tell us, and admits that nobody knows how dinosaurs slept or what colour their eyes were. Fresh from the Dig names the owl dinosaur: Shuvuuia, a chicken-sized dinosaur from the Mongolian desert with huge eyes and an inner ear to match a barn owl’s. Then a study that compared the eye rings of dozens of fossil animals with living ones: small meat-eaters were mostly out at night, big plant-eaters snacked around the clock, and big predators came out at dawn and dusk. And birds can see ultraviolet light that humans can’t, so dinosaurs may have been far more patterned than any picture shows. In the Dino-Mite Question, Noor, nine, from Birmingham, asks whether dinosaurs slept standing up or lying down. The best clue is Mei long, the “sleeping dragon”, a duck-sized fossil from China found curled up with its head tucked in, just like a bird. Then it’s Build a Dino Lab. Week nine is the eyes: small, cheap daytime eyes, or big eyes, a wide sclerotic ring and big optic lobes for working in the dark. Big eyes win, with a twist. Our dinosaur’s reflective skin, chosen back in episode five, would shine like a headlight under the moon and stand out at midday, so it hunts at dawn and dusk, when the night animals are going to bed, the day animals are only just getting up, and everyone is half asleep. Lions and foxes do the same. Next week, arms.See omnystudio.com/listener for privacy information.

Loads of dinosaurs had wings, but not many of them could fly. There’s a dinosaur in your garden right now, probably the one that keeps stealing your chips, because a seagull is a dinosaur, and so is every robin, pigeon and chicken. Feathers turn up again and again across the dinosaur family tree, and most of them had nothing to do with flying. Oviraptors spread their feathered arms over their nests to keep their eggs warm, and some parents have been found still sitting on them. Others used feathers for showing off and for keeping warm in the cool forests of north-east China. This week’s word is primaries. Hold your arm out: shoulder, elbow, wrist, hand. The primaries are the big, long, stiff feathers that grow from the hand, and they do the hard work of flying. Every bird that flies, from a hummingbird to an albatross, has between nine and eleven of them. So if you find a fossil wing, you can count. Lauren and Cassius Morrison hear from Dr Jingmai O’Connor, Associate Curator of Fossil Reptiles at the Field Museum in Chicago. She explains why Microraptor, with feathers on its arms and its legs, probably glided down from the trees like a flying squirrel, and why Anchiornis, with a skeleton almost exactly like Archaeopteryx, has 30 primaries and probably couldn’t fly at all. She also owns up to getting something wrong. She once wrote that Microraptor couldn’t cough up pellets, then looked again at a Microraptor with a whole lizard in its stomach. A skeleton that size can’t go all the way through, so it had to come back up, and she is now writing a paper to say so. As she puts it, saying “I don’t know” is the most powerful thing a scientist can say. Fresh from the Dig starts with Jingmai’s own brand new dinosaur, Jian changmaensis, a barn-owl-sized, four-winged cousin of Microraptor from about 120 million years ago in the Changma Basin in north-west China. It might finally explain the little bundles of smashed-up early bird bones found there for years. Then Yi qi, whose name means strange wing, a tiny dinosaur with bat-like skin wings that looked a lot like a mini dragon. And how scientists worked out the real colours of a dinosaur: Anchiornis was grey and black with white stripes on its wings and a rusty red crest, a bit like a woodpecker. In the Dino-Mite Question, Jonah, eight, from Glasgow, asks whether a chicken nugget is a dinosaur nugget. It is. And the wishbone in your roast chicken is the same bone you’d find in T. rex. Then it’s Build a Dino Lab. Week seven is the arms: four wings like Microraptor, or feathered arms only with bare scaly legs underneath. Lauren picks feathered arms with seven primaries and no leg wings. Seven is two short of what you need to fly, and that’s fine, because this dinosaur was built to run, big feathers on its legs would trip it up, and it’s already carrying a heavy tail, plates and a thagomizer. Jingmai would have chosen the same. Next week, our dinosaur gets a nose.See omnystudio.com/listener for privacy information.

The dinosaurs had around 160 million years on Earth, so there was never just one dinosaur climate. There were deserts, volcanoes and jungles, and there were forests at the North and South Poles, because for most of that time there was no permanent ice anywhere on the planet. Britain was subtropical to tropical. If you were packing for a trip, you would want a raincoat and an autumn jumper, not a snowsuit. This week’s word is super greenhouse. A greenhouse lets the sun’s heat in through the glass and makes it hard for it to get back out, and carbon dioxide in the air does the same thing to the whole planet. In the super greenhouse of the Cretaceous there was far more of it, sea levels were so high that a seaway split North America down the middle, and temperatures in some places may have reached 40 to 45 degrees. That is hotter than a hot bath. Fresh from the Dig is all about where dinosaurs lived. The dinosaur highway in Oxfordshire, a 150-metre run of tracks made by long-necked sauropods and the meat-eaters following them, was laid down in a warm, muddy lagoon, exactly the kind of ground that holds on to a footprint. The Carnian Pluvial Episode, roughly two million years of rain in the Triassic, spread forests across the hot, dry supercontinent of Pangaea, and it is one of the leading ideas for why dinosaurs took over. And in northern Alaska, inside the Arctic Circle, palaeontologists have found baby dinosaurs far too young to have migrated, which means dinosaurs lived there all year round, through months of darkness and months of midnight sun. Lauren and Cassius Morrison are joined by Professor Kirsty Edgar, a micropalaeontologist at the University of Birmingham, whose fossils are smaller than a grain of sand. She studies foraminifera, tiny plankton that build shells in the surface ocean and have been doing it for hundreds of millions of years. The oxygen in those shells comes in a lighter and a heavier form, and the mix a shell takes up depends on how warm the water is, so each one is a thermometer that never knew it was a thermometer. When they die the shells sink and pile up on the seabed in layers, oldest at the bottom. Kirsty has spent two-month research voyages drilling that seabed, from Tahiti to Hawaii and from Tasmania round to Perth, one of which set off straight into the tail end of a Southern Ocean storm. Otis, who is six and from Cardiff, wants to know whether he could have gone swimming in a 45-degree sea. Sadly not: a warm swimming pool is about 30 degrees, a hot bath is about 40, and anything else in the water would have been bigger than him and a better swimmer. Then it is Build a Dino Lab, where one real fact becomes one real piece of the perfect dinosaur. Week five is skin, and Kirsty’s advice is to make it pale, for the same reason a white T-shirt keeps you cooler than a black one. Lauren picks skin that reflects the sun, even though it makes the dinosaur easier to spot, because with a thagomizer and steak-knife teeth it can look after itself, and nobody wants a dinosaur that cooks. Next week, a tail. Probably.See omnystudio.com/listener for privacy information.

Nigersaurus grew around 500 teeth and replaced the whole lot roughly every two weeks. It never brushed them, never had to be careful with them and never once saw a dentist, because there was always another tooth coming up behind. The word for that is polyphyodont, and it is this week’s word. Humans get two goes. Milk teeth, then the set we are stuck with. Sharks, crocodiles and most dinosaurs are on a conveyor belt instead, and that changes what a tooth can be. If breaking one costs you nothing, your teeth are free to evolve into exactly the right shape for the job rather than something built to survive a fight, which is how theropods ended up with thin serrated blades in their mouths. Lauren and Cassius Morrison go to the Oxford University Museum of Natural History to meet Dr Emma Nicholls, who looks after 40,000 fossil animals, anything with a backbone. She explains that sharks have no bones at all, only cartilage, the same stuff as your ear, which is why nearly all we have of them is teeth. One tooth is enough to work out a great deal. Tall, thin and triangular means a fast pursuit predator shaped like a great white. Flat and crushing means something on the seafloor eating sea urchins. She also spent three weeks digging up the Rutland Sea Dragon, a ten-metre ichthyosaur found in a drained reservoir in the middle of England, and points out that it looks almost identical to a shark despite being a reptile and not related to one at all. Fresh from the Dig has Nigersaurus, nicknamed the sauropod lawnmower, whose fortnightly new set makes sense once you know it fed off the ground and swallowed grit with every mouthful. Diplodocus, eating higher up, got about 35 days out of a set. Plus the Oxford museum’s rebuilt fossil gallery, where Megalosaurus, named in 1824 and the first dinosaur ever described, is joined by a young Eustreptospondylus going on public display for the first time, part real bone and part 3D print. And Cassius’s own research reading the scratches and pits on theropod teeth under a microscope, with something from the UK he is not allowed to tell us about yet. Moosa, who is seven and from Leicester, wants to know whether dinosaurs ever got toothache. Then it is Build a Dino Lab, where one real fact becomes one real piece of the perfect dinosaur. Week three is slicers or crushers, and Lauren goes for tall, thin, curved, serrated theropod teeth, because a fast two-legged dinosaur chasing shellfish would be a waste of a good pair of legs. Next week, something bigger, and a word invented by a cartoonist.See omnystudio.com/listener for privacy information.

Dinosaurs ruled for 160 million years, and the thing that made them a runaway success was where their legs went. Not out to the side like a crocodile, but straight down underneath them, a stance that costs less energy and frees the arms up for other work. So how fast could they actually go? Footprints in Inner Mongolia, laid down 120 million years ago, put a medium-sized meat eater at around 45 kilometres an hour, quicker than Usain Bolt at his peak, and trackways in La Rioja in Spain clock theropods at almost exactly the same speed. A quarry in Oxfordshire turned up a dinosaur highway of nearly 200 footprints running over 150 metres, made by long-necked sauropods and by Megalosaurus, the first dinosaur ever named, back in 1824. Brazil has gone one better with Farlowichnus, a dinosaur named from nothing but its footprints, no bigger than a long-legged bird. And Tyrannosaurus rex, the one everybody assumes was quickest, was nothing of the sort. Lauren and Cassius Morrison are joined by Professor John Hutchinson of the Royal Veterinary College, who rebuilds dinosaurs inside a computer, gives them muscles and physics, and makes them run. He worked out that a seven-tonne T. rex would have needed around three tonnes of leg muscle to sprint, more than half its body, and the force would have snapped its legs, so it managed something closer to a brisk 15 miles an hour. He also refuses to say the legs are the most important part of a dinosaur. He says it is the pelvis, because the hips tell you what the animal actually did. Then it is time for Build a Dino Lab, where one real fact becomes one real piece of the perfect dinosaur. For week one the choice is two legs or four, and Lauren goes bipedal, because speed is useful whether you are running away from something or running towards fresh fruit. Next week, necks.See omnystudio.com/listener for privacy information.