Ambopteryx longibrachium – A New Bat-winged Dinosaur

Scientists from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), have identified a new species of flying dinosaur from Jurassic-aged strata in north-eastern China.  This dinosaur has been identified as a member of the Scansoriopterygidae dinosaur family and it had bat-like, membranous wings just like the related Yi qi, that was named and described back in 2015.  The little dinosaur, not much bigger than a starling, had a flap of skin from its arms to its torso, in essence a wing.  It has been named Ambopteryx longibrachium and this discovery supports the idea that within the forests of northern China during the Middle to the Late Jurassic, dinosaurs were experimenting with several different methods of gliding and powered flight.

A Life Reconstruction of the Newly Described Scansoriopterygid Dinosaur Ambopteryx longibrachium

Picture credit: IVPP (Chinese Academy of Sciences)

Ambopteryx longibrachium – Bizarre and Buck-toothed Little Flying Dinosaur

The fossil specimen was found by a local farmer who supplements his income like many folk in Liaoning Province by searching for fossils in the fine-grained sediments.  It is beautifully preserved and dates to around 163 million years ago, commenting on the discovery, one of the co-authors of the scientific paper, published this week in the journal “Nature”, Jingmai O’Connor of the IVPP stated:

“It would have been this tiny, bizarre-looking, buck-toothed thing like nothing alive today.”

The Beautifully Preserved Fossil Specimen (Ambopteryx longibrachium)

Picture credit: Min Wang IVPP (Chinese Academy of Sciences)

A Secondary Form of Flight That Does Not Involve Feathers

Close to the origins of flight, dinosaurs closely related to birds were experimenting with a range of different wing structures.  One of the most bizarre of these is the scansoriopterygid named Yi qi, (pronounced: Ee-chee), which was described and named in 2015.  This little dinosaur had membranous wings, supported by a curved, rod-like bone (styliform), attached to the wrist.

Soft tissue proximal to the arm bones was interpreted as bat-like wings, although this interpretation was not widely accepted by the scientific community.  However, the discovery of another type of scansoriopterygid dinosaur with the same type of wings demonstrates that members of the Scansoriopterygidae were indeed taking to the air.

The new dinosaur, Ambopteryx longibrachium (meaning “both-wing” and “long arm,” a reference to this second method of dinosaur flight, one that does not involve feathered wings), provides confirmatory evidence of the evolution of dinosaurs with bat-like, membranous wings.

Palaeontologist Steve Brusatte, (University of Edinburgh), when asked to reflect on the significance of this newly published scientific paper commented:

“This fossil seals the deal, there really were bat-winged dinosaurs.”

Ambopteryx longibrachium – Takes to the Air

Picture credit: Min Wang IVPP (Chinese Academy of Sciences)

An Evolutionary Dead End

The researchers conclude that marked changes in wing design evolved near the split between the Scansoriopterygidae and the avian lineage, the two clades took very different routes to becoming volant.  Furthermore, the scientists determine that the membranous wings supported by elongate forelimbs present in scansoriopterygids such as Yi and Ambopteryx was a short-lived evolutionary experiment and that the feathered, winged dinosaurs ultimately proved to be the more successful leading to the eventual evolution of the Aves.

The likes of Yi qi and Ambopteryx longibrachium were evolutionary dead ends.  Whether Ambopteryx was capable of sustained powered flight, or whether it moved from tree to tree entirely by passive gliding remains unknown.

Coming in to Land – Ambopteryx longibrachium

Video Image credit: Min Wang IVPP (Chinese Academy of Sciences)

Stomach Contents Preserved

The stomach contents of the little dinosaur have been preserved.  The Chinese scientists recovered pieces of bone and small stones (gastroliths), which modern birds use to grind plant material, indicating Ambopteryx may have been omnivorous.  It may have lacked pinnate feathers, but the body was covered by a downy fuzz to help this small dinosaur keep warm.  Jingmai O’Connor speculates that male Ambopteryx may have sported long, ornamental tail feathers, as seen in other scansoriopterygids such as Epidexipteryx (E. hui).

The scientific paper examines the anatomical traits that enabled a mode of flight.  The wings of Ambopteryx were formed by elongated arm bones (humerus and ulna).  Aves (birds), have elongated finger bones (metacarpals), in effect, different solutions found in nature to achieve the same aim – volant activity.

Professor O’Connor added:

“The main lift-generating surface of bird’s wings is formed by the feathers.  In bats, pterosaurs and now scansoriopterygids, you have instead flaps of skin that are stretched out in between skeletal elements.”

Yi qi was Not Alone

It seems likely therefore, that with the discovery of a second bat-winged scansoriopterygid, there may be numerous other fossils of bizarre dinosaurs that were adapted to a life in the trees awaiting discovery in Liaoning Province.

It now seems that flight evolved more than once in the Dinosauria, Yi qi was not alone and the scientific community will provide further insight in the near future with regards to the remarkable and arguably the strangest of all the dinosaurs the Scansoriopterygidae.  Such research might be hindered by the small body-size of these creatures, the Ambopteryx specimen represents a sub-adult animal, it would have measured in life around 32 cm in length and weighed just a few hundred grammes.

Epidexipteryx and Yi qi were also small, E. hui has been estimated to have measured 30 cm long and weighed less than 200 grammes, whilst Yi qi is estimated to have had a wingspan of less than 60 cm and it would have been not much heavier.  The fact that any specimens of these tiny arboreal dinosaurs have survived at all is remarkable in itself.

A spokesperson from Everything Dinosaur commented:

“Much of our knowledge about these tree-dwelling dinosaurs has been derived from fossils discovered in the last twelve years or so.  Our blog was started back in 2007 and over the course of the life of our blog we have charted the rise in the knowledge and awareness surrounding the curious Scansoriopterygidae.  There has even been a model of scansoriopterygid produced by a mainstream manufacturer.  PNSO introduced a model of Yi qi this year.  Who knows what other remarkable dinosaurs are awaiting discovery?”

The PNSO Yi qi Dinosaur Model

To read about the discovery of Epidexipteryx: Is it a Bird? Is it a Plane? No, it’s Epidexipteryx!

To read about the discovery of Yi qi: Yi qi The Dinosaur that Thought it was a Bat.

To view the Yi qi dinosaur model and the other figures in the PNSO model range: PNSO Age of Dinosaurs.

Suskityrannus hazelae – The Shape of Things To Come

The first of what will probably turn out to be numerous new theropod dinosaurs from southern Laramidia has been announced today.  Writing in the academic journal “Nature: Ecology & Evolution”, a team of international scientists have described a new species of relatively small-bodied tyrannosauroid that helps to fill a gap in the evolution of the tyrannosaur family.  Significantly, the new dinosaur, named Suskityrannus hazelae, has the same general body shape and feet adapted to running (arctometatarsalian feet), as the later, much larger tyrannosaurs such as Albertosaurus, Gorgosaurus and T. rex.  This suggests that tyrannosaurs evolved many of their characteristic features whilst they were relatively small, secondary predators.

When Suskityrannus roamed western North America some 92 million years ago (Middle Turonian faunal stage), this little theropod was the shape of things to come.

A Life Reconstruction of Suskityrannus hazelae

Picture credit: Andrey Atuchin

The Moreno Hill Dinosaur Assemblage

Suskityrannus heralds from the Zuni Basin of New Mexico, specifically the Moreno Hill Formation and it has been described based on two associated but fragmentary skeletons.  Even so, these fossils represent the most complete examples of early Late Cretaceous tryannosauroids described to date.

Dinosaur fossils from the Turonian faunal stage are exceptionally rare, the fossils from the Moreno Hill Formation have provided palaeontologists with an insight into the types of dinosaur that were the forerunners of the key groups of dinosaur that were to dominate the terrestrial ecosystems of North America towards the end of the Cretaceous.

For example, the beautiful life reconstruction of Suskityrannus by Andrey Atuchin (above),  shows a three-metre long theropod about to feed on some garfish that have become stranded as a result of a flood.  The pair of Zuniceratops are unconcerned about the proximity of the meat-eater, they are many times heavier and have nothing to fear from the fleet-footed tyrannosauroid.  In the background, to the right of the image a large ornithopod dinosaur can be seen, we think this is probably a life reconstruction of the basal hadrosauroid Jeyawati.

In essence, that is what makes the dinosaurs from the Moreno Hill Formation so significant.  These sediments were laid down before the diversification of the tyrannosaurids, hardrosaurids and ceratopsids, all key components in later Cretaceous dinosaur assemblages from North America.

A Powerful Bite

Named Suskityrannus hazelae, (pronounced Sus-key-tie-ran-us haze-ah-lie), analysis of the jaw bone indicates that this dinosaur had an elongated skull measuring between 25 and 32 cm in length.  Despite its small size, less than 3 metres long, with a hip height of around 1 metre, Suskityrannus had a powerful bite, foretelling the evolutionary direction of later tyrannosaurs which were to evolve massive skulls with bone crushing bite forces.

The Fossil Skeleton of S. hazelae Compared to the Dentary (Lower Jaw) of Tyrannosaurus rex

Picture credit: Virginia Tech

It is thought that the skeletal fossil material associated with Suskityrannus represent juveniles.

Suskityrannus hazelae What’s in a Name?

The name Suskityrannus hazelae is derived from “Suski,” the Zuni Native American tribe word for “coyote,” reflecting this tyrannosauroid’s position in the ecosystem as a secondary predator.  The species name honours Hazel Wolfe whose support made possible many expeditions to the Zuni Basin of New Mexico.

The first evidence, including a partial skull was found in 1997 by co-author Robert Denton (GeoConcepts Engineering).  The second, more complete specimen was found in 1998 by Sterling Nesbitt, a high school student at the time, but now based at the Department of GeoSciences (Virginia Tech).  Dr Nesbitt is the corresponding author for the scientific paper.  The fossils were housed at the Arizona Museum of Natural History for many years before they were formally studied.

Co-author, Steve Brusatte (School of GeoSciences, University of Edinburgh) commented:

“Suskityrannus is a key link between the enormous bone-crunching dinosaurs like T. rex and the smaller species they evolved from.  The new species shows that tyrannosaurs developed many of their signature features like a muscular skull, broad mouth, and a shock-absorbing foot when they were still small, maybe as adaptations for living in the shadows.”

Dr Sterling Nesbitt and Suskityrannus hazelae

Picture credit: Virginia Tech

The Moreno Hill and the Bissekty Formations

The Moreno Hill Formation is analogous to the Bissekty Formation of Uzbekistan.  Within the Northern Hemisphere, dinosaur fossils from the Turonian faunal stage are exceptionally rare, although thousands of miles apart, the strata are approximately the same age (around 90 million-years-old) and the dinosaur specimens found provide evidence of similar faunas.

The tyrannosauroid Timurlengia was named and described from fragmentary remains from the Bissekty Formation in 2016, the publication of a scientific paper on Suskityrannus will help palaeontologists to better understand how relatively small-bodied tyrannosauroids evolved into giant apex predators some twenty million years later.

To read about the discover of Timurlengia: Fossil Study Suggests How Tyrannosaurs Got Big.

How Big Were the Arms of Suskityrannus?

As for that other famous Late Cretaceous tyrannosaur body trait, the much reduced arms, scientists are very much in the dark about how big the forelimbs of Suskityrannus were.  Very little forelimb fossil material has been recovered.  Scientists can’t even say with any certainty whether Suskityrannus had two-fingered or three-fingered hands.  Cross-sectional analysis of slices of bone indicate that both known specimens were juveniles.

The fossils are providing further information on tyrannosauroid ontogeny.  Despite not being fully-grown, the authors are confident that Suskityrannus was not as big as its descendants, the famous apex predators of the Campanian and Maastrichtian faunal stages of the Cretaceous.

Commenting on the discovery a spokesperson from Everything Dinosaur stated:

“When we made our palaeontology predictions for 2019, the last prediction we made was that more tyrannosaurids would be named and described from fossil material associated with southern Laramidia.  We suggested that two new species would be named.  Suskityrannus hazelae has helped us to confirm our prediction made earlier this year, at least in part.  We are expecting more theropod news to come out of the southern United States over the next few months.  These are exciting times for anyone studying the Tyrannosauroidea.”

To read about the discovery of a tyrannosauroid from central Utah that lived approximately four million years before Suskityrannus: Fleet-footed Dinosaur Leaps 70-million-year Gap.

For a model of Suskityrannus, (whilst stocks last): Beasts of the Mesozoic Models.