Discovering Dinosaurs: The Ultimate Guide to the Age of Dinosaurs

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This diversity might be explained by the environments of the past,’ Kohta says. ‘The Cretaceous sediments in the Nemegt Basin suggest there were once a variety of moist and dry habitats.’

Stegouros is a bizarre anatomical mosaic. The dinosaur’s skull, teeth, and club-like tail are classically ankylosaur, resembling Ankylosaurus and other late armored dinosaurs. However, the dinosaur’s slender limb bones and pelvis resemble those of stegosaurs such as Stegosaurus, which had been extinct for tens of millions of years by the time of Stegouros. ( See how Stegouros may shake up the armored dinosaurs’ family tree.) Small dinosaurs can have thinner and more fragile bones, which make them more vulnerable to being damaged,’ Paul says. ‘From the fragments that survive, we know that alvarezsaurids certainly lived in other areas of the world, but we may not be seeing the full diversity of the species that lived there.’ One additional tooth was also identified as a troodontid, and another as a therizinosaur. However, these had to be additionally qualified by comparing their shape to known teeth, as they could not be identified by the machine learning models alone.

10. A Japanese dinosaur from the Mesozoic Era’s last chapter

Teeth found in Oxfordshire, Gloucestershire and Dorset are believed to belong to the maniraptorans, a group of dinosaurs, including Velociraptor, which include birds and their closest relatives. Kohta Kubo, a PhD student and lead author of new research describing the new species, says, ‘As most of Jaculinykus’ skeleton has remained in its original position, it could have been buried rapidly during a sandstorm or a catastrophic event.’ This is similar to how birds sleep, with the pose thought to help the animals keep warm by reducing heat loss. What fills this gap is still not known, but may include the 240-million-year-old partial fossil of an animal called Nyasasaurus parringtoni, discovered in Tanzania near Lake Nyasa in the 1930s.

An illustration of the "shark-toothed" dinosaur Ulughbegsaurus uzbekistanensis, which lived in what is now Uzbekistan about 90 million years ago. (Image credit: Julius Csotonyi)

The secrets of sleep

Artist's reconstruction of the world's oldest modern bird, Asteriornis maastrichtensis, in its original environment Simon Wills, a PhD student at the Museum who led the research, says, 'Previous research had suggested that the maniraptorans were around in the Middle Jurassic, but the actual fossil evidence was patchy and disputed. Along with fossils found elsewhere, this research suggests the group had already achieved a global distribution by this time.' Spicomellus ended up in the U.K. museum through the legally complex commercial trade in Moroccan fossils. After passing through the hands of several Moroccan wholesalers, the rib bone reached Moussa Direct, a U.K.-based fossil dealer that sold the specimen to the museum. T. rex wasn’t the only dinosaur with stubby arms. Time and again, large carnivorous dinosaurs evolved to have relatively short forelimbs—including a new species of carcharodontosaur described this year called Meraxes. The shared anatomy hints that being a meat-eater with a big head led dinosaurs like Meraxes to evolve a similar body plan to T. rex, with small arms that could be kept out of the way of struggling prey. More importantly, however, the skull and skeleton of Meraxes are more completely known than those of related dinosaurs such as Giganotosaurus. By comparing the known remains of Giganotosaurus, Tyrannotitan and related dinosaurs to Meraxes, paleontologists can better estimate the body sizes and anatomical particulars of these dinosaurs. Dinosaurs likely ran hot and cold Dinosaurs are often celebrated for being big, fierce and tough. The truth, however, is that they suffered from many of the same injuries and maladies that humans do. A study published this year in The Lancet reported on the first well-documented case of malignant bone cancer in a non-avian dinosaur. The animal, a horned dinosaur known to experts as Centrosaurus, probably coped with declining health before its eventual death in a coastal flood that caught its herd off-guard. Dinosaurs Weren’t in Decline When the Asteroid Hit