Gualicho shinyae – A Dinosaur with Arms Reminiscent of Tyrannosaurus rex

With the formal publication of the scientific paper describing a new species of carnivorous dinosaur from Argentina, the Theropoda just became a little bit more curious.  Gualicho shinyae has been erected and it shows both tetanuran (stiff tailed) and ceratosaurian anatomical traits.  G. shinyae can also lay claim to being the most basal member of the Tetanurae clade to exhibit the reduction of digit III on the hand.

Gualicho shinyae

Reports in the media have compared this new Late Cretaceous South American dinosaur with Tyrannosaurus rex.  These two dinosaurs may have had very reduced arms and only two fingers on each hand, but Gualicho is not closely related to the “King of the Tyrant Lizards”.  In fact it seems that Gualicho shinyae is an example of convergent evolution, that is, not closely related organisms evolve independently similar traits as a result of having to adapt to similar environments or ecological niches.

Just why many large meat-eating dinosaurs had reduced arms and vestigial digits remains a mystery.

An Illustration of a the New Dinosaur from Argentina

Picture credit: Jorge González and Pablo Lara

In the picture above two predatory dinosaurs (Gualicho shinyae) ambush a flock of hypsilophodonts.

The Mystery Over Short Arms and Reduced Digits in Theropod Dinosaurs

The third digit is reduced to nothing more than a metacarpal splint, very reminiscent of tyrannosaurids and just like all the known Late Cretaceous tyrannosaurs, the arms are also reduced in proportion to the body size.  Gaulicho is estimated to have been at least six metres long, but the forelimbs are no bigger than those of a child.

The left forelimb was recovered along with a short section of vertebrae from the back, the end portion of the tail, elements of both hind limbs including an articulated foot plus a left scapulocoracoid  A couple of rib bones and some gastralia (belly ribs) were also excavated.

The rest of the skeleton had been lost to erosion, but from these remains the researchers, which included scientists from the Field Museum (Chicago), the Dinosaur Institute of Los Angeles as well as palaeontologists from  Buenos Aires and Rio Negro Province, suggest that this new dinosaur is a neovenatorid with close affinities to the North African dinosaur Deltadromeus.

For models and replicas of theropod dinosaurs and other prehistoric animals: Dinosaur Models and Prehistoric Animal Replicas.

An Illustration of the Likely Skeleton of G. shinyae

The white shaded bones show the fossils of Gualicho that have been found.

Picture credit: PLoS One with additional annotation by Everything Dinosaur

Discovered in 2007

Discovered back in 2007, the specimen, which consists of around 5% of the total skeleton was excavated and prepared by staff of the Museo Patagónico de Ciencias Naturales.  The genus name is derived from “Gualichu”, a spirit revered by Patagonia’s Tehuelche people.  The field team encountered quite a lot of misfortune during the 2007 expedition and during the subsequent preparation work.  Researchers joked about the “curse of Gualichu”.  The species name honours Ms Akiko Shinya, the Chief Fossil Preparator at the Field Museum (Chicago).  It was Ms Akiko who found the first fossil evidence of this new type of dinosaur during the 2007 expedition to the Neuquén Basin of Patagonia (southern Argentina).

Chief Fossil Preparator Ms Akiko Shinya Showing where the Fossils were Found

Picture credit: PLoS One (Photo by Peter Makovicky)

A Mosaic Dinosaur (Gualicho shinyae)

Corresponding author Peter Makovicky (Field Museum) stated:

“Gualicho is kind of a mosaic dinosaur, it has features that you normally see in different kinds of theropods.  It’s really unusual, it’s different from the other carnivorous dinosaurs found in the same rock formation, and it doesn’t fit neatly into any category.”

Estimated to have weighed around 450 kilogrammes and to have been about six metres long, Gualicho has been assigned to the Allosauria clade and placed within the Neovenatoridae family, however, its exact taxonomic position remains unclear.  The scientists conclude that it resembles Deltadromeus, a contemporaneous Theropod known from North Africa.

Cenomanian Faunal Stage

The fossils of G. shinyae were excavated from sandstone strata located close to the base of the Huincul Formation.  Everything Dinosaur estimate that this dinosaur roamed what was to become Patagonia some ninety-five million years ago (Cenomanian faunal stage of the Late Cretaceous).

The New Dinosaur Discovery Adds to the Faunal Diversity of the Lower Part of the Neuquén Group

A schematic stratigraphic diagram showing the position of the Gualicho fossil find.

Picture credit: PLoS One

The picture above shows a schematic diagram of the lower part of the Neuquén Group of Upper Cretaceous strata exposed in the Neuquén Basin with the approximate level at which the holotype of Gualicho shinyae was collected from the base of the Huincul Formation.  The rocks contain a variety of vertebrate remains including a number of dinosaurs, especially saurischian (lizard-hipped) forms.

Diversity of Theropod Dinosaurs

The discovery of G. shinyae adds to the diversity of theropods known, for example a number of carcharodontosaurids are known from this formation (Mapusaurus and Taurovenator), along with several abelisaurids such as Skorpiovenator and Ilokelesia.  There has even been some fossils found that were described as belonging to a giant raptor (megaraptoran), this dinosaur was named Aoniraptor (A. libertatem) earlier this year, but similarities between the caudal vertebrae found and those now assigned to Gualicho, indicate that the Aoniraptor material may be synonymous with the holotype material of G. shinyae.

There have also be a large number of sauropod remains associated with this strata.  For example, a number of rebbachisaurids have been described along with several titanosaurs, including Argentinosaurus.

A Map Showing the Approximate Location of the G. shinyae Quarry

A map showing the approximate location of the fossil discovery (star).

Picture credit: PLoS One

The black star in the diagram to the left, indicates the approximate location of the G. shinyae quarry.

Everything Dinosaur Comments

A spokesperson from Everything Dinosaur commented:

“This new dinosaur discovery adds to the theropod diversity known from the Late Cretaceous terrestrial strata of the Neuquén Basin, northern Patagonia.  It also reinforces the belief of the close affinities between the Huincul Formation and rocks of a similar age laid down in North Africa.  In addition, with the discovery of a short-armed, two-fingered dinosaur that lived some twenty-five million years or so before the end Cretaceous tyrannosaurids, palaeontologists can perhaps learn why reduced forelimb size was so prevalent in large carnivorous dinosaurs.”

The scientific paper from which this article was compiled is: “An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina”.

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Dwarf Duck-billed Dinosaur with Facial Tumour

Scientists have identified the first recorded evidence of a benign facial tumour in the fossilised jaw bone of a duck-billed dinosaur (Telmatosaurus transsylvanicus).  This dinosaur died before adulthood, it is not known whether the facial tumour contributed to this dinosaur’s demise.

The paper published in the journal “Scientific Reports”, was written by an international team of scientists, which included PhD students Mihai D. Dumbravă (Babeș-Bolyai University, Romania) and Kate Acheson (Southampton University), along with Dr Zoltán Csiki-Sava (University of Bucharest, Romania), who led the field trip that found the jaw bones of this unfortunate reptile.  The facial tumour known as an ameloblastoma is a non-cancerous growth known to afflict mammals and reptiles, including our own species too.  This is the first time such a deformity has been documented in the fossil record.

An Artist’s Impression of the Juvenile Telmatosaurus with the Facial Tumour on the Left Dentary

A drawing of the facial features of Telmatosaurus showing the tumour on the left dentary.

Picture credit: Mihai Dumbravă with additional annotation by Everything Dinosaur

Commenting on the significance of the discovery, student Kate Acheson stated:

“This discovery is the first ever described in the fossil record and the first to be thoroughly documented in a dwarf dinosaur.  Telmatosaurus is known to be close to the root of the duck-billed dinosaur family tree, [Hadrosauridae] and the presence of such a deformity early in their evolution provides us with further evidence that the duck-billed dinosaurs were more prone to tumours than other dinosaurs.”

Telmatosaurus – A Primitive Member of the Hadrosauridae

The basal hadrosaur Telmatosaurus lived on the Hateg archipelago, a series of islands in the middle of the Tethys Sea.  A number of different dinosaurs are known from the Hateg Island group and the fossils of Telmatosaurus date from around 69-67 million years ago (Maastrichtian faunal stage of the Late Cretaceous).  Like many of the prehistoric animals known from these deposits, the four-metre-long Telmatosaurus exhibits “island dwarfism”, a lack of resources led to a decrease in the size of individuals within the population.

An Illustration of Telmatosaurus (T. transsylvanicus)

Telmatosaurus a primitive Hadrosaur of the Hateg archipelago.

Picture credit: Mihai Dumbrava

For models of hadrosaurs and other dinosaurs: PNSO Age of Dinosaurs Models and Figures.

Deformed Dinosaur Jaw Fossil

The fossil jaws were discovered more than ten years ago.  Comparison with other Telmatosaurus jaw material indicated that the lower portion of the left dentary was deformed.  The reason for the deformity was not made clear until the fossil was subjected to high resolution scans at the Switzerland based SCANCO Medical AG.  Scans revealed that the juvenile Telmatosaurus had been suffering from a condition known as “ameloblastoma”, a benign tumour which is known to affect the jaws of mammals and some modern reptiles.

Scans Reveal the Presence of an Ameloblastoma in a Dinosaur Fossil

Scientists scan the jaw fossils and compare the jaw to a human mandible.

Picture credit: Scientific Reports

The picture above shows (A) the two lower jaw fossils (dentary) of the Telmatosaurus in frontal view (anterior).  The abbreviation exo on the left jaw indicates the position of the tumour growing on the bone (exostosis).  Computer model (B) shows the left jaw bone with elements colour coded, for example, red shows the primary neurovascular canal, yellow the secondary neurovascular pathways, orange – functional teeth, blue – replacement teeth, light blue – segmented dentary bone, purple – lytic density areas.  Pictures C and D show three-dimensional micro CT scan images with a rectangular section cut out to show the exostosis (C) and (D), the portion of the dentary showing the external exostosis.

Close up Examination of the Fossil Bone

Cross-sectional scans reveal the presence of abnormal bone growth.

Picture credit: Scientific Reports

Assessing the Dinosaur Data

In the image above, (E) shows a cross-section of the jaw, with a highly magnified section (F), in the picture labelled “Scans Reveal the Presence of an Ameloblastoma in a Dinosaur Fossil”.  The middle image (G) is a cross-section of a second micro-CT and (H) provides a close up detail of that section.  Image (I) represents a cross-section of another CT image and (J) is a radiograph of the left dentary of a person exhibiting an ameloblastoma and (K) a further image showing a left jaw (H. sapiens) with an ameloblastoma.

Abbreviations:

cb = cortical bone; cbe = cortical bone expansion; cbt = cortical bone thinning; dt = dentary tooth; exo = exostosis; im = internal margin; itrb = internal trabeculae; lda = lytic density areas; mgr = mandibular groove; pnvc = primary neurovascular canal; rb = resorbed bone; rt = resorbed tooth; rtr = resorbed tooth roots; sba = soap bubble appearance; snvc = secondary neurovascular pathways.

Scale bars (A,B): 50 mm. Scale bars (C–I): 5 mm. The scale for (J,K) not reported.

The Placement of Telmatosaurus within the Hadrosauridae

A Simplified View Showing the Approximate Placement of Telmatosaurus within the Hadrosauridae

A simplified Hadrosauridae family tree showing Telmatosaurus as a basal member.

Picture credit: Everything Dinosaur

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Mihai D. Dumbravă explained:

“It was expected, due to the impoverished nature of the fauna, that our project to investigate diseases of the bone in the dwarf dinosaurs of the Haţeg County Dinosaurs Geopark would reveal some interesting results, but the discovery of a rare modern tumoural condition, and one that is so far unique in the fossil record, was a wonderful surprise.”

The Cause of Death?

As only the jaws of this dinosaur have been discovered, it is not possible to determine the impact of the ameloblastoma on the animal’s life.  However, Dr Zoltán Csiki-Sava, another of the authors of the scientific paper postulated:

“We know from modern examples that predators often attack a member of the herd that looks a little different or is even slightly disabled by a disease.  The tumour in this dinosaur had not developed to its full extent at the moment it died, but it could have indirectly contributed to its early demise.  The particular make-up of the rocks allowed us to identify that this fossil was preserved near the channel of an ancient river.”  

Student Kate Acheson added:

“In a setting like this, it is extremely rare to find the complete specimen, and so it is almost impossible to determine the specific cause of death.  One can only make an informed guess based upon the evidence we have.”

The academic paper published in the journal “Scientific Reports” and it is entitled:

“A dinosaurian facial deformity and the first occurrence of ameloblastoma in the fossil record.”

The Secretive and Solitary Oesia disjuncta

Research carried out by UK and Canadian academics has shed light on how Cambrian life-forms may have led to more complex creatures including vertebrates and ultimately our own species.  It turns out that a small sea worm Oesia disjuncta with its mix of anatomical traits, might point the way towards a better understanding of the Kingdom Animalia.  The fossils of Oesia have also provided evidence about how these worms kept themselves safe against the ever increasing number of predators by building long, tube-like homes to live in.

Oesia disjuncta

According to the scientists, whose work is published in the academic journal “BMC Biology”, the ancient Cambrian sea bed may have been marked by perforated tubes that resembled “exceedingly thin brandy snaps”, as one Everything Dinosaur team member reported it.  Some of these structures may have been more than five hundred millimetres in length, gargantuan by Cambrian standards.  The study, undertaken by scientists from the Royal Ontario Museum (Toronto, Canada), Cambridge University and two other Canadian universities (Toronto and Montréal), originated from a reassessment of fossils that were thought to have represented a type of marine green algae (Margaretia dorus).

Marble Canyon Quarry Oesia Fossil

Oesia fossil with labels (anterior – front end, posterior – rear end).

Picture credit: Royal Ontario Museum with additional annotation by Everything Dinosaur

To give an impression of scale of the specimen, the width of the photograph above is approximately three centimetres.

Learning More About Oesia disjuncta

Oesia disjuncta, the only species within the Oesia genus, has been known to science for more than 100 years.  It was described in 1911 by the great Charles D. Walcott, the American geologist who had discovered the Burgess Shale deposits (British Columbia, Canada) and the abundance of Cambrian fossils that they contain, two years earlier.  It had been described as a type of annelid marine worm (segmented worm), but this classification had subsequently fallen out of favour and a number of affinities had been suggested such a Oesia representing a basal chaetognath (arrow worm).

Recently, it had been proposed that this creature was taxonomically closer to the hemichordates, animals like acorn worms that have closer affinities to the chordates than they do to the Echinodermata (starfish, sea lilies, brittle stars and sea urchins.  This research supports the hypothesis that O. disjuncta should be placed within the hemichordates, which means it forms a link between marine worms and all the animals with backbones (vertebrates) and this includes our own species – H. sapiens.  The genus name for this worm, which lived a solitary life inside the protection of its tube, comes from a small lake (Lake Oesia), located just a few miles from the Burgess Shale quarry where the first fossils of this ancient animal were found.

An Illustration of Oesia Worms in their Tubes

An illustration of the Oesia worm living in its tube.

Picture credit: Marianne Collins

The Importance of the Marbel Canyon Site

In 2012, a new highly fossiliferous site was discovered, around 25 miles from the original Burgess Shale fossil quarries excavated by Walcott.  This location has yielded many more examples of Oesia and they are generally better preserved than the specimens discovered in the previous century.  The new quarries have yielded a number of new species as well as shedding more light on already described genera.  A study of these specimens has confirmed that Oesia was most likely a basal member of the hemichordates.  As such, being a hemichordate, it is nested within the superphylum Deuterostomia which also includes the vertebrates (amongst others).

Lead Author Karma Nanglu Pausing on the Trail up to the Marble Canyon Quarry

University of Toronto PhD student and lead author Karma Nanglu on the trail leading up to the Marble Canyon site.

Picture credit: Joe Moysiuk

Unravelling the Origins of Today’s Phyla

The bulk of the Kingdom Animalia which are more complex than the cnidarians (jellyfish), with their radial symmetry, are divided into two main groups:

1. Deuterostomia – bilateral symmetry mainly, with only the echinoderms showing radial symmetry, this group includes the vertebrates and acorn worms etc.
2. Protostomia – bilateral symmetry including the molluscs, arthropods, nematodes and worms.

These lineages are believed to share a common ancestor that lived during the Ediacaran geological period.  With the placing of Oesia within the deuterostomes, scientists hope that they may be able to identify the distant common ancestor of all the Deuterostomia.

A Filter Feeder

With more data on Oesia, it suggests that this common ancestor was very probably a “filter feeder”, sucking in water and straining out nutrients that were trapped on gill structures.  Oesia was such a filter feeder with “u-shaped” gills running down most of its body length.  The tube-like structure it lived in was highly porous, this would have allowed water to flow in and out of the tube aiding filter feeding.

Lead author of the research Karma Nanglu (University of Toronto) stated:

“Hemichordates are central to our understanding of how deuterostomes evolved.  Through them, we can get clues about the anatomy and lifestyle of the last common ancestor that we all share, and this adds further evidence to the hypothesis that the ancestor was a filter-feeder like Oesia.”

The tubes were quite spacious for Oesia, they are at least twice as wide as the creature’s body and many times longer.

Co-author of the scientific study, Professor Simon Conway Morris (Cambridge University) added:

 “Oesia fossils are pretty enigmatic,  they are very rare and until now we could not prove which group they belonged to.  Now we know that they were primitive hemichordates – perhaps the most primitive of all.”

This new research establishes Oesia was similar to extant marine acorn worms.  These worms have a proboscis, a reproductive collar region and a long, narrow body.  The tube may have acted as a sanctuary protecting the soft-bodied worm from an array of rapidly evolving predators.

Not Associated with Margaretia dorus

The researchers realised that Oesia must have lived in tubes because among the Marble Canyon finds there are dozens of examples where the fossil remains of the worm are found within those of what was thought to be the remains of the green algae Margaretia dorus.

Oesia also hints that at some point, acorn worms underwent an evolutionary development that led to them leaving their tubes and opting for an existence burrowing in the mud of the sea bed.  The researchers suggest that as more efficient predators evolved, living in the mud at the bottom of the sea may have been a more advantageous lifestyle.  Extant acorn worms occupy this niche, rather than an epifaunal, filter feeding habit, they live in the sediment and feed on the nutrients that it contains.

Fossils Reveal the Tube-Like Structures of Oesia

Fossils of the tube-like structures once thought to be algae but now identified as the home of Oesia worms.

Picture credit: BMC Biology

Professor Conway Morris explained:

“In its own depressing way this is a story of Darwinian competition.  The levels of competition and predation increased, life sped up and got harder and animals had to protect themselves more.  One way of doing this was to abandon life filter feeding in a tube, and instead to dig into the sediment and eat mud.  Once there, they found a new niche and were able to make a perfectly good life for themselves.”

The study, “Cambrian suspension-feeding tubicolous hemichordates”, is published in the journal BMC Biology.  Everything Dinosaur acknowledges the assistance of the Royal Ontario Museum in the compilation of this article.

Visit Everything Dinosaur’s award-winning website: Everything Dinosaur.