⊛ Avimimus – Resumenea

What is an Avimimus?

Avimimus was an oviraptosaurus theropod dinosaur that lived in Asia about 70 million years ago.. It had marked characteristics that relate it to the birds we know today.

It is known to have lived at the same time as sauropods and ornithomimids on the Mongolian plains. What is known about it is from a practically complete skeleton of a theropod, with a great resemblance to that of a bird.

His skull was quite fragmented, but the rest of the pieces were in very good condition. This made it possible to observe that he had a thin and long neck, a short skull with a toothless beak, which in itself was quite large.

His legs were long and thin, which makes it possible that he was a very skilled runner, with muscular legs that allowed him to run at high speed. His forelimbs were relatively short and had not yet grown into wings.

In any case, they had a light build, in addition to showing sharp and curved claws. Added to this is the fact that he could cross his arms against his body, just as birds can do with their own wings.

What differentiated it from birds was that it had a long, bony tail. As usual with oviraptors, it had feathers. Her ilium was horizontal, which was the base of her rather wide hips.

Avimimus discovery

Paleontologist Sergei Kurzanov was the one who discovered and described it in 1981. He initially referred to it as a find from the Djadokta Formation.

In 2006, in describing a new specimen, Watabe and a group of collaborators determined that he had made a mistake regarding these fossils. It is possible that Avimimus originated in the Nemeqt Formation, based on the fact that the skeleton did not have a tail.

This made Kurzanov assume that he did not possess it. However, the vertebrae showed the opposite.

Another specimen of Avimimus was found in 1996 and was described by Watabe in 2000. They also identified some small theropod footprints near the site, which could be Avimimus.

Another important find was a bed of bones, discovered in 2008 by a team of Mongolian, Canadian and American paleontologists, under the direction of Philip Currie.. It was located in the Nemeqt Formation about 10.5 meters above the Barun Goyot Formation in the Gobi Desert.

There they found the fossil remains of at least 10 Avimimus. Although it is believed that there were possibly more at the site. They were adult or subadult specimens, with little body variation. This would indicate that he was sociable and lived in small groups.

What does Avimimus mean?

The name Avimimus comes from the Latin terms avis What does it mean bird and mimus which translates as mock. The epithet portentosus means unusual. Therefore his name is translated as unusual bird imitator.

The Oviraptosauria family

The Avimimus integrates the Oviraptosauria, within the theropods. The name of this group means lizards that steal eggsand had both avian and maniptorid characteristics.

They came from a disappeared lineage of coelurosaurids from the Cretaceous period, which lived in Asia and North America. They had an unusual appearance and characteristics very similar to birds. This made it a topic that aroused much interest in the scientific community, when it was discovered by a team from the American Museum of Natural History, on an expedition to Central Asia, at the beginning of the 20th century.

There were later discoveries that further improved knowledge of this group, as they revealed the origin of the birds we know today.. They also shed new insight into special traits that distinguish them among living vertebrates, such as the ability to fly.

The resemblance between oviraptors and modern birds includes such particular characteristics as the lack of teeth, the pneumatization of its structure, the ornamentation of the skull, an unusual sliding jaw joint, the reduction of caudal vertebrae that formed a pygostylefeathers similar to modern ones and the same reproduction.

They mostly included small animals that did not exceed 3 meters in length. The largest of all was the Gigantoraptor, which had an exceptional length of 8 meters, with a volume of up to 1.5 tons.

The first oviraptorids appeared at the end of the Cretaceous, and are thought to have been largely omnivorous. They had a skull with a particular structure, short snouts and teeth deep in their mouth.

Specimens such as Rinchenia, Citipati and Oviraptor had a horny crest on the upper part of their skull, similar to that of cassowaries that exist today. They lacked teeth in their jaw, which makes it a little difficult to fully understand their eating habits. Although it is generally considered that they were omnivores.

This claim is based on the fact that a lizard was found in the stomach of an Oviraptor and two skulls of baby Troodon in a Citipati.

The Oviraptosauria had thin feathers, considering the fossil evidence that was detected in specimens such as Cauidipteryx. They also had a pygostyle or rump that can be seen in some birds and theropods, instead of a long, bony tail.

Avimimus Features

Fortunately, there is a good fossil record of Avimimus. Its resemblance to birds has allowed us to learn more about the evolution that various species have experienced on our planet. Keep reading to find out about this specimen.

Classification

From its beginnings, it was suggested that this dinosaur could be a close relative to birds, due to characteristics that had not been detected in other specimens until that day. Kurzanov claimed that Avimimus would actually be the most direct ancestor of birds and not Archeopteryx.

But this hypothesis did not obtain the necessary support from the taxonomic analyzes that were carried out later. Specialists generally think that it was part of primitive specimens, which were the Oviraptosauria.

Finally in 1981 Kurzanov placed Avimimus in its own family called Avimimidae. Sankar in 1991 created the order Avimimiformes to place Avimimus in it.. However, none of these names are used by paleontologists today.

Most agree that Avimimus ranks best among the Oviraptoridea, within the Elmisaurinae.

Habitat

The place where they found the remains of Avimimus was different at the time when this species existed. The long, clawed fingers on the legs of Avimimus are indicative that it lived in a humid, swampy, and wooded region.

Evidence also indicates that it lived in flocks. In fact, gregarious animals tend to gather around water, such as in ponds.

Feeding

Avimimus has been successively classified as herbivore, insectivore and omnivore. Researchers have not been able to deduce much about their diet based on fossil remains.

They have done so based on what they know of other records of Oviraptosaurus found in Mongolia, which also looked quite similar to birds. That is why it is thought that it would be consistent for it to have an omnivorous diet.

It had a toothless beak that would have been used to ingest different kinds of food.. Kurzanov, when he first described it, speculated that the top of its beak had a serrated edge, opening up the possibility of it eating insects.

This would also have served to tear up the vegetation. Although the possibility that it stole eggs from other animals is also considered. For some reason he is considered within the group of egg thieves.

Motion

With a structure comparable to that of the modern roadrunner, it is virtually certain that Avimimus could run fast and for a long time. Its legs were very long and thin.

The proportions of the thigh bones are also indicative that he was fast. The skeletons show that the shin bones were proportionally longer than the thighs, which is the same as modern ratites, which go at high speed much of the time.

Muscular scars were also found on the bones of his legs, which were indicative that he was a specialized runner. It is estimated that he could reach speeds of up to 69 kilometers per hour.

About your flight

Kurzanov speculated that the Avimimus could display weak flight. This was because feathers had not been found in other specimens, although their protuberances had been found.

The bones in his hand were fused like those of modern birds, and he interpreted that a ridge on the forearm bone had feathers attached to it.. In the same way, he indicated that the joints of the skeletons were like those of birds.

However, other evidence indicated that the wings were too short to maintain flight. That’s why he called it a cursorial bipedal theropod and compared its ability to fly to that of a chicken. He would have employed only occasional weak flight to hunt or flee danger.

In any case, paleontologists currently do not believe that it could fly in any way, even if its morphological characteristics seem to indicate that it was adapted to glide until reaching the ground.

About its feathers and tail

Although specialists disagree with Kurzanov regarding flight, they all believe that he did have feathers. It is possible that they protected them from changes in temperatures, that they served to display themselves in the mating rite, or both.

However, it was shown that it did have a tail. In the first description there was no evidence of this, but in subsequent investigations, it was found that it had one of reduced length.

When did Avimimus become extinct?

The strata in which the remains of Avimimus were found were dated between 85 and 70 million years ago. This places it in an advanced stage of the Cretaceous period.