II➤ Ouranosaurus – Resumenea

What is an Ouranosaurus?

Ouranosaurus was a herbivorous dinosaur that lived in the mid-Cretaceous period about 110 million years ago.. It was closely related to Iguanodon. It was characterized by having long spines on its back that formed elongated spinous processes on its column.

Initially it was thought that these would be covered by flaps of skin, which would form something similar to a sail. However, later research indicated that these spinous processes possibly had strong muscle tissues that supported them.

In the same way that happened with the Iguanodon, the Ouranosaurus also had a spine on the thumb of each hand, although smaller in size. Its head had an elongated snout and in the posterior area, in front of its eyes, it contained a small bony prominence.

Being a hadrosaur, it had a Duck beak with a flat mouth that ended with a tip similar to a beak, as is usually the case with these species.

Finding of the Ouranosaurus

French paleontologist Philippe Taquet led five expeditions between 1965 and 1972 in the Gaudoufaoua region of the Sahara Desert in Niger. The excavations were carried out in the Elrhaz formation that formed during the Early Cretaceous.

The first important discovery occurred in 1965 when 8 iguanodonts were found in the level of Innocents near the Emechedoui wells. Added to this were two other skeletons southeast of Elrhaz in Camp des deux Arbres.

These were obtained in 1996, obtaining a practically complete but dispersed skeleton and another of which approximately two thirds were recovered. The specimens found in 1967 were transferred to the Museum of Natural History in Paris. They were described in 1999 and named Lurdusaurus areatus.

There were no finds of iguanodontids during the third expedition, but in the fourth, which was carried out in 1970, they found a fairly complete skeleton devoid of the skull. After collection it became part of the National Museum of Natural History of France.

Later, in a collaboration between specialists from Italy and France led by Taquet together with the Italian paleontologist Giancarlo Ligabue, one more iguanodontid was found. This was donated to the Venice City Council, which in 1975 became part of the city’s Natural History Museum.

Taquet described two mostly complete specimens that were recovered in the first and fourth excavations. He gave them the name Ouranosaurus nigeriensis. The fossil remains included a skull with some articulation without the left jaw. Its forelimbs had some hand bones and it also had a large part of its hind limbs.

The specimen was returned to Niger and is today displayed in the National Museum of Boubou Hama in Niamey.

What does Ouranosaurus mean?

The term Ouranosaurus has roots in Arabic, a language in which it means recklessness, courage either courage. This meaning is similar for the tuareg, a language spoken locally in Niger and is a way of referring to the monitor lizard in the desert. The epithet is related to the Niger, which was where this species was discovered.

The suborder Iguanodontia

Ouranosaurus was part of the suborder Iguanodontia, which means iguana teeth. In turn, this was part of the ornithischians taxon and its diet was herbivorous. They lived between the middle Jurassic and the end of the Cretaceous. It included specimens such as Camptosaruus, Iguanodon and T.enontosaurus.

This group was the first to be discovered and described in the history of paleontology. Along with the hadrosaurs, they are the best known. They had an elongated skull that widened and flattened at the sides.

This family is made up of two groups whose main difference lies in body size. On the one hand there were the small iguanodontids that were mostly bipedal.

On the other hand were the large specimens such as Muttaburrasaurus which had dimensions of up to 15 m in length, which could weigh up to 8 tons.

Iguanodontids were quadrupedal and in some cases had a long spine on the thumb. Their skulls boasted a robust and thin structure, in most cases with a flattened snout.

This jaw had rows of teeth useful for chewing food, something that was common in evolved hadrosaurs.

The definition of this group came from Paul Sereno in 1998, who indicated it as a clade of which they are part Parasaurlophus walkeri but that does not include Hypsilophodon foxii. In 2005 this changed to add to the Thescelosaurus as a secondary external specifier, in the same way as Hyssilophodon.

Later in 2017 with the discovery of the Burianosaurus In the Czech Republic, it was indicated that the Iguanodon bernissartensis should be part of the group. In this way, the 2005 definition could cover more than what is understood.

It was therefore proposed as the last common ancestor of Iguanodon bernissartensis, Dryosaurus altus, Rhabdodon priscus and Tenontosaurus tilletti.

Similarities and differences with Iguanodon

Although it is considered within the Iguanodontidea family, many specialists consider that Ouranosaurus is actually a basal hadrosaur. This does not eliminate the fact that it has peculiarities that bring it closer to the iguanodon, worth noting.

To begin with there was the forelimb. In its hands, Ouranosaurus had five digits, of which the central three were the strongest, meaning it would better support its weight when it was not perched on its four legs. The inner digit consisted of just a thumb and the outer digit was more flexible.

The forelimbs were a little more than half the length of the hindlimbs. In this way they were shorter than those of Iguanodon. Likewise, not only was the tip of the thumb smaller, but the outer finger was reduced and underdeveloped.

It is thought that in the Iguanodon this fifth finger was prehensile and was used to wrap and knock down vegetation so that a greater amount of food could be obtained.

In Ouranosaurus it was not as flexible, and although it could be used it did not have the same capacity as in iguanodonts.

At first the lack of an adaptation that would have allowed it to eat easily seems intriguing. However, this is explained when it is pointed out that Ouranosaurus lived in lowlands, such as river deltas. The vegetation here was not very tall, even with its fast-growing reeds. In this area the food was actually close to the ground.

This would have kept Ouranosaurus standing on its four legs for the most part. We must also not forget that his limbs were short. This would reduce the distance between the food and your mouth when feeding.

In the same way, the fact that it fed on low vegetation meant that Ouranosaurus did not have to pull the leaves to consume them, which in its evolution meant that the fifth finger was not too flexible.

As a consequence, the pressure on the ground of the forelimbs would have been reduced, due to those moments when he walked on a ground flooded with water. This is why it is suggested that it was not a navigator like Iguanodon. On the contrary, it was a low browsing animal.

Characteristics of Ouranosaurus

To date, the only species described is the Ouranosaurus nigeriensis, which has been studied by paleontology specialists. The following are its main peculiarities.

Classification

The Ouranosaurus is a dinosaur a little more evolved than the Iguanodontia. It is an Ornithischian of the suborder Ornithopoda, which in turn is found in the suborder Iguanodontia. It is part of the Iguanodontidae family.

Feeding

Ouranosaurus was a herbivore that ate plants in its environment, using its beak and thumb to obtain plant matter. With its sharp teeth it could cut and grind hard, high-density material.

It had a flat beak, larger than the one Iguanodon had. The intermediate area had some solid teeth, which could be used for massive chewing of vegetables, which it processed after having torn them off with its beak.

His cheeks were of considerable size. They allowed him to chew his food without experiencing losses and made it easier for him to eat..

Habitat

Although its remains were found in the Sahara, Ouranosaurus lived in that area in the Cretaceous period. Therefore, the place had wide rivers and abundant, tropical foliage. It lived with species such as Elrhazosaurus and Lurdusaurus.

Beak, teeth and skull

The wide beak that Ouranosaurus had is indicative that it was on its way to being a hadrosaurid. It was made of keratin, making it perfect for pulling up soft, leafy plants that grew at the edges of water beds.

Its wide edge would have allowed it to pull up small grasses at the same time. Two-fifths of the way down the beak the teeth began. There was a space without teeth between the end of the teeth and the beak, which was called a diastema.

These were arranged in rows for those small spaces between them, from where replacement teeth appeared, with which the spaces were filled. In this way the line of teeth was constant.

This suggests that some of the plant matter Ouranosaurus ate was hard, including stems and roots. It could also have fed on harder vegetables, when it could not consume soft vegetation.

It is possible that what he consumed had certain limits. His jaws lacked strong muscle attachments, something that suggested his bite force was very weak. Herbivores did not have a very high bite unless they were especially adapted to eating tough plant fiber. That’s why you would probably be predisposed to eating rather soft vegetation.

Their teeth may have even slightly crushed the surface of the plant material, so that digestive enzymes could more easily extract the nutrients. They were high on his snout, so they wouldn’t get blocked by mud and dirt while he ate.

Possible predators

It is not an exaggeration to think that Ouranosaurus, especially the juveniles, were eventually attacked by the spinosaurid Suchomimus, although they were more likely to eat fish.

Juvenile iguanodon bones were found in the remains of a baryonyx, which supports this theory. Spinosaurids were found in river deltas, which also appear to have been where Ouranosaurus lived, increasing the possibility that it was predated by them. The Carcharodontosaurus was also a potential threat. Ouranosaurus also coexisted with giant crocodiles like Sarcosuchus.

neural spines

It is known that Ouranosaurus had neural spines in…