The Significance of the Pterosaur Allkaruen

A few days ago, Everything Dinosaur featured an article on this blog about a newly described Early Jurassic pterosaur named Allkaruen koi.  We were subsequently emailed by one young dinosaur fan asking us to explain the significance of this fossil discovery.  Why was the pterosaur Allkaruen important?

Time to Get Excited About Pterosaurs – Learning Lots about Flying Reptiles

White bar shows scale.

Picture credit: Scientific Reports/Xiaolin Wang et al

The photograph above shows the fossilised remains of Ikrandraco avatar, a new species of pterosaur described in 2014.

To read our recent article on the discovery of a new pterosaur (A. koi) from Patagonia (Argentina): New Long-Tailed Pterosaur from Patagonia.

Pterosaur Fossils are Exceedingly Rare

Fossils of flying reptiles are exceedingly rare, of the 130 or so genera described to date, most are known from only a few fragmentary fossils, mere scraps of bone and teeth.  The light, delicate, pneumatic bones of pterosaurs rarely survive the ravages of time and the fossilisation process.  Most corpses, don’t even get buried, the chances are the carcase would have been scavenged long before it settled on a lake bed or the bottom of a shallow sea.

Therefore, the naming of a new flying reptile species is, in itself, a significant event.  For Allkaruen koi, even more so, as the rocks in southern Argentina where the fossilised bones were found indicate that this flying reptile lived around 180 million years ago.

For models and replicas of pterosaurs and other prehistoric creatures: CollectA Deluxe Scale Prehistoric Animal Models.

A Beautiful Braincase

The new pterosaur genus has been erected after careful study of the skeletal elements including an almost perfect, three-dimensionally preserved braincase.  Most pterosaur fossils are crushed, distorted or compacted but not in this case, one of just a handful of very well-preserved flying reptile braincases known in the fossil record.  The braincase of Allkaruen shows a unique combination of characteristics of both the Rhamphorhynchoids (non-monofenestratan breviquartossans) and the Pterodactyloidea – let’s explain what this means.

The Pterosauria – the Order of reptiles that includes all these flying reptiles can be split into to distinct and very different groups.

1. Formerly referred to as the Rhamphorhynchoids (as the very well known Rhamphorhynchidae family is included in this group), but now known to include a number of other pterosaur families that evolved in the Triassic and the Jurassic, characterised by long-tails and a lengthy fifth digit.
2. The Pterodactyloidea essentially the vast majority of known pterosaurs, a Jurassic/Cretaceous radiation of flying reptiles with thin bone walls, relatively long metacarpals and much shorter tails.

The Pterosaur Allkaruen

So, in short, the researchers have a braincase from an Early Jurassic pterosaur that shows features of both groups, the basal group and the later, short-tailed, long toed, thin bone walled Pterodactyloidea.  By studying the braincase of Allkaruen the palaeontologists can learn more about how the Pterodactyloidea evolved.  They can see how the brains of flying reptiles changed over time.

A Phylogenetic Assessment of Allkaruen Compared to Rhamphorhynchus and the Later Pterosaur Anhanguera

Where within the Pterosauria Order does Allkaruen fit in?

Picture credit: PeerJ

The researchers compared the changing shape and structure of pterosaur brains, comparing Allkaruen with the brain anatomy of Rhamphorhynchus (representing the basal group), with the brain anatomy of a later Cretaceous pterosaur Anhanguera, a representative of the short-tailed Pterodactyloidea.  Allkaruen could be described as a sort of “halfway house” between these two groups, a snapshot in pterosaur evolution permitting scientists to gain “insights into the origin of the Pterodactyloid neurocranium and improve our understanding of the tempo and mode of pterosaur evolution.”

The scientists mapped the various elements of the brain by comparing the braincases of these three pterosaurs, from this information they could plot the evolution of the inner ear, essentially the balance organ, vital if you are going to spend a long time in the air.

A Larger Brain Volume

The brain volume of Allkaruen is much bigger than that of Rhamphorhynchus and from this it can be inferred that Allkaruen was a more advanced animal capable of better co-ordinated flight and faster reactions than the Rhamphorhynchidae.  The cerebellum (show in yellow in the three brain diagrams included in the picture above), is much larger in Allkaruen than it is in Rhamphorhynchus.  The cerebellum in vertebrates is found towards the back of the brain it coordinates and regulates muscular activity.  A bigger cerebellum is another indicator that Allkaruen was a better flyer than the more basal pterosaurs.  This and other evidence is helping palaeontologists to understand more about how the pterosaurs evolved.

That’s why this fossil discovery is so important.

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Allkaruen koi – Braincase and All

A team of international scientists including Leicester University’s David Unwin and Oliver Rauhut (conservator at the Bavarian Collection for Palaeontology and Geology), have announced the discovery of a new species of long-tailed pterosaur from Patagonia (Argentina).

A Long-tailed Pterosaur

Writing in the academic journal “PeerJ”, the researchers were able to infer new information about how pterosaurs adapted to an aerial lifestyle thanks to the three-dimensional preservation of the cranial material.  From this skull material, the team were able to gain fresh insights into the braincase and the structure of the inner ear.  The new species of pterosaur will help palaeontologists to better understand differences between the primitive, primarily long-tailed “rhamphorhynchoids”, also known as non-pterodactyloids and the more derived and later, short-tailed pterodactyloids.

An Illustration of the New Pterosaur (Allkaruen koi)

An illustration of the newly described Jurassic pterosaur from Argentina called Allkaruen.

Picture credit: Gabriel Lio

For models and replicas of pterosaurs and other creatures: Wild Safari Prehistoric World Models.

The Evolution and Radiation of the Pterosauria

The fossilised remains of this new pterosaur come from the Cañadón Asfalto Formation, exposed in the northern/central Chubut Province of southern Argentina.  The fossil material came from a single bedding plane formed from freshwater limestone deposits, indicating that there was a large, inland body of water present.  The fossils were scattered although elements such as the mandible preserved a degree of articulation.  The rocks of the Cañadón Asfalto Formation had been thought to be about 162 million  years of age (Callovian to Oxfordian faunal stages – latest Middle to earliest Late Jurassic), however recent radiometric and biostratigraphical analysis suggests that these rocks might be much older.

Research published in 2013 (Cúneo et al), indicates an age range for this formation of between 183 and 165 million years (Toarcian to Bathonian faunal stages).

The genus name comes from the local Tehuelche dialect word “all” for “brain” and “karuen” which means “ancient”, in recognition of the superb three-dimensional preservation state of the fossil  skull.  The species name means “lake” in the Tehuelche language, reflecting the fact that the fossils were found in lacustrine deposits,

Fossils and Line Drawings of the Allkaruen koi Material

Fossils of the braincase, line drawings of the braincase along with drawings of the mandible and vertebrae.

Picture credit: PeerJ

Two Main Types of Pterosaur

Pterosaurs have remarkable skeletal adaptations for life in the air and they were the first vertebrates to achieve powered flight.  Two major body plans have traditionally been recognised, rhamphorhynchoids (non-pterodactyloids) and the pterodactyloids.  These two types of flying reptile differ considerably in their general anatomy and also they exhibit very different head postures and neuroanatomy (nervous systems and the study of the brain).  Computerised tomography was employed to scan the uncrushed braincase that enabled the scientists to infer more information regarding the shape of the brain and the inner ear.

This study has provided new information on the origins of the highly derived neuroanatomy of pterodactyloids, as, until this new fossil discovery, only a few three-dimensionally preserved braincases of flying reptiles were known and these demonstrated a large morphological gap between the specimens.

The braincase of Allkaruen has helped fill in a portion of that gap to give scientists a better understanding of how the flying abilities of these reptiles evolved.

Dr Diego Pol (CONICET, Museo Paleontológico Egidio Feruglio, Trelew, Chubut, Argentina) and corresponding author for the published paper stated: 

“Allkaruen shows an intermediate state in the brain evolution of pterosaurs and their adaptations to the aerial environment.  As a result, this research makes an important contribution to the understanding of the evolution of all of pterosaurs.”

A Phylogenetic Analysis

A phylogenetic analysis was undertaken and Allkaruen is nested between monofenestratan breviquartossans (Rhamphorhynchidae) and derived pterodactyloids.  Given the age of the fossil and its phylogenetic affinities to Rhamphorhynchus and the pterosaur known as Darwinopterus it has been suggested that this flying reptile had a long tail with a diamond-shaped rudder on the end of it.  Analysis of the cranium indicates that Allkaruen had two parallel crests on the top of its skull and it appeared to have teeth restricted to the middle and anterior (front) part of its jaws.  Although the exact diet of this pterosaur is not known, given the context of the fossil material and the shape of the teeth, Allkaruen most likely fed on fish.

To read an article on the transitional fossil Darwinopterus: Darwinopterus – A Transitional Pterosaur.

Dr Oliver Rauhut has had a busy couple of weeks, he was also one of the principal authors of the scientific paper on the Early Jurassic meglosaurid Wiehenvenator.  To read about the “Monster of Minden”: Wiehenovenator – The “Monster of Minden”.

Everything Dinosaur is based in the UK.  We produce helpful and informative blog posts including articles about fossil finds.

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The “Monster of Minden” – Wiehenvenator albati

A new species of large, Middle Jurassic carnivorous dinosaur has been described.  Writing in the academic journal “Palaeontologica Electronica” the researchers, which include Dr Oliver Rauhut, (conservator at the Bavarian Collection for Palaeontology and Geology), identify this new theropod as a member of the Megalosauroidea.  Named Wiehenvenator albati, it could be a potential sister taxon to Torvosaurus and a dinosaur that might have been about the same size as Torvosaurus gurneyi, reaching an estimated length of around ten metres.

An Illustration of the Newly Described Middle Jurassic Theropod from Germany

Scale bar = 1 m (an illustration of Wiehenvenator).

Picture credit: Palaeontologica Electronica (based on an illustration of Torvosaurus by Scott Hartman

The picture above shows the known fossil bones of Wiehenvenator.

Wiehenvenator albati – A German Dinosaur

Fragmentary fossils including elements from the skull and jaws, caudal vertebrae, ribs and bones from the lower legs and ankle were excavated from a disused quarry located in Northrhine-Westphalia (Germany) back in 1999.  The fossils were found by chance, it was a routine inspection, however, once the first bones had been discovered a field team was brought in to ensure all the fossil material present could be collected.

The strata in which the fossil material was found are Middle Callovian in age (around 163 to 165 million years old) and they represent marine sediments.  During this time, much of the land that was to form western Europe lay under a warm, shallow tropical sea.  A number of small islands existed and it seems that this archipelago was home to this hunter, a dinosaur that is estimated to have weighed more than two tonnes.

Skull and Elements of the Jaws in their Anatomical Position

The skull and jaw fossils located in their anatomical position (Wiehenvenator).

Picture credit: Palaeontologica Electronica

“The Monster of Minden” – Wiehenvenator albati

Nicknamed “The Monster of Minden”, due to the town’s close proximity to the fossil dig site, Wiehenvenator was probably the apex predator on the island archipelago.  The teeth associated with this dinosaur are strongly recurved with the root making up more than two thirds of the tooth length.  The largest teeth identified so far (from the maxilla), measure in excess of 13 centimetres long.

The Teeth of Wiehenvenator albati (Various Views)

The strongly recurved teeth of Wiehenvenator.

Picture credit: Palaeontologica Electronica

Fossil Teeth

The picture above shows various views of the fossil teeth associated with the jawbones or found as loose items at the dig site.  The scale bar for 1 and 2 is 1 centimetre, the scale bar in the other images represents 5 centimetres (except picture 9).  The dinosaur was named Wiehenvenator for the Wiehengebirge, a chain of hills south of the town of Minden, where the holotype specimen was found and venator, Latin for hunter.  The trivial name honours Friedrich Albat, who found the holotype specimen.

Commenting on the significance of the discovery, Dr Rauhut stated:

“Apparently there was in these islands a wide range of sometimes very large predators mainly from the group of Megalosauroidea as finds from France and England, as well as the new predators from Germany show.  The Megalosauroidea were the first giant predatory dinosaurs of Earth’s history.”

Differences in the Middle and Late Jurassic Theropod Fossil Records

The discovery of Wiehenvenator adds to the number of large theropods known from the Callovian faunal stage of the Jurassic.  The research team comments on the number of large theropods from the Middle Jurassic that are classified as megalosauroids and they suggest that a rapid radiation of megalosaurs is suggested between the Toarcian and the Bathonian faunal stage of the Jurassic (approximately 183 to 166 million years ago).

The scientists postulate that this radiation and increase in the number of megalosaurs was probably triggered by the Pliensbachian-Toarcian extinction event that took place around 183 million years ago.

They comment that this extinction event may have been more significant for theropod evolution than the larger end Triassic mass extinction.  The team then go on to review the changes in theropod genera that took place from the Middle Jurassic onwards.

Two Views of the Right Maxilla (Upper Jaw Bone) of Wiehenvenator

Right maxilla of Wiehenvenator albati in lateral (1) and medial (2) views.

Picture credit: Palaeontologica Electronica

The picture above shows two views of the right maxilla of Wiehenvenator albati, top (1) lateral view and bottom (2) medial view.

Less Megalosaurs More Allosaurs

The fossil record indicates a faunal turnover from Megalosauroidea dominated Middle Jurassic to allosauroid/coelurosaur dominated Late Jurassic theropod faunas. The researchers plotted the number of different theropod fossils found globally between the Middle Jurassic to the Late Jurassic.  Although the paucity of the fossil record makes a complete analysis impossible, the team did infer that there was a change in the proportion of different types of theropod dinosaur represented as the Jurassic progressed.

The once dominant megalosaurs were replaced by coelurosaurs and allosaurs.

For models and replicas of a variety of theropod dinosaurs: PNSO Age of Dinosaurs Models.

Middle Jurassic Theropods Compared to Late Jurassic Theropods (Assessed by Clade)

A fossil record comparison of theropods (Middle Jurassic compared to Late Jurassic).

Picture credit: Palaeontologica Electronica

The Impact on Large Taxa (Apex Predators)

Theropod faunal turnover (taxa estimated to be >250 kgs in size).

Picture credit: Palaeontologica Electronica

Allosaurs Replacing Megalosaurs – Theropod Faunal Turnover

When body mass is considered and theropod dinosaurs estimated to be less than 250 kilogrammes in weight are removed, the impact of the rise in the number of coelurosaurs is lost, suggesting that these dinosaurs did not rise to the apex predator niche during this period.  Large megalosaurids which dominated the apex predator niche globally during the Middle Jurassic had been substantially replaced by allosaurids by the end of the Jurassic.

The scientists are quick to point out that these figures are not conclusive, bias because of the large number of theropods from the Upper Jurassic Morrison Formation is discussed along with the difficulties of undertaking analysis of this sort due to the relatively poor fossil record of large meat-eating dinosaurs over the time period studied.

However, an analysis of environmental preferences of allosauroids and megalosauroids indicates that the former preferred inland environments, whereas the latter are more common in nearshore environments.

From this it could be inferred that megalosaurids preferred to “be beside the seaside”.

The publication: “A new theropod dinosaur megalosaurid from the late Middle Jurassic (Callovian) of north-western Germany: Implications for theropod evolution and faunal turnover in the Jurassic.  By: Oliver WM Rauhut, Tom Huebner, and Klaus-Peter Lanser. In: Palaeontologia Electronica 2016.

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“Lucy” Most Likely Died after a Fall from a Tree

A team of researchers from Ethiopia and the United States have published a remarkable post-mortem on one of the most famous hominin fossils known to science.  It turns out that the 3.2-million-year-old Australopithecus afarensis known as “Lucy”, very probably died from injuries resulting from a fall from height, most likely a fall from a tree.

Computerised Tomography and “Lucy”

Computerised tomography was employed to study the fossilised bones whilst the specimen was on tour of America (Lucy’s Legacy: The Hidden Treasures of Ethiopia).  The high resolution scans helped the scientists to determine which of the many fractures in the bones related to injuries and which ones were as a result of more than three million years preserved in strata.

A Reconstruction of an Australopithecus afarensis Based on Fossil Material

A reconstruction of “Lucy” A. afarensis.

Perimortem Fractures

Lead author of the scientific paper, which has just been published in the journal “Nature”, Professor John Kappelman (University of Texas) explained:

“These fractures have been known since she was discovered.  I’ve looked at this fossil for thirty years and I knew that these fractures were there.”

“Lucy” was discovered in the Afar region in 1974, ironically this hominin got her nickname as “Lucy in the Sky with Diamonds”, the Beatles tune from the album “Sgt. Pepper’s Lonely Hearts Club Band”, had been played repeatedly by the research team at the dig site.

“Lucy” Killed in a Fall

It seems that a fall killed her and as since the fossils are associated with a flood plain with trees, it seems highly plausible that “Lucy” fell out of a tree.  This new study supports the idea that Australopithecus afarensis spent at least some of its time in the trees.  However, adaptations to a more terrestrial life, especially bipedal locomotion may have limited this species in terms of their ability to climb trees.  Being better adapted to walking upright meant a trade off between this and tree climbing ability.  In the case of “Lucy” this was to lead to fatal results.

The Fossilised Remains of “Lucy” A. afarensis

The fossilised bones of Lucy (approximately 40% of the skeleton).

Picture credit:  The world’s most famous fossil, known as “Lucy,” went on display for the first time outside of Ethiopia in the world-premiere special exhibition Lucy’s Legacy: The Hidden Treasures of Ethiopia.

A Dramatic “Vertical Deceleration Event”

The scans revealed a number of perimortem injuries (pathology related to death or shortly before death), particularly a crushed shoulder joint, consistent with a person reaching out their arms to try and break their fall.  The scans also revealed traumatic injuries to the ankle, leg bones, the kneecap, pelvis, ribs, skull, jaws and backbone.  When the research team examined these injuries and compared them to orthopaedic literature in relation to fall victims, the team found striking similarities between the fractures.

Commenting on how certain the researchers were with regards to the fall from height (vertical deceleration event), Professor Kappelman stated that the team’s hypothesis:

“It’s tested every day in emergency rooms all around the planet.”

“Greenstick Fractures”

A number of the perimortem fractures identified were “greenstick” breaks.  The bone had bent and snapped like a branch of a tree, something that only happens to healthy, living bones.  The scientists concluded that these traumatic injuries occurred when Lucy was alive, as they show no signs of healing and as the injuries were so catastrophic, they very probably all occurred at the same time, a consequence of a fatal accident.

The fatal fall also fits with the fact that Lucy’s tiny first rib is broken.  This small bone is heavily protected by the chest, if this is broken in an accident, as Professor Kappelman explains: “you’re having a bad day.”

A Shattered Shoulder Joint and Other Injuries

When the shattered shoulder joint was examined the team concluded (after reviewing the evidence with orthopaedic surgeons), that Lucy had tried to break her fall by reaching out her arms, as Professor Kappelman explained: “if our hypothesis stands up… it tells us that Lucy was conscious when she reached out her arms to break her fall.”

The Postulated Demise of “Lucy” – A Fall from a Tree

A reconstruction explaining the fatal injuries to “Lucy” – A. afarensis after a fall from a tree.

Picture credit: University of Texas

A Severe Impact

In a remarkable analysis the researchers plot the demise of Lucy and comment when each of her injuries was likely to have occurred.  The impact would have been so severe as to cause concomitant fractures usually such a fall would also damage internal organs; together, these injuries are hypothesised to have caused her death.

When fossils of Australopithecines are examined they appear to have been capable of both terrestrial and arboreal locomotion.  The authors suggest that the adaptations that facilitated bipedal, terrestrial locomotion compromised the ability of individuals to climb safely and efficiently in the trees.  This combination of features may have predisposed these hominins to more frequent falls from height.

Looking for Signs of Injury

Close inspection of other fossils for signs of injury has the potential to offer important insights about hominin lifestyle, through an understanding of the trauma that they suffered and the mechanisms by which they died.

With the cooperation of the Ethiopian Government a series of data files have been produced and made freely available to other researchers.  In addition, as a result of the 45,000 scans taken by the team, a number of bones from Lucy have been reconstructed, these too will provide valuable learning resources.

Professor Kappelman in His Anthropology Laboratory with Casts of “Lucy’s” Bones

Professor Kappelman examines casts of “Lucy” – A. afarensis.

Picture credit: University of Texas

“Lucy” and her kind the Australopithecus afarensis have been at the centre of a vigorous debate amongst palaeoanthropologists.  How much time did these hominins spend in the trees?  It is ironic therefore, to hypothesis that “Lucy” died as a result from a fall, probably out of a tree.  The fractured bones providing evidence of arborealism within this species.  This is one very “cold case” that may have been cracked.

One further question to ask, did “Lucy” fall or was she pushed?

To read an additional article on bipedalism in early hominins: Early Hominins Walked Upright so they could Carry more Food.