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long-necked dinosaur

Clockwise from top left, Musankwa sanyatiensis leg bones as they were discovered in the ground on Spurwing Island, Lake Kariba, Zimbabwe. Image courtesy of Paul Barrett; Musankwa sanyatiensis fossil bones in situ, after mechanical preparation, and after CT scanning. Image courtesy of Paul Barrett; and an artist reconstruction of Musankwa sanyatiensis showing position of fossil bones (in blue). Rendering by Atashni Moopen

By Daniel Dunaief

The dinosaur family tree has few members in Zimbabwe, as only four fossils have been found in the region.

Kimberley Chapelle

Recently, researchers from several universities, including Kimberley “Kimi” Chapelle, Assistant Professor in the Department of Anatomical Sciences in the Renaissance School of Medicine at Stony Brook University, described a new species of dinosaur from a 210 million year-old fossilized hind leg in the journal Acta Palaeontologica Polonica.

Reconstructing the entire dinosaur from the bones they discovered in Lake Kariba, the scientists, led by Paul Barrett from the Natural History Museum of London, estimated that this plant-eating sauropodomorph weighed about 850 pounds and was among the larger dinosaurs in the late Triassic period.

The first new dinosaur species described in the Mid-Zambezi Basin of Northern Zimbabwe in more than 50 years, the sauropodomorph survived a mass extinction event that wiped out about 76 percent of all terrestrial and marine creatures. The sauropodomoprh group includes animals like the enormous Brontosaurus, which came later in the evolution of the lineage. Chapelle was on the field expedition in 2017 when Barrett noticed the fossil sticking out of the ground.

The discovery was “extremely exciting, as there was a high chance it was going to be something new,” said Chapelle. “It was well-preserved in articulation and we knew the bones came from the same individual.” She participated in the lengthy process that involved excavating the rare find, creating a reconstruction, isolating the bones to look at the structure, describing the fossil and comparing it to other, closely-related dinosaurs to determine where it sits on the family tree.

The researchers named this species Musankwa sanyatiensis, using the name of the houseboat Musankwa on which they lived and worked as they searched for fossils during the dry seasons around the man-made Lake Kariba.

“Musankwa is cool because it’s one of only a handful of dinosaurs from Zimbabwe, a country with amazing fossil resources that have yet to be fully discovered,” explained Jonah Choiniere, a Professor in the Evolutionary Studies Institute at the University of Witwatersrand in Johannesburg South Africa, who served as Chapelle’s PhD advisor. “Because we don’t have any specimens of Musankwa in similar-age rocks in South Africa, it tells us that during the Triassic period there might have been slightly different species groups of dinosaurs in the two countries.”

The Earth looked considerably different when this long-necked dinosaur was searching for its plant meal, as the land masses of the planet were combined in one supercontinent called Pangaea. In that time, Musankwa’s predators likely included meat-eating therapods and crocodile-like reptiles, which are ancestors of modern crocodiles.

Keep your head up

Hunting for fossils in Zimbabwe, which presented an opportunity for this kind of discovery, came with some challenges.

Kimberley Chapelle with Jonah Choiniere at Lake Kariba. Photo from Jonah Choiniere.

For starters, researchers lived aboard the houseboat Munsankwa, whose name in the Tongan dialect means “boy close to marriage.” Lake Kariba, which was created between 1958 and 1963 and is the largest artificial lake and reservoir by volume, gets “really hot in the summer and all you want to do is swim,” said Chapelle.

That, however, is ill-advised, as modern crocodiles roam the waters of the lake so regularly that people stay far from the shoreline.

To combat the heat, Chapelle drank plenty of water, applied regular sunscreen and wore large hats and long sleeves to keep the strong rays of the sun off her skin. Additionally, the researchers worked between morning and afternoon. The scientific expedition had an armed game ranger with them, to keep scientists safe.

“When you’re looking at fossils, you are always looking at the ground,” Chapelle said. At one point, she looked up and saw a hippo about 50 feet from her. “You have to remember to be aware of your surroundings,” she  said.

Field experience

Choiniere, who inspired his former student to consider entering the field when he first arrived at the University of Witwatersrand, saw Chapelle in action when she first did some field work.

Chapelle’s scientific curiosity never faltered, despite some significant field misadventures that included staying in a rotten old farmhouse without plumbing, sleeping in tents in the freezing cold in the backyard of a rural pub, hiking through brambles over the side of a mountain, and touring around Germany eating nothing but stewed cabbage and pork in brown sauce, and staying three to a hostel room to save money.

“In [Chapelle’s] case, there was never any doubt — she loved the field from day one and has never looked back,” Choiniere explained.

Choiniere believes Chapelle has a “unique skillset among paleontologists,” as her talents include math, observations of shape and structure, histology, three-dimensional data processing and field work. Beyond her diverse skills, Choiniere appreciated Chapelle’s time management skills and her pleasant demeanor, which enabled her to greet him with a smile even when he delivered his part later than she anticipated.

A promising LI start

Chapelle, who started working at Stony Brook at the end of January, is enjoying a return to New York. A native of Johannesburg, South Africa, she  had done a postdoctoral fellowship at the American Museum of Natural History in 2021.

A current resident of Rocky Point, Chapelle lives close to the beach. She and her husband Dominic Stratford, an Adjunct Professor at Stony Brook and Archaeologist and Associate Professor at the University of the Witwatersrand in Johannesburg, brought their Australian Shepherd named Shango with them.

A runner who recently completed the Shelter Island 10K and who loves taking pictures, Chapelle, who is the daughter of a doctor, originally thought she’d want to become a veterinarian. When she took a course in her third year of college with Choiniere, she was hooked by the link between evolution and anatomy.

As for the recent paper, Chapelle is pleased that people can read about this newly discovered dinosaur.

“This is years and years of work that gets put into this,” she said. “It also gives us a push to keep finding new things and publishing.”

A rendering of the sauropod known as Mamenchisaurus sinocanadorum, which had a 15-meter-long neck, about 10 feet longer than a typical school bus. Credit: Júlia d'Oliveira

NEWS FROM STONY BROOK UNIVERSITY:

With their long necks and formidable bodies, sauropod dinosaurs have captured people’s imaginations since the first relatively complete sauropod fossils were discovered in the United States in the late 1800s. Now an international team led by Stony Brook University paleontologist Andrew J. Moore, PhD, has revealed that a Late Jurassic Chinese sauropod known as Mamenchisaurus sinocanadorum sported a 15-meter-long neck. The new analysis of this dinosaur, published in the Journal of Systematic Palaeontology, provides fresh insights on the evolution of the iconic sauropod body.

For sauropods, the long neck was the anatomical key to achieving large body size. To power such a large body, sauropods had to be efficient at gathering foodstuffs, and that’s what a long neck was built for. A sauropod could plant itself in one spot and hoover up surrounding vegetation, conserving energy while taking in tons of food. Having a long neck probably also allowed enormous sauropods to shed excess body heat by increasing their surface area, much like the ears of elephants. This way of life – long neck-fueled, quadrupedal gigantism – is not one that is available to mammals or any other form of life today. The sauropod lifestyle was exceptionally successful: their lineage appeared early in dinosaur evolutionary history and persisted until the final days of the Mesozoic, when an asteroid wiped out all dinosaurs (except birds).

Mamenchisaurus sinocanadorum was discovered in approximately 162-million-year-old rocks from the Xinjiang Uyghur Autonomous Region of northwest China in 1987 by the China–Canada Dinosaur Project team, for which it was named in 1993. At approximately 15.1 meters, its neck was more than six times longer than the necks of giraffes, the longest-necked animals alive today, and about 10 feet longer than a typical school bus.

The question of which sauropod had the longest neck is not straightforward. Because of their size, the largest sauropods tend to be some of the most poorly known: it’s very hard to bury such a large animal in sediment and thus safeguard it for fossilization.  Some fragmentary fossils suggest that other sauropod lineages independently evolved necks over 10 meters (32.8 feet) in length. However, poor preservation of these specimens and their closest relatives makes estimates of their neck length speculative.

According to Moore, Assistant Professor in the Department of Anatomical Sciences in the Renaissance School of Medicine at Stony Brook University, although Mamenchisaurus sinocanadorum is known only from a handful of bones from the neck and skull, the research team was able to reconstruct its evolutionary relationships and thus make comparisons to the unusually complete skeletons of its closest relatives. This allowed them to conclude that Mamenchisaurus sinocanadorum had a neck approximately 15.1 meters (49.5 feet) long, the longest neck that can be confidently inferred for any known sauropod.

Their research stems from on-going work to comprehensively document the anatomical diversity and evolutionary history of the family Mamenchisauridae, a radiation of particularly long-necked sauropod dinosaurs that roamed East Asia and possibly other parts of the world from the Middle Jurassic to the Early Cretaceous (approximately ­174–114 million years ago).

“All sauropods were big, but jaw-droppingly long necks didn’t evolve just once,” says Moore. “Mamenchisaurids are important because they pushed the limits on how long a neck can be, and were the first lineage of sauropods to do so. With a 15-meter-long neck, it looks like Mamenchisaurus sinocanadorum might be a record-holder — at least until something longer is discovered.”

How sauropods managed to evolve such long necks and hulking bodies without collapsing under their own weight remains something of a biomechanical puzzle. Remarkable specimens like Mamenchisaurus sinocanadorum provide some clues. For example, like their living cousins, birds, most sauropods had air-filled bones, which would have lightened their skeletons by removing heavy marrow and bone tissue.

Using computed-tomography (CT) scanning, Moore and colleagues found that the vertebrae of Mamenchisaurus sinocanadorum were mostly air (about 69–77% of their volume) – comparable to the lightly built skeletons of storks and other birds.

However, such featherweight skeletons would also be more prone to injury. To combat this, Mamenchisaurus sinocanadorum had 4-meter-long rod-like cervical ribs, bony extensions of the vertebrae that created overlapping bundles of rods on either side of the neck. These bundles would have stiffened the neck of Mamenchisaurus sinocanadorum, increasing its stability and making it possible to build such a lightweight neck.

“Biomechanical studies of the mamenchisaurid neck suggest that it was elevated at only a relatively shallow angle above the horizontal (20-30°). However, even at this relatively shallow angle, the extreme length of the neck would still mean that the animal’s head could reach heights of around 7.5 to 10 m above ground level, facilitating feeding on tree foliage,” says co-author Paul Upchurch, PhD, a Professor of Palaeobiology from the University College London.

“Mamenchisaurus sinocanadorum underscores how much we can learn about sauropod evolution even from very incomplete specimens,” adds co-author Ye Yong, director of the Research Center of Jurassic Stratigraphy and Paleontology at the Zigong Dinosaur Museum in China’s Sichuan Province.

The research was funded by numerous organizations including the United States National Science Foundation, The Royal Society of London, and the National Natural Science Foundation of China.