Dinosaur size comparison to humans: 172 life-size animals

What you are walking through

How big were dinosaurs beside a person? This dinosaur size comparison puts 172 prehistoric animals at real size beside a visitor at an eye height of 1.6 m. Most people first meet dinosaurs as skeletons in a museum hall, standing on a plinth and lit from below. It is hard to judge their size that way. A plinth adds a metre, the hall is huge, and you look up at the bones from a few steps away. This exhibit puts 172 prehistoric animals on open ground at their real size and lets you walk up to them at an ordinary eye height of 1.6 m.

The park is about 600 m across, roughly the size of 80 football pitches. It is laid out by age. The ground gets younger as you go east: a small Permian corner, then the Triassic, two Jurassic areas, and four Cretaceous areas split by continent. Along the south edge runs a beach and a sea, split by age in the same way, and pterosaurs fly over the areas where they lived. Fences with gates separate the ages, and a sign at each gate gives the dates.

Of the 172 animals, 137 are dinosaurs and 35 are not: pterosaurs, sea reptiles, crocodile relatives, Dimetrodon and other relatives of mammals, and a few early mammals. Most plant-eaters live in herds of two to five, and the park holds about 350 animals in all. Faceless figures 1.7 m tall stand beside the animals the guide visits, so you always have a person to compare with.

Every body is built in code from a list of measurements. There are no scanned or downloaded models. Lengths and masses come mostly from the Natural History Museum in London, and the article explains where the other numbers come from and where scientists still disagree.

How big they really were

Here is every animal in the park, oldest first. Length runs from the nose to the tip of the tail; for pterosaurs the figure is the wingspan. A range means the sources disagree or the fossils are too incomplete to give one number. Where the sources give no mass, the table says so rather than inventing one.

A few of these numbers need a word of explanation. The Stegosaurus model follows Sophie, the most complete Stegosaurus skeleton, a young adult 5.6 m long whose mass the museum worked out in 2015. Larger Stegosaurus specimens reached about 9 m. The T. rex hip height of 4.0 m follows the Field Museum in Chicago, which gives SUE, the largest T. rex skeleton found, as 13 feet tall at the hip.

Checking the sizes against a person

The person figures make the numbers easier to feel. A 1.7 m person standing next to the T. rex reaches a little above its knee. The hips are at 4.0 m, which is 4.0 / 1.7 = 2.4 people.

Brachiosaurus changes the scale of the whole Jurassic area. Its back slopes up from the hips to the shoulders because the front legs are longer than the back legs, and the neck rises from there. The model's head is 12.6 m above the ground, which is 12.6 / 1.7 = 7.4 people standing on each other's heads, or the roof of a four-storey building.

Mass grows faster than length. If you scale a body up while keeping its shape, mass goes up with the cube of the length. Try it with the T. rex and the Velociraptor. Velociraptor is 1.8 / 12 = 0.15 times as long, so a T. rex shrunk to that length would weigh 7,000 × 0.15³ = 7,000 × 0.003375 ≈ 24 kg. The museum gives Velociraptor 7 kg, about a third of that, because it was a slim animal with a long thin tail, while T. rex had a deep chest and a heavy head.

Diplodocus and Brachiosaurus show the same thing from the other side. Diplodocus is longer, 26 m against 22 m, but the museum puts it at 15 tonnes against almost 47. Most of a Diplodocus is neck and a long, thin tail. The field guide draws each animal beside a 1.7 m person and a 12 m bus, all at one scale, so you can compare any two.

Why the park is split by time

The fences are not there to keep the animals from fighting. They separate animals that never lived at the same time.

The dinosaur age lasted about 165 million years, from roughly 230 to 66 million years ago. That is so long that the first and last dinosaurs are further apart in time than the last dinosaurs are from us. Stegosaurus and T. rex lived at least 145 − 68 = 77 million years apart. Using the middle of each range, the gap is close to 80 million years, more than the 66 million years since the asteroid impact that ended the age of dinosaurs. The board on the road at the edge of the Jurassic area draws all of this on one line.

The Cretaceous alone lasted about 79 million years, so even that area is split. Spinosaurus, Giganotosaurus and Argentinosaurus lived in South America and Africa roughly 100 to 90 million years ago and never met T. rex. The Gobi area holds the animals of Mongolia from about 85 to 70 million years ago. The North American area holds the last dinosaurs, including T. rex and Triceratops, which lived side by side until 66 million years ago. Even within one area the dates do not all overlap, so read the dates on each name tag.

Not every animal here is a dinosaur

Dinosaurs are one group of reptiles with a particular build: legs held straight under the body, and a hip socket that is open in the middle. Many animals that people call dinosaurs are something else.

Pterosaurs, such as Pteranodon and Quetzalcoatlus, were flying reptiles. They were close cousins of dinosaurs, sharing an ancestor in the Triassic, but they are a separate branch. Their wings were skin stretched from one hugely long finger to the body and legs. The sea reptiles, plesiosaurs, ichthyosaurs and mosasaurs, are not dinosaurs either. Mosasaurus was a giant lizard, related to today's monitor lizards and snakes. Deinosuchus belongs to the crocodile line.

Dimetrodon is the most surprising. It is not a reptile in the everyday sense at all. It belongs to the synapsids, the group that includes mammals, and it died out about 40 million years before the first dinosaurs appeared. It sits in its own Permian corner for that reason. In the field guide and on the name tags, every animal that is not a dinosaur says so.

Birds, on the other hand, are dinosaurs. Archaeopteryx, in the Late Jurassic area, is a small feathered dinosaur with wings, teeth and a bony tail, one of the earliest birds or bird relatives known.

Why size estimates disagree

Many of the ranges in the table are wide, and the reason is usually the fossils themselves.

Argentinosaurus is known from a few back bones, part of the hip and a piece of a leg bone. Its length of 30 to 35 m and mass of about 70 tonnes come from scaling up its relatives. Mosasaurus is mostly known from skulls, so its length is worked out from the length of the jaw, and estimates run from about 11 m to 18 m. Ichthyotitan is known from two pieces of jawbone, and the 25 m estimate depends on which relative is used to scale it.

Mass is harder than length. Scientists either scale from the thickness of leg bones, which carried the weight, or build a model of the body and work out its volume. The two methods can disagree by half. Even well-known animals like Brachiosaurus have published masses ranging from under 30 to over 50 tonnes. The park uses one source per animal where it can, and shows a range where the sources it uses disagree.

Feathers and skin

Feathers have been found with fossils of many small meat-eating dinosaurs. In the park, the animals with feathers fall into two groups, and the field guide says which is which.

The first group has direct evidence. Archaeopteryx and Microraptor are preserved with feathers in fine-grained rock, and fossil pigment shows that Microraptor's feathers were black with a glossy sheen. Velociraptor has quill knobs on a forearm bone, where long wing feathers attach in birds.

The second group has feathers because their close relatives do. No feathers have been found with Deinonychus, Utahraptor, Oviraptor, Gallimimus or Therizinosaurus, but feathers are known in close relatives of each, so the models give them feathers too.

T. rex is covered in scales. In 2017 a team led by Phil Bell described small patches of fossil skin from T. rex and its close relatives from the neck, hips and tail, and all of them show small scales. Carnotaurus is also known from skin impressions with rows of scales. Edmontosaurus mummies keep large areas of scaly skin. The large plant-eaters in the park are all scaly.

Plants of each age

The plants change from area to area because plants changed too. There are no flowering plants in the Triassic or Jurassic areas. Flowering plants first appear clearly in the Cretaceous fossil record, and early ones were small and rare; a few disputed fossils may push them back into the Jurassic. So the Jurassic forest is conifers, monkey-puzzle-like Araucaria trees, ginkgos, cycads, tree ferns and horsetails, with a thick layer of ferns on the ground.

The Early Cretaceous area looks much the same, with a few small flowering shrubs. In the North American area at the end of the Cretaceous, flowering trees and shrubs are common, along with palms and conifers. Grass is almost absent everywhere. The oldest grass fossils known are from the very end of the Cretaceous in India, found in fossil dung of plant-eating dinosaurs, so grass existed but was not the lawn it is today.

How the model walks

Each walking animal is built from a row of oval cross-sections along the body, from the tail tip to the neck, plus a head, legs and arms. The cross-sections are joined into one smooth skin bent by a chain of bones. The legs are separate jointed chains, with the joint angles worked out every frame so that each foot lands on the ground and stays planted while the body moves over it.

Two-legged animals swing their legs half a stride apart. Four-legged ones move their legs one after another: a hind leg, the front leg on the same side, the other hind leg, then the other front leg, the pattern elephants use at a walk. The speeds are relaxed, from about 0.7 to 1.6 m/s depending on leg length. They are walking speeds for the display, not top speeds.

Animals stop to look around, turn their heads towards you when you come close, and stop if you stand in the way. Plant-eaters whose path crosses the river or the beach stop there to drink. Herds follow a leader along a loop, each on a slightly wider or narrower path. There are no sounds: nobody knows what these animals sounded like, and the park does not guess.

How a park this big stays fast

A model this large would be slow if every animal were drawn in full. Only the few animals closest to you are full jointed models. Animals further away are drawn as one simple statue per species, all copies of a species in a single drawing call, and the ones at the edge of view are flat cut-outs painted from the same outline. Plants are grouped in 100 m squares and only built when you first come near, and small plants such as ferns are only drawn close to you. On slow devices the park pulls in the horizon and turns off shadows after a few slow seconds.

How the model differs from the real animals

The animals are simplified. The 61 walking animals share a handful of body templates (big two-legged hunters, small feathered ones, long-necked sauropods, plated, horned, armoured, duck-billed and dome-headed dinosaurs, a crocodile and a sail-backed synapsid) stretched to each species' length and proportions and given its crests, horns, plates or sails. The proportions match skeletal reconstructions in outline, not bone by bone. The colours are guesses, since colour is known for only a handful of small feathered dinosaurs. The animals never run, eat, fight or lie down.

Moving around the park

On a computer, walk with WASD or the arrow keys, turn with Q and E, and drag with the mouse to look around. Walking is 3 m/s; hold Shift to run at 8 m/s. Clicking the ground makes you walk to that spot. On a phone, push the joystick at the bottom left, all the way to run, and drag on the right half to look around.

The travel buttons, or keys 1 to 4, change how you move: walking, running, a park jeep at 15 m/s with your eyes 2.4 m up, and flying at 25 m/s about 45 m above the ground, where nothing blocks you. Crossing the whole park takes about three minutes on foot, 75 seconds running, and under half a minute flying.

The map in the top left shows every animal as a dot and you as a red arrow. Click anywhere on it to go there; the corner button makes it bigger, and M does the same. The field guide (button or G) lists all 172 animals with a search box, filters by age, food, size and kind, and sorting. Choosing an animal opens a card with its dates, where it was found, its size beside a person and a bus, and the sources, and "Go there" takes you to it. Animals you have seen close up get a tick.

Version 4: 172 animals from every continent

The park now holds 172 kinds of prehistoric animal: 137 dinosaurs and 35 that are not. Among the 35 are 11 pterosaurs, 12 sea reptiles (ichthyosaurs, plesiosaurs and mosasaurs), and 12 synapsids and crocodile relatives, from the tusked Placerias to Repenomamus, a mammal that ate young dinosaurs. The fossils come from 28 countries, including Australia, India, Madagascar, Niger and South Korea.

For the 82 new dinosaurs, length, age, place and food are copied from the Natural History Museum's Dino Directory page for each animal, and the weight is shown only when that page gives one. For the 24 new animals that are not dinosaurs, and for the two Korean dinosaurs, the ages are the range of rock stages listed in the Paleobiology Database, a research database run by universities. When none of the cited pages gives a length, the field guide says "no figure in these sources" and shows the length the model was built at, marked as a model value. Colour is a guess for every animal except the few where fossil pigment has been studied.

The new animals also bring new head shapes to the models. Lambeosaurus has a hatchet-shaped crest, Saurolophus a solid spike, Tsintaosaurus a crest pointing forward, Guanlong a thin blade along its snout and Citipati a tall casque. Sauropods now carry their necks at different angles: Giraffatitan high, Dicraeosaurus low. These are model choices that follow published skeletons in outline; the angle a living sauropod held its neck is still argued over.

Korea's dinosaur coast

The south coast of South Korea is one of the richest places in the world for dinosaur footprints and eggs. In 2002 Korea put five sites on its list for World Heritage: Haenam, Boseong, Yeosu, Hwasun and Goseong. Goseong alone has more than 4,000 dinosaur footprints in about 420 trackways, in layers about 120 million years old. Hwasun has meat-eater trackways up to 52 m long, and on the Yeosu islands one trackway runs for 84 m.

The footprint bed in the Early Cretaceous area is modelled on these sites. Four kinds of trail cross it. Big round prints in pairs were left by a sauropod: the small front foot lands just ahead of the large back foot. Three blunt toes, in three trails walking side by side, belong to ornithopods moving as a group. A single narrow trail with long steps and sharp, slim toes was made by a theropod. Small three-toed marks near the edge are bird tracks, which Korea's coast is known for.

Boseong is famous for eggs. Clutches of round eggs lie in red rock, and some nests are about 1.5 m across. The egg site in the East Asia area is a model of that kind of find. Bones are much rarer in Korea than footprints and eggs. Two dinosaurs in the guide are named after Korean places: Koreaceratops, a small horned dinosaur from Hwaseong described in 2011, and Koreanosaurus, a small plant-eater found near the Boseong egg site.

Nests, eggs and parents

Maiasaura means "good mother lizard". In Montana, its nests were found close together, bowls of mud with eggs and young inside, and the young in the nests had worn teeth. They had been eating for some time while still in the nest, which suggests that the adults brought them food. The nesting ground in the North America area shows seven nests with clutches of eggs beside a Maiasaura herd.

Other finds point the same way. Citipati skeletons have been found sitting on nests with their arms spread over the eggs, the way birds brood. Hypacrosaurus nests have embryos inside the eggs, and Massospondylus eggs from South Africa hold some of the oldest dinosaur embryos known. Not every dinosaur looked after its young, but some clearly did.

Reading the rocks at the fossil dig

At the fossil dig in the Late Jurassic area, a cut through the ground shows the layers that hold dinosaur fossils. From the bottom up the model shows red Triassic sandstone, grey-green Jurassic mudstone, yellow Cretaceous sandstone, a thin dark clay and then later soil. Lower layers were laid down first, so they are older. That simple rule is how a fossil hunter knows which age a bone comes from before any laboratory dates it.

In front of the cut a skeleton lies half out of the ground inside a string grid. Diggers use the grid to record where each bone lay before it is lifted, because the position of the bones tells how the animal died and was buried. No real quarry shows all these layers in one wall; the model puts them together so you can see the order.

The last day of the Cretaceous

About 66 million years ago an asteroid between 10 and 15 km wide hit the Earth near what is now the Yucatán Peninsula in Mexico. The thin dark clay at the top of the dig stands for the layer laid down worldwide after the impact; in many places it is rich in iridium, a metal that is rare in the Earth's crust and more common in asteroids. In the North America area and over the Cretaceous sea the sky shows the asteroid just before it struck. About three quarters of all animals died out after the impact, including every dinosaur except the birds.

Challenges

The challenge panel (button or T) has fourteen questions answered from the park and the guide. The first eight ask for the biggest meat-eater, three dinosaurs with feathers in their fossils, an animal that did not live in the Jurassic, the owner of a set of footprints, dinosaurs shorter than a person is tall, who lived closer in time to T. rex, a dinosaur found in Korea, and an animal that is not a dinosaur. Six more come from the hidden finds and the moving animals: find five finds, feel the ground shake beside a walking T. rex, name the owner of a fossil dropping, pick the two Korean egg sites, name the dinosaur found with 34 young, and pick the meat-eater with a tail built for swimming. The first two check themselves as you walk. The answers are worked out from the same data as the field guide, so if a number changes, the answer changes with it. Solved challenges get a star in the panel and on the matching animals in the guide, and they are remembered on your device. The panel also lists the five scenes in the park, with a button to go to each.

Hidden finds around the park

Twenty-one small fossil sites are hidden around the park, away from the roads and the animals' paths. They have no marker on the map. Walk up to one and a card opens with what it is, a link to the animal in the field guide and the source; the find gets a red star on the map and a star in the challenge panel, where the ones still missing are listed with the area they are in. Each find is modelled on a real discovery:

• In the Triassic area: logs of petrified wood like those of Arizona's Petrified Forest, buried in a river more than 200 million years ago, and on the Triassic beach a slab with an ichthyosaur embryo in birth position, after a Chaohusaurus fossil from China about 248 million years old.
• In the Late Jurassic area: a sloping rock face with bones in it, after the wall of about 1,500 bones at Dinosaur National Monument; a slab of Solnhofen limestone like the one that held the first Archaeopteryx in 1861; a heap of polished stomach stones beside a sauropod's ribs; and at the fossil dig, a flag on the thin dark clay that Luis and Walter Alvarez found to be rich in iridium.
• In the Early Cretaceous area: one adult Psittacosaurus with 34 young inside half a square metre; a feathered dinosaur tail in amber from Myanmar; a Sinosauropteryx with a dark back, pale belly and banded tail; long filament feathers beside a Yutyrannus skull; and on the footprint bed, a survey frame for the Goseong trackways and a pterosaur trail like those of Uhang-ri in Haenam.
• In the East Asia area: a broken egg at the Boseong egg site, a clutch of eggs like those of Gojeong-ri in Hwaseong, and an oviraptorid sitting on its nest with its arms spread over the eggs.
• In the South America and Africa area: a field of sauropod eggs like Auca Mahuevo in Patagonia, where some eggs hold embryos with fossil skin, and the deep paddle of a Spinosaurus tail from Morocco.
• In the North America area: a Maiasaura nest with young, a giant coprolite from Saskatchewan that is 30 to 50 percent broken bone, SUE's skull, and on the beach a rock with the same dark layer under the asteroid in the sky.

The models are simplified: sizes are close to the real finds where the source gives a size and otherwise drawn to read well, and no real site has all of these things in one place.

Animals that move, footsteps and the size photo

Animals in the middle distance used to stand still as statues. Now their tails swing, their heads and necks turn slowly, and their legs swing in step when the herd walks. This is done on the graphics card by bending the statue's points according to where they sit along the body, so it costs no extra drawing. Two herds are on the move: ten Edmontosaurus and ten Centrosaurus walk two abreast around their loops and stop only to drink. Both are known from bonebeds that hold many animals of one kind.

The Footsteps button turns on sound and a shaking ground. Near a walking animal heavier than about four tonnes you hear each step, louder the closer and heavier it is, and the view shakes a little. Nothing plays until you turn it on.

In the field guide, each animal that walks has a Size photo button. It draws the animal side on, with a 1.7 m person and a 12 m bus on the same ground and a 5 m scale bar, using a camera without perspective so every length in the picture is to the same scale. You can save the picture as an image.