A new clade of bizarre, prehistoric reptiles has recently been named.
Called Protopyknosia, it is currently only known from three incomplete skulls. But what little is known is astonishing.
Protopyknosians had large domes on their heads reminiscent of the famous pachycephalosaur dinosaurs.
However, the protopyknosians lived during the Triassic Period, long before the pachycephalosaurs,
and were not dinosaurs themselves, but instead more distant relations who evolved their domed heads as the result of convergent evolution.
Protopyknosia is currently only known from two species, Triopticus primus and Kranosaura kuttyi, both from the Late Triassic.
Triopticus primus was named in 2016 and is only known from part of a single skull,
which besides the dome also preserves an endocast of its brain and part of an eye socket.
Its name translates to “first tri optic”, in reference to an pit in the skull resembling a third eye and how nothing else like it was known at the time.
Triopticus was found in the Dockum Group in Texas.
The second species of protopyknosian, Kranosaura kuttyi, was named and described in March 2021,
though its fossils were first found in 1999 in the Indian Maleri Formation
It is known from two skull domes though lacks a preserved endocast of its brain.
Its name means “Kutty’s helmet lizard”, in honor of T. S. Kutty, who found the fossils.
It was only with Kranosaura’s recent description and its similarities with Triopticus
that the clade Protopyknosia was formerly named to unite these odd, domed reptiles.
Protopyknosia seems to be part of Archosauriformes, the clade that includes dinosaurs, crocodilians, and relatives of the two group,
but it does not seem to be part of the advanced group Archosauria. Given the limited fossils,
beyond this it is not clear where it fits in Archosauriformes. This makes any reconstruction of the rest of the body highly speculative.
Most of the Kranosaura reconstructions in this video are based on allokotosaurs, perhaps because of the strange headgear of the allokotosaur Shringasaurus.
But while they were close relatives of the archosauriforms, allokotosaurs were outside of Archosauriformes proper.
Likewise, while many of the Triopticus reconstructions have a long snout, this is likewise pure speculation.
Examples of non-archosaurian Archosauriformes includes proterosuchids,
eryothrosuchids,
euparkeriids,
proterochampsians,
as well as a number of similar reptiles outside of these groups.
Because of the limited remains, no estimate has been given for protopyknosian size.
However, the domes were not large and Triopticus was stated to was probably have been no larger than an alligator at most, and was most likely smaller.
As Kranosaura’s dome was slightly larger than that of Triopticus, its body was probably a bit larger as well.
Protopyknosian domes are outwardly very similar to those of pachycephalosaur dinosaurs, as well as some Permian synapsids.
However, there are differences between them.
Protopyknosians domes were formed from five rounded protuberances,
referred to as bosses, on the top of the skull, with the dome itself formed from the boss in the middle.
Given how the domes were roughly textured, it seems that they were covered in keratin, making them even larger in life.
The bone of these domes was divided into three layers. The bone in the inner layer was the densest
while the bone in the outmost layer was the least dense. Pachycephalosaurs also had three layers of bones in their domes,
Pachycephalosaurs also had three layers of bones in their domes,
The actual purpose of protopyknosian domes is not entirely clear. In general, such features are usually thought to be the result of sexual selection,
either for visual display or used for combat between competing males. Examination of the bone pathology of pachycephalosaur skulls has found what
appears to be scars from such contests, heavily suggesting that they did indeed headbutt each other.
Another suggested function of domes has been defense against predators.
However, protopyknosians may have used their domes for an additional purpose: hunting.
While it is unclear what Triopticus and Kranosaura ate without fossils of their teeth, all other known archosauriforms outside of Archosauria were carnivores.
Therefore, protopyknosians may have been carnivores as well, using their domes as a weapon to stun and kill prey.
Out of all of these possibilities, Kranosaura’s skull offers some clues in narrowing it down.
Unlike other domed species, the back of Kranosaura’s dome was relatively delicate. However, the front had much denser bone, potentially allowing for ritualistic combat between rivals.
However, given the greater potential for damage to the delicate portions of the dome in less controlled settings,
this makes the idea of using them as weapons, either offensively or defensively, comparatively unlikely.
Triopticus lacked both the dense bone on the front of the dome and the more delicate parts, suggesting it may have used its dome differently than Kranosaura did.
The pit mentioned earlier was between the five bossess, though it was smaller in Kranosaura.
The exact purpose of this pit is uncertain, but it looks vaguely like the socket for a parietal eye, sometimes called a "third eye".
This is a photoreceptive organ present on the head of some animals, including many reptiles.
However, parietal eyes were already lost in the first archosauriforms and there doesn’t seem to have been any way for it to connect to the brain in either species.
Therefore, the primary hypothesis is that the pit is simply a byproduct formed from how the bosses grew.
Regardless of whether or not protopyknosians had a “third eye”, given the size of Triopticus’s eye sockets,
the actual eyes of Triopticus were rather large. Combined with the size of the optic nerves as determined from CT scans,
it seems that Triopticus at least had very good eyesight.
CTs scans of Triopticus’s brain case reveled that the shape of its brain was typical of most archosauriforms,
though it had some similarities with the pachycephalosaurs, likely as a result of the shape of their brains of both groups needing to accommodate their large domes as they evolved.
Triopticus’s brain also had a large flocculus lobe, a section of the brain that is involved in motor functions.
It also had long semi-circular canals in the inner ear, which would have aided in it in holding a stabile gaze.
Beyond this, very little is known about protopyknosians, On the bright side, despite their rarity they seem to have had a widespread distribution across Pangea,.
This suggests that their fossils could be found in a wide variety of locals. Hopefully, wherever they are found, they will help us learn more about these fascinating reptiles.
Thank you for watching. I hope you learned something interesting.
If you would like to learn more about Protopyknosia, the links to the three research papers on the group are in the description, though the last one is behind a paywall.
Have a great day, and, if you enjoyed the video, please remember to hit the like button.