Plateosaurus

About Plateosaurus

Adaptation to Gigantism and Flexible Growth

Plateosaurus was a basal (early) sauropodomorph that lived in the Late Triassic. Although small compared to the super-giant sauropods of the Jurassic and later, it boasted an astonishing size (up to 4 tons in weight) for a land animal of the Late Triassic. It is characterized by a plump, massive torso and a long neck.

The secret to being able to move actively despite its huge body was that it had an efficient respiratory system similar to that of birds. We know that there were cavities inside the bones of their necks and backs, into which sac-like organs called "air sacs" connected to the lungs penetrated. This allowed them to efficiently take in oxygen through a mechanism where air always flows in one direction, while lightening the bones.

An interesting characteristic of Plateosaurus is that there are extreme individual differences in size even among adults. There was extreme variation in size, from small individuals of 4.8 meters in length to huge individuals exceeding 10 meters. It is thought that this is because they had a unique ability called "developmental plasticity," which allowed them to flexibly change the timing of when they stopped growing depending on the environment and abundance of food.

Evolutionary Dynamism Prompted by Bipedalism and Morphological Constraints

Plateosaurus lived a completely bipedal lifestyle.
In the past, it was thought that "they usually walked on four legs and stood up on two legs only when eating leaves from high trees" (they were sometimes depicted like that on stamps as shown below). However, recent analysis using skeletal modeling has revealed that Plateosaurus was physically unsuited for quadrupedal walking.
As a result of analyzing the joint structure of the forelimb bones (radius and ulna), it was found that the movement of pointing the palms toward the ground, called "pronation," was impossible.

Because of this, it was concluded that Plateosaurus was a "bipedal animal" that walked only on its hind legs. The forelimbs, which were not used for walking, had large curved claws, which are thought to have been used as "grasping organs" to firmly pull branches of plants closer, and as powerful weapons to protect themselves from carnivorous dinosaurs.

The super-giant sauropods like Brachiosaurus that appeared in the later era (Jurassic) were all quadrupedal, but they achieved evolution by rebuilding the structure of their arms in order to regain this once-lost "ability to point their hands toward the ground."

Collapse of the Gastrolith Hypothesis and Digestive Mechanism

Recent research has shown that despite its huge body, Plateosaurus had a very small head and weak jaw strength. The teeth were broad and leaf-shaped (with serrations on the edges), and instead of grinding (chewing) plants in its mouth, it plucked them from branches and swallowed them mostly whole.

Then, how did it digest the large amount of plants it swallowed whole?
For a long time, it was widely believed in the paleontology community that "like the gizzard of a bird, Plateosaurus intentionally swallowed a large amount of stones (gastroliths) and rubbed the stones together in its stomach to grind up plants and aid digestion."

However, a detailed examination of fossil groups of hundreds of individuals discovered in Europe revealed that there is not a single specimen with definite gastroliths (bio-gastroliths) stored for digestion. If they routinely had gastroliths, a large amount of stones should emerge from the stomach area that became fossilized, but since there were none, the long-standing gastrolith hypothesis was called into question.

Currently, it is thought that Plateosaurus housed an extremely long intestine inside its huge, heavy, barrel-shaped torso, where it digested plants.

Herd Life and the "Mud-miring Trap"

In a wide area of Europe (Germany, France, Switzerland, etc.), Plateosaurus fossils have been found in a dense state called a "bonebed" with over 50 individuals. It is thought that they formed herds and migrated across the plains.

In the past, flash floods or mass deaths due to droughts were suspected as the reason why such a large amount of fossils were found in the same place. However, currently, the "Mud-miring trap" theory is the most likely.

During the rainy season, some parts of the plains became dangerous places where the surface looked dry but underground was fluid mud. When an adult Plateosaurus weighing several tons walked there, its massive weight concentrated on its two legs, and it sank deeply into the mud. Being bipedal, it couldn't crawl up with its front legs, so it got stuck and became a fossil.
The fact that many of the fossils found in bonebeds are "adult individuals" is explained by the fact that children (juveniles), who were lighter in weight, were able to escape without sinking into the mud.

Genus Description Prior to "Dinosaur" and Taxonomic Reorganization

Plateosaurus was first discovered in 1834 near Nuremberg, Germany. Three years later, in 1837, the German paleontologist Hermann von Meyer named it a new genus, Plateosaurus (Plateosaurus engelhardti).

Because the British paleontologist Richard Owen proposed the word and classification "Dinosauria" in 1842, Plateosaurus is an animal that was named 5 years before the concept of dinosaurs was born.

After that, too many fossils were discovered all over Europe, so 29 different names (synonyms) were given based on only slight differences, causing confusion in the classification.
Furthermore, the fossil that was first used as the standard (holotype) in 1837 was fragmentary and lacked the features to distinguish it from other dinosaurs. Therefore, in 2019 (about 180 years after the definition of the first holotype), the International Commission on Zoological Nomenclature (ICZN) newly recognized a perfect full skeleton—a specimen from Germany—as the standard (neotype), and the representative species name of Plateosaurus was redefined as "Plateosaurus trossingensis".

Dinosaur Fossil Found in the Deepest Place in the World

The most surprising discovery about Plateosaurus did not come from land, but from the bottom of the sea.

In 1997, a drill excavating the seabed to search for oil in the "Snorre oil field" in the North Sea off the coast of Norway pulled up a cylindrical rock (core) from a depth of 2,256 meters below the seabed. Smashed bone fragments were buried in it.

As a result of examining the bone tissue closely under a microscope, it was proven to be a Plateosaurus bone. This is the "deepest dinosaur fossil in the world" certified by Guinness World Records.
A drill with a diameter of only about 10 centimeters pinpointed and hit a dinosaur bone more than 2,000 meters deep underground. This miraculous discovery also proved that the North Sea, which is currently a deep sea, was land where Plateosaurus roamed during the Late Triassic.

Plateosaurus Stamp and Fossil Gallery