Monday, January 3, 2011

The Top Dinosaur Discoveries of 2010

The Top Dinosaur Discoveries of 2010

2010 has been a good year for dinosaurs. Numerous new species have been named, long-awaited conference proceedings have been published, new techniques for studying the past have been devised, and scientists finally allowed us to answer one of the most confounding questions in dinosaur science. There was so much new dinosaur science that it was impossible to cover it all here (in fact, an accepted manuscript describing a new, giant horned dinosaur from New Mexico called Titanoceratops was just made available while this post was being prepared), but here is a breakdown of the top discoveries discussed here at Dinosaur Tracking over the past 12 months.

Before the Dinosaurs

There is much that remains unknown about the origin and early evolution of dinosaurs, but several discoveries announced this year have helped to fill in the early history of dinosaurs and their close relatives. Tracks made by the precursors of dinosaurs – the dinosauromorphs – found in the 249-million-year-old rock of Poland suggest that the ancestors and close relatives of the first dinosaurs originated not long after the great Permian mass extinction 251 million years ago. Creatures of this antiquity can be tricky to identify. Azendohsaurus, once thought to be an early dinosaur, was reclassified this year as being only a distant cousin, and the newly-described creature Asilisaurus was somewhat dinosaur-like but not a dinosaur itself.

Funky Theropods

Multiple theropod dinosaurs were described this year, but two exceptional species stand out. One, the carcharodontosaurid Concavenator, had a short sail on its back and may have had tubular bristles growing out of its forearms. The other, the raptor Balaur, had only two fingers on each hand and a double set of hyperextendable sickle claws on each foot. (And, while not as anatomically strange, the first specimens of Linheraptor described this year were absolutely gorgeous.)

Other notable theropod news included the discovery that a specimen of the small predator Juravenator from the famous Jurassic limestone quarries of Germany preserved traces of both scales and feathers, traces of predatory dinosaurs digging after mammals in their burrows found in Utah, and that the idea that Sinornithosaurus was venomous was rightly called into question. Paleontologists also confirmed that many, if not most, coelurosaurs did not exclusively dine on meat, making this group of dinosaurs one of the strangest and most varied of all.

Of course, no list would be complete without mention of some of the studies about that most famous group of theropods, the tyrannosaurs. The Canadian Journal of Earth Sciences devoted a special issue to Albertosaurus, the tyrannosaur Bistahieversor was named, direct evidence was found of cannibalism among Tyrannosaurus, the identity of the purported tyrannosaur from Australia was debated, damaged bones showed that Tarbosaurus could be delicate with its massive jaws, and one study found that Tyrannosaurus and other predatory dinosaurs had some extra “junk in the trunk.”

Year of the Ceratopsians

Although theropod dinosaurs regularly make headlines, 2010 was notable for the exceptional number of new studies about horned dinosaurs. The year’s major story was the formal publication of the idea that the dinosaur called Torosaurus was really an adult stage of Triceratops – an argument which will require further study to resolve – but paleontologists were also thrilled to see the publication of the New Perspectives on Horned Dinosaurs volume, a landmark publication in the study of this group. Multiple new species of ceratopsians were described this year, as well. In addition to those announced in the conference volume, Koreaceratops, Zhuchengceratops, Utahceratops, Kosmoceratops, Sinoceratops, and Ajkaceratops (the first confirmed ceratopsian from Europe). Our understanding of ceratopsians is rapidly changing, and I am currently working on a formal academic article reviewing the significant discoveries which were announced this year.

Armored Dinosaurs

Multiple new analyses published this year have altered our perspective of the armored stegosaurs and ankylosaurs. Regarding stegosaurs, in particular, an issue of the Swiss Journal of Geoscience included a spate of papers about the relationships and biology of these dinosaurs, including studies on stegosaur soft tissue, their relatively weak jaws, their posture, the history of stegosaur discoveries, and stegosaur diversity in the Late Jurassic of North America. Furthermore, a pair of studies by Phil Senter on the forefeet of Stegosaurus and the ankylosaurs Edmontonia and Peloroplites have shown that these dinosaurs had a semi-tubular arrangement of lower limb bones similar to that seen among some sauropod dinosaurs, changing our understanding of how these armored dinosaurs walked.

Sauropods and Their Kin

The long-necked, large-bodied sauropods are among the most iconic of the dinosaurs, but new discoveries are rapidly changing our understanding of their origin and evolutionary history. The discovery of the sauropodomorph Sarahsaurus from Arizona has helped identify an evolutionary pattern in which these dinosaurs migrated into North America multiple times during the Early Jurassic rather than just being part of a single move northward. Another sauropodomorph described this year, Seitaad, provided further evidence for this hypothesis.

A presentation at this year’s Geological Society of America meeting caused a stir by claiming to have found tracks of juvenile sauropod dinosaurs running only on their hindlimbs. Paleontologists are awaiting further details about these fossil footprints. Most of the known sauropod tracks are quite a bit larger, and footprints made by some sauropods may have formed deathtraps which later preserved smaller dinosaurs like Guanlong and Limusaurus.

One sauropod nest site in Argentina was found in close proximity to geysers, vents and other features associated with geothermal activity – the dinosaurs selected a naturally-heated nursery. Nesting sites were not always safe, though. A different nest site in India contained the remains of a snake that had been feeding on baby sauropods.

Even well-known sites and old collections are yielding new discoveries. A juvenile Diplodocus skull collected decades ago has helped show how the diets of these dinosaurs changed as they aged. This specimen came from Dinosaur National Monument, and a geologically younger, Early Cretaceous site from the national park also yielded the skulls of a previously-unknown sauropod called Abydosaurus.

Dinosaur Colors

The biggest announcement of the year was that scientists have finally found a way to detect the colors of some dinosaurs. The technique has only been applied to feathered dinosaurs, but by comparing microscopic structures in preserved dinosaur feathers to their counterparts in modern birds, paleontologists have finally been able to fill out parts of the dinosaur palette. The first study, published in Nature, looked at just part of the tail plumage of Sinosauropteryx, while the second study (published the following week in Science by the team that had pioneered the techniques being utilized) reconstructed the entire feather colors of Anchiornis. These were just initial reports in what is sure to become a very active area of research. At long last, scientists will be able to provide answers about what has traditionally thought to be a question incapable of resolution.

Those are just a few selection from stories we covered here during 2010. What were your favorite dinosaur stories from the past year?

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