Dinosaurs Reveal the Geographical Signature of an Evolutionary Radiation

The fact that the dinosaurs came to dominate terrestrial ecosystems during the Mesozoic is not controversial.  There is plenty of fossil evidence to suggest that dinosaurs evolved into a myriad of different species (some 1,300 genera have been described to date), these fossils are geographically widespread.  Thanks, in part, to their origins on the supercontinent Pangaea and to the vagaries of continental drift, dinosaurs lived all over the world, from the Antarctic to the Arctic circle.

Evolutionary Radiation of the Dinosaurs

However, not that much is known about how the dinosaurs spread and became globally distributed.  Indeed, just how quickly the Dinosauria radiated and how soon they rose to prominence in terrestrial ecosystems remains very much open to debate.  Researchers from the University of Reading have attempted to map the geographical spread of the “terrible lizards” and they conclude that the migration of dinosaurs around the world was so rapid, that eventually they ran out of land to colonise and this might have contributed to their extinction.

Dinosaurs Spread from South America to the Rest of the World

Picture credit: Everything Dinosaur

The Evolution of the Dinosaurs – It’s a Bit of a Puzzle

Just when and where the dinosaurs rose to dominate the land is hotly debated.  The fossil record for early dinosaurs is very poor and extremely fragmentary.  This problem is compounded by the blurring of the definition of the Dinosauria, as living alongside the true dinosaurs for tens of millions of years were their closely related counterparts which together with the dinosaurs comprise the clade Dinosauromorpha.  Palaeontologists can find it extremely difficult to distinguish between a true Triassic dinosaur and a contemporary dinosauromorph.  It seems that in the Triassic, the ancestral forms of the Dinosauria, lived alongside the true dinosaurs for millions of years.

This problem is compounded by the fact that the dinosaur/pterosaur/bird branch of the Archosauria (Avemetatarsalia), were in the evolutionary shadow of the crocodile branch of the “ruling reptiles” the Crurotarsi, for much of the Middle and Late Triassic.  If you were able to interview a Coelophysis or a Tawa (both dinosaurs from the famous Ghost Ranch location of New Mexico), they would have described an ecosystem dominated by other types of archosaur, not dinosaurs.  With the exception of the abundance of Coelophysis specimens, there are relatively few dinosaur fossils from the Ghost Ranch location, dinosaurs may have only made up around 20% of the terrestrial fauna.

Coelophysis – A Typical Example of a Triassic Theropod

Picture credit: Matt Celeskey

Jumping into the Jurassic

After the End Triassic mass extinction event, it seems to have been a different story.  The dinosaurs seem to have rapidly risen to dominance and soon the landscape was being dominated by giant herbivores such as the long-necked cetiosaurs and the first super-sized carnivores such as Dilophosaurus, Cryolophosaurus and the first of the megalosaurs.  The Reading University team modelled the spread of the dinosaurs by reconstructing the dinosaurs’ ancestral locations (using South America as the starting point for the dinosaur radiation), they then examined the spatial mechanisms that underpinned the spread of the Dinosauria.  The research shows that the speed of this expansion meant that the dinosaurs quickly became cosmopolitan and subsequently ran out of land.  This lack of space then seriously impeded their ability to produce new species.

Typical Early Jurassic Dinosaurs Show an Increase in Size Compared to Late Triassic Counterparts

Picture credit: Everything Dinosaur

Building Upon Previous Research

This new study, published in “Nature Ecology and Evolution”, builds upon previous research from Reading University, published in 2016, that concluded that the dinosaurs were in decline around 50 million years before the mass extinction event that saw the demise of the non-avian forms.

To read Everything Dinosaur’s article about the 2016 study: The Fifty Million Year Decline of the Dinosaurs.

Lead author of this new research, evolutionary biologist at the University of Reading, Ciara O’Donovan explained:

“Fossil evidence has shown us where the dinosaurs started out and where they died, but there is an important middle period that little was known about.  Our research fills this gap in prehistory by revealing how the dinosaurs spread, how fast they moved and what directions they moved in through time.  The dinosaurs exploded out of South America in a frenzy of movement to cover the planet.  It was during this time that diverse forms evolved and eventually led to species such as the fearsome Tyrannosaurus rex, Archaeopteryx (the earliest bird) and the gigantic, long necked Diplodocus.  This honeymoon period could not last forever though, and the dinosaurs eventually filled every available habitat on Earth.  There was nowhere new for species to move to, which may have prevented new species from arising, contributing to the dinosaurs’ pre-asteroid decline.  In essence, they were perhaps too successful for their own good.”

Using a Novel Statistical Analysis

The Reading University team developed a novel, statistical analytical method to help reveal where the ancestor of every dinosaur species lived.  This data was plotted onto a three-dimensional world map.  The analysis revealed that the dinosaurs spread virtually unchecked across the landmass of Pangaea at a rate of 1,000 kilometres (600 hundred miles), per million years.  They dominated every terrestrial habitat, across the globe as the supercontinent of Pangaea broke apart.

Sympatric Speciation

As the space left available for the Dinosauria to expand into was used up, the evolutionary driver for the development of new species might have changed.  The scientists conclude that dinosaurs initially diversified into new kinds driven by the expansion into new environments and habitats, but this driver for change was gradually replaced by sympatric speciation (new species evolving to exploit new niches within their existing environment).  This fundamental change in the way that dinosaurs evolved could have left them vulnerable to global catastrophes such as the extra-terrestrial impact event and the subsequent climate devastation that occurred some sixty-six million years ago.

Dinosaurs in Decline Many Millions of Years Before the End Cretaceous Mass Extinction

Picture credit: Don Davis (commissioned by NASA)

Dr Chris Venditti, evolutionary biologist at the University of Reading and co-author of the paper, commented:

“Early dinosaurs had a blank canvas and spread quickly across the devastated Earth, taking up every opportunity in their path.  Virtually every door was open to them as there was no competition from other species.  The inability of the dinosaurs to adapt rapidly enough as the Earth became full may explain why they were in decline prior to the asteroid strike, and why they were so they were so susceptible to almost total extinction when it hit.”

The scientific paper: “Dinosaurs Reveal the Geographical Signature of an Evolutionary Radiation” by Ciara O’Donovan, Andrew Meade and Chris Venditti published in Nature Ecology & Evolution.

Everything Dinosaur acknowledges the help of the University of Reading in the compilation of this article.

View the Everything Dinosaur website: Everything Dinosaur.

Fossil from South Wales Identified as New Triassic Species

In the 1950s the Pant-y-ffynnon Quarry in South Glamorgan (Wales), provided a wide variety of vertebrate fossils giving palaeontologists an insight into the fauna of an ancient Triassic archipelago.  However, a comprehensive analysis of the fossil material was not carried out.  Scientists from the University of Bristol including an undergraduate student have undertaken a systematic review of the specimens and this has resulted in the naming of a new species of Rhynchocephalian.  The little reptile has been named Clevosaurus cambrica and this newly described animal hints at adaptive radiation for the clevosaurs on the island chain.  In addition, since the researchers found no evidence of any reptiles in excess of two metres, they propose that the palaeofauna represents a possible example of insular dwarfism.

The concept of insular dwarfism (sometimes referred to as the “island rule” involves residents of islands with limited resources tending to become smaller overtime when compared to their mainland counterparts.

A Three-Dimensional Computer-generated Image of the Jawbone of C. cambrica

Picture credit: Bristol University

Clevosaurus cambrica – “Gloucester Lizard from Wales”

Emily Keeble’s final-year project for a degree in palaeontology at the School of Earth Sciences, (Bristol University) involved a reappraisal of the  Pant-y-ffynnon Quarry specimens.  Working alongside her course supervisors, the undergraduate was able to identify a new species of Clevosaurus, a type of reptile that was widespread across the supercontinent Pangaea in the Late Triassic.  Clevosaurus was named after “Clevum”, the Latin name for the city of Gloucester, as a number of species have been identified from this locality.  The trivial name “cambrica” honours Wales, where the fossil quarry is located.

In the Late Triassic, the hills of South Wales and the south-western part of England formed an archipelago that was inhabited by early dinosaurs, crocodylomorphs distantly related to modern crocodiles and alligators along with representatives of the Sphenodontidae such as the clevosaurs.  The once diverse and geographically reptile family – the Sphenodontidae is today, represented by the rare Tuatara (Sphenodon punctatus) which is limited to a few small islands off New Zealand.

Clevosaurus cambrica Would Have Looked Like a Tuatara

Picture credit: Everything Dinosaur

Commenting on the significance of her discovery, Emily said:

“The new species, Clevosaurus cambrica lived side-by-side with a small dinosaur, Pantydraco, and an early crocodile-like animal, Terrestrisuchus.  We compared it with other examples of Clevosaurus from locations around Bristol and South Gloucestershire, but our new beast is quite different in the arrangement of its teeth.”

Clevosaurus cambrica has been identified based on some articulated bones and some isolated fragments.  An analysis of the teeth in the jaws provided evidence that this small reptile probably was an insectivore.  The shape of the teeth and their arrangement identified the fossil as a new species.

Professor Mike Benton, a co-author of the paper and one of Emily’s supervisors added:

“We were lucky to find quite a lot of the skeleton and Emily was able to scan the blocks and make 3-D reconstructions of the skull, neck, shoulder and arm region.”

Evidence of Insular Dwarfism

The researchers conclude that the archipelago held a relatively impoverished fauna, dominated by rhynchocephalians such as the clevosaurs.  The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago.  Adaptive radiation is the term used to describe the evolutionary process whereby organisms diverge from a common ancestor to fill a multitude of different ecological niches, think of Darwin’s finches on the Galapagos Islands, for example.

Co-author of the paper and co-supervisor of Emily Dr Whiteside (Bristol University) explained:

“The dinosaurs, crocodiles, and lizards were isolated to some extent on their islands, and perhaps smaller ones were better at surviving in the changed ecologies of the islands.”

The scientific paper: “The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures, South Wales, UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)” by Keeble et al published in the Proceedings of the Geologists’ Association.

Everything Dinosaur acknowledges the help of a press release from Bristol University in the compilation of this article.

Visit the Everything Dinosaur website: Everything Dinosaur.

Culture Ministry Investigates Sale of Atlasaurus Caudal Vertebrae

Moroccan authorities are investigating the sale of a dinosaur’s tail that was sold by the Mexican auction house Morton, to an anonymous buyer for around $97,000 USD ($1.8 million Mexican pesos).  The auction, which took place last Tuesday, was held in Mexico City.  It helped to raise funds for the reconstruction of schools damaged by earthquakes that occurred in Mexico during the autumn.  Any sum over the reserve price was to be donated to the earthquake relief fund.

The Dinosaur Tail (Atlasaurus imelakei) on Display Prior to the Auction

Picture credit: Reuters/Daniel Becerril

Atlasaurus imelakei

The four-metre long specimen, weighs around 180 kilograms and represents a partial tail of a sauropod dinosaur from Morocco called Atlasaurus (A. imelakei).  Regarded as a member of the macronarian group of sauropods, Atlasaurus was distantly related to Brachiosaurus and Giraffatitan.  It lived in North Africa during the Middle Jurassic (Bathonian faunal stage) and it is known from numerous isolated bones and articulated specimens.  Atlasaurus had very long limbs, proportionately longer than most other members of the Sauropoda.   Its neck was relatively short compared to later macronarians.

Palaeontologists have speculated that the proportionately longer legs evolved to help this herbivorous dinosaur reach food, that other plant-eating dinosaurs could not obtain.  The long legs of Atlasaurus are regarded as an example of an evolutionary adaptation to achieve niche partitioning within North African dinosaurs.

Culture Ministry Becomes Involved in the Mexican Dinosaur Auction

The auction of the fossilised tail bones has come to the attention of the Moroccan Ministry of Culture, which has launched an investigation to find out the origin and provenance of the fossil material.  The fossil was sold as part of a specialist auction, managed by the Morton Auction House.  A percentage of the sale proceeds being reportedly donated to the Bancomer Foundation to help support reconstruction efforts in those parts of Mexico affected by the recent earthquakes.  Media reports suggest that around $21,500 USD ($400,000 Mexican pesos), was to be donated from the sale of the fossil.

The fossil very likely originated from the Azilal region of Morocco.  The specimen has been restored, around 70% of the material is actual fossil bone.  Steps are being taken to determine how the specimen ended up in the auction.  This is not the first time Moroccan authorities have intervened in a case like this.  In April 2017, a Late Cretaceous plesiosaur fossil exhibit was removed from a Paris auction after an agreement was reached with the Binoche and Giquello auction company.

Tracing the Tale of a Tail

Several sources have stated that the Atlasaurus tail bones were acquired by the Morton Auction House from the Petra Gallery, which specialises in the sale of fossils and minerals.  The acquisition by the Morton Auction House from the Petra Gallery has been confirmed by Morton’s Press and Public Relations representative Kristina Velfu.

Ernesto Durán, the director of the Petra Gallery has stated that the fossil was bought legally in the United States and both a receipt and legal import document are available to prove the purchase as legitimate.

In Mexico, the selling of fossils found within the country is illegal, as they are considered part of the country’s heritage.  However, the law in Mexico does not prohibit the sale of fossils found outside its borders.  The Atlasaurus specimen very probably originated in Morocco, the authorities are interesting in tracing how the fossil came to be in the United States, where it was excavated from and what documentation (if any), exists with regards to its movement out of the country.

We at Everything Dinosaur, will watch how this story unfolds.

Diluvicursor pickeringi – Turkey to Rhea-sized Herbivore from the Early Cretaceous

Analysis of the fossilised remains of a little ornithopod have led to the establishment of a new species of dinosaur, one that roamed the Australian-Antarctic rift valley approximately 113 million years ago.  Described from an almost complete tail and a partial right hind limb including foot bones, the dinosaur has been named Diluvicursor pickeringi (pronounced di-loovy-cursor pickering-i).

The species name honours David Pickering, (formerly Museums Victoria’s Vertebrate Palaeontology Collections Manager), a scientist who played a key role in the study of Early Cretaceous vertebrate fossils from the Otway and Gippsland Basins of the Australian State of Victoria.  David sadly passed away following complications after a serious car accident whilst the fossil material was being prepared and studied.

An Illustration of a Pair of Diluvicursor pickeringi Feeding Near a Fast-flowing River

Picture credit: P. Trusler

A Fossil Discovery in 2005

The fossils of this dinosaur described as being about the size of a turkey or a rhea (estimated maximum total body length, including tail at around 2.3 metres), were found on five slabs of rock that form part of a deposit representing a log jam event created in a high-energy (fast-flowing) river.  Writing in the academic journal “Peer J”, the authors of the scientific paper state that this newly described herbivorous dinosaur will help to shed new light on the phylogenetic relationships and the diversity of Ornithopoda of the Southern Hemisphere.

Dr Matt Herne (University of Queensland) and the corresponding author for the paper explained the significance of the fossils, which were excavated from a sea platform near Cape Otway.

He stated:

“Diluvicursor shows for the first time that there were at least two distinct body-types among closely related ornithopods , small, two-legged plant-eating dinosaurs in this part of Australia.  One called Leaellynasaura was lightly built with an extraordinarily long tail, while the other, Diluvicursor, was more solidly built, with a far shorter tail.”

The Holotype Fossil Material of Diluvicursor pickeringi

Picture credit: Peer J

A Fast Running Dinosaur

Analysis of the leg bones suggest that Diluvicursor was a fast running dinosaur.  The corpse of this dinosaur, representing a juvenile animal, came to rest mixed up with other debris deposited by a fast-flowing river.  The genus name reflects these two conclusions, Diluvicursor translates as “flood runner”.

The Proposed Body Shape of Diluvicursor with the Known Fossil Bones in Skeletal Position

Picture credit: Peer J

Volunteer prospector George Caspar discovered the fossil material in 2005 whilst exploring a coastal shore platform which forms part of the Eumeralla Formation of south-eastern Australia.   It is likely the carcass became trapped and buried along with flood-transported tree stumps, logs and branches in deep scours at the base of what was once a powerful river.

Dr Herne added:

“The Diluvicursor skeleton was discovered in 2005, but it’s taken this long to fully understand the geology of the area where it was found, and also Diluvicursor’s relationships.  Much of the fossil vertebrate material from this site has yet to be described, so we hope to discover further dinosaur species, specimens and other exciting animals there.”

Diluvicursor pickeringi with an Injured Foot

A close examination of the right foot of the Diluvicursor specimen suggest that this dinosaur may have injured its foot some time before it perished.  Some of the bones are not aligned correctly and although this could be as a result of taphonomy, preserved roughened bone surfaces, suggest some form of trauma or disease.  The scientists conclude that the affected joint in the foot could have been immobilised.  The researchers are hopeful that further examination including a scan of the foot using synchrotron radiation X-rays will produce more data.

The Pathology on the Right Foot of the Diluvicursor Specimen

Picture credit: Peer J

There are plans to display the post cranial fossil material at Melbourne Museum and the aim is to build up a much more complete picture of the palaeoenvironment of this part of Gondwana during the Albian faunal stage of the Cretaceous.  Other scientists involved in this study include Dr Steven Salisbury, PhD student Jay Nair and Dr Vera Weisbecker (University of Queensland), along with colleagues from Monash University.

The scientific paper: “A New Small-bodied Ornithopod (Dinosauria, Ornithischia) from a Deep, High-energy Early Cretaceous River of the Australian–Antarctic Rift System” by Matthew C. Herne​, Alan M. Tait, Vera Weisbecker, Michael Hall, Jay P. Nair, Michael Cleeland and Steven W. Salisbury published in Peer J.

Everything Dinosaur acknowledges the help of the University of Queensland in the compilation of this article.

Visit the Everything Dinosaur website: Everything Dinosaur.