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/Palaeontological articles

Articles, features and information which have slightly more scientific content with an emphasis on palaeontology, such as updates on academic papers, published papers etc.

17 03, 2019

New Study “Cracks” Dinosaur Egg Mystery

By | March 17th, 2019|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Dinosaurs Innovated When it Came to Egg Production

Many museums include the fossilised remains of dinosaur eggs amongst their natural history collections and palaeontologists are aware that reptiles were laying eggs on land long before the dinosaurs evolved, but what we know about the evolution of reptile eggs (amniotic eggs in general), is largely based on inference and conjecture.  The problem is, for the first 100 million years or so of amniote evolution, there is very little fossil data related to reptile reproduction to study.  What we do know, is based on Middle Jurassic to Late Cretaceous fossils.  Although, dinosaur eggs are rare, the examples we do have, such as those associated with Asian oviraptorids demonstrate that dinosaur eggs had thick, hardened shells.  However, a new study suggests that it was not always like this and that the three main Sub-orders of the Dinosauria probably evolved thick, tough eggs independently.

Examples of Eggs from Different Archosaurs (Avian and Non-avian Dinosaurs)

Examples of fossil Archosaur eggs.

Examples of whole or partial fossilised eggs.

Picture Credit: Royal Society Open Science

Studying Some of the World’s Oldest Dinosaur Eggs Reveals New Information

Writing in the on-line, open access journal “Scientific Reports”, a team of scientists, including Robert Reisz (University of Toronto Mississauga) and Koen Stein (Royal Belgian Institute of Natural Sciences, Brussels), have examined some of the oldest examples of dinosaur eggs known and revealed new information about the evolution of dinosaur reproduction.  The researchers examined the eggs and eggshells of three coeval, but geographically widely distributed Early Jurassic basal Sauropodomorph dinosaurs (Sinemurian faunal stage).  These fossils came from Argentina, China and South Africa and include the eggs of Massospondylus and Lufengosaurus.  Their analysis showed that the basal Sauropodomorph eggs all had the basic structure, they had a thin calcareous layer less than 100 microns thick.  This thin shell layer contrasts strongly with the much thicker calcareous shells associated with Late Jurassic and later dinosaur eggs.

At approximately 195 million years old, they are the earliest known eggs in the fossil record, and they were all laid by similar, herbivorous dinosaurs that ranged in size from four to eight metres in length and were the most common and widely spread dinosaurs of their time.  These types of plant-eating dinosaur were the forerunners of the giant Sauropods of the Jurassic, dinosaurs such as Brontosaurus, Diplodocus and Brachiosaurus.

A Massospondylus Nesting Site (Life Reconstruction)

Massospondylus nesting site - life reconstruction.

Massospondylus (basal Sauropodomorpha) nesting site. Massospondylus fossil eggs from South Africa were used in the study.

Picture Credit: Julius Csotonyi

Putting the research into context Professor Reisz explained:

“Reptile and mammal precursors appear as skeletons in the fossil record starting 316 million years ago, yet we know nothing of their eggs and eggshells until 120 million years later.  It’s a great mystery that eggs suddenly show up at this point, but not earlier.”

The researchers concluded that these Early Jurassic eggs represented a step in the evolution of dinosaur reproduction, their shells were paper-thin and brittle, proportionately much thinner than the eggs of extant birds.  However, thicker, tougher eggshells in the Dinosauria were to evolve across all three Sub-orders later.  The much thicker eggshells associated with Sauropods, Ornithischian dinosaurs and the Theropoda must have evolved independently.

Professor Reisz added:

“We know that these early eggs had hard shells because during fossilisation they cracked and broke, but the shell pieces retained their original curvature.”

Other authors of the scientific paper include Edina Prondvai and Jean-Marc Baele.  Shell thickness was analysed along with membrane thickness, mineral content and distribution of pores, looking for clues about why these early eggs might have developed hard shells.  The scientists concluded that hard-shelled eggs evolved early in dinosaur evolution, with thickening of the calcareous layer (greater than 150 microns), occurring independently in several groups, but a few million years later other reptiles also developed hard-shelled eggs.  One possibility is that hard and eventually thicker shells may have evolved to shield dinosaur embryos and other reptiles from predators.

Professor Reisz commented:

“The hard shells would protect the embryos from invertebrates that could burrow into the buried egg nests and destroy them.”

Linked to Increased Oxygen in the Atmosphere

Advanced mineralisation of amniote eggshell including those of dinosaurs (≥150 microns in thickness), in general occurred not earlier than the Middle Jurassic and may correspond with a global trend of an increase in atmospheric oxygen.  If there were higher levels of atmospheric oxygen, then this would facilitate more efficient gaseous exchange through the porous eggshell and across the egg membranes.  More efficient diffusion would permit the evolution of thicker eggshells, which in turn would offer greater resistance to damage and more protection from predators.

A Lufengosaurus Embryo

The embryo of a Lufengosaurus

New research into 195 million-year-old baby dinosaurs and their eggs.

Picture Credit: D. Mazierski

Raising Further Questions About Mesozoic Reproduction Strategies

The study raises some intriguing questions that may well lead to further research projects.  For example, palaeontologists are aware that many types of marine reptile evolved viviparity (live birth), whilst the fossil evidence for the terrestrial Dinosauria seems to indicate that they continued to rely on egg laying.  Why didn’t the highly diverse dinosaurs evolve different reproductive strategies over their 160 million years of existence?

Everything Dinosaur acknowledges the assistance of a press release from the University of Toronto in the compilation of this article.

The scientific paper: “Structure and Evolutionary Implications of the Earliest (Sinemurian, Early Jurassic) Dinosaur Eggs and Eggshells” by Koen Stein, Edina Prondvai, Timothy Huang, Jean-Marc Baele, P. Martin Sander and Robert Reisz published in Scientific Reports.

11 03, 2019

New Australian Ornithopod Described

By | March 11th, 2019|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Galleonosaurus dorisae – A New Aussie Dinosaur

A new type of Australian dinosaur has been described from the fossilised remains of five upper jaw bones (maxillae) found at the Flat Rocks locality in the Wonthaggi Formation in the famous Gippsland Basin of Victoria.  Five small-bodied Ornithopods are now known from the state of Victoria.  The new plant-eating dinosaur has been named Galleonosaurus dorisae.  The jaw bones are of different sizes and this has permitted palaeontologists to plot growth changes in these little dinosaurs as they matured.

Writing in the Journal of Palaeontology, the researchers which include Matthew Herne (University of New England, New South Wales) and Alistair Evans (Monash University, Melbourne), used detailed CT-scans of the fossil material to gain fresh insights into the structure and morphology of the cranial anatomy and dentition of small Australian Ornithopods.  The research leading to the establishment of this new genus has also helped to define more clearly other small Ornithopods known from the Gippsland Basin and the Otway Basin located on the opposite side of Port Phillip Bay.

A Life Reconstruction of the Newly Described Ornithopod Galleonosaurus dorisae

Galleonosaurus dorisae illustrated.

A life reconstruction of the newly described Australian Ornithopod Galleonosaurus dorisae.

Picture Credit: James Kuether

“Galleon Lizard”

When the scientists were examining the maxillae, their shape reminded them of the upturned hull of an old-fashioned sailing ship – a galleon.  It was the morphology of the jaw that inspired the genus name “Galleon Lizard”.  The species or trivial name honours Doris Seegets-Villiers for her geological, palynological, and taphonomic work on the Flat Rocks fossil vertebrate locality.

Jaw Fossils and a Tooth with a CT-scan of the Fossil Material

Galleonosaurus fossiils and a CT-scan of a jaw.

Fossil jaw bones, a single tooth and a CT-scan image of a jaw bone (Galleonosaurus dorisae).

Picture Credit: Herne et al

Niche Partitioning in Ornithopods

The plethora of vertebrate fossils at the Flat Rocks site, suggests that several more dinosaurs await discovery.  However, for the moment, the researchers are confident that Galleonosaurus shared its habitat with at least one other small, light, fast-running Ornithopod – Qantassaurus intrepidus.  The jaws of Qantassaurus are more robust and more powerful.  The researchers were able to confirm that Q. intrepidus is uniquely characterised by a deep, foreshortened dentary (lower jaw).  This suggests that the robust Q. intrepidus and the more gracile jawed G. dorisae fed on different vegetation, they did not compete directly for food, an example of niche partitioning.

Dr Herne described Galleonosaurus:

“We know it would have been a two-legged, quite agile plant-eating dinosaur.  It seems that Galleonosaurus was no doubt closely related to possibly as many as four or five other species that look a little bit similar and were similar sizes, but we can tell they’re different by the anatomy of the jaws and the teeth.”

A Lush Conifer Dominated Rift Valley with an Immense Volcanic Mountain Chain to the East

Extensive research on the Otway Formation material to the west of Port Phillip Bay in conjunction with research on the geology of the Gippsland Basin have permitted scientists to build up a picture of what life was like in this part of Australia during the Early Cretaceous.  The dinosaurs lived in an extensive rift valley that had formed as Australia began to separate from Antarctica. Conifer forests dominated and at such high latitudes, the lush environment would have been subjected to long periods of extensive daylight in the summer, but conversely the winters would have been cold with little daylight each day.  Although the Earth’s climate was much warmer than today during the Early Cretaceous, it is quite possible that these little dinosaurs would have had to endure winter temperatures close to freezing.

Gondwana in the Early Cretaceous (Barremian Faunal Stage)

Gondwana in the Early Cretaceous.

Around 125 million years ago, although Gondwana was breaking up, Australia was still linked to Antarctica with a large volcanic mountain range to the east.

Picture Credit: Herne et al

A Skeletal Reconstruction of the Skull of Galleonosaurus and the Anatomical Position of Jaw Material

Jaw fossils of Galleonosaurus dorisae.

An illustration of the skull of Galleonosaurus dorisae with fossil elements placed in the correct anatomical position.  The lower jaw shown in the image might pertain to G. dorisae based on a reassessment of other known lower jaw elements associated with Q. intrepidus and Atlascopcosaurus loadsi.

Picture Credit: Herne et al

A Phylogenetic Analysis

The scientists conclude that a highly diverse, small-bodied Ornithopod fauna flourished in the periodically disturbed, high-latitude, riverine floodplain environment of the Australian-Antarctic rift valley during the Early Cretaceous (Barremian to Early Albian faunal stage).  A phylogenetic analysis places Galleonosaurus as the earliest member of the Elasmaria, a clade of Gondwanan Ornithopods distantly related to the Hypsilophodonts.

The Five Victorian Ornithopods – Spanning 12 million years

The Lower Cretaceous rocks either side of Port Phillip Bay were laid down at different times during the Cretaceous.  The Gippsland Basin deposits close to the town of Inverloch, were laid down around 125 million years ago, however, the Otway Basin deposits (Eumeralla Formation), represent younger material laid down in the Early Albian (113 million years ago).

  1. Leaellynasaura amicagraphica – named in 1989 (Early Albian faunal stage), from the Eumeralla Formation (Otway Basin).
  2. Atlascopcosaurus loadsi – also named in 1989 from the Eumeralla Formation.
  3. Diluvicursor pickeringi – named in 2018 (Eumeralla Formation).  To read an article about the discovery of this dinosaur: Fast-running Ornithopod from Victoria.
  4. Qantassaurus intrepidus named in 1999 from the Wonthaggi Formation (Gippsland Basin) – older strata associated with the Barremian faunal stage of the Early Cretaceous.
  5. The newly described Galleonosaurus dorisae (2019), also from the Wonthaggi Formation.

Dr Herne stated:

“The interesting thing about that whole coast line is it gives us a decent age range over quite a long period.”

A spokesperson from Everything Dinosaur commented:

“It is likely that many more small dinosaurs are going to be named and described in the future.  Fossil finds from Victoria will, most likely, lead to further revisions of Gondwanan Ornithopod taxonomy.”

6 03, 2019

Twisting and Turning Tyrannosaurs Made them Top Predators

By | March 6th, 2019|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles|0 Comments

New Study Suggests Tyrannosaurids More Manoeuvrable than Other Large Theropods

Researchers at the University of Wisconsin-La Crosse and the Oklahoma State University Centre for Health Sciences have applied mathematical models to assess the manoeuvrability of predatory dinosaurs.   This research, published in the on-line journal PeerJ, involving numerous collaborators, suggests that large bodied Tyrannosaurs were more agile and able to turn more sharply than other similar sized Theropods such as Allosaurs and carcharodontosaurids.

A Large Tyrannosaur Attacks a Styracosaurus

Daspletosaurus fighting a horned dinosaur.

Tyrannosaur fighting a horned dinosaur.  A new study suggests that large bodied Tyrannosaurs may have been surprisingly agile.

Picture Credit: John Gurche

A Factor in the Evolutionary Success of Tyrannosaurs

The research involving complex mathematics, a study of animal anatomy and physics compared how rapidly meat-eating dinosaurs could turn their bodies.  In summary, the scientists concluded that Tyrannosaurs could attack smaller, faster and more dangerous prey.  It is suggested that the greater manoeuvrability of these carnivores may have been a factor in their evolutionary success.

Associate Professor at the University of Wisconsin-La Crosse, Eric Snively, in collaboration with co-author Haley O’Brien (Oklahoma State University Centre for Health Sciences) along with several other leading palaeontologists such as Professor Phil Currie (University of Alberta), demonstrated that whether a Tyrannosaur was dog-sized or a fully-grown, mature adult, it retained its agility and manoeuvrability.

Three-dimensional Computer Models Used to Test Tyrannosaurid Manoeuvrability

Assesing the agility of tyrannosaurids.

Computer models were created to examine the agility of tyrannosaurids.

Picture Credit: University of Wisconsin-La Crosse

Enhanced Agility Compared to Other Super-sized Theropods

Tyrannosaurs were assessed to be more agile as they had relatively short bodies (anteroposteriorly short thoracic regions, and cervical vertebrae that aligned into posterodorsally retracted necks).  In summary, shorter bodies meant less turning resistance and even their tiny arms helped!  In addition, long, tall ilia bones (part of the hip), provided plenty of room for huge leg muscle attachments that gave the power needed for rapid turns and pivots.

The Size of the Ilia (Hip Bones) was Used to Infer Muscle Size Along with Postulated Tail Depth

Tyrannosaur agility, mapping the position of leg locomotor muscles.

Mapping muscle groups to assess the agility of tyrannosaurids.  Tyrannosaur musculature was compared to that of an extant alligator.

Picture Credit: PeerJ

In terms of the fastest results from the Tyrannosaur family, a horse-sized juvenile T. rex turned the quickest for its size, followed by the giant T. rex “Sue”, the enormous, mature adult from the Field Museum (Chicago).

Eric Snively described the T. rex turn as something akin to a “slow-motion-ten-tonne figure skater from hell,” quite apt in a way as T. rex fossils are known from the Hell Creek Formation.

Biomechanical Model Has Implications for Large Theropod Hunting Strategies

The researchers used very accurate anatomical assessments and rigorous statistics to create three-dimensional models that could then be tested for their range of movements.  Different Theropods were examined including Dilophosaurus, Ceratosaurus, Giganotosaurus, Sinraptor as well as numerous Tyrannosaurs at different growth stages as well as smaller members of the Tyrannosauroidea Superfamily such as Raptorex.  With respect to other Theropods, tyrannosaurids were found to be increasingly agile without compromising their large body mass, such that in a pairwise comparison, tyrannosaurids were achieving the same agility performance as much smaller Theropods.  For example, a 500 kg Gorgosaurus had slightly greater agility scores than the 200 kg Eustreptospondylus, and an adult Tarbosaurus nearly twice the agility scores of the lighter Sinraptor.

The Oxford University Specimen of Eustreptospondylus Used in the Study

Eustreptospondylus dinosaur skeleton exhibit.

The fossil specimen on display (E. oxoniensis).

Picture Credit: Everything Dinosaur/Siri Scientific Press

Enhanced agility and tight manoeuvrability in tyrannosaurids suggest that T. rex et al had superior abilities when it came to pursuing and subduing prey.  This new research may have important implications when it comes to examining how large Theropods hunted.

If tyrannosaurids were more agile and able to manoeuvre faster than other large predators they may have been more adept than earlier, super-sized, apex predators when it came to catching agile prey.  It is postulated that this capability of tyrannosaurids is consistent with coprolite evidence that indicates that tyrannosaurids fed on juvenile Ornithischians.  Furthermore, it is proposed that healed Tyrannosaur bite marks on fossilised remains of adult horned dinosaurs and Hadrosaurs indicate an ability to outmanoeuvre quadrupedal prey.

A spokesperson from Everything Dinosaur commented:

“Whilst this is a fascinating piece of research, it is important that we don’t entirely discount observations of modern-day predator/prey interactions.  Often an apex predator will select a weakened, or sick animal within a herd to attack.  In addition, young animals are particularly vulnerable as they are smaller and less experienced in avoiding predators compared to adult animals.”

The largest non-tyrannosaurids, including Giganotosaurus, often lived in habitats alongside Sauropod dinosaurs.  These associations may suggest that allosauroids may have preferred less agile prey than did tyrannosaurids.  It is also possible that stability conferred by high rotational inertia, as when holding onto giant prey, was more important for allosauroids than turning quickly.

The researchers intend to undertake research to assess the manoeuvrability of ceratopsids and other prey such as duck-billed dinosaurs before applying the same techniques to examine Tyrannosaur bite forces.

3 03, 2019

Late Triassic Frogs of North America

By | March 3rd, 2019|Dinosaur and Prehistoric Animal News Stories, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

The Earliest Equatorial Record of Frogs

Researchers including palaeontologists from the Department of Geosciences at Virginia Tech, have identified tiny fossil fragments collected from Upper Triassic deposits in Arizona that provide evidence of the oldest known frogs from North America.  Although, no new genus has been erected, the scientists are confident that further study of the microfossils at the location may yield skull and jaw bones which will result in the naming of new species.

A Little Chinle Frog Has a Close Encounter with a Phytosaur

A suggested encounter between a frog and a phytosaur.

A Chinle frog encounters a phytosaur. It is likely that phytosaurs would have fed on amphibians.

Picture Credit: Andrey Atuchin

The fossils are composed of several tiny pieces of hip bone, (from the ilium), they were collected last May from three separate locations within the famous Chinle Formation and they have been dated to between 223 and 213 million years ago.  The bones represent the earliest equatorial record of the Salientia, the group that includes stem and crown-frogs.  These tiny amphibians, little more than two centimetres in length, are not direct ancestors of modern frogs (Anura).

One of the authors of the scientific paper, published in the journal Biology Letters, Assistant Professor Michelle Stocker, stated that these fossils underscore the importance of microfossil collection, analysis and study as it helps palaeontologists to build up a more comprehensive picture of an ancient ecosystem.

Assistant Professor Stocker explained:

“This new find highlights just how much there is still to learn about the Late Triassic ecosystem and how much we can find when we just look a little closer.  We are familiar with the charismatic Archosaurs from the Chinle Formation, but we know that based on other ecosystems, they should make up a small percentage of the animals that lived together.  With this new focus, we are able to fill in a lot of those missing smaller components with new discoveries.”

Time-calibrated Stratigraphic and the Geographical Distribution Across Pangaea of Triassic and Jurassic Anurans

The stratigraphic and biogeographic distribution of Triassic and Jurassic fossil frogs.

Time-calibrated stratigraphic and biogeographic distribution of Triassic and Jurassic Period anuran specimens.

Picture Credit: Biology Letters

The image above shows (a) the stratigraphic sequence indicating the three fossil examples of Chinle frogs and their relationship to the Early Jurassic Prosalirus (MNA 291) from the Kayenta Formation (Arizona), whilst (b) shows the biogeographic distribution of fossil anurans from the Jurassic and Triassic.  Note, the proximity of the Late Triassic Chinle frogs to the equator.  Photograph (c) shows an eyelash sized fossil ilium whilst (d) and (e) are computerised scans of the same fossil material shown in lateral and medial views.  Scale bars equal 1 millimetre.

Long and Hollow Hip Bones

The fossil material gathered from extensive sieving  and screen washing of sediments in order to obtain microvertebrate fossils, consists of long, hollow hip bones with the hip socket offset rather than centred, anatomical traits that are characteristic of frogs and that help to support their hoping style of locomotion.  Stocker and her collaborators include fellow scientists from Virginia Tech, Arizona’s Petrified Forest National Park, and the University of Florida’s Museum of Natural History.

The Chinle frogs share more features with living frogs and Prosalirus, a genus of Early Jurassic frog found in sediments from the present-day Navajo Nation (Arizona), than to Triadobatrachus, an Early Triassic frog discovered in Madagascar.

Stocker added:

“These are the oldest frogs from near the equator.  The oldest frogs overall are roughly 250 million years old from Poland [Czatkobatrachus] and Madagascar, but those specimens are from higher latitudes and are not equatorial.”

Comparing the Ilia of Stem Anurans

Comparing fossilised hip bones from stem anurans (frogs).

Comparing the ilia of stem anurans and those of extant frogs (Ascaphus, Leiopelma, Alytes and Barbourula) scale bar = 1 mm.

Picture Credit: Biology Letters

Co-author Sterling Nesbitt (Virginia Tech), commented:

“Now we know that tiny frogs were present approximately 215 million years ago from North America, we may be able to find other members of the modern vertebrate communities in the Triassic Period.”

This is the first time that frog fossils have been found in sediments associated with phytosaurs and early members of the Dinosauria.

The research team hope that further work screening and washing sediments from the Chinle Formation sites, will yield more information about the tiny animals that lived alongside some of the first dinosaurs in North America.

A spokesperson from Everything Dinosaur stated:

“The sieving and screen washing methodology employed to discover the tiny hip bones and fossil material associated with Late Triassic frogs could also be used to help identify other small animals that lived in this ecosystem, animals such as salamanders, early squamates and even small mammals.”

Everything Dinosaur acknowledges the assistance of a press release from the Virginia Tech College of Science in the compilation of this article.

The scientific paper: “The Earliest Equatorial Record of Frogs from the Late Triassic of Arizona” by Michelle R. Stocker, Sterling J. Nesbitt, Ben T. Kligman, Daniel J. Paluh, Adam D. Marsh, David C. Blackburn and William G. Parker published in Biology Letters.

26 02, 2019

Middle Cambrian Worm – Amiskwia Finds a Home

By | February 26th, 2019|Dinosaur and Prehistoric Animal News Stories, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Weird Prehistoric Worm Finally Gets Classified

Ever since Charles Doolittle Walcott, discovered the now famous Burgess Shale deposits of Cambrian-aged fossils in British Columbia, palaeontologists have marvelled at the amazing snapshot of ancient marine life the fossils represent.  One of the enduring mysteries surrounding many of the preserved remains is how to classify the more than 500-million-year-old-fossil specimens.  One such Burgess Shale creature, a prehistoric worm with jaws – Amiskwia sagittiformis and its equally ancient cousin A. sinica from the roughly contemporaneous Maotianshan shales of Yunnan Province, China have finally found a home on the Tree of Life.

A Fossil of Amiskwia sagittiformis (Burgess Shale)

Amiskwia sagittiformis from the Burgess Shale.

The fossil, Amiskwia sagittiformis from the Burgess Shale (508 million years old), preserving bilateral jaw elements inside its head.

Picture Credit: Luke Alexander Parry/University of Bristol – Yale University

Analysis of Fossils from the Smithsonian Institute

Researchers from Bristol University in collaboration with a former colleague now based at the University of Yale, have identified that this soft-bodied creature is a stem lineage to arrow worms that possesses the jaw apparatus seen in microscopic gnathiferan worms.  This new analysis of ancient fossils helps to link recent DNA studies on the bristle-jawed arrow worms (Chaetognatha), indicating that these worms are related to the Gnathifera, tiny, unsegmented worms with primitive jaws that like the chaetognaths, are found in marine environments.

The scientists conclude that the soft-bodied taxon Amiskwia possesses characters intermediate between chaetognaths and gnathiferans.

A Close View of the Head of an Extant Arrow Worm

A photograph of the head of an arrow worm.

The head of the arrow worm, Parasagitta elegans.  This group of animals (Chaetognatha), are the closest living relatives to the Amiskwia genus.

Picture Credit: Rafael Martin Ledo/Consejería de Educación de Cantabría

Originally Described by Walcott

Like many of the Burgess Shale animals, an original description of Amiskwia was published by Walcott (1911).  Walcott made the connection with extant arrow worms (chaetognaths).  These unsegmented worms are predators and they use the spines on their head for catching prey.  Despite the remarkable degree of preservation of Burgess Shale specimens, fossils of Amiskwia are very rare when compared to other Burgess Shale Middle Cambrian biota.  Fossils of Amiskwia sinica are also very rare in the Chinese Maotianshan shales.  These types of creatures may have comprised a scarce component of the Middle Cambrian marine fauna, or perhaps, there is a fossil preservation bias.

With few fossils to study, there was widespread debate amongst scientists with regards to Walcott’s conclusions regarding the taxonomy of Amiskwia.  The renowned American palaeontologist, Stephen Jay Gould (1941-2002), re-ignited the controversy by speculating that these little, soft-bodied, squished fossils represented an organism that had no modern relatives.  Gould proposed that Amiskwia was an experiment in evolution that ultimately failed leaving an extinct lineage and no modern-day descendants.

The problem with Walcott’s idea that Amiskwia was related to arrow worms was that scientists were unable to find evidence of any grasping spines at the anterior end of the animal in any of the fossils.  Instead, many researchers proposed that Amiskwia was a representative of another group of worms the ribbon worms (Nemertea).

When Dr Jakob Vinther from the University of Bristol’s Schools of Earth Sciences and Biological Sciences and Luke Parry (Yale University), studied specimens of Amiskwia, kept at the Smithsonian Institute, they found something that had been overlooked by the previous researchers.

Dr Vinther explained:

“I coated the specimen with ammonium chloride smoke to make the relief of the fossil stand out and then I could see that in the head was a pair of robust elements.”

A Set of Jaws

Interpreting these structures as a set of jaws, their resemblance led the scientists to the conclusion that there was a link between these fossils and the Gnathifera.  In essence, the Amiskwia fossil material represents a sort of half-way stage between two important groups of invertebrates.  Amiskwia had the jaw apparatus of a gnathiferan, but the body plan of an arrow worm.

A Microscopic Member of the Gnathifera – the gnathostomulid Rastrognathia macrostoma

The gnathostomulid Rastrognathia macrostoma.

The gnathostomulid Rastrognathia macrostoma, these microscopic animals have a jaw apparatus similar to Amiskwia, which scientists now propose are amongst the closest living relatives of living arrow worms.

Picture Credit: Martin Vinther Sørensen/SNM Denmark

This study in conjunction with the recent DNA analysis, confirms that Amiskwia is the fossil link between the Gnathifera and arrow worms, the Chaetognatha.  This research was originally conducted some years, ago but was not published as the paper’s conclusions lacked supporting evidence from other studies.

Dr Vinther added:

“The bizarre combination of anatomy seemed altogether alien back in 2012.  Some people have proposed that there could be a relationship between arrow worms and gnathiferans based on their shared possession of a jaw apparatus, both made of a substance called chitin.  However, there was little other evidence to suggest a relationship, such as evidence from phylogenetic analyses of DNA.”

Co-author of the scientific paper, Luke Parry stated:

“It altogether seemed like heresy to propose that gnathiferans and arrow worms may be related back then so we held off publishing our intriguing results out of fear of criticism from our peers.  However, new DNA studies have since emerged that found arrow worms to be more and more closely affiliated to the Gnathifera in the Tree of Life.  In particular, some researchers found that arrow worms share a duplication of the important Hox genes with a gnathiferan, the rotifers.  We suddenly felt no more in a deadlock situation.”

Now the authors have published their findings in the journal Current Biology. The study follows a new phylogenetic study, which finds robust support for arrow worms forming an evolutionary group with gnathiferans.

The Inferred Phylogeny of Amiskwia and its Position in Relation to the Gnathifera and the Chaetognatha

Amiskwia inferred phylogeny.

Inferred phylogeny. Thumbnails at the bottom of the figure show reconstructions of relevant extant and extinct gnathiferan and chaetognath taxa.

Picture Credit: Current Biology

Scientists have pieced together a little bit of the enigmatic Burgess Shale and the Chinese Maotianshan biotas and linked them to modern organisms.  Amiskwia has been found a place on the Tree of Life.  It is a stem lineage to arrow worms that possess the jaw apparatus seen in gnathiferan worms.

This jaw evolved into the fearsome grasping spines in living arrow worms, which play an important role in  marine ecosystems.

The scientific paper: “Bilateral Jaw Elements in Amiskwia sagittiformis Bridge the Morphological Gap between Gnathiferans and Chaetognaths” by Jakob Vinther and Luke A. Parry published in Current Biology.

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

22 02, 2019

Fleet-footed Tyrannosaur Leaps 70-million-year Gap

By | February 22nd, 2019|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

The Diminutive Tyrannosaur Moros intrepidus

A small, but speedy dinosaur is the newest member of the Superfamily Tyrannosauroidea, a distant relative of the most famous dinosaur of all Tyrannosaurus rexT. rex et al might have a reputation for being giant, bone-crunching apex predators, but for much of their evolutionary history, the Tyrannosaurs have been rather over-shadowed by other super-sized dinosaur carnivores.  Indeed, it was only in the last few million years of the Cretaceous that these types of Theropod emerged as the apex predators of northern latitudes.  The new dinosaur, named Moros intrepidus, at approximately 78 kilograms (data range 53 to 85 kilograms), around the same bodyweight as a South American Jaguar (Panthera onca), is about ninety times lighter than its famous top-of-the-food-chain relative.

Ironically, contrary to public opinion, M. intrepidus might just be more typical of the Tyrannosauroidea bauplan than its more famous relatives – Gorgosaurus, Albertosaurus and T. rex.

The Newly Described Moros intrepidus from the Late Cretaceous of Central Utah

Life reconstruction Moros intrepidus.

Moros intrepidus from the Late Cretaceous of central Utah.

Picture Credit: Jorge Gonzalez

Teeth and a Hind Limb from a New Theropod

The fossilised remains of a partial right leg consisting of a femur, a tibia, metatarsal bones and some toe bones from the fourth toe were discovered in sediments representing the lower Mussentuchit Member of the Cedar Mountain Formation located in Emery County (Utah).  These fossils, in conjunction with isolated teeth from the front portion of the upper jaw (premaxilla) found nearby provide the basis for this new taxon.  The deposits represent a terrestrial environment, a large delta and they date from approximately 96 million years ago (Cenomanian faunal stage of the Late Cretaceous).

Moros intrepidus represents the oldest known Cretaceous-aged tyrannosauroid discovered to date in North America. It extends the definitive fossil record for these types of dinosaurs by around 15 million years.

The Temporal Relationships and Phylogeny of the Tyrannosauroidea

Moros intrepidus fills a 15-million-year evolutionary gap.

Phylogenetic and temporal relationships between tyrannosauroids and an examination of faunal turnover.  The Allosaurs/Megaraptor apex predator niche was gradually taken over by Tyrannosaurs.

Picture Credit: Nature Communications Biology

In the diagram (above), the section on the left (a), shows the fossil record gap between Late Jurassic tyrannosauroids and much larger Late Cretaceous members of the Tyrannosauridae family such as Lythronax (L. argestes).  Section (b) demonstrates the temporal range of these Theropods and the change in bauplan, whilst (c) demonstrates key evolutionary anatomical changes.  The blue and pink coloured shapes in (d) reflect the transition from Allosaur/Megaraptoran dominated ecosystems to Tyrannosaur dominated palaeoenvironments.

A Changing of the Guard When it Comes to Apex Predators

Palaeontologists know that the Tyrannosaur lineage dates back a long way.  For example, basal tyrannosaurids such as Stokesosaurus (S. clevelandi) are known from Upper Jurassic deposits of Utah.  By the Late Cretaceous (Campanian faunal stage), Tyrannosaurs were large and had become the iconic apex predators beloved by dinosaur fans and film directors.  The fossil record for North American Tyrannosaurs was essentially blank, giving palaeontologists a T. rex skull-sized headache when it came to piecing together how these Theropods changed over time.

The discovery of Moros helps to narrow a 70-million-year-gap in the fossil record of tyrant lizards in North America.

Lead-author of the study, published in “Nature Communications” Lindsay Zanno of the North Carolina Museum of Natural Sciences explained:

“When and how quickly Tyrannosaurs went from wallflower to prom king has been vexing palaeontologists for a long time.  The only way to attack this problem was to get out there and find more data on these rare animals.”

A Silhouette of M. intrepidus Showing the Anatomical Position of the Known Fossil Material

Moros intrepidus silhouette showing placement of known fossil elements.

Silhouette of M. intrepidus showing known fossil elements.  Key = (g) femur, (h) tibia, (i) fourth metatarsal, (j) second metatarsal, and (k) pedal phalanges of the fourth digit.   Scale bar (c) 1 m, (g–k) 5 mm.  Note the tooth (views d-f) are not to scale.

Picture Credit: Nature Communications Biology

Living in the Shadow of Siats meekerorum

In 2013, two of the authors of the Moros intrepidus paper, Lindsay Zanno and Peter Makovicky (Field Museum, Chicago), published a study on a large allosauroid from similar-aged sediments.  The dinosaur, named Siats meekerorum is estimated to have measured around 12 metres in length, dwarfing the contemporary Moros, which had a hip height of around 1.2 metres.  The researchers conclude that within a palaeoenvironment dominated by giant, allosauroid Theropods, Tyrannosaurs such as M. intrepidus relied on their speed and small size and would have kept out of the way of the larger predators.

A spokesperson from Everything Dinosaur commented:

“During the Cenomanian, tyrannosauroids like Moros intrepidus were secondary predators within an ecosystem dominated by apex predators from a completely different part of the Theropod family tree.  For the greater part of the Tyrannosaur evolutionary history, these types of dinosaurs were marginal predators, living in the shadow of much bigger carnivorous dinosaurs.”

A Life Reconstruction of Siats meekerorum with two Tyrannosauroids shown in the Foreground

Siats meekerorum .

Siats meekerorum has nothing to fear from these two Tyrannosaurs.  Moros intrepidus may have scavenged the kills of larger Theropods but these types of tyrannosauroid were very much the secondary predators.

Picture Credit: Julio Laceardo

To read Everything Dinosaur’s article on the discovery of Siats meekerorumUnravelling the Apex Predators of the Cretaceous Before Tyrannosaurs

Phylogeny Points at Asian Ancestry

A study of the longer limb bones indicates that the individual was around six to seven years of age when it died.  It was likely to have reached its adult size.  A phylogenetic assessment indicates an affinity with Asian Tyrannosaur taxa, in essence, the ancestors of famous North American dinosaurs such as Gorgosaurus and Tyrannosaurus rex migrated into North America from Asia.

Assistant Research Professor Zanno stated:

“T. rex and its famous contemporaries such as Triceratops may be among our most beloved cultural icons, but we owe their existence to their intrepid ancestors who migrated here from Asia at least 30 million years prior.  Moros signals the establishment of the iconic Late Cretaceous ecosystems of North America.”

Views of the Lower Leg Bones from the Right Leg of M. intrepidus

Views of the lower leg bones of Moros intrepidus.

Right tibia (a–f) and right fourth metatarsal (g–l) of M. intrepidus (NCSM 33392).

Picture Credit: Nature Communications Biology

What’s In a Name?

The etymology of this new tyrannosauroid reflects the later faunal turnover that led to the apex predator roles in North America being dominated by Tyrannosaurs.  The genus name is from the Greek “Moros”, the embodiment of impending doom, for the descendants of this fast-running dinosaur were to evolve into some of the largest and most formidable terrestrial predators known to science.  The species name is from the Latin “intrepidus”, a reference to these intrepid dinosaurs making the migration from Asia into North America and their subsequent dispersal.

Size is Not Everything

Although around ninety times lighter than Tyrannosaurus rex, Lindsay warns against underestimating the predatory abilities of Moros.

She added:

“Moros was lightweight and exceptionally fast.  These adaptations, together with advanced sensory capabilities, are the mark of a formidable predator.  It could easily have run down prey, while avoiding confrontation with the top predators of the day.  Although the earliest Cretaceous Tyrannosaurs were small, their predatory specialisations meant that they were primed to take advantage of new opportunities when warming temperatures, rising sea-level and shrinking ranges restructured ecosystems at the beginning of the Late Cretaceous.  We now know it took them less than 15 million years to rise to power.”

The scientific paper: “Diminutive fleet-footed tyrannosauroid narrows the 70-million-year gap in the North American fossil record” by Lindsay E. Zanno, Ryan T. Tucker, Aurore Canoville, Haviv M. Avrahami, Terry A. Gates and Peter J. Makovicky published in Nature Communications Biology.

19 02, 2019

“The Dinosaurs Rediscovered” – New Book About Dinosaurs

By | February 19th, 2019|Book Reviews, Dinosaur Fans, Main Page, Palaeontological articles, Press Releases|0 Comments

“The Dinosaurs Rediscovered” – New Book About Dinosaurs

Everything Dinosaur has received an uncorrected proof of the eagerly awaited new dinosaur book by Professor Michael Benton.  Team members are looking forward to reading about how research into the Dinosauria has been revolutionised over the last two decades or so.  Professor Benton is one of the leading lights in vertebrate palaeontology and has written over fifty books covering a wide range of prehistoric animals and events from deep time.  As the head of the world-renowned Palaeobiology Research Group at the University of Bristol, Professor Benton has been involved in and led some of the most insightful and ground-breaking studies into the dinosaurs, helping to re-write scientific understanding.

“The Dinosaurs Rediscovered” – Exploring the Revolution in Dinosaur Research

A new dinosaur book "The Dinosaurs Rediscovered".

“The Dinosaurs Rediscovered” by Professor Mike Benton.

Picture Credit: Thames & Hudson/Everything Dinosaur

The Changing Story of the Dinosaurs

The book runs to 336 pages with 163 illustrations (23 in colour), it explores the changing story of the dinosaurs, highlighting how the application of 21st Century technologies have revealed new information about these remarkable reptiles, information that had been locked deep inside their fossilised bones and teeth.  Trace fossils are also explored in detail and Professor Benton demonstrates how biomechanical engineering combines with computer modelling and digital dinosaurs to calculate how fast Theropod dinosaurs could run.  The work of the famous Bristol Dinosaur Project is covered and naturally, Bristol’s very own dinosaur Thecodontosaurus (T. antiquus) is included, but Professor Benton does not just feature dinosaurs from the south-west of England, this impressive publication provides a global perspective on the Dinosauria.  This beautifully written book includes chapters on feathered dinosaurs and even explores whether dinosaur DNA could be used to resurrect the Dinosauria.

The Book includes Chapters on Feathered Dinosaurs and Explores Whether Dinosaur DNA could be Found Preserved in Amber

Feathered dinosaur illustration.

An illustration of the feathered dinosaur, about to become stuck in amber.  Professor Mike Benton introduces the reader to some amazing recent dinosaur discoveries.

Picture Credit: Cheung Chung-Tat

An Engaging Account

This is an engaging account of the evolution of the “terrible lizards” and is aimed at readers with a general interest in life in the past as well as academics and students.  Fans of prehistoric animals and dinosaur devotees don’t have to wait too long before this book is published.  The hardback is due out on April 25th (published by Thames and Hudson).

The Front Cover of Professor Benton’s New Book

"The Dinosaurs Rediscovered".

The jacket cover of the new book about dinosaurs “The Dinosaurs Rediscovered”.

Picture Credit: Thames & Hudson

18 02, 2019

A New African Titanosaur is Announced

By | February 18th, 2019|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Mnyamawamtuka moyowamkia – Heart-shaped Tail Bones Help to Flesh Out Titanosaur Evolution

Scientists writing in the on-line, open access journal PLOS One, have published details of a new species of African Titanosaur.  It took several years to carefully remove the fossil material from a high cliff wall overlooking the Mtuka riverbed in south-western Tanzania, but the fossils, representing a not fully mature dinosaur, are providing palaeontologists with important information about how African ecosystems changed over the course of the Cretaceous.  The new Titanosaur has been named Mnyamawamtuka moyowamkia (pronounced Mm-nya-ma-wah-mm-too-ka mm-oh-yo-wa-mm-key-ah).  The name is derived from Kiswahili for “animal of the Mtuka river with a heart-shaped tail”.

The heart-shaped tail element of the name refers to the strange shape of the most intact middle caudal vertebra described in the paper.  It bulges out at the sides (dorsolateral expansion of the posterior articular surface of the centrum), a unique tail bone morphology that resembles the shape of a romantic, love heart.

A Life Reconstruction of a Pair of  Mnyamawamtuka moyowamkia Titanosaurs

Mnyamawamtuka moyowamkia illustration

Mnyamawamtuka moyowamkia life reconstruction.

Picture Credit: Mark Witton

The first evidence of the dinosaur fossils was noted in 2004 and some fossils were excavated from the cliff face, in what were quite hazardous conditions, with field team members having to be lowered over the cliff on numerous occasions to work on the exposed bones.  Annual excavations took place until 2008, it was important to keep returning to the site as the fossils were in danger of being lost to the river in seasonal floods.

A Line Drawing of the Quarry Site Showing the Extent of the Annual Excavations

Quarry map of M. moyowamkia site.

Quarry map showing the layout and excavation timeline of the M. moyowamkia fossil material.

Picture Credit: PLOS One

Around 110-100 Million Years Old

The specimen was excavated from the Mtuka Member of the Cretaceous Galula Formation, which was deposited around 110 to 100 million years ago (Aptian to Cenomanian faunal stage of the Cretaceous).  A substantial portion of the postcranial skeleton has been recovered.

Dangerous Work!  The Excavation Site in 2007

The location of the Mnyamawamtuka moyowamkia fossils.

The quarry dig site above the Mtuka riverbed in south-western Tanzania.

Picture Credit: Ohio University

Commenting on the importance of this discovery, in relation to the evolution of African Titanosaurs, lead author of the paper, Dr Eric Gorscak, a recent PhD graduate of Ohio University and now an assistant professor at the Midwestern University (Illinois), stated:

“Although Titanosaurs became one of the most successful dinosaur groups before the infamous mass extinction capping the Age of Dinosaurs, their early evolutionary history remains obscure, and Mnyamawamtuka helps tell those beginnings, especially for their African-side of the story.  The wealth of information from the skeleton indicates it was distantly related to other known African Titanosaurs, except for some interesting similarities with another dinosaur, Malawisaurus, from just across the Tanzania–Malawi border.”

Adding to the Diversity of Titanosaurian Sauropods from Africa

The field team responsible for this discovery have also found the fossilised remains of two other Titanosaurs in this part of Africa.  In 2017, Everything Dinosaur reported upon the discovery of Shingopana songwensis.

To read about S. songwensisA New Species of African Titanosaur is Named

In addition, Rukwatitan bisepultus another Titanosaurian Sauropod dinosaur, was named and described in 2014: A New Species of Titanosaurian Sauropod Rukwatitan bisepultus

The researchers conclude that Mnyamawamtuka moyowamkia was distantly related to both Shingopana songwensis and Rukwatitan bisepultus, fossils of which come from younger Cretaceous sediments, although it did share some anatomical characteristics with Malawisaurus dixeyi from Malawi, that might have been contemporaneous.  This new fossil discovery is helping palaeontologists to better understand the distribution of Titanosaurs between Africa and South America and their evolutionary relationships.

Heart-shaped Tail Bones

One of the middle caudal centra (tail bone from the middle portion of the tail), exhibits a unique dorsolateral expansion of the posterior articular surface of the centrum.  This unique characteristic was found to be present in the most intact middle caudal vertebra described.  This unique shape inspired the dinosaur’s name.

Heart-shaped Tail Bone Centrum (Rear View)

Heart-shaped tail bone.

A posterior view of a middle caudal vertebra showing the characteristic heart shape.  The term dle = dorsolateral expansion.

Picture Credit: PLOS One

Tail Bones of Different Titanosaurs Compared

Titanosaur tail bne comparison.

A comparison of caudal vertebrae between three Titanosaurs. Mnyamawamtuka moyowamkia (A), compared with Malawisaurus dixeyi (B) and Lohuecotitan pandafilandi of the Late Cretaceous of Spain (C). Posterior views and lateral views, scale bar = 10 cm.  The term dle = dorsolateral expansion.

Picture Credit: PLOS One

The scientific paper: “A New African Titanosaurian Sauropod Dinosaur from the Middle Cretaceous Galula Formation (Mtuka Member), Rukwa Rift Basin, Southwestern Tanzania” by Eric Gorscak and Patrick M. O’Connor published in PLOS One.

8 02, 2019

New Species of Late Cretaceous Oviraptorid Named

By | February 8th, 2019|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Gobiraptor minutus – The Diversity of the Oviraptoridae in the Late Cretaceous

A new species of oviraptorid dinosaur (Oviraptoridae family), has been described by an international team of scientists.  The little dinosaur was probably feathered and it possessed thickened jaws, an adaptation to feeding on hard food items such as seeds, nuts or the shells of bivalves, molluscs and crabs (durophagous).   The fossilised remains of a single, very young individual were found in the Altan Uul area of Ömnögovi Province, Mongolia, in strata from the famous Upper Cretaceous Nemegt Formation.  The new species has been named Gobiraptor minutus and it helps to demonstrate that this part of Asia in the Late Cretaceous was home to diverse variety of oviraptorids, many of which, probably occupied specialist niches within the ecosystem in a bid to minimise competition for resources.

A Life Reconstruction of Gobiraptor minutus

Gobiraptor minutus life reconstruction.

A life reconstruction of Gobiraptor minutus.

Picture Credit: Do Yoon Kim with additional annotation by Everything Dinosaur

Rare for the Altan Uul Area of Southern Mongolia

Oviraptorid fossil specimens are relatively rare in the Altan Uul area of the Gobi Desert, however, within the Upper Cretaceous deposits exposed within the Gobi Desert, some ten oviraptorid taxa have so far been named and described.  Gobiraptor increases the diversity of oviraptorids known from the Nemegt Formation and demonstrates that these types of Theropod dinosaurs were exceptionally abundant in the mesic environment* of that part of the world during the Late Cretaceous.

A mesic environment* – is a term used in ecology to describe an environment with a moderate amount of water.  Much of this part of Asia during the Late Cretaceous may be associated with a dry, arid environment, for example numerous types of other Theropod fossils come from strata that represent almost desert-like conditions.  These fossils are found in the older Barun Goyot Formation which was laid down under more arid conditions.  The rocks in which the fossils of Gobiraptor were found consist mainly of river channel deposits, indicating that the palaeoenvironment changed and the environment became considerably wetter.

Thus, the finding of a new member of the Oviraptoridae family in the Nemegt Formation, which consists mostly of river and lake deposits, confirms that these dinosaurs were extremely well adapted to wet habitats.

Fragmentary Fossils and Skeletal Reconstruction of Gobiraptor minutus

Gobiraptor minutus skeletal reconstruction.

Grey shaded bones indicate known fossil material.  Note scale bar on skeletal drawing – 10 cm.

Picture Credit: PLOS One

Robust and Thickened Jaws Hint at a Dietary Specialism

Gobiraptor minutus, can be differentiated from other members of the Oviraptorosauria clade in having unusually robust and thickened jaws.  This unique mandibular morphology suggests that Gobiraptor was adapted to feeding on hard food items, it used its strong jaws to crush, indicating potential niche partitioning in the palaeoenvironment to reduce competition amongst small Theropods and within the local population of oviraptorids.  Osteological analysis of the femur suggests that the fossil material represents a very young individual.

The phylogenetic analysis carried out by the researchers defines Gobiraptor as a derived oviraptorid closely related to three taxa from the Ganzhou region of southern China, but, ironically, the analysis suggests that it was rather distantly related to other Nemegt oviraptorids which, as the results of recent studies, are also not closely related to each other.

The authors propose that different dietary strategies may explain the wide taxonomic diversity and evolutionary success of this group of dinosaurs in this part of Asia.

Post-cranial Elements of G. minutus

Post-cranial elements of Gobiraptor.

Left femur in caudal view (A) and medial view (B).  Partial right humerous (C) and ilium (D).  (E) left metatarsal I and pedal digit I in medial view.  (F) left pedal digit IV in lateral view.  Scale bar = 5 cm.

Picture Credit: PLOS One

The genus name honours the Gobi Desert, whilst the specific epithet is from the Latin for small, a reflection on the small size of the holotype.

The scientific paper: “A New Baby Oviraptorid Dinosaur (Dinosauria, Theropoda) from the Upper Cretaceous Nemegt Formation of Mongolia” by Sungjin Lee, Yuong-Nam Lee , Anusuya Chinsamy, Junchang Lü, Rinchen Barsbold and Khishigjav Tsogtbaatar published in PLOS One.

1 02, 2019

Pachyrhinosaurus perotorum – New Research is Published

By | February 1st, 2019|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles|0 Comments

Puzzling Pachyrhinosaurs – The Remarkable Pachyrhinosaurus perotorum

Researchers from the Perot Museum of Nature and Science (Dallas, USA), in collaboration with the University of Toronto (Canada), have published an update on their research into one of the most remarkable Late Cretaceous dinosaurs known to science.

Back in 2011, Everything Dinosaur reported that field work in the high Arctic led by palaeontologists from the Perot Museum of Nature and Science had uncovered the fossilised remains of at least ten individual dinosaurs representing a new species of Ceratopsian.  This horned dinosaur, a Pachyrhinosaur, was named Pachyrhinosaurus perotorum and it became the third species to be assigned to this centrosaurine genus.  With numerous specimens to study, the palaeontologists could gain a fresh perspective on how horned dinosaurs changed as they grew up and develop a better understanding of the cranial ornamentation associated with the Ceratopsidae.

The Ontogeny of P. perotorum

Illustrating the ontogeny of a Pachyrhinosaurus (P. perotorum).

How a baby P. perotorum grew up.  With numerous individuals represented at the same dig site, palaeontologists can examine variation within a species and assess how these dinosaurs changed as they matured.

Picture Credit: Perot Museum of Nature and Science

Updating Their Findings

The authors of the original scientific paper describing P. perotorum, Anthony Fiorillo and Ronald Tykoski, have published a new report in conjunction with Kentaro Chiba of the Department of Ecology and Evolutionary Biology at the University of Toronto, updating their research and providing more information on how this species can be distinguished from the two other species of Pachyrhinosaurus.  The continued preparation of fossil specimens collected from the type locality, the  Kikak-Tegoseak Quarry (Prince Creek Formation), has produced more skull elements to study.  The researchers note that their original reconstruction of the type parietal bone was incorrect, the parietal along with the squamosal bone form the neck frill in horned dinosaurs.  The parietal of P. perotorum is similar to the parietal bones of the other species – P. canadensis and P. lakustai.

It is postulated that Pachyrhinosaurus perotorum can be identified by an upturned tip of the rostrum, a dorsally shifted rostral bone lacking a sharply downturned, parrot-like beak and an enlarged median ridge at the posterior end of the nasal boss.  Other differences in cranial morphology are also tentatively proposed in the new scientific paper, published in the Journal of Systematic Palaeontology.

A Speculative Illustration of the High Northern Latitude Ceratopsian Pachyrhinosaurus perotorum

A northern Ceratopsian with a shaggy coat.

A speculative illustration of Pachyrhinosaurus perotorum with a shaggy coat of feathers.  Although northern Alaska was warmer in the Late Cretaceous than today, it would have been distinctly chilly, too cold for ectothermic reptiles and it has been speculated that the dinosaur biota of high latitudes may have been specifically adapted to cold climates.  In this illustration, Pachyrhinosaurus has been depicted with a long, shaggy coat of feathers to help keep out the cold.

Picture Credit: Mark Witton

The Sister Taxon of P. canadensis

A cladistic analysis undertaken by the team using this new dataset in conjunction with previous research confirms that the Pachyrhinosaurus genus is monophyletic (all descended from a common ancestor) and that Pachyrhinosaurus canadensis is the sister taxon to P. perotorum.  In addition, this research supports the idea that parietal and squamosal frill ornamentations alone do not adequately address the variables in craniofacial morphology needed to distinguish between species of Pachyrhinosaurus.

The continuing research into horned dinosaurs that lived at high latitudes is helping palaeontologists to gain a better understanding of a unique ecosystem that existed towards the end of the dinosaur age.  Pachyrhinosaurus perotorum is not only the youngest Pachyrhinosaur species known, it is also the geologically youngest known centrosaurine.  With three species assigned to the genus, Pachyrhinosaurus is the most speciose of all the Centrosaurinae genera.

A spokesperson from Everything Dinosaur commented:

“Pachyrhinosaurus perotorum holds a special place in Ceratopsidae research.  It lived at a higher latitude than any other horned dinosaur known to science and, as a consequence, had to endure some very tough and harsh climatic conditions.  Whether this dinosaur was a seasonal migrant to the area in summer to take advantage of the 24-hours of daylight that permitted abundant plant growth, or whether this reptile was a permanent resident remains uncertain.  However, the discovery of the fossilised remains of a juvenile at the Kikak-Tegoseak Quarry, suggests that this dinosaur could have been indigenous to northern Alaska during the Maastrichtian faunal stage.”

To read Everything Dinosaur’s original article from 2011 that announced the discovery of a third species of Pachyrhinosaurus: A New Species of Pachyrhinosaurus – P. perotorum.

The scientific paper: “New Data and Diagnosis for the Arctic Ceratopsid Dinosaur Pachyrhinosaurus perotorum” by Ronald S. Tykoski, Anthony R. Fiorillo and Kentara Chiba published in the Journal of Systematic Palaeontology.

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