The Most “Ugly” Pareiasaur Discovered to Date – Bunostegos

By | June 25th, 2013|Dinosaur and Prehistoric Animal News Stories, Palaeontological articles|0 Comments

Pareiasaur from Niger with Bizarre Lumps and Bumps on Its Head

A team of international scientists have discovered that animals living in what was one of the central parts of the super-continent known as Pangea may have become geographically isolated, this led to a number of ancient genera surviving into the Late Permian, whilst these creatures became extinct elsewhere.

One of the more remarkable of these “living Permian fossils” was the cow-sized, herbivorous Pareiasaur which has been named Bunostegos akokanensis.  The term Pareiasaur refers to a diverse group of reptiles, the “shield lizards”.  These animals were heavily built, robust creatures whose bodies were covered in bony spikes, horns and plate-like projections.  Bunostegos is known from a partial skull and it is distinctive as this specimen has more bumps and lumps on its skull than any other known species of Pareiasaur described to date.

The skull material has been dated to around 260 million years ago (Late Permian), it was found a few years ago during fieldwork exploring the Moradi Formation of central Niger.  A research paper has just been published in the academic publication “The Journal of Vertebrate Palaeontology”.  The genus name means “knobbly roof” a testament to the strange lumps and bumps on the animal’s skull, which in life may have been covered in skin, rather like the bumps on the top of a giraffe’s head.  The species name honours the town of Akokan in central Niger, which is close to where the fossil material was found.

An Artist’s Impression of Bunostegos akokanensis

Lumpy and bumpy Pareiasaur.

Lumpy and bumpy Pareiasaur.

Picture Credit: BBC Media Images

Better known Pareiasaurs such as the three-metre long Scutosaurus have provided scientists with evidence that some of these skull and facial features developed with age.  Cheek projections in conjunction with nose and lower jaw spikes seem to have become more prominent as individuals grew larger and matured.  This has led some palaeontologists to speculate that these features were used in mating displays or fights amongst rivals (intra-specific competition).  If this is the case, then the skull material unearthed in Niger might represent a particularly old individual.

A Typical “Shield Lizard” – Scutosaurus

Robust, heavily armoured Pareiasaurs.

Robust, heavily armoured Pareiasaurs.

Picture Credit: Everything Dinosaur

Analysis of the skull has led the researchers to conclude that Bunostegos is related to older and more primitive Pareiasaurs, but it seems to have persisted in Niger whilst related species died out many millions of years previously.  This would have made Bunostegos a “living fossil”, a survivor from an ancient line of reptiles that had gone extinct elsewhere.  For much of the Permian, the land masses of the Earth were joined together into a huge super-continent (Pangea).  Scientists had thought that much of the fauna and flora was relatively uniform, in theory an animal could have walked from near to the South Pole almost to the North Pole.  The Middle and Late Permian fossil record documents a uniformity in fauna and flora as similar fossil species have been found in what would have been (back in the Permian), geographically dispersed locations.

However, this research work, focusing on the Moradi Formation of Upper Permian strata suggests that there was an isolated habitat in the central part of Pangea that enabled distinctive fauna and flora to evolve and more primitive reptiles to persist.  Bunostegos may have been around during the Late Permian as deserts surrounded its habitat providing a natural barrier preventing animals leaving the area and other creatures coming in.

Great Care is Taken when Excavating Fossil Material

Examining fossil material what we term a "dig station".

Examining fossil material what we term a "dig station".

Picture Credit: BBC Media Images

Commenting on the strange appearance of this reptile, Dr. Linda Tsuji from the University of Washington (Seattle) stated:

“We can’t say for sure, but it is most likely that the bony knobs on the skull of Pareiasaurs did not serve a protective function.  They vary quite markedly in size and shape between different species, with some species lacking prominent knobs entirely, so I think that they were purely ornamental. The most probable use was for inter-specific [between species] or intra-specific [within species] recognition.”

These deserts would have proven to be impenetrable barriers to these creatures, the fauna and flora would have been constrained to a central area, arid but with enough water and food to sustain an ecosystem.

Christian Sidor of the Department of Anatomy, New York College of Osteopathic Medicine, Old Westbury, New York, a co-author of the scientific paper concluded that:

“Our work supports the theory that central Pangea was climatically isolated, allowing a unique relict fauna to persist into the Late Permian.”

Elsewhere on the landmass of Pangea, animals and plants had much more freedom of movement with many fewer natural barriers.  This is reflected in the relatively uniform fossil record as found today in places such as South Africa and South America.

A View of the Bunostegos Skull Material

Two photographs of the skull material are at the top viewed as if looking down onto the fossil material.

Two photographs of the skull material are at the top viewed as if looking down onto the fossil material.

Picture Credit: Journal of Vertebrate Palaeontology

The line drawing below is an illustration of the skull, as if viewed from looking down onto the top of the skull (dorsal view).

A spokesperson from Everything Dinosaur stated:

“It is important to explore the geological and fossil record of the super-continent known as Pangea, especially the Upper Permian deposits.  The end of the Permian is marked by the greatest mass extinction in the history of life on our planet and scientists are still uncertain how this mass extinction event came about”.