|Name Meaning||Dense forest lizard||Height||2.5 meters (8.2 feet)|
|Pronunciation||Pik-no-ne-mo-sore-us||Length||8.9 meters (29.2 feet)|
|Era||Mesozoic – Late Cretaceous||Weight||3.6 tons (7,900 lbs)|
|Classification||Dinosauria, Saurischia, & Theropoda||Location||Brazil (South America)|
Meat-eating dinosaurs are known to have very small forearms.
But one abelisaurid dinosaur takes the cake when it comes to dinosaurs with small arms.
The Pycnonemosaurus had forearms that were more reduced than that of the famous T. rex.
However, it was still one of the top predators in its ecosystem.
Pycnonemosaurus lived in South America during the Late Cretaceous Period.
Pycnonemosaurus is known from fragmentary remains recovered from rocks of the Adamantina Formation located in Brazil.
This region of South America has reported very few dinosaurs.
So not only was Pycnonemosaurus the biggest of its kind, but it was also the largest predatory dinosaur known from Brazil.
Unfortunately, not a lot is known about this dinosaur.
So far, only fragmentary remains have been found, and they were quite irritated due to exposure to the elements.
Still, the remains of this dinosaur were enough to determine its size and some of its basic attributes.
In this article, we’ll describe one of South America’s biggest carnivores that ruled the forests of Brazil during the Late Cretaceous Period.
In 2002, scientists recovered five incomplete teeth, some leg and hip bones, and parts of the tail vertebrae of the Pycnonemosaurus.
The remnants were unearthed from rocks of the Bauru Group in Brazil.
These are the only bones of this theropod dinosaur found so far.
So much of what we know about the appearance of this dinosaur is based on these bones and comparison with other abelisaurid dinosaurs.
Pycnonemosaurus was a typical abelisaur with greatly reduced forearms and long muscular hindlimbs that were built for speed.
It had a short and deep skull, relatively large for its body.
The jaws were lined with sharp, serrated teeth, typical of theropod dinosaurs adapted for carnivorous feeding.
But arguably, the most impressive attribute of this dinosaur is its size.
Initially, the Pycnonemosaurus was estimated to be about seven meters (23 feet) long, with a weight estimate of about 1.2 tons.
However, more recent analysis has found that it was probably larger than this.
A new length of about 8.9 meters (29.2 feet) has been proposed for this dinosaur.
It probably weighed as much as 3.6 tons, based on the new estimate.
While it wasn’t as big as the T. rex or any of the larger tyrannosaurids, the Pycnonemosaurus was one of the biggest of its kind.
It is the largest formally described dinosaur in the Abelisauridae family.
Since no cranial bones of this dinosaur have been recovered, it isn’t clear if it had horns like the Carnotaurus or a low ridge above its eyes, similar to the Aucasaurus.
The tail vertebrae show signs of awl-like projections that tend to diminish towards the distal caudals of the dinosaur.
Habitat and Distribution
The name Pycnonemosaurus is from the Greek words “pycnós,” which means dense, and “némos,” which means woods or forests.
It translates as “dense forest lizard.”
The name is a reference to the Mato Grosso State, where fossils of this dinosaur were found.
Today, the state is known for its dense forests, wetlands, and savanna, but the climate would have been slightly different back in the Cretaceous Period.
Back in the Cretaceous Period, the region where this dinosaur lived was most likely a wetland habitat located near riverbanks or lakeshores.
Some parts of this region may have been forested, but the Amazon rainforest, which covers most of the region where this dinosaur lived today, was not yet formed back in the Cretaceous.
The Late Cretaceous climate in South America and other parts of the world was generally warm and humid.
High atmospheric carbon dioxide levels contributed to the greenhouse effect, raising global temperatures.
The region’s climate was probably influenced by its latitude and proximity to the ocean.
Behavior and Diet
Pycnonemosaurus was a bipedal dinosaur which means it walked on its two hindlimbs. The forearms were too reduced to be useful for locomotion.
It was basically just wrists with small stubby “fingers.”
The hind limbs, on the other hand, were long and muscular.
This dinosaur also had a long and thick tail.
A combination of these anatomical features suggests that this dinosaur was built for speed, an adaptation that would have been important for pursuing prey effectively.
Pycnonemosaurus was the top predator in Brazil during the Late Cretaceous Period.
The ecosystem where this dinosaur lived supported a healthy population of the sauropod dinosaurs.
Some of these, such as Adamantisaurus mezzalirai and Gondwanatitan faustoi, were contemporaneous with the Pycnonemosaurus, and this dinosaur probably preyed on them.
Although they were active predators, the bite force of the Pycnonemosaurus and other abelisaurid dinosaurs was less than that of the tyrannosaurs.
This means they were a little less efficient as predators and would have hunted prey differently.
The lack of forearms meant jumping to grasp the flank of prey would have been unlikely.
Taking down prey for the Pycnonemosaurus would have involved swift pursuit while inflicting slashing bites with its shark-like serrated teeth.
The blood loss from these injuries would help weaken and slow down prey enough for the dinosaur to deliver a fatal bite to the prey’s jugular or skull.
Although no direct evidence has been found for this, the Pycnonemosaurus likely hunted in pairs or even small family groups.
A fully-grown Pycnonemosaurus would have been capable of taking down prey like the Gondwanatitan faustoi on its own.
However, the hunt would have been considerably easier if they worked in pairs.
As a group, they would have been capable of taking down large prey like the Adamantisaurus mezzalirai.
They also targeted sick or wounded dinosaurs, juveniles, and dead or dying individuals.
This would have been easier prey for an opportunistic carnivore like the Pycnonemosaurus, but they would have hunted prey actively too.
Like other dinosaurs, Pycnonemosaurus would have reproduced sexually, with males and females mating during specific seasons of the year.
After mating, female Pycnonemosaurus laid eggs in nests.
So far, no preserved eggs or nests of this dinosaur have been found, but it’s safe to assume that they laid their eggs in well-protected areas.
There’s no evidence that the Pycnonemosaurus raised its young or provided any form of parental care.
Hatchlings were most likely on their own, hunting smaller prey in their ecosystem.
Abelisaurids were generally slow-growing dinosaurs, which is unusual since dinosaurs and other reptiles are known for their fast growth rate.
Studies of the Majungasaurus, a relative of the Pycnonemosaurus, showed that it took nearly 20 years for the dinosaur to grow to its full adult size.
The same result has been observed for several other abelisaurid genera.
This suggests that the Pycnonemosaurus also grew very slowly, reaching maturity after several years.
Evolution and History
Pycnonemosaurus was a member of a family of theropod dinosaurs known as the abelisaurids.
The oldest members of this family evolved during the Middle Jurassic Period about 170 million years ago.
And a few genera, including the Pycnonemosaurus, persisted until the Late Cretaceous Period.
Abelisaurids show an upward trend in their size as they evolved over the course of the Mesozoic.
They reached their maximum size during the Middle Cretaceous Period, about 95 million years ago.
Pycnonemosaurus evolved around this time and lived till the Late Cretaceous Period.
This increase in size meant the Pycnonemosaurus was bigger than any of the other abelisaurid dinosaurs.
The different members of the abelisaurid family also show different specific adaptations.
For instance, the Carnotaurus, which is arguably the most popular member of the family, was a horned theropod dinosaur.
Due to the fragmentary remains, it isn’t clear if the Pycnonemosaurus showed any specialized adaptation apart from its size.
It isn’t clear if the Pycnonemosaurus evolved into another abelisaur or if it was present until the end of the Cretaceous Period when all the non-avian dinosaurs died off.
Interactions With Other Species
Given its size and the absence of any other notable theropod dinosaurs, Pycnonemosaurus was most likely the unchallenged apex predator in its ecosystem.
It lived alongside various sauropod dinosaurs, including the 7-meter-long Gondwanatitan faustoi and the 13-meter-long Adamantisaurus mezzalirai.
These sauropods were slow-moving herbivores whose only defense against predators was their massive size.
Since the Pycnonemosaurus was equally sized or even bigger than they were, it would have hunted and taken them down relatively easily.
Pycnonemosaurus may have hunted other carnivores as well, including members of its own genus.
Cannibalism isn’t unheard of in the world of the abelisaurids.
Majungasaurus, a relative of the Pycnonemosaurus, is known to have been cannibalistic.
However, this was probably not a regular occurrence.
While the Pycnonemosaurus was the top carnivore in Brazil, it wasn’t entirely unchallenged.
A few other predators lived in its shadows as well.
The Stratiosuchus, a type of hypercarnivorous crocodilian, lived in the same region as the Pycnonemosaurus.
It would have competed for the same prey and probably preyed on Pycnonemosaurus hatchlings in the right circumstances.
Smaller crocodilians like the Mariliasuchus were present as well.
While the meter-long predator could not have competed directly with the Pycnonemosaurus, it may have preyed on dinosaur eggs and hatchlings.
Pycnonemosaurus is not very well-known both to the general public and to researchers.
Despite its size and possibly remarkable features, it remains one of the least-known members of its family due to the fragmentary nature of its remains.
This dinosaur was described for the first time in 2002 by Alexander Kellner, Diogenes Campos, and colleagues based on a few teeth, tail vertebrae, and leg bones, leaving a lot to speculation.
The bones were well-preserved but were probably damaged by recent exposure shortly before they were found.
However, scientists were able to determine that the Pycnonemosaurus was the biggest abelisaurid and one of the largest predatory dinosaurs from its country.
The location where this dinosaur was found is one of the most significant things about it.
Only a few species of dinosaurs are known from Brazil, and theropods are particularly rare.
Pycnonemosaurus is the best-known abelisaurid from the country.
And the fact that it was the largest predator around helps scientists to paint a clearer picture of what the terrestrial ecosystem of the country might have looked like during the Late Cretaceous Period.
Further scientific research and the discovery of new fossils of this dinosaur may help further reconstruct its habitat and provide more specific information about various aspects of this dinosaur’s life that are currently unknown.
Pycnonemosaurus is a genus of carnivorous theropod dinosaurs that lived in South America (specifically Brazil) during the Late Cretaceous Period.
It was an abelisaurid dinosaur, alongside others like the Carnotaurus.
Pycnonemosaurus is the biggest abelisaurid dinosaur ever found and was the top predator in its ecosystem.
This dinosaur hunted sauropods and other animals around.
It was a bipedal dinosaur with highly reduced forearms that probably served no real purpose.
The hindlimbs, on the other hand, were long and muscular.
Pycnonemosaurus ruled the plains and forests of Brazil during the Late Cretaceous Period and may have survived until the final days of the dinosaurs on the continent.