Everyone has seen giraffes, but have you heard of the "long-necked dinosaur"?

Although the Mesozoic Era is called the "Age of Dinosaurs", it was not dinosaurs that actually ruled the oceans, but rather marine reptiles such as thalassosaurs, ichthyosaurs, mosasaurs, pygmysaurids and finned sauropods.

Among the finned dinosaurs, the most successful were the plesiosaurs (Plesiosauria), and the most classic image of the plesiosaur was the Elasmosaurus .

Restoration of the Slice Dragon (drawn by D.Bogdanov)

Mysterious figure in the ancient ocean

Today, Kansas is a vast high plain with countless farms, known as the "breadbasket" of the United States. However, 80 million years ago in the Late Cretaceous, it was a completely different scene.

At that time, the eastern and western parts of North America belonged to Laramidia and Appalachia, and Kansas was located on the Western Interior Seaway that separated the two.

In this mysterious and disappeared sea, a thrilling chase is taking place. A large group of Enchodus are fleeing in panic, and several dolphin-sized Dolichorhynchops are chasing them by flapping their large and long flippers.

Suddenly, a spear-toothed fish that had just escaped from the "jaws and teeth" of a long-beaked dragon was swallowed by a huge mouth that appeared out of nowhere. Then, the spear-toothed fish school was attacked again and again, suffering heavy losses. These elusive hunters were lamellae, and their 7-meter-long necks flexibly shuttled among the fish schools.

At this moment, the situation suddenly changed. The long-beaked dinosaur that was chasing the school of spear-toothed fish began to flee in all directions. It turned out that the overlord of the Cretaceous ocean - Mosasaurus appeared.

The Longicorn was one of the fastest marine reptiles in the ocean at that time. Without an ambush, the Mosasaur could not catch up with it, so it turned its attention to the group of Lacerosaurs.

Although lone young elasmosaurus would sometimes be attacked by mosasaurs and sharks, adult elasmosaurus were able to protect themselves with their huge size and the power of the group.

The group of lamellae quickly protected the young dragons behind them, leaving the mosasaur no chance to attack. Seeing that the other "dragon" was more numerous and not too hungry, the mosasaur wisely swam away. The lamellae that escaped continued to enjoy their feast.

The fuse of the "fossil war"

In the late 19th century, there were two famous paleontologists in the United States - OC Marsh and ED Cope. The competition between them was so fierce that the famous "Fossil War" in scientific history broke out. The fuse of the "Fossil War" was the Sphenosaur.

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In 1867, a military doctor at Fort Wallace, Kansas, found some fossils in the wilderness. These fossils were handed over to Cope after many twists and turns. After identification, Cope found that these fossils belonged to plesiosaurs, and then asked the soldiers at Fort Wallace to collect the whole fossil.

In 1869, Cope named the fossil Elasmosaurus platyurus and proposed that it was very different from previously discovered plesiosaurs - it had a long tail and a short neck.

Restoration of the skeleton of a dinosaur with the wrong head and tail (cited from Cope 1896)

However, Cope's mentor, J. Leidy, pointed out that Cope had mixed up the cervical and caudal vertebrae of the Sphenosaur. Knowing that he had made a fool of himself, Cope was anxious to retrieve all the papers. But Marsh, who had been secretly competing with Cope, deliberately kept the paper and publicized Cope's mistake. As a result, the two broke up completely.

After that, the two men and their fossil hunters used the Midwest of the United States as a battlefield and launched a "fossil war" that had a profound impact on later paleontology.

The Secret of More Than Seventy Cervical Vertebrae

When talking about plesiosaurs, everyone may think of their long necks, but in fact, plesiosaurs also have short-necked types: such as the Pleistosauridae, Pliosauridae, Glechosauridae and Dimopodiospondylidae. It should be noted that the short-necked plesiosaurs actually originated from different ancestors.

There are also long-necked types: such as plesiosaurs, Microsauridae, Cryptosauridae and Elasmosauridae. The neck length of Elasmosaurus and its Elasmosauridae is particularly prominent even among the long-necked plesiosaurs.

The total length of the elasmosaurus is about 12 meters, of which the neck length accounts for 7 meters. Most mammals only have 7 cervical vertebrae, even giraffes are no exception.

Sauropod dinosaurs with very long necks generally had only 12 to 19 cervical vertebrae; and the long-necked "Protorosauria" (Dinocephalosaurus), which was regarded as an "engineering nightmare", had only 27 cervical vertebrae.

However, Elasmosaurus actually has 72 cervical vertebrae, and Albertonectes, which also belongs to the Elasmosauridae family, even has as many as 76 cervical vertebrae! This is the largest number of cervical vertebrae among known vertebrates.

Skeleton model of the Elasmosaurus at the CCID of the University of Alberta, Canada (Photo by IQRemix on Wikipedia)

Paleontologists agree that the long neck of the Sphenodon helped it to hunt prey, but there is controversy over the mobility and range of its neck, which naturally affects the restoration of the Sphenodon's predatory behavior.

In the past, many paleontologists believed that the long neck of the Slippery Dragon was very flexible, and could even reach out of the water to prey on pterosaurs and seabirds in the air. Later, some people pointed out that the neck of the Slippery Dragon was very stiff and could not move freely.

An early reconstruction of the Scutellaria sphenodon (by CRKnight)

Most paleontologists now believe that although the neck of the Slippery Dragon could not be lifted out of the water, it still had a certain degree of flexibility. The Slippery Dragon could follow the school of fish, use its long neck to put its tiny head into the school of fish, and carry out predation activities without anyone noticing.

Fly underwater? Eat rocks?

Compared to its long neck, the head of the Sliposaurus is very small, slender and triangular. The number of teeth is not large, with 20 teeth in the upper jaw (6 in the premaxilla and 14 in the maxilla), and only 17 to 19 teeth in the lower jaw (dentary). The teeth in the front are larger, then gradually become smaller towards the back, and the upper and lower jaw teeth interlock with each other.

The teeth of the Sliposaurus are typical of marine reptiles, with elongated crowns, round cross-sections, and many longitudinal ridges on the crown surface. Such teeth help penetrate the body of slippery fish or cephalopods, preventing prey from easily escaping.

Although the elasmosaurus fed on marine animals such as fish and cephalopods, people have found many pebbles in the abdominal cavity of their fossils , which paleontologists call "gastroliths."

The gastroliths were not produced in the body of the lamelliosaur, but were swallowed by them consciously. Although some modern reptiles and birds also swallow sand and gravel to help digestion, there are different opinions on why the lamelliosaur swallowed pebbles. Some people think that it was to help digestion like modern animals, while others think that it was to help it maintain its body balance in the water.

Gastrolith of Elasmosaurus (cited from Williston 1914)

"Pisuke" in "Doraemon: Nobita's Dinosaur" is a Futabasaurussuzukii, which belongs to the same plesiosaur family as the Scaphosaurus.

Although in the animation "Pizu" was hatched from an egg by Nobita, in reality, plesiosaurs do not lay eggs, but directly give birth to young.

The Shuangye Suzukisaurus to which "Pizhu" belongs is a close relative of the Laminosaurus

Paleontologists have discovered that there are small skeletons in the abdominal cavity of a Keichousaurus specimen that is very similar to the ancestor of plesiosaurs. These skeletons are very complete and show no signs of digestion, indicating that they were not swallowed. This proves that the pterygian species to which plesiosaurs belong would give birth directly to their young.

In addition, paleontologists have discovered a large fetal skeleton in the fossils of the plesiosaur Polycotylus, indicating that plesiosaurs would give birth to larger and fewer offspring.

Therefore, plesiosaurs such as Elasmosaurus ensure the continuation of the population by increasing the survival rate of their offspring rather than producing a large number of offspring. This type of strategy is called the "K reproductive strategy."

Comparison of the size of the mother and fetus of Dimopodius (cited from O'Keefeet Chiappe 2011)

Unlike ichthyosaurs and mosasaurs that swam by swinging their bodies, plesiosaurs such as Elasmosaurus mainly relied on strong flippers to paddle to propel themselves forward in the water. In order to facilitate this special mode of movement, their shoulder girdle and waist girdle became flat and moved to the ventral side of the body.

By comparing them with modern aquatic quadrupeds, paleontologists believe that the flippers of plesiosaurs moved in an "underwater flight" manner, that is, the limbs moved vertically to the direction of travel.

Among animals that also use "underwater flight" as a method of movement, plesiosaurs and turtles are most similar. Unlike turtles, which mainly rely on their front flippers to move, plesiosaurs also have well-developed hind flippers, so their methods of movement are not exactly the same.

Author: Zhao Yue

Editor: Dong Xiaoxian

Reviewer: Zhang Chao, Li Peiyuan