Theropod Diversity Study (Upper Cretaceous South Pyrenees Basin of Spain)

Large dinosaur bones might make the headlines and attract the most media attention, but an analysis of shed theropod teeth, some of them tiny, indicate that there were potentially many more different types of theropod dinosaur roaming around Spain in the Late Cretaceous.   Dinosaurs were able to replace teeth that they shed.

A meat-eating dinosaur for example, could lose hundreds of teeth over its lifetime and although no other part of it might be preserved as a fossil, these teeth could potentially provide an insight for palaeontologists as to the diversity of theropod dinosaurs in a given area.  That’s exactly what has happened as researchers from Spain and Canada have identified a further six non-avian dinosaurs in Upper Cretaceous strata from the South Pyrenees Basin (Spain).  Only two theropod dinosaurs had been known from this region prior to this new study.

Isolated Teeth Fossils Hint at Theropod Diversity on the Iberian Peninsula

scale bar = 5mm

Picture credit: Acta Palaeontologica Polonica

Theropod Teeth Hint at Diversity in Ecosystem

Publishing their work in the academic journal Acta Palaeontologica Polonica, the research team, which included lead author Angelica Torices, (University of Alberta) and famous Canadian palaeontologist Professor Phil Currie, have quadrupled the theropod dinosaur diversity in the areas studied.  At least one of the new types of theropod would have been “large”, although it is difficult to classify down to little more than taxonomic family level.

It has been speculated that the teeth indicating a large predator could represent either an abelisaurid like Tarascosaurus, (it has been proposed that the fragmentary fossil material assigned to this genus shows affinities to the Abelisauridae), known from Upper Cretaceous strata of France or a possible tyrannosaurid.

The Study Area

The area of study consists of eight localities from Treviño County, Huesca and Lerida, including the exceptional site of Laño, an abandoned sand quarry, strata of which represents Upper Cretaceous and Early Palaeogene deposits.  The study of 142 isolated teeth suggests that theropod numbers may have been underestimated elsewhere in the world.

Commenting on the research, Angelica Torices, (University of Alberta), explained:

“Studying these small parts helps us to reconstruct the ancient world where dinosaurs lived and to understand how their extinction happened.”

The post-doctoral fellow in biological sciences added:

“Teeth are especially important in the study of Upper Cretaceous creatures in Spain and the rest of Europe because we don’t have complete skeletons of theropods from that time in those locations.  We have to rely on these small elements to reconstruct the evolution of these dinosaurs, particularly the theropods.”

Reconstructing the Fauna

This study shows the value of isolated and fragmentary teeth fossils in helping to reconstruct the fauna in an ancient environment, when more other, more complete material, such as skeletal material is not present.

Locations of the Fossil Sites in the Study and Their Stratigraphical Sequence

The fossil study localities.

Picture credit: Acta Palaeontologica Polonica

Theropod Teeth

A spokesperson from Everything Dinosaur commented:

“We have long suspected that the dinosaurs were more diverse than previously thought at the end of the Mesozoic.  However, the lack of fossilised bones that can provide an identification down to genus level has hampered scientists in the study of European dinosaurs.  It is this “under storey” of prehistoric life that can provide palaeontologists with a more complete understanding of the palaeofauna.  Tiny teeth can be just as important as the largest dinosaur bones.”

The research will have implications for the way in which the extinction of the dinosaurs at the end of the Cretaceous is viewed.  If this study is typical, then theropod diversity in the north of Spain does not experience a significant decline over the Campanian to Maastrichtian faunal stages.

Small Dinosaurs such as Dromaeosaurids were Present

A typical “raptor”.

Picture credit: Everything Dinosaur

Lead author Angelica Torices stated:

“It completely changes the vision of the ecosystem.  We now understand that these dinosaurs disappeared very quickly in geological time, probably in a catastrophic event.  Climatic models show that we may reach Cretaceous temperatures within the next century, the only way we can study biodiversity under such conditions is through the fossil record.”

The study of 142 Late Cretaceous theropod teeth reveals that theropods were much more diverse in northern Spain towards the end of the “Age of Dinosaurs” than previously thought.

First Elasmosaur Specimen Found in Alaska

Alaska may be famous for many things, but in palaeontological circles it is the Dinosauria that usually grab the headlines when it comes to the largest and most sparsely populated U.S. State.  However, an expedition to the remote Talkeetna Mountains by scientists from the University of Alaska Museum of the North have discovered cervical vertebrae from a large plesiosaurid, an elasmosaur, the first marine reptile of this type to have been discovered in the most northerly part of the USA.

Life in Alaska some Seventy Million Years Ago

Elasmosaurs illustrated.

Picture credit: James Havens

Alaska’s First Elasmosaur

Elasmosaurus was one of the last and the largest of the long-necked plesiosaurids.  During the Late Cretaceous, North America was divided by a huge inland sea (the Western Interior Seaway), elasmosaur fossils have been found in a number of U.S. States as well as in Canada, this new discovery is significant as not only is it the first elasmosaur to be found in Alaska, it supports the theory that large marine reptiles lived at very high latitudes.

Although, Late Cretaceous Alaska was much milder than it is today, it would still have been cold with surface sea temperatures dropping to near freezing at times and for much of the year there would have been very little daylight.  This isolated fossil discovery provides evidence that large marine reptiles (the specimen is believed to exceed eight metres in length), did indeed live in the far north, and it tantalises palaeontologists who can speculate on whether this creature was a permanent resident or whether elasmosaurs were seasonal migrants.

An Extraordinary Long Neck

The most striking feature of the elasmosaurids were their extraordinarily long necks.  Approximately, fifty percent of the animal’s entire body length was made up of its neck.  These reptiles had over 70 cervical vertebrae, ten times the amount than in the neck of a human being (Homo sapiens).  Described back in 1868 from fossil remains found in Kansas, only one species is regarded as valid at the moment, E. platyurus.

The story of the first Alaskan elasmosaurid, began a few years ago.  Curvin Metzler a keen, amateur fossil collector who enjoyed hiking and exploring the slopes of the Talkeetna range found several fragments of fossil bone close to a steep hillside.  These were the first vertebrate fossils that he had found in the area and knowing that they could represent something important he contacted the Earth Sciences curator at the University of Alaska Museum of the North, Patrick Druckenmiller and persuaded him to visit the location.

Patrick and a couple of colleagues duly visited in June and they were able to follow the bone erosion trail leading back to a section of strata in the hill where a good portion of the skeleton including some beautifully preserved, articulated cervical vertebrae lay exposed.

A Cervical Vertebrae (arrowed) Eroding out of the Surrounding Matrix

The red arrow points to a neck bone eroding out of the cliff.

Picture credit: Patrick Druckenmiller/additional annotation by Everything Dinosaur

Exciting Discovery

Commenting on his discovery, Mr Metzler stated:

“I’m mostly interested in finding invertebrates, so when I saw the first vertebra I knew it was a bone from something. I didn’t want to disturb anything in the cliff so it was exciting to talk to Pat.  We are lucky to have someone in the State who works with fossils.”

Identifying the Last Resting Place of a Marine Reptile

Curvin Metzler (left), who discovered the elasmosaur fossil and Patrick Druckenmiller examine the spot where bones were found sticking out of the cliff in the Talkeetna Mountains.

Picture credit: Patrick Druckenmiller

A New Species?

This could represent a new species, but it is too early to tell.  Although the team were able to collect a substantial portion of the exposed remains, there is probably more of the fossil specimen buried in the rock face, trouble is, there is more than ten metres of overburden on top and the fossil collecting season this far north is very short.

Undeterred Dr Druckenmiller explained:

“We got a good chunk of the animal but there is still more to excavate.” 

A field team will return to the site next summer to complete the extraction work.

Preparing Elasmosaurid Vertebrae in the Field

Wrapping the articulated cervical vertebrae in burlap and plaster to protect the fossils during removal.

Picture credit: Patrick Druckenmiller

A spokesperson from Everything Dinosaur outlined the importance of this discovery, explaining that there were a number of Mesozoic aged formations in Alaska, many of which had yielded marine reptiles, but the rocks that had provided marine reptile fossils from this State were much older than the Talkeetna strata.

To read about the discovery of a Triassic marine reptile from Alaska: Thalattosaur discovered in Alaska at Low Tide.

A Geologically Younger Specimen

In the press release from the Museum, the strata is estimated to be around 70 million years of age (Maastrichtian faunal stage), whereas, most Elasmosaurus fossils from North America are associated with older Campanian faunal stage deposits.

A Model of an Elasmosaurus

Cretaceous plesiosaur – Elasmosaurus model.

Picture credit: Everything Dinosaur

Many models of Elasmosaurus depict this creature with a flexible, snake-like head.  This is inaccurate, Elasmosaurus had a very stiff neck, however, it still was a very effective hunter of fish.  The enormous neck enabled it to get up close to shoals before the bulk of the body came into view.  The sharp, interlocking teeth made an efficient fish grab.

Recently, Safari Ltd introduced an updated replica of Elasmosaurus, to view this model and others in the Safari Ltd range: Safari Ltd. Prehistoric Animal Models.

Dinosaur Skeleton and 213 Fossilised Eggs Recovered in Raid

Chinese police seized a total of 213 dinosaur egg fossils and an almost complete fossil of a small herbivorous dinosaur in a raid on a house in Guangdong Province (southern China).  Despite there being strict laws about the illegal removal and sale of ancient artefacts such as fossils in China, there is a significant trade in fossils from China, most of which are smuggled out of the country destined for the more lucrative markets for illegally sourced fossils in Europe and the United States.

A Huge Haul of Illegally Obtained Fossil Material

The Psittacosaurus was crated, either this is how it was sent from northern China or it was being prepared for illegal export.

Picture credit: Xinhua News Agency

Authorities Raid House

The seizure took place on July 29th and was reported by the State run news agency – Xinhua.  The eggs come from a local construction site close to Heyuan City (Guangdong Province), they were looted by locals after workers uncovered a series of dinosaur egg fossils, discoveries of which have been reported over the last three months or so.  The eggs date from the Late Cretaceous, and this part of southern China is famous for its extensive dinosaur nesting site deposits.

Unfortunately, thefts of fossils are common as it is difficult for the authorities to keep track of each new fossil discovery.  Back in 2011, Everything Dinosaur team members reported on the return to China of a number of dinosaur eggs that had been illegally smuggled into the United States.

To read more about this: The Return of Stolen Dinosaur Eggs to China.

Fossil Thefts and Dinosaur Eggs

Chinese officials believe that local residents raided the construction site where a number of dinosaur egg fossils had recently been uncovered.  The fossils were being stored at a local address, most likely prior to being sold onto a middle man who would then forward the illegally obtained items onto other dealers for sale to private collectors abroad.  The skeleton found at the address has been identified as being that of a Psittacosaurus, fossils of which have been found throughout northern China.  Although Everything Dinosaur has no specific information on this specimen, it has been suggested that this fossil comes from the Liaoning Province (north-eastern China), perhaps from the Yixian Formation.

The Psittacosaurus fossil specimen is much older than the eggs, the strata that makes up the Yixian Formation is cited as being Lower  Cretaceous, the Psittacosaurus may be more than 120 million years old.

An Illustration of the Dinosaur Psittacosaurus

A typical psittacosaurid.

Picture credit: Everything Dinosaur

Dinosaur Eggs – Chinese Legislation

Although China has some of the strictest legislation in the world in a bid to stop the exploitation of its rich fossil heritage, policing dig sites, many of which are found as a result of building projects and not by scientific fieldwork, is extremely difficult.  Illegal excavations for dinosaur fossils are believed to be common in Guangdong Province.  Some locals steal the fossils and keep them at home, whilst others are part of a network which smuggles the material out of the country, destined for the black market in fossils overseas.

The Fossils were Scattered All Over the House

Police raid house and discover hundreds of dinosaur eggs.

Picture credit: Xinhua News Agency

A spokesperson from Everything Dinosaur commented:

“This raid by the Chinese authorities might just deter would-be fossil thieves and make them think twice about the illegal removal of fossils. Sadly, we suspect that despite prompt police action in this case the smuggling and illegal sale of fossils from China is widespread and much more international co-operation is required in order to bring an end to this practice.”

Chinese Officials Inspect and Catalogue the Seized Fossils

Inspecting and sorting the fossilised eggs.

Picture credit: Xinhua News Agency

Which Dinosaurs Laid These Eggs?

When asked to speculate on the type of dinosaur that laid the eggs, a spokesperson from Everything Dinosaur stated that the red sandstone around Heyuan City has yielded tens of fossils of dinosaur egg specimens.  The larger eggs in the photograph were most likely laid by duck-billed dinosaurs.  The smaller eggs were probably laid by oviraptorids.

“Although we cannot be certain, the smaller eggs may have been laid by a dinosaur known as Heyuannia huangi.  This small, theropod, believed to be a member of the oviraptorids, a group of very bird-like dinosaurs, was named and described back in 2002 from a number of fossils found in the same strata as the eggs.”

Structural Secrets of Theropod Teeth

Theropod dinosaurs, the majority of which were carnivorous, had a distinct advantage over other Mesozoic predators.  Their teeth had a deeply folded, serrated tooth structure that allowed them to rip and tear into the bodies of their victims.  This crucial, layered structure to the teeth has been identified by researchers from the University of Toronto Mississauga, with the assistance of colleagues from Taiwan and published today in the academic journal “Scientific Reports.”

A Specialised Tooth Structure for Feeding on Large Prey

Gorgosaurus feeding – thanks to its specialised teeth.

Picture credit: Daniele Dufault

The picture above shows a feathered Gorgosaurus, a member of the Tyrannosauridae family, feeding on a young Corythosaurus.

Theropod Teeth

The research team used scanning electron microscopes and a synchrotron located in Taiwan to study a wide variety of theropod teeth from the collections of Canadian museums, including the Royal Tyrrell, and the Royal Ontario Museum.  Meat-eating dinosaurs in the study, included Gorgosaurus, the Triassic predator Coelophysis, Tyrannosaurus rex, Allosaurus, and the giant African theropod Carcharodontosaurus.  Other non-Dinosauria creatures involved in the teeth study were Smilodon spp. and the shark O. megalodon, as well as early archosaurs, as the scientists tried to identify the evolutionary origins of these rather unique inter-dental folds.

Extant animals were also included in the research.  The only living animals with similar dentition and internal teeth structures are the Monitor Lizards, most notably the formidable Komodo dragon (Varanus komodoensis).  It is the largest lizard alive today and specialises in hunting large animals, thus reinforcing the theory put forward by the Canadian research team that these inter-dental folds evolved specifically to assist with predation of large herbivores.

Hidden Complexity of Dinosaur Teeth

Dr Kirstin Brink, a post-doctoral researcher in the Department of Biology, one of the authors of the paper commented:

“What is so fascinating to me is that all animal teeth are made from the same building blocks, but the way the blocks fit together to form the structure of the tooth greatly affects how that animal processes food.  The hidden complexity of the tooth structure in theropods suggests that they were more efficient at handling prey than previously thought, likely contributing to their success.”

Dr Kristin Brink with one of the Theropod Teeth Examines the Evidence

A special arrangement of layers of dentine at the base of each serration in the tooth.

Picture credit: University of Toronto Mississauga

The picture above shows Dr Brink examining the special arrangement of layers of dentine at the base of the each tooth serration (denticle).  She is holding a tooth from the giant theropod Carcharodontosaurus.

Dinosaur Bite Forces

A lot of research has been undertaken into the bite forces of extinct animals, but this is the first time a study of this type has been carried out.  The teeth may have an outer coating of enamel, just like our teeth, but the tough dentine inside has a unique configuration of dental folds and this gives the teeth of theropod dinosaurs enlarged serrations, ideal for tearing into flesh.

The shape of the teeth (morphology) and their development, both in terms of their evolution and how they develop in an individual. can provide palaeontologists with a lot of information on the evolution of extinct animals and provide insights into feeding behaviour.

Theropod teeth, the only group of the Order Dinosauria, known to have produced meat-eaters, are characterised by the presence of serrations, known as denticles on the cutting edges of their teeth.  These serrations vary between genera, with troodontids for example, having relatively large denticles, whilst spinosaurids have proportionately much smaller ones.

Ziphodont Teeth

Teeth that are serrated along the cutting edge are referred to as ziphodont teeth.  In a study, Everything Dinosaur reported upon last year, the same University research team, examined the ziphodont teeth of Dimetrodon (D. grandis).  They concluded that the serrations gave this pelycosaur an evolutionary advantage over other Permian predators.

To read more about this study: Dimetrodon with Teeth Like a Steak Knife.

In this new paper, the researchers conclude that the structures previously thought to prevent tooth breakage, instead, first evolved to shape and maintain the characteristic denticles throughout the life of the tooth.  The relatively novel and complex dental folds produced at the base of the teeth characterises the theropods, with the exception of those genera that evolved a modified diet and a less meat intensive diet.  The scientists conclude that these teeth structures are vital for allowing the predation and consumption of large prey animals.

A Close up of a Gorgosaurus Tooth (Royal Ontario Museum Collection)

A close up of the tooth of Gorgosaurus – G. libratus

Picture credit: Scientific Reports

Examing the Skull and Teeth of Gorgosaurus

The picture above shows an illustration of the skull of the tyrannosaurid Gorgosaurus (A), drawing by Danielle Dufault.  The complete tooth (ROM 57981) is shown in (B) with extreme close ups of the denticles on the cutting edges of the tooth.  The tooth illustrated is from the upper jaw (maxilla).

Key

• dej = dentine/enamel junction
• e = enamel (outer coating of the tooth)
• if = inter-dental fold
• is = inter-dental sulcus
• pd = primary dentine

The Sharp Edges of Predators Teeth Viewed Under Scanning Electron Microscopy

Theropod teeth have two sharp edges these are called carinae.

Picture credit: Scientific Reports

Theropod Teeth Up Close

The cutting edges (carinae) of various predators (all are examples of ziphodont teeth).  Pictures are from scanning electron microscopy images.  Note the scale bars and the pictures to the right of the black and white images are thin cross sections showing internal structure.

Key

• C = unknown phytosaur
• D = Coelophysis bauri
• E = Allosaurus fragilis
• F = Carcharodontosaurus saharicus
• G = Gorgosaurus libratus
• H = Tyrannosaurus rex

This adaptation may have played an important part in the initial radiation and subsequent success of the Theropoda as terrestrial apex predators.  After all, the theropod body shape and bauplan, especially those teeth, permitted them to dominate terrestrial ecosystems for the best part of 160 million years.

How do we Know that Zhenyuanlong was Quite Big?

A few days ago, on July 16th, Everything Dinosaur team members published an article that featured the newly described Chinese dromaeosaurid dinosaur known as Zhenyuanlong suni.  We explained why the dinosaur called Velociraptor was used to help give this new dinosaur discovery context and outlined some of the more intriguing aspects of the fossil, that perhaps had been missed by more general media outlets.  However, we did receive an email about our article from a young dinosaur fan so we thought it best if we followed up our original article by providing some additional information about this little feathered carnivore.

To read our article (July 16th) on Z. suni: The Winged Dragon from Liaoning Province.

A Newly Described Dromaeosaurid from China

Very probably a ground-dwelling predator.

Picture credit: Zhao Chuang

Young Alex, wrote into Everything Dinosaur to ask, how do scientists know how big this dinosaur was and how big was it compared to other feathered dinosaurs found in China?  We wrote to Alex explaining in a little more detail about what the scientists who studied the fossil material concluded.

The academic paper describing this new type of “raptor” was published in the journal “Scientific Reports”.  The authors were Professor Junchang Lü (Institute of Geology, Chinese Academy of Geological Sciences, Beijing) and Dr Stephen Brusatte (School of GeoSciences, University of Edinburgh).

Early Cretaceous North-eastern China

Around 125 million years ago, the area of north-eastern China, now known as Liaoning Province was covered in a lush, temperate forest.  Large lakes featured in the environment and nearby volcanoes occasionally erupted and buried the area in fine ash, this explains the exceptional state of preservation of much of the Liaoning fossil material.

Living in the forests were a large number of different types of “raptor”, members of the Dromaeosauridae dinosaur family.  So far six genera have been described but it is very likely that more feathered dinosaur discoveries will be made in the future.

The six genera of dromaeosaurids described so far (with date described):

1. Sinornithosaurus (named in 1999)
2. Microraptor (named in 2000)
3. Graciliraptor (named in 2004)
4. Tianyuraptor (named in 2010
5. Changyuraptor (named in 2014)
6. Zhenyuanlong (2015)

So How Does Zhenyuanlong Compare?

The fossilised remains of Zhenyuanlong are nearly complete, but the end of the tail is missing.  The skeleton measures 126.6 cm long, when compared to the large dromaeosaurid Tianyuraptor it has been estimated that with the whole of the tail, this animal would have measured more than five feet (165 cm) in length.  It was probably not quite fully grown when it died so it might have reached a length of around 1.8 metres.

When it comes to comparing the sizes of different types of dinosaur, it is the limb bones that palaeontologists turn to.  The thigh bone (femur) for example, is often used to make comparisons between dinosaurs.  To estimate how big a dinosaur was, the length and the circumference of the femur is often measured.  In simple terms, the bigger and the more robust the femur, the bigger the dinosaur.

Comparing Other Dromaeosaurids to Zhenyuanlong suni

As all the Liaoning dromaeosaurid species discovered so far have at least one thigh bone as part of their fossil material, and as the size of the thigh bone strongly correlates to body size, measuring the length and overall size of the thigh bone is a useful way of comparing the sizes of different dinosaurs.

A Table Comparing the Femur Lengths and Overall Size of Liaoning Dromaeosaurids

Size comparisons between Liaoning dromaeosaurids.

Table credit: Everything Dinosaur

* Depends on the species and the specimens measured

** Depends on the species as there are three species of Microraptor currently known.

So based on the length of the thigh bone, scientists can see that Zhenyuanlong (Z. suni) is much bigger than most of the other dromaeosaurids known from Liaoning.  It seems to be about the size of Tianyuraptor.

What Does Zhenyuanlong suni Mean?

Time to answer one other question about this new dinosaur, this time sent in by Sophie.  Sophie asked what does Zhenyuanlong mean?

The Holotype Specimen of Zhenyuanlong suni

Large-bodied, short-armed Liaoning dromaeosaurid

Picture credit: Chinese Academy of Geological Science

Zhenyuanlong suni means “Mr Zhenyuan Sun’s dragon”.  The word “long” means dragon in Chinese (hence other dinosaur names such as Guanlong and Dilong) and the rest of the name honours Mr Zhenyuan Sun, who was able to acquire the holotype specimen for the scientists to study.

There is a spectacular modelof Zhenyuanlong in the Beasts of the Mesozoic model series: Beasts of the Mesozoic Figures and Models.