The longest neck ever seen in the animal kingdom: That was Mamenchisaurus

Researchers have made a new estimate for the neck length of Mamenchisaurus, which lived in what is now China more than 150 million years ago. “We must always assume that there is still a larger one to be found somewhere.”

Jack Tamise

Few creatures have defied the physical laws of what is anatomically possible to the same extent as sauropods. These oversized dinosaurs moved using column-like limbs that supported their massive bodies, had whip-like tails to ward off predators, and used long necks to reach leaves.

The long neck is a defining feature of almost all sauropods, but if there was one species that took the cake, it was Mamenchisaurus, which roamed what is now China in the late Jurassic period. In a study published last week in the Journal of Systematic Paleontology, researchers said the neck of Mamenchisaurus was estimated to have been around 50 feet (15 meters) long. This is the bus average. It is also the longest neck of any sauropod, and possibly the longest neck ever recorded in the entire animal kingdom.

Fragmented remains

In 1987, paleontologists unearthed the partial skeleton of a sauropod protruding from the rust-colored sandstone of the dinosaur-rich Shishogu Formation in northwestern China. The remains were fragmentary, consisting mostly of a lower jaw, pieces of skull, and a few vertebrae, but they pointed to a massive animal that shook the swampy plains of the region alongside primitive dinosaurs 162 million years ago.

The researchers named the dinosaur Mamenchisaurus sinocanadorum and related it to many other long-necked sauropods from East Asia. But the true size of Mamenchisaurus has remained a mystery. No other fossil remains of sauropods have been discovered, so scientists can only examine those few vertebrae.

This was the case for many of the largest dinosaurs, says Andrew Moore, a Stony Brook University paleontologist who studies sauropod anatomy. “What is particularly puzzling and frustrating is that the necks of the longest are often the most missing items from the fossil record. This is for the simple reason that it is difficult to bury something this large,” said Moore, who led the new study.

So he turned to the fossils of several close relatives of Mamenchisaurus, most notably Xinjiangtitan, a slightly older sauropod discovered in 2013 in northwestern China. Remarkably, researchers have excavated the entire spine of Xinjiangtan. At about 13 meters long, it is the longest complete neck in the fossil record. “Using more complete but smaller specimens, we can extend its range and get a very good estimate of what Mamenchisaurus looked like,” Moore explains.

After comparing Mamenchisaurus and Xinjiangtitan, Moore and his team concluded that Mamenchisaurus’ neck was about 15 meters long. This is about half of the estimated total body length and equates to just over eight straight giraffe necks.

hollow vertebrae

To determine how Mamenchisaurus handled its trailer-length neck, Moore and his colleagues used a tomography scanner to analyze the animal’s vertebrae. Instead of marrow and heavy tissue, the interior of the vertebrae of the sauropods in life contained large air sacs, similar to those of modern birds such as storks and pelicans. These empty sinuses accounted for up to 77 percent of the volume of each bone, which greatly reduced the weight of the mammhencisaurus’ spine.

Reconstruction of the Mamenchisaurus skeleton in Chiba, near Tokyo.EPA photo

Neck relief was essential for all sauropods, says Cary Woodruff, a paleontologist at the Frost Museum of Science in Miami who specializes in the study of sauropods. “A long neck like this is a lot of weight that you have to put away from your body,” said Woodruff, who was not involved in the new study. “If you have to hold a hammer with an outstretched arm, your arm gets tired quickly.”

Although its vertebrae were hollow, Mamenchisaurus’ neck was far from weak. During the first excavations, paleontologists discovered a fossilized strip of bone tissue several meters long. It may be a rigid extension of the vertebra – often called the cervical rib – that runs the length of the neck and supports light bones like a brace. While this reduced the flexibility of its neck, these ribs helped keep the sprawling structure stable. Woodruff: “Although it had a lot of bones in it, it wasn’t like a rattlesnake that could curl up. It was actually more of a pub.”

Mamenchisaurus, with its fortified spine, likely held its neck horizontally at a relatively obtuse angle above the ground. But since his neck was so long, he could still pluck leaves from the tops of many trees. This may have helped the sauropods squeeze into a unique niche in an ecosystem that might have been crowded with other giant herbivores.

However, according to the researchers, several groups of sauropods appear to have evolved extremely long necks that may rival those of Mamenchisaurus. “We don’t really know what the limits of the possible are because they’re constantly changing as more and more discoveries are made,” said Moore. “We must always assume that there is still a larger one to be found somewhere.”

© New York times

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