Azendohsaurus – Not a Dinosaur, as Homer Simpson would say DOH!

A prehistoric reptile that roamed what was Africa in the middle of the Triassic that was once thought to be a primitive herbivorous dinosaur has been proven to be something altogether different.  Analysis of new fossil material has identified this plant-eating reptile that shared the Triassic with the diversifying dinosaurs and pterosaurs, an animal named Azendohsaurus, as a member of the Archosauromorpha.

Azendohsaurus not a Dinosaur

A careful new analysis of Azendohsaurus madagaskarensis using more complete skull material aligns this Middle Triassic reptile with a very different and very early branch of the reptile evolutionary tree.  Although it has several anatomical features that are similar to early herbivorous dinosaurs, new research by a team of scientists at the American Museum of Natural History (AMNH), indicates that this animal was wrongly assigned to the Dinosauria.

The holotype specimen of Azendohsaurus consists of fragmentary teeth and jaws that were discovered in 1972 close by (and named after) a small village in the Moroccan Atlas mountains.  The perils of naming a genus of dinosaur based on teeth evidence alone is well documented, take for example the taxonomic difficulties which are still being encountered nearly 200 years after the naming and describing of the dinosaur genus known as Iguanodon.

The Crystal Palace Iguanodon Figures

A pair of Iguanodons study the Crystal Palace landscape.  This dinosaur genus was first identified from fossil teeth. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

However, the discovery of new, much more complete fossil material, including skull material and a number of individual specimens at a site in southwestern Madagascar has enabled scientists at the American Museum of Natural History (New York) to revise the classification of this particular Triassic reptile.

In a paper published in the scientific journal “Palaeontology”, the researchers state that many aspects of Azendohsaurus are far more primitive than previously assumed, which in turn means that its plant-eating adaptations, similar to those found with some early dinosaurs, were developed independently.  This is evidence of covergent evolution, where different organisms evolve the same adaptations to cope with their environments and the ecosystem.

Commenting on the new research, John J. Flynn, curator in the Division of Palaeontology at the AMNH stated:

“Even though this extraordinary ancient reptile looks similar to some plant-eating Dinosaurs in some features of the skull and dentition, it is in fact only distantly related to Dinosaurs.  With more complete material, we re-assessed features like the down-turned jaw and leaf-shaped teeth found in A. madagaskarensis as convergent with some herbivorous dinosaurs.”

Diagrams show a reconstruction of the skull of the new species of Azendohsaurus.  On top is a lateral or side view, and on the bottom, a palatal or roof of the mouth view.  Note the teeth covering the palate, a highly unusual feature among reptiles, and the down-turned front end of the lower jaw, a feature found independently in many herbivorous archosauromorphs.

This particular creature was initially described and published as an early dinosaur in the scientific journal “Science” over a decade ago, but the completeness of the more recently unearthed and studied fossils has provided the first complete glimpse of what this animal looked like and was related to.  A. madagaskarensis was not a dinosaur.

A Member of the Archosauromorpha

A. madagaskarensis lived during the period of time that dinosaurs and other archosaurs such as crocodiles and pterosaurs were beginning to diversify.  During this part of the Mesozoic one hemisphere (western) was dominated by a huge ocean (the Panthallassic Ocean) and the other hemisphere (eastern) was dominated by an enormous super-continent (Pangaea).  It is possible to have fossils of the same animal found in Morocco and the island of Madagascar today, as during the Triassic, Madagascar and Morocco formed part of Pangaea.  Madagascar did not break away from Africa until towards the end of the Mesozoic.

A. madagaskarensis was 2 to 4 metres long and weighed between 20 and 50 kilogrammes.   A. madagaskarensis was an efficient herbivore with teeth modified for slicing vegetation covering not only its jaws but also the roof of its mouth.

John J. Flynn described this animal as:

“a veritable four-legged weed-whacker.”

Even though early archosaurs were commonly thought to be primarily carnivorous, A. madagaskarensis shows that traits associated with herbivory were much more widespread across archosaur reptiles.

Commenting on this new study, André Wyss, Professor at the University of California (Santa Barbara) stated:

“Now there are many more cases of herbivorous archosaurs.  We are rethinking the evolution of diet and feeding strategies, as well as the broader evolution of the group.”

“This is the way science works,”

added Flynn, commenting on the reinterpretation of the fossils.

“As we found and analysed more material, it made us realise that this was a much more primitive animal and the dinosaur-like features were really the product of convergent evolution.”

André Wyss went onto state, that in many ways Azendohsaurus was turning out to be much more interesting as a non-dinosaur archosaur, than scientists could have imagined if it has stayed assigned to the Dinosauria as just another generic herbivore from the Middle Triassic.

Piecing together a prehistoric animal even when there is a copious amount of fossil material and data to work on is a very difficult task, with just the teeth and fragments of jaws to work with misinterpretations can occur.  However, once more fossils have been discovered a more thorough analysis can take place.  It is not uncommon for new material to lead to the revision of previously accepted work.  So Azendohsaurus is not a member of the Dinosauria after all, as Homer Simpson would say Doh!

We are grateful for the American Museum of Natural History (AMNH) for information on this subject area.

Everything Dinosaur stocks an extensive range of models of archosaurs, including dinosaurs, pterosaurs and crocodilians: Archosaur Models and Prehistoric Animal Figures.

Archaeopteryx Reveals Chemical Link Between Dinosaurs and Birds

A team of Anglo/American researchers have published a new study on one of the most famous of all the creatures in the fossil record, Archaeopteryx.  Thanks to the use of some very sophisticated technology; the team have revealed a chemical link between this primitive Jurassic bird and modern birds.

This crow-sized bird displays an unambiguous mix of characteristics from two linked groups of animals – Theropod dinosaurs and Aves (birds).  The skeleton, beautifully preserved in a number of specimens from Solnhofen (Germany) shows many features of small, meat-eating, cursorial dinosaurs.  Archaeopteryx had a three-fingered hand like that of a theropod dinosaur but a four-toed foot with the first toe potentially reversed to the other three to help it perch in trees like a bird.  Earlier specimens of Archaeopteryx had been interpreted as having a perching adaptation, but the specimen used in the chemical analysis shows evidence of Archaeopteryx not having a reversed first toe.  The jaws were lined with fine, needle-like teeth and Archaeopteryx had a long, bony reptilian tail.  However, the most strikingly birdlike feature of Archaeopteryx is the feathers, exquisitely preserved in the fine-grained, lithographic limestone in a number of specimens.

A Model of the Jurassic Bird Archaeopteryx

Papo Archaeopteryx “ancient wing” by Papo.  Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

The model in the photograph (above) is the Papo Archaeopteryx figure.  To view the Papo model range: Papo Prehistoric Animals.

In the study, published in the scientific journal “The Proceedings of the National Academy of Sciences” new light is shed (literally one of the fossils was exposed to powerful X-rays), on the chemical relationship between dinosaurs and birds.

Extremely strong X-ray beams and other high tech equipment reveal that in the Archaeopteryx fossil studied, (The Thermopolis specimen, described in 2005 and on display at the Thermopolis museum in Wyoming, USA), chemical components of feathers, the residues of decayed organic materials remain in association with the fossilised bones.  Such residues would not be apparent in a visual inspection and the traces of feathers would remain undetected in a conventional analysis.

The use of such powerful x-ray equipment and sophisticated technology is helping to provide palaeontologists with new data on long extinct creatures.  The research, led by scientists at the University of Manchester and the U. S. Department of Energy’s SLAC National Accelerator Laboratory has led to the chemical mapping of the fossil and elements of the surrounding matrix.  Using powerful computer programmes, the X-ray data and chemical analysis has helped the team map out the chemical signature of the Archaeopteryx specimen used in the study.

The feathers contain phosphorous (P) and sulphur (S), these same chemical elements are found in the feathers of Neornithes (modern birds).  Trace amounts of copper  (Cu) and zinc (Zn) were also found in the fossilised bones.  Like birds today, Archaeopteryx may have required those elements to stay healthy.

Commenting on the research work, University of Manchester palaeontologist Phil Manning said:

“Archaeopteryx is to palaeontology what Tutankhamen is to the science of archaeology.  It’s simply one of the icons of our field.  You would think that after 150 years of study, we would know everything we need to know about this animal, but guess what – we were wrong.”

Lead author geochemist Roy Wogelius from The University of Manchester added:

“We talk about the physical link between birds and dinosaurs, and now we have found a chemical link between them.  In the fields of palaeontology and geology, people have studied bones for decades.  But this whole idea of the preservation of trace metals and the chemical remains of soft tissue is quite exciting.”

The researchers found significantly different concentrations of elements in the fossil than in the surrounding rock matrix, confirming that the chemicals are remnants of the animal and not minerals leached from the surrounding rock into the fossil.

A Cast of a Famous Archaeopteryx Fossil

Archaeopteryx fossil cast. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

SLAC physicist Uwe Bergmann, who led the X-ray scanning experiment, stated:

“People have never used a technique this sensitive on Archaeopteryx before.   Because the SSRL beam is so bright, we were able to see the teeniest chemical traces that nobody thought were there.”

Sophisticated technology such as the synchrotron are becoming as important to palaeontologists as the trusty geological hammer.  The use of such equipment is helping scientists to learn fresh insights and to gain new data about the organisms that make up our fossil record.  It is not really surprising to see the same “chemical fingerprint” of feathers in a fossil of an ancient bird as you would expect to find in a modern bird.  This X-ray scanning technique may have more significant implications when studying less well preserved theropod fossils.  The lithographic limestones in which the feathers of Archaeopteryx are preserved have enabled exquisite details of the specimen to be studied.  Other theropod fossils, perhaps those preserved in coarser grained sandstones may not show the presence of feathers.  Under X-ray scanning, a different picture may emerge, the chemical fingerprint of feathers could be inferred from the analysis of elements within the fossil matrix.  Scientists may be able to infer the existence of other feathered dinosaurs, even though no trace of the delicate feathers themselves have been preserved.

Pterosaur Jawbone Hints at Greater Diversification of Ornithocheirids in North America

The fossilised mandible of a flying reptile (pterosaur) is helping scientists to piece together a puzzle that has confused palaeontologists for generations.  Pterosaurs, those winged reptiles, the first vertebrates to evolve powered flight, ruled the skies for much of the Mesozoic.  From their Triassic origins; this group of reptiles rapidly diversified and although they began to decline in numbers towards the end of the Cretaceous, the last of their kind persisted to the very end of the Mesozoic.

Flying Reptile

However, one particular family of pterosaurs, the Ornithocheiridae (the name means bird hand), despite being widespread and numerous were almost absent from the fossil record of Cretaceous North America.  This omission had puzzled scientists.  The Ornithocheiridae consist of a number of genera, fossils of which have been found in England, Europe, South America, Australia and Asia but to date only one fragmentary pterosaur fossil from the whole of North America has been ascribed to this particular family of flying reptiles.  Most of these fossils date from the Early Cretaceous and some specimens represent species that may have rivalled the later Azhdarchidae as being the largest flying creatures ever.  Ornithocheirus for example, a genus that represents ten species, may have had a wingspan in excess of 13 metres.  However, the true size and diversity of this genus is difficult to assign accurately as the vast majority of pterosaur fossils relating to Ornithocheirus are fragmentary and poorly preserved.

However, the fossil finds of Ornithocheiridae in the whole of North America has just been doubled, thanks to the discovery of a 95-million-year-old jawbone.  In a paper published in the scientific publication “The Journal of Vertebrate Palaeontology”, the jawbone, discovered in Texas, four years ago is formerly described and a new genus of ornithocheirid announced.  Enter Aetodactylus halli (the name means Hall’s eagle finger – after Lance Hall the amateur fossil hunter who found the fossil in 2006).

This pterosaur was very probably a fish-eater (indicated by dentition in the jawbone), it soared over what is now Dallas, approximately 95 million years ago (Cenomanian faunal stage).  For much of the Cretaceous, North America was divided in two by a shallow sea (the Western Interior Seaway).  It is likely that there were many ornithocheirids living at the time, but the geological conditions and their delicate, air-filled bones reduce the likelihood of fossil preservation.  The jawbone indicates that this animal may have had a wingspan in excess of 3 metres.

A Scale Drawing of an Ornithocheirus

Ornithocheirus “bird hand” a scale drawing.

Picture credit: Everything Dinosaur

For replicas of ornithocheirids and other flying reptiles: CollectA Age of Dinosaurs Popular Range.

The fossil jawbone is compelling scientists to review the evidence for ornithocheirids in North America, commenting on the discovery Timothy Myers of Southern Methodist University’s Huffington Dept. of Earth Sciences stated:

“The fossil hints at a diversity of pterosaurs in the Cretaceous of North America that wasn’t previously realised.”

The only other North American pterosaur fossil ascribed to the Ornithocheiridae was discovered here, too, suggesting that the dearth of other ornithocheirids in North America might be more a function of geography and geology than actual biological distribution.

The press release describing the discovery of this new genus of flying reptile states:

“The ancient sea that covered Dallas provided the right conditions to preserve… the delicate bones of flying reptiles that fell from their flight to the waters below.  The rocks and fossils here [Texas] record a time not well represented elsewhere in North America.  That’s why two species of ornithocheirids have been found here but nowhere else, and that’s why discoveries of other new fossils are sure to be made….”

Lance Hall the amateur fossil collector who found the jawbone, discovered the specimen eroding out of an exposed piece of shale near a road southwest of Dallas.  It seems likely that this animal’s body was swept out to sea, or perhaps it fell from the sky into the sea, sunk and was rapidly buried at the bottom in soft mud.

American scientists are hopeful that more fossils will be found in the strata, helping to shed further light on the diversity of Pterosaur genera in the region.

Baby Dinosaurs may have had Different Feathers from their Parents

In a few weeks time those garden birds that have nested and raised a brood successfully will be seeing their youngsters fledge and leave the nest.  A baby Blackbird for example, will moult, losing its downy insulation of feathers and develop feathers that are indistinguishable from its parents.  This youngster, that just a short while ago was an embryo, will look very similar to an adult of its species.  However, in a new paper published in the scientific journal “Nature” it seems that juvenile dinosaurs may have looked strikingly different from their parents.

Feathered Dinosaurs

In a study of two fossils one of an adult, the other of a juvenile dinosaur of the same species; by Chinese scientists, there is evidence to suggest that theropod dinosaur species at different growth stages may have had dramatically different feathers.  The fossils may indicate that as dinosaurs grew, their feathers changed dramatically.  This is the first time that such evidence has been seen in the fossil record and the interpretation of these two fossils, both recovered from the fossil rich Yixian Formation of western Liaoning (northern China), is being hotly debated by both palaeontologists and ornithologists.

The sedimentary rock formations of Liaoning Province are world famous due to the remarkably well-preserved Cretaceous fossils that they contain.  Much of our knowledge about feathered dinosaurs is due to the myriad of amazing and superbly well-preserved fossils of small theropod dinosaurs that have been discovered in quarries from this part of China.  The fine-grained, siltstones were formed by volcanic ash from nearby volcanoes that frequently erupted during the Early Cretaceous.  Animal and plant remains that had become deposited in lakes in the area were rapidly buried by the ash and this has led to the remarkable state of fossil preservation.  A number of small, feathered theropod dinosaurs are known from the area, dinosaurs such as Sinosauropteryx and Sinornithosaurus as well as birds, plant remains and even insects.

The dinosaur fossils that have attracted so much interest over how feathers may have changed dramatically as dinosaurs grew and reached maturity; are those of the small, oviraptorid Similicaudipteryx (Similicaudipteryx yixianensis).  This particular theropod is known from three specimens and it was formerly named and described in 2008.  Crucially, the local farmers who help the scientists to find fossils, found examples of an adult, whilst the other two fossils represent younger animals.

A Juvenile Similicaudipteryx

Photographs show a fossil of a juvenile Similicaudipteryx on the left with the fossilised remains of an adult on the right.  A team of researchers from the Institute of Vertebrate Palaeontology and Palaeoanthropology (IVPP) from Beijing have interpreted the fossils and produced a paper suggesting that unlike modern birds, the plumage and feathers of dinosaurs changed as these animals grew and reached maturity.

Similicaudipteryx was a small, bipedal, feathered dinosaur it was closely related to Caudipteryx (another feathered dinosaur discovered in Liaoning).

An Image of Caudipteryx

An image of the small, feathered dinosaur Caudipteryx.

To view models and replicas of feathered dinosaurs take a look at the Wild Safari Prehistoric World model range: Safari Ltd. Wild Safari Prehistoric World Models.

The fossils indicate that this little theropod had a maturation pattern not seen in modern birds.

Commenting on the paper, one of the authors, Xing Xu of the IVPP stated:

“This baby dinosaur has bizarre flight feathers, which are strikingly different from those of adults.  These 125-million year old fossils expand our knowledge of feather evolution.”

The wing and tail feathers of the more mature dinosaur resemble quill pens. These ‘pennaceous’ or contour feathers have a central shaft that runs through its entire length. Conversely, the feathers of the younger dinosaur have a flat, ribbon-like stem at one end, but the more familiar pennaceous feather at the tip.  The early juvenile also has smaller wing feathers than tail feathers, but this size difference is less significant in the specimen that represents an older more mature specimen.

Neither adults or juveniles could fly, it is likely primitive feather-like structures first developed to help insulate and keep warm these small active animals.  In mature adults, the feathers may have become more ornate and might have played an important role in communication and display.

Palaeobiologists say that if the Chinese team’s interpretation of the fossils is correct, it would be the first time that juvenile dinosaurs have been shown to have a different type of feather from adults.

Mike Benton from the University of Bristol (UK) added:

“Modern birds don’t make such a transition.  Apart from the downy feathers of newborns, all later stages of modern birds are characterised by the same flight feathers. This paper marks the first step in attempts to disentangle the evolution of developmental sequences among birds and their ancestors.”

However, some ornithologists and developmental biologists have questioned the conclusions made in the Chinese paper.  They query whether the younger fossil shows a ribbon-like feather or is instead from the bird’s moulting phase.

Yale University’s Richard Prum, a leading ornithologist and expert on bird plumage stated:

“Feathers are complicated.”

When modern birds regenerate their feathers, the new ones grow rolled-up in a tube sheath.  Prum has commented that the fossilised feathers of the younger dinosaur could be interpreted as a preserved image of feathers emerging from their sheath; like modern feathers in active moult.

But IVPP scientist Xu maintains that this finding is “not an artefact of preservation or temporary morphology” based on the proportions of the feathers.  If the juvenile feathers were simply in active moult, he would expect the ribbon-like part of the feather to be shorter.  If the Chinese interpretation of the fossil data is correct then this will be the first demonstration that these feathered dinosaurs could undergo changes of plumage as they grew and matured.

Pictures show an artist’s interpretation of the Similicaudipteryx fossils, the juvenile is in the foreground with the adult just behind.

Using work done by Prum, Chuong and others, Xu and his colleagues at the IVPP suggest that the unusual partially-pennaceous feather might be a result of the delayed expression of genes that are activated earlier in modern birds.

Canadian palaeontologist Phil Currie commented:

“Dinosaurs had been experimenting with feathers and feather-like structures for a period of at least 25 million years before the dinosaurs described here [Similicaudipteryx].  The wonderful thing about this paper is that it provides developmental clues that may force palaeontologists, ornithologists and developmental biologists to recognise a broader spectrum of possibilities rather than looking for some simple answer.”

New Fast Running Dinosaur Discovered in China (Xixianykus zhangi)

Scientists have described a new species of fast running dinosaur from China.  The dinosaur has been named Xixianykus zhangi.

Heralded as a sort of dinosaur equivalent of the cartoon bird roadrunner, scientists have announced the discovery of a new type of fast running theropod dinosaur.  This tiny creature with short thigh bones and long lower leg bones seems to have been built for speed.  Being agile and able to run fast would have been extremely handy for this 50 cm long dinosaur, despite not having to worry about “Wile E Coyote” there would have been plenty of predators wanting to put Xixianykus on the menu.

Remains of this new species were found in the spring of 2009 by a local farmer in China’s Henan Province (eastern China) an area already famous for its Cretaceous dinosaur fossils.  The strata from which the incomplete fossil of this new dinosaur was found dates from approximately 85 million years ago (Santonian faunal stage).  A paper on this new dinosaur, believed to be an alvarezsaurid has been published in the scientific journal “Zootaxa”.

Alvarezsaurids

Alvarezsaurids are a bizarre group of theropod dinosaurs, known from fossils found in China and south America.  Typically small, with even the largest specimens known such as Alvarezsaurus (from which the group gets its name) and Patagonykus being less than 2 metres long (and most of this length is tail), this is a very enigmatic branch of the Dinosauria.  However, classifying alvarezsaurids as dinosaurs is not that straight forward.  They have many bird-like features, such as specialised forelimbs, breast bones, fused ankles and narrow skulls.  Most likely feathered, to help insulate them and keep these small, active animals warm (no evidence of alvarezsaurids evolving the ability to fly), it is believed these animals inhabited forests and open plains.  The short thighs, long shins and feet are indicative of a cursorial lifestyle and suggest that these creatures were very fast runners indeed.  This new partial specimen, now formerly named Xixianykus zhangi, although just over half a metre long, had proportionately very long lower legs, indicating that it was a very fast runner.  With legs measuring 25 cm long these were extreme, even for the lightly built fast running Alvarezsauridae.

An Illustration of the new Alvarezsaurid (Xixianykus zhangi)

Picture credit: Matt Van Rooijen

Xixianykus zhangi

Commenting on the ratio of the upper leg bones to the lower leg bones, palaeontologist David Hone of the Chinese Academy of Sciences (Beijing), one of the scientists responsible for the study of this new dinosaur said:

“These proportions imply it could put great long strides in and move fast.”

Although the forelimbs have been lost it is likely that it had short, stubby arms with a single digit on each hand.  The digit had a massive claw on it, this and the arms are adaptations to a very specialised lifestyle.  Scientists believe that the forelimbs were adapted to digging, perhaps these little dinosaurs were specialist insectivores, breaking into termite mounds and feeding on the insects contained within.

Features of the vertebrae and the pelvic area support the idea of Xixianykus being a dinosaur adapted for digging.

David Hone stated:

“The front of the body is adapted not to twist, which saves energy when running and provides a brace for digging actions”.

X. zhangi was most likely an endurance runner, using minimal energy to cover long distances in its search for food.  It may have lived in flocks, although there is no fossil evidence as yet to support this hypothesis.

With its long, slender legs it would have had the ability to run away from trouble should any Cretaceous predator decide to try to catch it.

A Model of a Typical Aalvarezsaurid

The amazing desert accessory pack featuring a replica of an  alvarezsaurid – Mononykus (Beasts of the Mesozoic).

To view the Beasts of the Mesozoic model range: Beasts of the Mesozoic Articulated Dinosaur Models.

Everything Dinosaur acknowledges the assistance of a media release from the Chinese Academy of Sciences (30th March 2010) in the compilation of this article.