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Description
Estemmenosuchus mirabillis

The Permian Era was an era when the first fully terrestrial vertebrates rose up and became the dominant organisms on land. The most prominent were the synapsids. At this point, during the Mid-Permian, from around ~270-260,000,000 years ago one group had filled most niches on land. A subgroup of synapsids known as sphenacodontidae had died out, and in their place were the therapsid synapsids. A more derived group that would eventually give rise to modern mammals. Among the most basal of the therapsids were the Dinocephalians, literally meaning "Terrible Heads". These were animals that included both large herbivores, omnivores, and apex predators. The most unique family of this group were the Estemmenosuchidae, known for their bizarre headgear. And none were more bizarre than Estemmenosuchus mirabillis.

History and Discovery:

Its discovery is not as well recorded compared to other Permian animals. This genus of synapsid was native to Russia and two valid species were discovered in the 1960s. As such, details about its discovery are not as well documented. What is known is that this creature was unearthed in the Perm Region of Russia. An area west of the Ural Mountains. Paleontologist Peter Konstantinovich Chudinov is credited with naming the two valid species, Estemmenosuchus uralensis and Estemmenosuchus mirabillis. The name of this species in particular derives from the Greek and means "Crowned Crocodile" and the species name, "mirabillis" also Greek means wonderous.
However, this is not a crocodile, nor is it even closely related to them. Like all therapsids, Estemmenosuchus is more closely related to mammals than to any crocodilian. Most paleontologists call these creatures "stem-mammals" because they broke off from the group of creatures that would give rise to mammals. So while they possess some features similar to reptiles, they also have some traits shared with mammals (as will be discussed later).

Evolution and Taxonomy:

Like its discovery, Dinocephalians and Estemmenosuchus' evolutionary history is not well known. They probably evolved as early as 280,000,000 years ago during the Kungurian epoch of the Permian, but no fossils have been discovered from this era. They replaced the more famous Synapsids, like the sphenacodontids, which include animals like Dimetrodon.
Of all the animals in the Permian, Estemmenosuchus and its kin were among the most basal of all therapsid synapsids. With primitive features such as not having a secondary palate that divided the nasal and oral regions of its skull. Along with that, it had an underdeveloped mouth with a small dentary bone, and most notably, it had sprawled limbs. However, they did have some more advanced features compared to more basal synapsids. Their limbs while sprawled, were more erect than other synapsids such as the Caseids. In fact, they also had a more advanced pelvis compared to less derived synapsids. This pelvis enabled a more erect posture of their hindlimbs compared to other synapsids. Finally, even for Dinocephalians, the tail was much shorter and probably held off the ground.

Description:

In terms of appearance, this species literally took the "crowned" prefix in its name to a new level. The larger species E.uralensis had far less developed of a "crown" region. With two small nubs protruding out of its head, but it was at least half as big as E.mirabillis. With E.mirabillis, being around 3ft tall and 10ft long. Its skull was just over a foot-and-a-half long, and atop its skull, it possessed two distinctive antler-like structures on its head. However, unlike antlers which are made of keratin, these were actually bony extensions of the frontal area of the skull which protruded out of the skull. It also has a more prominent extension near the front of its skull with E.mirabillis having the more pronounced extension compared to E.uralensis.

Purpose of Structure:

The "crown" on its head was probably used for display. Some have posited it could have been used for combat for territory or for rival males to compete for mates. However, no studies on its "crown" have been done to see if it would have been used for rutting purposes like modern deer or bovines. Also, with such a small sample size, paleontologists don't know if the distinctive skull extensions were exclusive to males or universal to both sexes of Estemmenosuchus.\

Skin impressions:

What's really significant about this animal is that this is the only synapsid paleontologists have skin impressions from. Described in 1968, by Peter Chudinov, the skin was completely hairless described as reminiscent of an amphibian or a hippo's skin. In 1983, a partial skeleton also had skin impressions near the pelvis, and it had osteoderms on it. It was also described by Chudinov and was described as being similar to a Mylodontid Ground Sloth's skin. Given it was near the pelvis, it suggests this was a region the osteoderms were there for protection.

Habitat and Behavior:

Furthermore, the skin impressions enable paleontologists to get a better insight into its habitat. With Estemmenosuchus likely inhabiting a tropical swampy habitat, similar to modern-day hippos.
Moreover, despite its fierce appearance and formidable dentition, this creature was not a ferocious predator. While some members of Dinocephalians are known for being predators like Anteosaurus and Titanophoneus, this creature was likely a herbivore and probably filled the niche of a hippopotamus. And given the sprawled forelimbs and more erect hindlimbs would have enabled the creature to better graze or browse off plant material in the swamps of Permian Russia. Its sprawled posture allowing it to more easily lower its head down to the ground.
Also, in terms of intraspecific combat, its possible that, like a hippo, it would use its teeth to fight between rivals over territory or for mates. If it filled the niche of a hippo, its not out of the realm of possibility. As its incisors were elongated and are reminiscent of Hippo's tusks.
Others paleontologists have suggested this creature could have supplemented its diet with some meat as well, perhaps being an omnivore. While not confirmed, its not out of the question as the dentition of this animal does not appear to be exclusively geared towards meat or plants, so its likely it could have been used to process some meat.

Extinction:

Estemmenosuchus and its dinocephalian kin would vanish in the mid-to-late-Permian, approximately 260,000,000 years ago. It was during an extinction event known as the Capitanian Mass Extinction Event where these awe-inspiring animals would become extinct.
While not as severe as the infamous "Great Dying", it was still a fairly significant extinction event. In fact it was more severe than both the Triassic-Jurassic and even the KT Extinction Event. The causes of this extinction have been theorized to be a volcanic trap event that polluted the atmosphere, raised the temperature across the planet and caused massive climatic changes that wiped out countless groups of animals. In their place, the infamous gorgonopsians would replace Dinocephalians as apex predators and the basal reptiles known as Parareptilians would replace the herbivorous species like Estemmenosuchus.
While these animals have vanished from the planet, they nonetheless represent a unique period in Earth's History. A time when synapsids became more advanced and started to diversify in a variety of niches across the planet.
___________________________________________________________________________________________
Instead of doing Cotylorhynchus for Synapsid Week (which EVERYONE seems to do) I decided to do an animal that was just as bizarre.

Details on the skin were taken from this blog post:
Estemmenosuchus skin and osteoderms – Incertae Sedis (wordpress.com)

Original Model and Skin by Tyranachu. No modifications were made on my end. The pose I put this guy in was based off of Suchomimus62 's artwork of this creature:
Estemmenosuchus 2.0 by Suchomimus62 on DeviantArt

Will this be in PMP? No. Paleontologists don't even know what animals lived alongside Estemmenosuchus and I can't flesh out this region in the Permian. I just wanted to cover a creature for Synapsid Week and this was among the most unique.

The weight I sort of took a wild guess and estimated around 800-1100lbs which I think is fairly accurate given its size and diet.

Small Note: On Wikipedia, the Paleontologist who discovered it is Petr Tchudinov. But in the Blog Post its Peter Chudinov. I went with that since maybe it was just a mistranslation so I decided to correct it and give it the proper anglicized spelling.

Original model and skin by Tyranachu:
Estemmenosuchus (Tyranachu) | ZT2 Download Library Wiki | Fandom

Description
Estemmenosuchus mirabillis

The Permian Era was an era when the first fully terrestrial vertebrates rose up and became the dominant organisms on land. The most prominent were the synapsids. At this point, during the Mid-Permian, from around ~270-260,000,000 years ago one group had filled most niches on land. A subgroup of synapsids known as sphenacodontidae had died out, and in their place were the therapsid synapsids. A more derived group that would eventually give rise to modern mammals. Among the most basal of the therapsids were the Dinocephalians, literally meaning "Terrible Heads". These were animals that included both large herbivores, omnivores, and apex predators. The most unique family of this group were the Estemmenosuchidae, known for their bizarre headgear. And none were more bizarre than Estemmenosuchus mirabillis.

History and Discovery:

Its discovery is not as well recorded compared to other Permian animals. This genus of synapsid was native to Russia and two valid species were discovered in the 1960s. As such, details about its discovery are not as well documented. What is known is that this creature was unearthed in the Perm Region of Russia. An area west of the Ural Mountains. Paleontologist Peter Konstantinovich Chudinov is credited with naming the two valid species, Estemmenosuchus uralensis and Estemmenosuchus mirabillis. The name of this species in particular derives from the Greek and means "Crowned Crocodile" and the species name, "mirabillis" also Greek means wonderous.
However, this is not a crocodile, nor is it even closely related to them. Like all therapsids, Estemmenosuchus is more closely related to mammals than to any crocodilian. Most paleontologists call these creatures "stem-mammals" because they broke off from the group of creatures that would give rise to mammals. So while they possess some features similar to reptiles, they also have some traits shared with mammals (as will be discussed later).

Evolution and Taxonomy:

Like its discovery, Dinocephalians and Estemmenosuchus' evolutionary history is not well known. They probably evolved as early as 280,000,000 years ago during the Kungurian epoch of the Permian, but no fossils have been discovered from this era. They replaced the more famous Synapsids, like the sphenacodontids, which include animals like Dimetrodon.
Of all the animals in the Permian, Estemmenosuchus and its kin were among the most basal of all therapsid synapsids. With primitive features such as not having a secondary palate that divided the nasal and oral regions of its skull. Along with that, it had an underdeveloped mouth with a small dentary bone, and most notably, it had sprawled limbs. However, they did have some more advanced features compared to more basal synapsids. Their limbs while sprawled, were more erect than other synapsids such as the Caseids. In fact, they also had a more advanced pelvis compared to less derived synapsids. This pelvis enabled a more erect posture of their hindlimbs compared to other synapsids. Finally, even for Dinocephalians, the tail was much shorter and probably held off the ground.

Description:

In terms of appearance, this species literally took the "crowned" prefix in its name to a new level. The larger species E.uralensis had far less developed of a "crown" region. With two small nubs protruding out of its head, but it was at least half as big as E.mirabillis. With E.mirabillis, being around 3ft tall and 10ft long. Its skull was just over a foot-and-a-half long, and atop its skull, it possessed two distinctive antler-like structures on its head. However, unlike antlers which are made of keratin, these were actually bony extensions of the frontal area of the skull which protruded out of the skull. It also has a more prominent extension near the front of its skull with E.mirabillis having the more pronounced extension compared to E.uralensis.

Purpose of Structure:

The "crown" on its head was probably used for display. Some have posited it could have been used for combat for territory or for rival males to compete for mates. However, no studies on its "crown" have been done to see if it would have been used for rutting purposes like modern deer or bovines. Also, with such a small sample size, paleontologists don't know if the distinctive skull extensions were exclusive to males or universal to both sexes of Estemmenosuchus.\

Skin impressions:

What's really significant about this animal is that this is the only synapsid paleontologists have skin impressions from. Described in 1968, by Peter Chudinov, the skin was completely hairless described as reminiscent of an amphibian or a hippo's skin. In 1983, a partial skeleton also had skin impressions near the pelvis, and it had osteoderms on it. It was also described by Chudinov and was described as being similar to a Mylodontid Ground Sloth's skin. Given it was near the pelvis, it suggests this was a region the osteoderms were there for protection.

Habitat and Behavior:

Furthermore, the skin impressions enable paleontologists to get a better insight into its habitat. With Estemmenosuchus likely inhabiting a tropical swampy habitat, similar to modern-day hippos.
Moreover, despite its fierce appearance and formidable dentition, this creature was not a ferocious predator. While some members of Dinocephalians are known for being predators like Anteosaurus and Titanophoneus, this creature was likely a herbivore and probably filled the niche of a hippopotamus. And given the sprawled forelimbs and more erect hindlimbs would have enabled the creature to better graze or browse off plant material in the swamps of Permian Russia. Its sprawled posture allowing it to more easily lower its head down to the ground.
Also, in terms of intraspecific combat, its possible that, like a hippo, it would use its teeth to fight between rivals over territory or for mates. If it filled the niche of a hippo, its not out of the realm of possibility. As its incisors were elongated and are reminiscent of Hippo's tusks.
Others paleontologists have suggested this creature could have supplemented its diet with some meat as well, perhaps being an omnivore. While not confirmed, its not out of the question as the dentition of this animal does not appear to be exclusively geared towards meat or plants, so its likely it could have been used to process some meat.

Extinction:

Estemmenosuchus and its dinocephalian kin would vanish in the mid-to-late-Permian, approximately 260,000,000 years ago. It was during an extinction event known as the Capitanian Mass Extinction Event where these awe-inspiring animals would become extinct.
While not as severe as the infamous "Great Dying", it was still a fairly significant extinction event. In fact it was more severe than both the Triassic-Jurassic and even the KT Extinction Event. The causes of this extinction have been theorized to be a volcanic trap event that polluted the atmosphere, raised the temperature across the planet and caused massive climatic changes that wiped out countless groups of animals. In their place, the infamous gorgonopsians would replace Dinocephalians as apex predators and the basal reptiles known as Parareptilians would replace the herbivorous species like Estemmenosuchus.
While these animals have vanished from the planet, they nonetheless represent a unique period in Earth's History. A time when synapsids became more advanced and started to diversify in a variety of niches across the planet.
___________________________________________________________________________________________
Instead of doing Cotylorhynchus for Synapsid Week (which EVERYONE seems to do) I decided to do an animal that was just as bizarre.

Details on the skin were taken from this blog post:
Estemmenosuchus skin and osteoderms – Incertae Sedis (wordpress.com)

Original Model and Skin by Tyranachu. No modifications were made on my end. The pose I put this guy in was based off of Suchomimus62 's artwork of this creature:
Estemmenosuchus 2.0 by Suchomimus62 on DeviantArt

Will this be in PMP? No. Paleontologists don't even know what animals lived alongside Estemmenosuchus and I can't flesh out this region in the Permian. I just wanted to cover a creature for Synapsid Week and this was among the most unique.

The weight I sort of took a wild guess and estimated around 800-1100lbs which I think is fairly accurate given its size and diet.

Small Note: On Wikipedia, the Paleontologist who discovered it is Petr Tchudinov. But in the Blog Post its Peter Chudinov. I went with that since maybe it was just a mistranslation so I decided to correct it and give it the proper anglicized spelling.

Original model and skin by Tyranachu:
Estemmenosuchus (Tyranachu) | ZT2 Download Library Wiki | Fandom