Comparison of the size of some sauropod dinosaurs with humans (Source: Globe Science, October 2023, graphic: Scott Hartman)
I don't know if I'll get cervical spondylosis.
Compared to most sauropods, giraffes have pitifully short necks. Most giraffes have necks between 1 meter and 2 meters in length, while sauropod dinosaurs can often have necks of several meters or even more than ten meters.
The animal with the longest neck found so far is a sauropod called Mamenchisaurus sinocanadorum, which lived in the Jurassic period. In 1993, fossilized necks and skulls were discovered in Xinjiang, on the mainland, and in a study published last year in the Journal of Systematic Palaeontology, researchers analyzed the fossils using a new method to reestimate the neck length of the Mamenxisaurus at about 15.1 meters, more than seven times the length of a giraffe's neck.
Restoration of the Mamen Creek Dragon (Image: Júlia d Oliveira)
Unfortunately, such a rare beast is long gone. This can't help but make people wonder what kind of daily life this super-long neck animal had before it was born.
For example, with a 15-meter-long neck, how should the Mamenxi dragon sleep?
"The Dragon in Sleep"
It's easy to find out how the giraffe sleeps, because we can observe them directly on Earth today. But for extinct dinosaurs, almost all we know about them comes from fossils.
When a dinosaur dies, if the body is buried by sand or silt in a short period of time, the skin and muscles gradually decay, and finally the skeleton remains, and then after millions or even tens of millions of years of complex petrification process, the bones gradually petrify, and it will become the dinosaur fossils we are familiar with.
To know how a dinosaur slept, we might need a fossil that fully reflects its sleeping position.
But many dinosaur fossils are extremely incomplete, sometimes with only one tooth, one leg bone, and a few ribs...... And those dinosaur fossils with relatively intact skeletons were found with very distorted bodies. Only a handful of fossilized bones appear to remain in the dinosaur's posture – possibly due to momentary burial of the dinosaur by volcanic rocks or sandstorms.
Therefore, it takes a dinosaur to be suddenly buried in its sleep, then turned into a complete fossil, and successfully discovered by human scientists, so that we have a chance to intuitively know the position in which it sleeps.
This dinosaur fossil in a sleeping position is extremely rare, but not none. One of the most famous is the "Mei Long" found on the mainland, and we have found at least two relatively complete fossils of Mei Long, which means "asleep" in its name, because scientists believe that the fossil appeared to be in a sleeping position when it was found.
寐龙化石(Bruce McAdam - CC BY-SA 2.0)
The two fossils are in almost identical posture to the sleeping posture of many birds today: the body sits on folded hind limbs, the forelimbs folded beside them, and the neck bent backwards on one side of the body.
The sleeping position of modern birds (Image Credit: Pixabay)
In addition to the meosaurus, other dinosaur fossils that appear to be in a sleeping position have been found, and like the meosaurus, their posture is similar to that of modern birds. Such a posture is beneficial for modern birds to conserve body heat while sleeping. These fossil evidences suggest that this sleeping position evolved during the non-avian dinosaur period.
But we haven't solved the question of how sauropods with extra-long necks slept and slept.
Fossil evidence is lacking
The question is a thorny one, and it remains a mystery to this day.
One important reason is that there are too few complete skeleton fossils of sauropods compared to meosaurs.
The first fossil of a meosaurus was only about 50 centimeters long, and this small dinosaur could easily form a complete fossil because a small seasonal flood could have buried them intact. For sauropod dinosaurs, which can be tens of tons in size, a landslide or flash flood of sufficient scale is needed to completely bury their bodies and become fossils, but such events may only occur a few times a decade or a century in a given area.
Patagosaurus fossils at the Field Museum of Natural History in the United States. Patagosaurus is one of the largest sauropods ever recorded, and it is speculated that it could weigh more than 50 tons (Source: By Zissoudisctrucker - Own work, CC BY-SA 4.0)
In addition, sauropods had particularly uneven bones, with thick and strong limbs, but the bones of the spine and head were often fragile. These fragile bones are often destroyed by landslides and flash floods that bury them, which is one of the reasons why their fossilized bones are often incomplete. Therefore, it is not easy to obtain a complete set of sauropod dinosaur fossils, and it is even more of a luxury to expect a fossil to be able to preserve a certain state of their life.
But we can still make some reasonable guesses about how long-necked sauropods slept.
Why is the neck so long
The most important thing to guess about how sauropods slept is to think about how to put their necks, so we need to understand why they have such long necks.
Current research suggests that sauropods had a huge body that required them to consume a lot of food every day, but each time they moved the body, they used a lot of energy. As a result, they have evolved long necks and are able to quickly eat large pieces of food without moving too far away, which is a very energy-efficient lifestyle.
Different sauropod dinosaurs have a large variation in the proportions of each part of the body. Some groups have necks and tails that form an elegant balance, others that are out of proportion, some with majestic front legs longer than hind legs, while others have shoulders low and neck and head close to the ground.
Source: October 2023 issue of Global Science, illustrated by Scott Hartman
But how do they support such a large neck and body without collapsing due to their own weight – the special structure of the neck bones plays a big role in this? When studying Mamenxisaurus, the research team used computed tomography (CT) technology to find that the vertebrae of Mamenxisaurus were very light, and like many sauropods, it was filled with an airsac-like structure, and air accounted for 69%~77% of its volume. There are also some 4-meter-long rib-like bones extending from the vertebrae in the neck of the Mamenxisaurus to increase neck stability.
For sauropod dinosaurs, we might be able to refer a little bit to giraffes. When a giraffe sleeps, it is sometimes standing and sometimes lying down, and the neck is mostly upright as it is awake, although the angle may be slightly lower. Only rarely, (only 3 minutes of 4.6 hours of sleep) will giraffes curl their necks back when sleeping on their backs.
卧着睡觉的长颈鹿(图片来源:SCHWIERIN,1996)
However, the length of the neck of Mamenxisaurus is more than seven times that of a giraffe's neck, which does not fully refer to the sleeping position of giraffes, as do other sauropods. Scientists have analyzed that different sauropod dinosaurs may exhibit completely different neck postures when exercising different behaviors (such as feeding and drinking). So to really figure out how they actually sleep, we don't have a lot of information at the moment. But because of this, we have a little more expectation for the revelation of the mysterious private life of these prehistoric monsters.
Source | Global Science