Psittacosaurus Gets its Head Examined

Researchers from the Chinese Academy of Sciences, in collaboration with colleagues from Carleton University (Ottawa, Canada) and Bristol University, have produced a new study on the Early Cretaceous Asian dinosaur Psittacosaurus (P. lujiatunensis).  This new research, published in PeerJ, provides the first detailed survey of Ceratopsian braincase changes as a dinosaur grows.  Three growth stages were studied – hatching, juvenile and adult and as Psittacosaurus got bigger, so its brain changed in shape.  Furthermore, the study suggests that these little, herbivorous dinosaurs changed posture as the aged.  When young they were facultative quadrupeds, but as they matured they favoured a bipedal stance.

Psittacosaurus Gets Its Head Examined

A typical psittacosaurid.  A model of Psittacosaurus (CollectA Psittacosaurus).

Picture Credit: Everything Dinosaur

Hundreds of Fossil Specimens Examined

Hundreds of Psittacosaurus fossil specimens were examined.  These fossils herald from the Early Cretaceous (Barremian–Aptian) of China, specifically from the Yixian Formation.  The lack of fossils representing dinosaurs at different growth stages limits ontogenetic studies, but Psittacosaurus is an exception, it is one of the better represented members of the Ornithischia.  The cranial and endocranial morphology of Psittacosaurus has been well documented, but only cursory details have been published on the bones surrounding the brain.

Comparing Skulls Psittacosaurus “Parrot Lizard” Compared to a Parrot 

Comparing skulls.  The skull of an adult Psittacosaurus – P. gobiensis (left) is compared with an adult parrot (right).

Picture Credit: Mike Hettwer

From Hamster-sized Hatchlings to Two-metre-long Adults

From hamster-sized babies these dinosaurs grew relatively quickly into two-metre-long adults.  As they grew, their brain changed in shape from being crammed into the back of the head, behind the huge eyes in the hatchling, to being longer, and extending under the skull roof in the adult animals.  The braincase provides evidence that supports the idea that these dinosaurs changed posture as they got older.  The position and the orientation of the semi-circular canals, which helped these dinosaurs with their balance, changed as they grew.

Corresponding author of the paper, Claire Bullar (University of Bristol School of Earth Sciences), commented:

“I was excited to see that the orientation of the semi-circular canals changes to show this posture switch.  The semi-circular canals are the structures inside our ears that help us keep balance, and the so-called horizontal semi-circular canal should be just that – horizontal – when the animal is standing in its normal posture.  This is just what we see, with the head of Psittacosaurus pointing down and forwards when it was a baby – just right for moving on all-fours.  Then, in the teen or adult, we see the head points exactly forwards, and not downwards, just right for a biped.”

Dinosaur Brains from Baby to Adult (left to right)

A study of the brain of Psittacosaurus (ontogenetic study).  Head posture if the lateral (horizontal) semi-circular canal is parallel to the ground, in hatching (A), juvenile (B) and adult (C) Psittacosaurus lutjiatunensis.  Images not to scale.

Picture Credit: Claire Bullar/Institute of Vertebrate Palaeontology and Palaeoanthropology

The change in posture is supported by postcranial fossil evidence.  The relative limb lengths indicate that a juvenile Psittacosaurus would have moved around on four legs, but by the age of two or three, they switched to a bipedal posture, standing upright on their elongate hind legs.  This would have freed up the arms and hands to help with gathering food.  The team used reconstructions created from micro-computed tomography scans of well-preserved skulls to plot the ontogenetic changes.

Co-supervisor Dr Qi Zhao from the Institute of Vertebrate Palaeontology and Palaeoanthropology (IVPP) in Beijing, where the specimens are housed, added:

“It’s great to see our idea of posture shift confirmed, and in such a clear-cut way, from the orientation of the horizontal ear canal.  It’s also amazing to see the results of high-quality CT scanning in Beijing and the technical work by Claire to get the best 3-D models from these scan data.”

Skulls of Psittacosaurus (P. lujiatunensis) Showing Different Growth Stages

Ontogenetic skull sequence from hatchling to adult (Psittacosaurus).  Hatchling (IVPP V15451) – (A) in lateral view.  (B) Hatchling in dorsal view.  (C) Juvenile (IVPP V22647) in lateral view. (D) Juvenile in dorsal view.  (E) Adult (IVPP V12617) in lateral view.  (F) Adult in dorsal view. All shown to the same scale; scale bar represents 2 cm.

Picture Credit: Claire Bullar/Institute of Vertebrate Palaeontology and Palaeoanthropology

Co-author Professor Michael Ryan (Carleton University) contributed:

“This posture shift during growth from quadruped to biped is unusual for dinosaurs, or indeed any animal.  Among dinosaurs, it’s more usual to go the other way, to start out as a bipedal baby, and then go down on all fours as you get really huge.  Of course, adult Psittacosaurus were not so huge, and the shift maybe reflects different modes of life: the babies were small and vulnerable and so probably hid in the undergrowth, whereas bipedalism allowed the adults to run faster and escape their predators.”

Professor Michael Benton (Bristol University), another collaborator in this study commented:

“This is a great example of classic, thorough anatomical work, but also an excellent example of international collaboration.”

Everything Dinosaur acknowledges the assistance of a press release from Bristol University in the compilation of this article.

The scientific paper: “Ontogenetic braincase development in Psittacosaurus lujiatunensis (Dinosauria: Ceratopsia) using micro-computed tomography” by C. Bullar, Q. Zhao, M. Benton and M. Ryan in PeerJ — the Journal of Life and Environmental Sciences.

Adratiklit boulahfa – The Oldest Definitive Stegosaur

A team of British scientists in collaboration with colleagues from Morocco, have announced the discovery of a new species of armoured dinosaur, described from remains found in the Atlas Mountains.  The dinosaur has been named Adratiklit boulahfa and it is the first stegosaur to have been found in northern Africa.  Adratiklit is also the oldest definitive stegosaur described, it having roamed Morocco some 168 million years ago (Bathonian faunal stage of the Middle Jurassic).  This fossil discovery is significant, as it hints at the possibility of more armoured dinosaurs likely to be found on the continents that once made up the ancient landmass of Gondwana.

A Life Restoration of the Newly Described North African Stegosaur Adratiklit boulahfa

A life restoration of Adratiklit boulahfa based on the closely related Dacentrurus.  The scale size estimate for this dinosaur has been compiled using the left humerus (NHMUK PV R37007).

Picture Credit: Everything Dinosaur

The Third Stegosaur from Africa

The fossils were acquired by the Natural History Museum (London).  The material consists of cervical and dorsal vertebrae and the left humerus.  Although fragmentary, these fossils permitted the scientists to erect a new armoured dinosaur genus.  Although the exact provenance of these fossils is unclear, they probably came from the siltstone deposits of the El Mers II Formation located in the Middle of the Atlas Mountains (Fès-Meknes, northern Morocco).  The age of this formation has been dated biostratigraphically based on ammonite fossils.  Adratiklit is only the third stegosaur known from Africa, although a phylogenetic assessment carried out by the researchers, indicates that it was probably more closely related to European stegosaurs such as Dacentrurus (D. armatus).

Views of the Left Humerus Ascribed to A. boulahfa

Views of the left humerus ascribed to A. boulahfa.  NHMUK PV R37007, left humerus referred to Adratiklit boulahfa in A, lateral, B, posterior, C, medial, D, anterior, E, dorsal and F, ventral views.  Note the white scale bar.

Picture Credit: Gondwana Research/Maidment et al

The two other stegosaurs known from Africa described to date are:

• Kentrosaurus – K. aethiopicus from the Late Jurassic (approximately 156-148 million years ago), fossils found in Tanzania
• Paranthodon P. africanus from the Early Cretaceous (approximately 139-131 million years ago), fossils come from Cape Province, South Africa

What’s in a Name?

The generic name (Adratiklit), is from the local Berber terms for “mountain” and “lizard”, whilst the trivial epithet refers to Boulahfa, the likely site of the fossil discovery.  Commenting on the significance of this stegosaur from Morocco, lead author Dr Maidment commented:

“The discovery of Adratiklit boulahfa is particularly exciting as we have dated it to the Middle Jurassic.  Most known stegosaurs date from far later in the Jurassic period, making this the oldest definite stegosaur described and helping to increase our understanding of the evolution of this group of dinosaurs.”

One of the Two Dorsal Vertebrae Preserved (A. boulahfa)

Views of the holotype fossil specimen (dorsal vertebra) of Adratiklit boulahfa.  NHMUK PV R37366, holotype specimen of Adratiklit boulahfa.  Dorsal vertebra in A, anterior, B, posterior, C, left lateral, D, right lateral, E, dorsal and F, ventral view.

The Implications for Stegosaurs and Ankylosaurs from Gondwana

The Stegosauria together with the Ankylosauria form a clade within the Ornithischian dinosaurs, this is referred to as the Eurypoda, which has been defined to include the iconic armoured dinosaurs Ankylosaurus, Stegosaurus and their most recent, common ancestor and all its descendants.  The fossil record suggests that stegosaurs were more common than ankylosaurs in the Jurassic, but during the Cretaceous the ankylosaurs rose in prominence and the stegosaurs as a group went into decline.

It is important to note that numerous members of the Eurypoda are known from Mesozoic rocks that made up the northern landmass of Laurasia, but only a few Eurypoda taxa are known from the super-continent of Gondwana.

The Global Distribution of Eurypoda Fossil Finds (Stegosaurs and Ankylosaurs)

A map showing the known fossil distribution of the Eurypoda.  The grey dots indicate the presence of fossils associated with the Eurypoda clade.  More dinosaurs assigned to the Eurypoda have been found in areas associated with Laurasia, in contrast fossils representing the Eurypoda from Gondwana are relatively sparse.

Picture Credit: Tom Patterson, Nathaniel Vaughn Kelso et al from naturalearthdata.com, along with Bjørn Sandvik via Wikimedia Commons.

Writing in the academic journal, “Gondwana Research”, the scientists conclude that it remains unclear whether these types of armoured dinosaurs were genuinely rare in Gondwanan Mesozoic ecosystems, or whether their poor fossil record on southern continents is the result of sampling bias.  The discovery of a Moroccan stegosaur hints at the possibility that there could be many more armoured dinosaurs awaiting discovery in South America, India, Africa, Madagascar, Australia and Antarctica.

The scientific paper: “North Africa’s first stegosaur: Implications for Gondwanan thyreophoran dinosaur diversity” by Susannah C. R. Maidment, Thomas J. Raven, Driss Ouarhache and Paul M. Barrett published in Gondwana Research.

The “Scunthorpe Pliosaur” – What is it?  When and Where Did it Live?  What it May Have Eaten and Lived Alongside

A few weeks ago, we set young palaeontologist Thomas a challenge, could he research and write an article for posting up onto the Everything Dinosaur blog.  Thomas has taken up our offer and here is the first of his articles, it provides information on a prehistoric animal close to Thomas’s  heart the “Scunthorpe Pliosaur”.

The “Scunthorpe Pliosaur”, a specimen announced earlier this year, was a large plesiosauroid belonging to the family Pliosauridae and is related to the better known pliosaurs such as Pliosaurus and Liopleurodon in fact, it may have lived alongside and directly competed with these two better-known pliosaurs at some point.  It has been estimated at 8 metres long.

The “Scunthorpe Pliosaur” on Display at North Lincolnshire Museum

Rose Nicholson from North Lincolnshire Museum, palaeontologist Richard Forrest and Darren Withers from Stamford and District Geological Society with the “Scunthorpe Pliosaur”.

Picture Credit: North Lincolnshire Museum

When and Where Did it Live and Where was it Found?

The “Scunthorpe Pliosaur” lived around 160 to 155 million years ago in what is now north Lincolnshire (England).  These fossils date from the Late Jurassic and the United Kingdom 160 million years ago was a very mysterious place.  Whilst marine fauna is decently represented in the fossil record, there is still much science does not know about the seas from this time and this new specimen may help open up a new window into that mysterious world.  The terrestrial fauna on the other hand, is poorly represented and full of mystery with one of the only described theropods being the British Metriacanthosaurus from Dorset (a close relative of Sinraptor from China).  The pliosaur specimen was recovered from a CEMEX quarry.

Partially Excavated Fossils at the Excavation Site

Ribs and a vertebra in situ.

Picture Credit: Yorkshire Geological Society

What Did it Live With and What Might it Have Eaten?

Inhabiting the seas alongside the “Scunthorpe Pliosaur” were other pliosaurs, plesiosaurs, turtles, fish, ichthyosaurs, squid, ammonites, marine crocodiles, sharks and more.  Some of these animals include the pliosaurs Liopleurodon, Simolestes and Pliosaurus which would have competed with it and the plesiosaurs Cryptocleidus and Colymbosaurus which could have been prey of the pliosaur especially the latter plesiosaur’s young.

Palaeontologist Richard Forrest Holding a Fossil Tooth

Richard Forrest holding a pliosaur tooth.

Picture Credit: North Lincolnshire Museum

Looking at the “Scunthorpe Pliosaur’s” dentition, the known teeth of this pliosaur are reminiscent of teeth associated with Pliosaurus (Pliosaurus brachydeirus),  a species which has been found in Lincolnshire.  From this comparison, it can be concluded that the Scunthorpe individual possibly preyed upon other marine reptiles and other large marine fauna.  Stomach content of related pliosaurs and bite marks left by them on their prey show that pliosaurs like the Scunthorpe specimen would have been hunting a wide range of hard bodied marine prey from large ammonites to plesiosaurs and ichthyosaurs, however, they wouldn’t have shied away from preying on softer bodied animals.

Like most pliosaurs, the “Scunthorpe Pliosaur” probably had a very powerful sense of smell, good eyesight, acute hearing and a powerful bite, all necessary adaptations for a hunting pliosaur to have in order to hunt effectively.

Holding a Fossilised Pliosaur Tooth

Holding a fossil tooth.

Picture Credit David Haber

The ecology at the time would have consisted of kelp forests, reefs, coastal shallows and a steep pelagic drop-off that plummets into a benthic zone.  Pliosaurs such as Liopleurodon, Pliosaurus and the “Scunthorpe Pliosaur” probably used these drop-off points as ambush spots to strike unsuspecting prey from below.

When attacking prey, Pliosaurs would have come up from below like white sharks and either rammed or bitten prey in one massive disabling blow to the prey item to prevent it’s escape.   In conclusion, the “Scunthorpe Pliosaur “was a large pliosaur which could have occupied the apex predator niche in its warm, shallow coastal ecosystem hunting all manners of prey from fish and squid to marine reptiles using sight, hearing and smell to track down its prey and applying similar hunting strategies to modern Great Whites to secure and catch that prey.  This discovery is an important one as it opens up a window into a little known area of the Late Jurassic British seas and helps palaeontologists piece together that ancient ecosystem over 155 million years ago.

Holding the Ancient History of North Lincolnshire

History in your hands, part of the fossilised skeleton.

Picture Credit: The Stamford and District Geological Society Facebook page

Our thanks to Thomas for compiling this article on the “Scunthorpe Pliosaur”.