Dinosaurs ruled the Earth for roughly 165 million years - from the Late Triassic about 230 million years ago until the mass extinction event 66 million years ago. That's a span of time so vast it makes all of human civilization look like a rounding error. During that stretch, dinosaurs evolved into an astonishing range of forms: two-legged predators the size of buses, four-legged herbivores that weighed more than a dozen elephants combined, and feathered creatures no bigger than a pigeon.
This page lists 50 well-known dinosaur species (and a few closely related prehistoric reptiles) in alphabetical order. Each entry includes the geological period, diet, estimated body length, and taxonomic group. Whether you're studying paleontology, helping a kid with a school project, or settling a debate about which dinosaur was biggest, an alphabetical reference makes it easy to find what you need. Got your own dinosaur list to sort? Paste it into the tool above.
The Three Great Periods
Dinosaurs lived across three geological periods within the Mesozoic Era. The Triassic Period (252 to 201 million years ago) is where it all started. Early dinosaurs like Coelophysis and Herrerasaurus were mostly small, bipedal predators that shared the landscape with other reptile groups. Plateosaurus, one of the first large herbivores, appeared late in this period and hinted at the enormous sizes to come. The Triassic ended with a mass extinction that wiped out many of the dinosaurs' competitors and opened ecological space for them to diversify.
The Jurassic Period (201 to 145 million years ago) was the age of giants. Sauropods like Brachiosaurus, Diplodocus, and Apatosaurus reached staggering sizes - Diplodocus alone stretched 85 feet from nose to tail. Predators grew to match: Allosaurus was the apex carnivore of the Late Jurassic, reaching 32 feet in length. Stegosaurus roamed with its distinctive back plates, and Archaeopteryx appeared as one of the earliest links between dinosaurs and birds. The Jurassic was warmer and wetter than today, with no polar ice caps and lush vegetation covering most landmasses.
The Cretaceous Period (145 to 66 million years ago) was the longest and last dinosaur era. Flowering plants appeared and spread across the globe, changing ecosystems fundamentally. Tyrannosaurus Rex, Triceratops, Velociraptor, and Spinosaurus all lived during the Cretaceous - though not all at the same time or in the same place. The period ended abruptly when an asteroid roughly 6 miles wide struck what is now the Yucatan Peninsula in Mexico. The American Museum of Natural History estimates that about 75% of all species on Earth went extinct in the aftermath.
Carnivores, Herbivores, and Everything Between
The split between meat-eaters and plant-eaters is one of the most basic ways to classify dinosaurs. Carnivorous theropods walked on two legs and ranged from chicken-sized Compsognathus (about 3 feet long) to the 43-foot Giganotosaurus, which may have been slightly larger than T. Rex. Most theropods had sharp, curved teeth and clawed forelimbs built for grasping prey. The dromaeosaurids - Velociraptor, Deinonychus, and Utahraptor - carried a distinctive sickle-shaped claw on each foot that they likely used to slash at prey while pinning it down.
Herbivorous dinosaurs developed a wide array of defenses against these predators. Ankylosaurus carried a full suit of bony armor plates and a massive tail club that could shatter bone on impact. Triceratops had three forward-facing horns and a solid neck frill. Stegosaurus bore rows of upright plates along its back and sharp tail spikes (paleontologists call them "thagomizers"). The hadrosaurs - duck-billed dinosaurs like Parasaurolophus, Corythosaurus, and Edmontosaurus - relied more on herd behavior and speed, though Parasaurolophus also had a hollow cranial crest that may have functioned as a resonating chamber to produce low-frequency calls audible over long distances.
A few species don't fit neatly into either camp. Gallimimus was likely an omnivore, using its toothless beak to eat both plants and small animals. Therizinosaurus is one of the strangest dinosaurs ever found - a theropod (the group that includes all the carnivores) that evolved into a massive, pot-bellied herbivore with claws over 2 feet long. Its exact lifestyle remains debated, but those claws were probably used for pulling down tree branches rather than attacking prey.
Not Actually Dinosaurs (But Close)
A few creatures on this list aren't technically dinosaurs, though popular culture groups them together. Pteranodon and Quetzalcoatlus were pterosaurs - flying reptiles closely related to dinosaurs but belonging to their own separate order. Quetzalcoatlus, with a wingspan of up to 36 feet, was the largest animal that ever flew. It stood as tall as a giraffe when on the ground and likely hunted by stalking across open plains like a giant stork, snatching up small dinosaurs and mammals.
Similarly, Mosasaurus, Plesiosaurus, and Nothosaurus were marine reptiles, not dinosaurs. Mosasaurus was a massive oceanic predator that ruled Late Cretaceous seas, growing up to 50 feet long with jaws powerful enough to crush ammonite shells. Actual dinosaurs were exclusively land-dwelling animals - no true dinosaur species lived in the ocean, though some (like Spinosaurus) were semiaquatic and spent significant time in rivers and coastal waters. The Smithsonian Institution maintains one of the most comprehensive dinosaur fossil collections in the world and provides detailed information about how these groups relate to each other.
Size Extremes
The size range among dinosaurs is hard to overstate. At the small end, Microraptor was a four-winged feathered dinosaur about 2.5 feet long - roughly the size of a crow. Compsognathus was similarly tiny. These small theropods were agile, fast, and probably hunted insects and lizards. On the other end of the scale, Dreadnoughtus may be the most massive dinosaur for which we have solid measurements. Based on a remarkably complete skeleton discovered in Argentina in 2005, Dreadnoughtus weighed an estimated 65 tons and measured 85 feet long. Its femur alone was over 6 feet tall. The name means "fears nothing" - and at that size, it had good reason.
Among carnivores, the title of largest predator is still debated. Tyrannosaurus Rex is the most famous candidate at about 40 feet long and 9 tons, but Giganotosaurus (43 feet) and Spinosaurus (possibly 50 feet or more) both have strong cases. Spinosaurus is particularly interesting because recent fossil discoveries have radically changed our understanding of it. Originally reconstructed as a standard bipedal predator, it's now believed to have been semiaquatic, with a paddle-like tail for swimming and a long crocodile-like snout for catching fish. It may have spent more time in water than on land.