How dinosaurs have changed

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

The very first genus of dinosaurs, Megalosaurus bucklandii, was named in 1824. Now paleontologists describe several new species every month, the freshest of them - Tlatolophus galorum - was described in May 2021. For two centuries of research, scientists not only discovered new types of dinosaurs, but also clarified information about already known ones: new finds appeared, methods of their analysis were improved, and at the same time, paleontologists had new ideas and interpretations. Therefore, our ideas about how these animals looked also changed - sometimes beyond recognition.

There are four main periods of the concept of dinosaurs:

1. Laying the foundations (1820-1890). From many dinosaurs only individual bones are known, they are depicted as similar to lizards or dragons;
2. Classic period (1890-1970). Dinosaurs are portrayed as clumsy heavyweights: kangaroo-like predators with tails dragging along the ground, semi-aquatic herbivores with exorbitantly bloated bodies.
3. Renaissance (1970-2010). It is understood that dinosaurs were mobile, active animals and were closer to birds in metabolism than to reptiles. Therefore, in the images, the tails finally come off the ground, the muscles increase. At the same time, feathers are found in many small (and not so) dinosaurs.
4. Soft tissue revolution (since 2010). New methods of studying soft tissues appeared, and work began on the reconstruction of the color of feathers and other integuments.

Consider how ideas about several famous dinosaurs changed through these eras.

Iguanodon

In 1825, the English paleontologist Gideon Mantell described the iguanodon (Iguanodon bernissartensis) with several teeth very similar to those of an iguana - hence the name. Nine years later, fuller remains were found near Maidstone, including a pelvis and parts of the limbs. On their basis, Mantell performed the following reconstruction:

In 1854, an exhibition of sculptures of ancient animals, including the iguanodon, was opened in London's Crystal Palace. Due to health problems, Mantell was unable to participate in the work on the exhibition, and another English paleontologist, Richard Owen, acted as scientific adviser. Under his leadership, the iguanodon became heavier and began to resemble a hippopotamus:

In 1878, a large burial of almost complete skeletons of iguanodons was found in Belgium, and four years later the skeleton was presented to the public, mounted under the guidance of the Belgian paleontologist Louis Dollot. It became clear that Owen's reconstruction was largely wrong. The iguanodon rose on its hind legs, assuming a kangaroo-like position, and the "horn" turned out to be a thorn on the big toe of its forepaws.

This image lasted for a century, until the 1980s. For example, here is a classic image of an iguanodon:

The revolution in dinosaur research known as the "Dinosaur Renaissance" also affected the iguanodon. Close relatives of the iguanodon were discovered - tenontosaurus, saurolophus, uranosaurus. In the 1980s, British paleontologist David Norman wanted to compare them to the iguanodon … and found that there had been no detailed description of the iguanodon since Dollo, that is, since the late 19th century. In the end, Norman did it himself.

He described in detail the skeleton of a dinosaur and showed that earlier the appearance of the iguanodon was restored incorrectly. The structure of the cervical and sacral spine, tail and forelegs all indicated that the iguanodon held the tail and torso horizontally, resting from time to time on the forelimbs.

This idea of the iguanodon has survived to this day. Therefore, today the iguanodon is represented as follows:

Spinosaurus

The remains of a spinosaurus (Spinosaurus aegyptiacus) were originally found in Africa in 1912, and were described by the German paleontologist Ernst Stromer von Reichenbach in 1915. Then fragments of the lower jaw, several vertebrae and other bones were found. Stromer wrote that in front of him is clearly a "very highly specialized" animal, although there is nothing highly specialized on the reconstruction - he is depicted as a Tyrannosaurus with a crest on its back.

In 1944, during the bombing of Munich, the fossils were destroyed, although the description and sketches of the German paleontologist survived. The Stromer concept lasted until the mid-1980s, when the baryonyx (Baryonyx walkeri), a carnivorous dinosaur, a close relative of the spinosaurus, was described in Great Britain.

Its remains were much better preserved - so much so that fish scales were even found in the stomach area, so that the baryonyx became the first authentically fish-eating dinosaur. Considering the common features of baryonyx and spinosaurus - elongated "crocodile" jaws, tapered teeth without notches, huge claws - Spinosaurus also began to be considered fish-eating. In fact, from a "tyrannosaur with a crest on its back," he turned into a "baryonyx with a crest." This is how we see him in the movie "Jurassic Park 3".

The work of Nizar Ibrahim, published in 2014, was a real revolution in the history of the study of spinosaurus. In it, a new incomplete skeleton of a young spinosaurus was described, including the remains of limbs. It turned out that the hind limbs of the dinosaur were much shorter than previously thought.

This is how a version appeared that Spinosaurus did not just eat fish, but in general led a semi-aquatic lifestyle and actively swam. This was supported by weighted limb bones (to make it easier to dive, the bone marrow cavities in the limb bones were reduced), an elongated body, sensory pits at the ends of the jaws, like in crocodiles, and strongly shortened hind legs with flattened claws.

Paleontologists did not have a spinosaurus tail, so it was reconstructed in a generalized way, by analogy with other carnivorous dinosaurs. But Ibrahim's team continued excavations, found the tail, and in 2020 presented its description, which confirmed the "waterfowl" hypothesis.

It turned out that the vertical (spinous) processes of the tail vertebrae of the spinosaurus were very high, so the tail was high and flat, like a newt or fish. Many land-based carnivorous dinosaurs have tails at the end that are rigid and inactive, like sticks - this helped them maintain balance while running. In Spinosaurus, however, it was very flexible, which made it possible to use it as an oar.

But this is not the end. This year, paleontologists David Hawn and Thomas Holtz released an article in which they questioned whether a predator as large as a spinosaurus could deftly chase fish underwater. They suggested that the spinosaurus looked more like a huge heron or stork: it wandered in shallow water, dipping its muzzle into the water and grabbing a passing fish. So far, no one has objected to them, so today the spinosaurus looks like this:

Therizinosaurus

Therizinosaurus cheloniformis has changed, perhaps more strongly than all the dinosaurs we know. In 1948, its remains were found - huge ungual phalanges and fragments of ribs, and in 1954 they were described by the paleontologist Yevgeny Maleev (1). Therizinosaurus holds the record for the size of claws among all known animals - even an incompletely preserved ungual phalanx is 52 centimeters long, and in fact it was also covered with a horny sheath during its lifetime. Because of its huge claws and strong ribs, Maleev suggested that therizinosaurus was an aquatic turtle-like animal, and cut off algae with its claws. Here's a reconstruction from a 1954 article:

In 1970, another Soviet paleontologist, Anatoly Rozhdestvensky, showed that therizinosaurus was not a relative of turtles, but belonged to theropods, that is, carnivorous dinosaurs (2). But the exact taxonomic affiliation of Therizinosaurus remained unclear until 1993, when Alxasaurus elesitaiensis was described. After him, it became clear that the previously found segnosaurus, erlicosaurus and therizinosaurus are related to each other and belong to the same family. The family was named after the earliest found representative - therizinosaurus.

We still have only the metacarpal bone and ungual phalanges of the forelimbs of Therizinosaurus, as well as several hind bones - the talus, calcaneus, metatarsal bones, several phalanges of the fingers. Even the fragments of the ribs that were initially found are no longer considered to belong to therizinosaurus and are not taken into account in the newest survey works.

The appearance of therizinosaurus was restored by analogy with the closest relatives - the Mongolian alshazavr and the American notronichus. Instead of Maleev's "tortoise", he is now a huge bipedal animal with a short tail, long neck and gigantic claws. Since another of its relatives, the Beipiaosaurus, has plumage, the Therizinosaurus is often depicted with feathers, although their volume varies depending on the artist's imagination. The exact structure of its covers can only be clarified by new finds.

It is possible that when the rest of the skeleton is found, the Therizinosaurus will surprise paleontologists.

Tyrannosaurus

Tyrannosaurus rex is perhaps the most famous dinosaur, the largest land predator of all time. The closest rivals - Spinosaurus and Giganotosaurus - are, according to some estimates, longer than Tyrannosaurus, but weighed less. In addition, this is one of the most studied dinosaurs, it is represented by several dozen specimens, from young to adults, from scattered bones to almost complete skeletons.

Tyrannosaurus was described by the American paleontologist Henry Fairfield Osborne in 1905.

In accordance with the ideas of that time, the dinosaur was depicted as a slow creature with a tail dragging along the ground. This is how he appears in the painting by the artist Charles Knight (note the Tyrannosaurus in the background):

In Western literature, this painting is still considered one of the most famous depictions of Tyrannosaurus rex. She was inspired by the creators of King Kong in 1933, Disney's Fantasy and A Million Years BC.

In fact, for the whole world, Tyrannosaurus Rex was exactly like that until Jurassic Park came out. Not too changed in appearance, the new Rex has become completely different in behavior. It was now a fast, muscular animal. Its tail did not touch the ground, and the tyrannosaurus was running at the speed of a jeep.

Today, it is believed that he could not run so fast - to run at a speed of 40 kilometers per hour and higher, the muscles of the legs of the tyrannosaurus had to occupy up to 86 percent of the body weight. Now its speed is estimated at 18 kilometers per hour. But new research shows that the Tyrannosaurus was a very resilient and efficient walker.

In 2004, an older relative of Tyrannosaurus rex, the Dilong paradoxus, was described, and in 2012, the Yutyrannus huali. Both are famous for being covered with thick, short filamentous feathers, similar to those of an emu. The question immediately arose: what about the tyrannosaurus itself? Is it possible that he also inherited the plumage from his ancestors? Therefore, in 2012-2017, many images of a Tyrannosaurus appeared in the following spirit:

In 2017, an article was published summarizing all the data on the integument of the Tyrannosaurus rex and its relatives. Few skin prints have been found - only a few square centimeters from the pelvis, neck and tail - but nothing similar to feathers has been found.

Stegosaurus

Stegosaurus (Stegosaurus stenops) was first described in 1877. Initially, scientists believed that the plates on his back lay horizontally, like shingles. Hence the name: "Stegosaurus" means "indoor lizard".

It soon became clear that the plates were vertical on the back. The only question was how. There were several options:

• the plates went in one row
• the plates went in two parallel rows
• the plates went in two rows and were slightly offset from each other

The discoverer of the stegosaurus himself, Otniel Charles Marsh, depicted the plates going in one row:

However, with such an arrangement, there would simply not be enough space for the plates. Especially considering that in life they were additionally covered with a horny sheath.

In 1914, Charles Gilmore published an article in which he argued that the stegosaurus' plates were offset from each other. Since then, this arrangement has been generally accepted.

The dinosaur renaissance also affected the stegosaurus: it became more energetic, the tail off the ground. The first and second "Jurassic Parks" are largely outdated, but the stegosaurus in the second film is quite modern.

Surprisingly, in the 2015 film Jurassic World, we again see a stegosaurus with a low-hanging tail, almost dragging along the ground.

In the same 2015, a description of the almost complete skeleton of a stegosaurus was published, which was nicknamed Sophie. Unlike other stegosaurus finds, which were rather fragmentary, Sophie survived 85 percent, which is a lot for a dinosaur. The find made it possible to clarify some of the structural features of the animal. For example, the torso was shorter and the neck was longer than previously thought.

Brontosaurus

The long neck of a brontosaurus (Brontosaurus excelsus) is as famous as the plates of the stegosaurus and the tiny forelegs of the Tyrannosaurus. It was discovered by Othniel Charles Marsh in 1879.

The same Marsh in 1877 described another very similar dinosaur - the Apatosaurus. In fact, the two dinosaurs were so similar that in 1903 another American paleontologist, Elmer Riggs, wrote an article claiming that brontosaurus and apatosaurus are synonyms, that is, in fact, they are the same species. And according to the priority rule, a valid name must be Apatosaurus excelsus.

In this sense, the name Brontosaurus is an example of the divergence between science and popular literature. In 1905, the skeleton of an apatosaurus was installed in the American Museum of Natural History, but the then head of the museum, Henry Fairfield Osborne, decided to write "brontosaurus" on the plaque - and the name went public. As a result, the name "apatosaurus" appeared in scientific publications throughout the entire XX century, but brontosaurus are found in popular science (and not only) books every now and then. For example, it is with them that the heroes of "Plutonia" face.

The history of the name brontosaurus was continued in 2015, when an article was published with a revision of the diplodocid family (to which the apatosaurus belongs). The authors examined 81 species of dinosaurs, 49 of them are diplodocides. And they came to the conclusion that Apatosaurus excelsus is quite different from other apatosaurs to distinguish it not just as a separate species, but in a separate genus, Brontosaurus excelsus. At the same time, two more species of brontosaurs were identified: Brontosaurus parvus and Brontosaurus yahnahpin. So 110 years later, the name "brontosaurus" returned to scientific use.

In addition to the name, ideas about the lifestyle of this animal have also changed. At first, it was believed that Brontosaurus and other sauropods lived in water like hippos. They were supposedly too heavy to walk on land. In 1951, a study came out that showed that a brontosaurus completely submerged in water would not be able to breathe due to excessive water pressure. And a number of studies in the 1970s (for example, Becker's 1971 article) confirmed that brontosaurus, diplodocus and their relatives were completely land animals. The footprints also showed that the tail of the brontosaurus did not trail along the ground.

And the 2004 article finally dispelled the myth about the aquatic brontosaurus. Computer simulations have shown that the bulky air sacs in the body would cause brontosaurs to float to the surface like traffic jams. They were physically unable to stand with all four feet at the bottom of the reservoir, with their bodies completely submerged in the water.

Deinonychus

The remains of a Deinonychus antirrhopus were found during excavations carried out by Yale University in 1964. More than 1,000 scattered bones have been found from at least three individuals. In 1969, they were described by paleontologist John Ostrom. The bones clearly belonged to an active dexterous predator, and it was after the discovery of deinonychus that scientists gradually began to change the idea of dinosaurs. They gradually ceased to be considered sluggish, clumsy animals, and began to be presented as active, agile, with a fast metabolism.

Today this transition is known as the “dinosaur renaissance”. In 1974, Ostrom wrote a monograph in which he described in more detail the similarity of Deinonychus with birds and "resurrected" the theory, which had been discarded by that time, that birds descended from dinosaurs.

Below is a work by Robert Becker, which served as an illustration for the 1969 article. The skull on Deinonychus had not yet been found at that time, therefore the proportions of the head are averaged, "allosaurus". The position of the front paws is also incorrect: in fact, the hands should have looked at each other, as if a lizard was clapping its hands. Deinonychus does not look like a bird here, but it is clearly an active animal.

Ostrom and Becker's ideas were supported by another scientist, Gregory Paul. In his 1988 popular science book Carnivorous Dinosaurs of the World, he developed the idea that dinosaurs were active and fast animals. Paul is a "unifier", that is, when classifying dinosaurs, he likes to group many species into the same genus.

In his opinion, deinonychus is so similar to another carnivorous dinosaur, the Velociraptor, that they should be placed in the same genus Velociraptor. Therefore, in his book, instead of Deinonychus antirrhopus, Velociraptor antirrhopus appears. Under this name, he entered the book, and then the film "Jurassic Park".

However, the cinematic animal turned out to be much larger than its real prototypes: the real Deinonychus was about 3.4 meters in length, and the Velociraptor was 1.5 meters at all. Today, of the found dromaeosaurids (the group to which both the Velociraptor and the Deinonychus belong), the yutaraptor is the closest in size to the cinematic "raptors".

But the main difference between velociraptors from "Park …" and especially "Jurassic World" from real dinosaurs is that they do not have feathers. The first prints of feathers were found back in the 1990s. Since then, feathers of one kind or another have been found on many dinosaurs, including the Velociraptor. Rather, not the feathers themselves were found on him, but special tubercles on the ulna, which correspond to the places of attachment of the feathers.

Neither feathers nor tubercles that speak of them have been found in the Deinonychus himself, but given its resemblance to a Velociraptor, it is logical to assume that he was feathered. Therefore, today it is believed that Deinonychus looked something like this:

Psittacosaurus

Psittacosaurus mongoliensis was discovered in 1923 in Mongolia. Since then, more than 75 specimens have been found, including about 20 complete skeletons with skulls. In addition, individuals of all ages were found, from pups to adults. Therefore, Psittacosaurus has been studied very well. As a result, he holds the record for the number of different species: up to 12 species are distinguished in the genus Psittacosaurus. By comparison, the vast majority of dinosaur genera include exactly one species.

Due to good knowledge, the appearance of the psittacosaur has not changed too much.

Compare:

However, even the most seemingly well-studied dinosaur can throw surprises. In 2016, an article was published describing a specimen of psittacosaurus from the Senckenberg Museum in Frankfurt am Main. So far, it has not been assigned to a specific species, although it is listed on the museum plate as Psittacosaurus mongoliensis.

The fossil was exceptionally well preserved, which made it possible to study the soft tissues of the animal. It turned out that the ankle of the psittacosaur was connected to the tail by a leathery membrane - patagium. On the tail of the animal, a row of hollow bristles was found, and they did not extend along the entire length of the tail. This immediately raised a lot of questions. Are the bristles on the tail a "primitive" trait that the Psittacosaurus inherited from its ancestors? And if so, then perhaps all ceratopsians, including the protoceratops and the famous Triceratops, had similar bristles? On the other hand, it is possible that only the genus Psittacosaurus had setae, or even only this particular species of psittacosaurus.

Finally, this specimen retained the remains of cellular organelles - melanosomes, which contained pigments. The pigments themselves were not preserved, but the shape of the melanosomes, as it turned out, is associated with the color of the pigments. Therefore, the reconstruction of the psittacosaurus shown below is as close to reality as possible without a time machine.