Tag Archives: Stegosaurus

Tank-like dinosaur fossil discovered in Chile could show how spike-tails became club-tails

Seventy-something million years ago, a dinosaur had the worst day. It got stuck, potentially in a quicksand-type trap, and never made it out. Now, paleontologists working in Chile have uncovered its fossil, which was excellently preserved — and they believe the dinosaur can help us better understand how an important group of dinosaurs evolved and developed in the Cretaceous.

The life appearance and environment of the new species of armoured dinosaur Stegouros elengassen. The image reflects the paleoenvironment of meanders and lake bodies in a deltaic fan at the edge of the old Austral basin, with plant assemblages reconstructed from fossils at nearby levels, typical of this region of Gondwana. Paleoartist credit: Mauricio Álvarez.

Ankylosaurs are a group of armored dinosaurs dating to the very end of the Cretaceous Period, about 68–66 million years ago. They measured up to 6-8 meters (20-26 ft), weighed 8 metric tons, and walked on four limbs. They had a large, robust body and were covered in extremely solid plates that served as a strong defense against predators. The bones in their skull and other parts of the body were fused together, making the entire structure even more solid. But most notably, they had a strong tail club that researchers believe was used to defend both against predators and in combat against other members of its own species. Ankylosaurs were built like a tank, and they could pack quite a punch as well.

We know a lot about ankylosaurs — or at least some of them. They evolved on both Laurasia and Gondwana, the two continents resulting from the break-up of the supercontinent Pangea. But while ankylosaurs from the northern Laurasia are rather well-known, those from Gondwana (which are the earliest group) are poorly understood. This new study could shed new light on them.

An early Ankylosaur

Armored dinosaurs from Gondwana are enigmatic, write the authors of a study describing the fossil from Chile — which is why the new find is so intriguing, said Alexander Vargas, one of the study authors, for ZME Science.

“The new dinosaur is a transitional ankylosaur: an evolutionary link between the typical Ankylosaurs of the northern hemisphere, and older lineages of armored dinosaurs. It is the first good skeleton from South America and the first named species of Ankylosaur for this continent (only unnamed scraps and pieces had been previously discovered) , and it proves that ankylosaurs from the southern hemisphere were radically different from those of the north, having separated from them very early in evolution, and evolving different kinds of tail weaponry.”

3-D model (sculpture) of the life appearance of the new species of armoured dinosaur Stegouros elengassen. Paleoartist credit: Lucas Jaymez. Social media: @dinoesculturas.

The newly-discovered dinosaur was named Stegouros elengassen. It has some of the distinctive skull features characteristics of other ankylosaurs, but the rest of its skeleton is strikingly primitive, showing stegosaur-type characteristics — stegosaurs lived much earlier, going extinct around 100 million years ago.

Stegosaurs also had a weapon-like tail, but unlike the ankylosaurs (whose tail is like a club), the stegosaurs’ tails consisted of spikes. The newly-discovered Stegouros has somewhat of a hybrid tail — it has seven pairs of flattened, bony deposits fused together, which could mark a transition from one group to the other.

The researchers were fortunate to find such a well-preserved fossil, Vargas explained.

“The fossil of Stegouros was preserved with its posterior half (“waist down”) fully articulated and complete, in a deeper position than the anterior half of the animal, which was scattered and missing a few elements. The evidence suggests that the posterior half of the animal was buried quickly at a river bank, while the upper half lay exposed for a while and fell apart before it, too, was buried. It is possible that this dinosaur was stuck in a death trap such as quicksand; its legs were straightened out, which is uncommon (they are folded in most carcasses), and it was also found belly down, unlike carcasses of armoured dinosaurs that have been transported by a river, which tend to be belly up.”

3-D model (sculpture) of the life appearance of the new species of armoured dinosaur Stegouros elengassen. Paleoartist credit: Lucas Jaymez. Social media: @dinoesculturas

However, the digging conditions were very rough, the researcher added in an email. The block of rock containing the fossil was on top of a very steep hill, and at some point, researchers only had five days of work until freezing conditions came. A small team of 5-6 people worked in rough conditions bordering hypothermia and one of them suffered an accident, falling down and breaking his rib.

In the end, though, this hard work and sacrifice bore fruit. In light of these findings, the authors conclude that after Laurasia and Gondwana split up, ankylosaurs on the two different continents also started evolving in different ways. However, the finding also shows just how much we have yet to learn about ankylosaurs, how they emerged and spread at the end of the Cretaceous.

Digital reconstruction of the unique tail weapon of the new species of armoured dinosaur Stegouros elengassen. The tail was encased in pairs of dermal bones; a portion of the dermal bones has been digitally sliced away, to reveal the tail vertebrae within. Different colors signal physically separate bones; many dermal bones have fused into a single unit (liliac). Credit: José Palma and Joao Francisco Botelho.

If you’re curious about what the day of an armored dinosaur in the Cretaceous was like, we asked Vargas just that. Here’s what he said:

“Stegouros lived in a delta that opened in a fluvial fan, like that of the Nile River, with winding rivers and islands between them We have found abundant evidence of Nothofagus forests, such as those found today from central to southern Chile, along with herbaceous vegetation and ferns. It is a typically southern environment from the late Cretaceous and one of the few continental deposits that we have in the entire Southern Hemisphere at this time. Stegouros was a herbivore that may have preferred living near water. It had a tough skin laid with small ossicles and larger osteoderms as well as its impresssive tail weapon so it probably got little trouble from predatory dinosaurs such as small Noasaurids or even large Megaraptorids (tough to chew).”

The research was published in Nature.

10 of the Weirdest Prehistoric Creatures

Eons ago, many millennia before written history, bizarre animals roamed the Earth. The most renowned of these prehistoric creatures were the dinosaurs. Countless films have been made featuring these great reptiles. But during the various epochs of our world’s prehistory there existed many other weird and wonderful beasts. And many of them had names that were even weirder.

You will find some of these to be even more fascinating than dinosaurs. It was in this era before the dominance of mankind that life on Earth underwent a great deal of evolution. And, in fact, the Earth itself, its land masses and oceans, also evolved drastically.


Credit: Wikimedia Commons.

Credit: Wikimedia Commons.

Living in the late Devonian period, Ichthyostega was one of the earliest amphibian-like animals. It had the head and tail of a fish, and it needed to return to the water in order to breed. The feature which differentiated Ichthyostega from lobe-finned fish was the limbs. In Ichthyostega, the fins were jointed, with leg and toe bones. Ichthyostega‘s foot was odd by modern standards. It had eight toes.


Sharovipteryx. Credit: Wikimedia Commons

Scientists believe Sharovipteryx to be an ancestral link to the winged reptiles the pterosaurs. Not classified as a true pterosaur itself, it lived in the early Triassic period over 240 million years ago. It’s in a class of its own. The creature’s remains have been unearthed at the Madygen Formation in Kyrgyzstan, Central Asia. It was a mere one foot in length. It had four appendages which seem to have possessed thin flaps of skin like wings. The two forelimbs were quite short, and the rear limbs were much longer. Some theorize this design enabled Sharovipteryx to jump with ease. Paleontologists believe its mode of transportation was more like gliding than true flying.


Longisquama. Credit: Wikimedia Commons.

Longisquama. Credit: Wikimedia Commons.

This creature was what has been called a diapsid. The diapsids were a reptilian subclass which eventually would evolve into the most important reptile subclass. But it began as a small group of climbing and gliding reptiles. The diapsids lived in forests located on the supercontinent Pangea during the Triassic period. Thus, Pangea was the place Longisquama would have called home.

The skeleton’s most stunning feature is a double row of long scale-like structures running along its back, forming six to eight pairs. It had one pair of scales for each of its pairs of ribs. The scales had a central hollow vein, like bird feathers. But unlike feathers, Longisquama‘s scales seem to have been formed of flat sheets and not genuine plumes. This is the creature featured in this article’s header image.


Illustration of an Aetosaur. Credit: Wikimedia Commons.


Stagonolepis was an aetosaur, sometimes also synonymically referred to as a stagonolepid. The Triassic world was filled with a vast variety of crocodilian species. The aetosaurs were unique among the early crocodiles since they were herbivorous. Unlike modern crocs, they were vegetarians. And Stagonolepis was one of the most prevalent of the stagonolepids at the close of the Triassic. Its long, narrow body was armor-coated, and it was capable of reaching a length of nine feet. Some artist renderings depict a creature which rather resembles a modern armadillo.


Credit: Wikimedia Commons.

Credit: Wikimedia Commons.

The caseids were another group of early reptiles. No reptile living today looked as odd as the Casea. The massive pig-like body, tiny head, overhanging upper jaw with peg-like teeth, and lower jaw with no teeth gave Casea a goofy look. These prehistoric creatures had large ribcages and were capable of reaching four feet long. Their prime occurred in the late Permian period. The term “casea” means “cheesy.”


Nothosaurus. Credit: Wikimedia Commons.

Nothosaurus. Credit: Wikimedia Commons.

Nothosaurs were related to the plesiosaurs but did not always have the best physical capabilities for coping with marine life. These reptiles did not have gills. So they had to come up to the surface for fresh air. Their long necks which would have easily been able to sneak into a school of fish were a big asset when it came to catching their prey.

Nothosaurus is one example of a nothosaur. Others such as Ceresiosaurus, Pachypleurosaurus, and Lariosaurus are also classified as nothosaurs. A good deal of our basic understanding of these marine reptiles comes from Dr. Oliver Rieppel of the Field Museum, Chicago, Illinois. Nothosaurus itself lived in the mid-Triassic, and its name’s meaning is translated as “false lizard.” Scientists have considered two possibilities as to how the animals gave birth to their offspring. The eggs were laid on the sandy shores like modern sea turtles. Or a Nothosaurus would give live birth to its young at sea just as some sharks do today.


3D Model of Stegosaurus

You know, it would be kind of unfair not to include at least one dinosaur in this list. (Although, cinema and literature have almost made them overrated.) What is so special or weird about Stegosaurus apart from the fact that it was a dinosaur? Well, it isn’t really. It is primarily included on this top ten list in order to clear up some misconceptions and mysteries surrounding its public consideration. Dwelling in the prehistoric Americas in the late Jurassic period, Stegosaurus had bony plates along its back and small ossicles covering its throat.

In relation to the creature’s mass, it has the smallest brain of all dinosaurs. Speaking of brains, here is another fun fact which some people still may have never heard. For a time, scientists were throwing out the hypothesis that a certain organ located in the tail of a Stegosaurus was responsible for performing some actions in the dinosaur’s posterior end.

However, the mass of nerves or whatever organ it may have been is no longer considered to have been a true brain. As for its renowned plates, scientists have made several speculations as to their function. They could have been for simple body defense when sparring with its peers or evading predators. They might have been for storing up heat during the day to then “burn up” after the sun went down. Or the plates even could have a means to attract mates.




Artist Rendering of Thylacosmilus


Thylacosmilus obviously has the body style of a saber-toothed tiger. Interestingly enough, the animal also happened to be a marsupial. A marsupial is simply an animal which has a pouch of skin in which to carry its newborn young for a period. Modern marsupials include kangaroos and opossums. Living in the late Tertiary period, Thylacosmilus had strong, long-lived family relationships. Any restoration is far from perfect since a full skeleton has never been found.


Credit: Frontiers of Zoology.

Credit: Frontiers of Zoology.

Considered a pronghorn, Tsaidamotherium lived in the late Tertiary and bears some resemblance to the musk ox of present-day. Its body shape seems related to that of bovines. Tsaidamotherium was a grazing creature like many of its Miocene peers and lived on the Mongolian plains. It possessed one great cylindrical horn ontop its forehead and directly in the center. Another much smaller horn was located directly adjacent to it.

The likely function that its larger horn is supposed to have carried out was perhaps for display to attract a counterpart of the opposite gender. At first glance then, this creature could resemble the description of the mythical beast the unicorn. Dougal Dixon states this same relation in The World Encyclopedia of Dinosaurs and Prehistoric Creatures.


Artist Depiction of Megatherium. Credit: Wikimedia Commons.


As the name implies, this brute was a pretty large mammal. It was actually a giant ground sloth related to modern sloths. An inhabitant of South America during the Quaternary period, an adult standing on its hind legs could reach a height of 20 feet. Megatherium was previously regarded as a slow tree ripper. But recent studies show that its great claws might have been used for stabbing and killing. If this was the purpose of its claws, it would make the giant sloth the largest predator of the South American plains.

FossilFriday: A Magnificently Fossilized Stegosaurus

Image via

Image via Houston Museum of Naturel Science.

This is a fossilized in-ground Stegosaurus currently exposed at the Houston Museum of Natural Science. The Stegosaurus is one of the most easily recognizable species of dinosaurs, living until about 150 million years, and this remarkable fossil does a fantastic job at highlighting it.

Ironically, although many people associate it with the T-Rex, the Stegosaurus is actually much more ancient. T-Rex actually lived until 65 million years ago – closer to humans than the Stegosaurus.

A large, heavily built, herbivorous quadruped, Stegosaurus had a distinctive and unusual posture, with a heavily rounded back, short fore limbs, head held low to the ground, and a stiffened tail held high in the air. Its array of plates and spikes has been the subject of much speculation, and we still don’t know exactly what the purpose of the plates was. The spikes were almost certainly involved in defense, but the plates might have served a defensive purpose, but they might have also been used for thermoregulating purposes or as a mating display. The largest Stegosaurs likely weighed over 5,000 kgs (11000 pounds).