The Top Ten Dinosaur Discoveries of 2021

The key finds and moments in a year packed with amazing stories about the terrible lizards

The tyrannosaur Nanuqsaurus, which lived in the Arctic, with its young. New evidence suggests dinosaurs nested in the cold, dark region. James Havens

There’s never been a better time to be a dinosaur fan. New species are being described at a fast-and-furious pace, with 42 species named just this year, and paleontologists have also been investigating and arguing about everything from patterns of dinosaur evolution to the ethics of fossil collecting. This year’s finds help set up the studies and debates that we’ll be sure to see in the years ahead, and these are some of the most important dinosaur-focused stories that have been unearthed in 2021.

Armored Dinosaur Swung an Unusual Tail

Ankylosaurs were herbivores that lived during the Late Cretaceous period. Lucas Jaymez via Nature

The armored ankylosaurs are classic dinosaurs, often envisioned as “living tanks.” Some of the last and largest, like Ankylosaurus itself, even had heavy clubs made of bone at the end of their tails. But paleontologists are learning that ankylosaurs evolved a greater variety of defensive armor than previously known. Stegouros elengassen, described this year from bones found in the 72-to-75-million-year-old rock of Chile, was an ankylosaur with a fern-like splash of bones at the end of its tail. No dinosaur has a tail quite like it, which is making paleontologists wonder what other unusual arrangements armored dinosaurs might have sported way back when.

Fuzzy Dinosaur From Brazil Stirs Ethics Debate

Ubirajara Jubatus
An artist's rendering of Ubirajara jubatus, a newly described dinosaur species featuring two sets of rods sticking out of its shoulders and a mane of fluffy proto-feathers. Artwork © Bob Nicholls / 2020

Late in 2020, an international team of paleontologists described an unusual new dinosaur from Brazil named Ubirajara jubatus that was housed at a German museum. This feathery dinosaur was the first of its kind to be found with ribbon-like protofeathers growing out from its shoulders. But the bigger issue is how a fossil from Brazil came to be ensconced in Germany, far from the dinosaur’s home country. There are conflicting accounts of how the fossil was exported from Brazil, which may have been illegal, and the #UbirajaraBelongstoBR campaign on social media has put pressure on the State Museum of Natural History Karlsruhe to repatriate the fossil. The museum has refused to do so, with the decision intensifying the ongoing debate and arguments over colonialism in paleontology.

Tyrants Once Dominated Their Environments

Gorgosaurus Jaw
A paleontologist measures the jaws of a Gorgosaurus. Royal Tyrrell Museum

Tyrannosaurs may have been just as tyrannical as their name implies. Multiple studies published in 2020 and 2021 have underscored the same conclusion, that large tyrannosaurs—like T. rex itself—shouldered out their carnivorous competition by changing dramatically as they aged. While young tyrannosaurs were lithe and only capable of hunting small prey, a teenage growth spurt turned the meat-eaters into huge, bone crushing predators. In this way, a single species like T. rex or Gorgosaurus could fill multiple niches in the same habitat with young and juvenile animals taking up the roles that would normally be filled by other small species of carnivore.

Predators Once Towered Over Smaller Tyrannosaurs

Ulughbegsaurus and Timurlengia
The apex predator Ulughbegsaurus was much larger than the contemporaneous tyrannosaur Timurlengia. Julius Csotonyi

Tyrannosaurs weren’t always large and in charge. In fact, for tens of millions of years, tyrannosaurs were tiny while other forms of giant, carnivorous dinosaurs filled the apex predator role. Paleontologists are still trying to understand how tyrannosaurs eventually took over as top carnivores in the northern continents of the Late Cretaceous, and a new species named this year from Uzbekistan helps flesh out the story. At about 30 feet long, Ulughbegsaurus was far larger than the tyrannosaur in its same habitat and was more closely related to dinosaurs like Allosaurus. Why these huge, “shark toothed” dinosaurs ceded many habitats to tyrannosaurs remains unknown, but the new find helps paleontologists narrow down where to look for answers.

Scientists Discover Baby Dinosaur Fossils in the Arctic

Baby Dinosaur Fossils
Baby dinosaur bones and teeth from northern Alaska Current Biology

Paleontologists have known that dinosaurs lived within the Arctic Circle for decades now, but whether or not those dinosaurs stayed year-round has remained a difficult question to answer. A set of embryonic and very young dinosaurs uncovered from Alaska’s North Slope helps resolve the debate. Paleontologists have found tiny bones and teeth from embryonic and hatchling dinosaurs that lived in the Cretaceous Arctic, environments that would have experienced several months of cold and darkness each year. The finds indicate that dinosaurs were nesting and raising their young in this place, which speaks to just how adaptable dinosaurs were to different habitats and climates.

Dinosaurs Hung Out With Their Peers

Mussaurus Patagonicus
Mussaurus patagonicus raised its young in a communal breeding ground. Jorge Gonzalez

Some dinosaurs tended to gather together with peers of the same age. That’s the conclusion of a new study that investigated the social habits of a long-necked, herbivorous dinosaur called Mussaurus that lived around 200 million years ago. At a fossil site replete with dinosaurs of different ages, paleontologists found eggs and hatchlings together, juveniles together and adults alone or in pairs. This is a biological phenomenon called “age segregation” where social groups are determined by age, which supports similar interpretations about other dinosaur sites. Instead of multi-generational herds, dinosaurs tended to hang out with other dinosaurs their own age.

The “Smallest Dinosaur” Is Really a Lizard

An artist’s rendering of the 99-million-year-old lizard once thought to be a dinosaur based on a specimen found in amber. Stephanie Abramowicz / Peretti Museum Foundation / Current Biology

Early in 2020, paleontologists announced what was heralded as the smallest dinosaur yet found. Only, it wasn’t. Experts immediately questioned the identity of Oculudentavis khaungraae and rumor had it that a second specimen indicated that this creature was actually a 99-million-year-old lizard. A paper confirming the identity of Oculudentavis as a lizard finally appeared this year, but the story is bigger than fossil identity. Both specimens of Oculudentavis were found encased in amber extracted from Myanmar, a country in which control of amber mines has been associated with genocide and human rights violations. Even through fossils in Myanmar amber are beautiful, paleontologists are debating the ethics of publishing on specimens that may be tied to a black market fueling the conflict.

Paleontologists May Have Found the Biggest Dinosaur

Paleontologist Unearthing 98-million-year-old Fossil
A paleontologist excavating a 98-million-year-old fossil that may belong to the largest land animal ever. CTyS-UNLaM Science Outreach Agency

South America keeps turning up enormous dinosaurs. Not long after the announcement of the 121-foot-long, 63-ton Patagotitan named in 2017, paleontologists working in Argentina have announced another giant that may be even bigger. The incomplete fossil skeleton does not yet have a name, but it appears to be new and may be larger than Patagotitan. It may be quite some time before paleontologists can declare a winner. All the contenders for the title of “largest dinosaur” are known from incomplete specimens, which makes size estimates and comparisons challenging.

Stubby-Armed Dinosaurs Ate Insects

An illustration of a long-legged alvarezsaurs hunting an insect at night. Viktor Radermacher

Alvarezsaurs are some of the strangest dinosaurs known. Most were small, about turkey size, and they’re immediately recognizable by their short, thick arms tipped with a blunt claw. Paleontologists have expected that these dinosaurs were insectivores and maybe even ate social insects like termites, but additional evidence has been hard to gather. Studies of alvarezsaurs published this year, however, indicate that the eyes and ears of these dinosaurs were adapted to hunting small prey—like insects—at night, a very different niche than the usual dinosaur image.

Scientists Get to the Bottom of Dinosaur Butts

Dinosaur Cloaca Fossil
This fossil is the oldest known preserved dinosaur cloacal vent. Jakob Vinther, University of Bristol and Bob Nicholls / 2020

There’s still a lot of basic information we don’t know about dinosaurs. For example, until now paleontologists didn’t really know what a dinosaur’s butt looked like. Comparisons to birds and crocodiles led experts to think that dinosaurs, too, had a single external opening called a cloaca. It’s the opening for where the urinary, excretory and reproductive orifices exit the body. But a study published this year has offered experts their first detailed look at a dinosaur cloaca and its resemblance to the same setup in crocodiles. This is just the first discovery of its kind among hundreds of species, however, which means discussion of dinosaur rumps will have a long tail.

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