Though overshadowed by Syria, Brexit, the Olympics, and the U.S. presidential election, 2016 was another fruitful year for news stories about paleontology and ones about dinosaurs in particular. Scientists discovered not only new species, but also unseen aspects about these creatures as a whole -- from countershading Psittacosaurus scales (above) to fossilized Iguanodon brains (left).
Compared to these developments, the new dinosaurs of 2016 may seem inconsequential or bland. None were as overtly bizarre as Yi qi, the tiny, leathery-winged "dino-bat" announced last year; nor were any as large as 2014's Dreadnoughtus, the most complete super-sized dinosaur to date. Context matters, however, and this year's four most important dinosaurs bridged some gap in our understanding of these creatures' evolutionary history.
DINOSAURS OF THE YEAR
(Brazil, 230 million BCE)
Until 2016, every single known meat-eating dinosaur belonged to a huge group called the theropods. At first glance, the newly-discovered Buriolestes ("Buriol's robber", after the local landowning family) has all the trademarks of these predators: It walked on two long legs, had a mouth full of sharp, serrated teeth, and was probably equipped with large hands ending in hook-like claws.
Yet based on several subtle features (including the somewhat down-turned tip of the lower jaw), this dinosaur's discoverers classified it as one of the earliest sauropodomorphs -- a member of the same group as Apatosaurus, Brachiosaurus, and countless other long-necked, multi-ton grazers. Buriolestes demonstrates that long before they became the largest herbivores (and animals) ever to walk the planet, at least some of these dinosaurs were small, nimble carnivores. As the Triassic Period (252-201 million BCE) progressed, these dinosaurs would outgrow and outlast rival reptiles like the dicynodonts and rauisuchians, forsaking flesh for foliage in the process.
(Alabama, 85-83 million BCE)
Discovered in New Jersey in 1838, Hadrosaurus is the first dinosaur known from substantial remains, as well as the namesake of the duck-billed, plant-eating hadrosaurs. As Americans moved westward, however, so too did the focus of American paleontology. Today, all of the best-known American dinosaurs are from Montana, Wyoming, Utah, and Colorado. Hadrosaurs were among the most successful dinosaurs all time, but even they are known mostly from the Rocky Mountain region and China, and most lived during the final ten million years of the Cretaceous Period (76-66 million BCE).
This story of discovery came full circle in 2016 with the debut of Eotrachodon (“dawn rough tooth” or “early Trachodon” — an allusion to a discarded hadrosaur genus named in 1856). The new dinosaur was found near Montgomery, Alabama, and predates other early hadrosaurs by about five million years. Also, unlike Hadrosaurus, this new dinosaur is known from a complete skull. While all of these herbivores share the same general body plan, the shape of their skulls varies wildly across different species and plays a huge role in determining their relationships with one another. Most broad-billed hadrosaurs with no hollow head crests belong to a branch called saurolophines, while those with narrower bills and dramatic head crests belong to the lambeosaurines (see opposite image).
This new dinosaur, however, doesn't seem to belong to either sub-family. Professor Greg Erickson, one of the first paleontologists to study Eotrachodon, believes that hadrosaurs originated in the eastern North America, which during the Cretaceous was separated from the western half by a narrow sea. By the end of the period, these herbivores were the most successful dinosaurs on Earth, ranging from Utah to Spain and from Alaska to Antarctica.
Timurlengia (Uzbekistan, 90 million BCE)
Because of their fame and instant familiarity, T. rex and its kin regularly get more press coverage each year than any other dinosaur group.
In 2016, that buzz was justified: In the middle of March, paleontologists announced not only the discovery of a pregnant T. rex from Montana, but also a very different kind of tyrannosaur from Uzbekistan. Though most people know them as colossal top predators, these theropods began as small, lower-tier carnivores during the mid-Jurassic Period (around 165 million BCE) and most remained that way throughout the Late Jurassic and Early Cretaceous. Like hadrosaurs, the largest and most famous tyrannosaurs didn't evolve until the last ten million years of the Cretaceous. Dating from the mid-Cretaceous (roughly 90 million BCE), Timurlengia helps bridge the gap between early and late tyrannosaurs.
This dinosaur is currently known from several separate specimens, none of which are even near complete. Even so, scientists discovered enough remains to infer its anatomy and lifestyle. In life, this predator was about the length and weight of a modern tiger. Unlike the thick, banana-sized teeth of T. rex, those of Timurlengia were thin and knife-like -- better-suited for stripping flesh than for crushing bone. Like earlier tyrannosaurs, it probably had three fingers on each hand instead of two.
The most important part of Timurlengia to survive fossilization, however, is a partial brain case: CT scans revealed that this predator had a more sophisticated brain and larger inner ear bones than its predecessors. Based on this discovery, paleontologists Hans-Dieter Sues and Stephen Brusatte (see video above) hypothesize that later tyrannosaurs owe their size and success to the expanding brain and sharpening senses of Timurlengia and other mid-Cretaceous ancestors. Conveniently enough, these predators emerged around the same time that larger meat-eating dinosaurs like the carcharodontosaurs and spinosaurs went extinct.
Timurlengia's name honors Timur (often anglicized as "Tamerlane"), the 14th century Central Asian conqueror whose empire spanned from eastern Turkey to the Himalayas. By the end of the Cretaceous, the tyrannosaurs ruled a much larger domain, extending from Mongolia to Texas if not further.
(China, 72-66 million BCE)
Animals occasionally die or have their remains discovered in extraordinary circumstances, but rarely both: In modern southeastern China, a bird-like theropod became entrapped and died in mud or quicksand. Around 70 million years later, construction workers uncovered this dinosaur while using dynamite to lay the foundations for a new high school. Though the explosives destroyed part of its tail and limbs, the specimen was still surprisingly intact, with its arms still outstretched and its complete skull and neck raised just above the rock surface. This unlucky creature -- eventually named Tongtianlong ("road to heaven dragon") -- spent its final moments trying to free itself from the muck.
Tongtianlong belonged to the oviraptorosaurs, a family famous for their toothless, parrot-like beaks, bony head crests, and bold feathers (including long "tail-fans" and "wings" for display). They were widespread throughout Asia and North America by the Late Cretaceous and ranged from chicken- to giraffe-sized animals. Tongtianlong, in fact, is the sixth oviraptorosaur known from the Nanxiong Formation alone, distinguished from other species by an unusually broad and dome-like crest. While some experts believe that dinosaurs were already in decline at the end of the Cretaceous, the sheer range and diversity of these animals suggests that some groups were still flourishing just before they went extinct.
Dracoraptor- Primitive theropod from Wales dating to the very beginning of the Jurassic.
Fukuivenator- Creatively-named, omnivorous theropod from Early Cretaceous Japan that lived alongside Fukuisaurus, Fukuiraptor, and Fukuititan.
Gualicho- Light-weight, carnivorous theropod from mid-Cretaceous Argentina with short, tyrannosaur-like arms despite being more closely related to Allosaurus and Giganotosaurus.
Machairoceratops- Large ceratopsian from Late Cretaceous Utah. One of the strangest of its kind yet discovered, it had two pairs of horns, the longer of which bent forward from the top of its frill.
Savannasaurus- Titanosaur from mid-Cretaceous Australia with brachiosaur-like proportions (i.e. a longer-than-usual neck, a shorter-than-usual tail, and longer fore limbs than hind limbs).
Wiehenvenator- Large megalosaur about 30 feet long from mid-Jurassic Germany. Nicknamed "the monster of Minden" after a nearby town.
Alcovasaurus- Stegosaur from Late Jurassic Wyoming, formerly known as "Stegosaurus longispinus". Alcovasaurus had a shorter tail but longer spines than its famous relative.
Forminacephale- Pachycephalosaur with a deeply pitted skull from Late Cretaceous Alberta, originally dubbed "Stegaceras brevis".
Meroktenos- Sauropod ancestor from Late Triassic Lesotho. Previously known as "Melanorosaurus thabanensis".
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