New Paper Published on Edmontosaurus

Scientists from the Canadian Museum of Nature in collaboration with colleagues from the Beijing Museum of Natural History have published a paper in the on-line academic journal PLOS One that provides a fresh analysis of the iconic North American dinosaur Edmontosaurus.  The researchers effectively develop the ideas put forward when this duck-billed dinosaur was first described a hundred years ago and help to highlight the differences between the two species currently assigned to the Edmontosaurus genus.  In addition, they cast doubt over the recently named and described Alaskan Hadrosaur Ugrunaaluk kuukpikensis (named and described in 2015), instead they suggest that these fossils belong to a species of Edmontosaurus.

The “Lizard from Edmonton” Named in 1917

The Wild Safari Prehistoric World Edmontosaurus dinosaur model.

Picture credit: Everything Dinosaur

For models and replicas of Edmontosaurus and other hadrosaurs: Wild Safari Prehistoric World Figures.

Cranial Anatomy of Edmontosaurus regalis

The scientists, which included Dr Jordan Mallon (Canadian Museum of Nature), who recently published a new paper casting doubt on how to tell female from male dinosaurs: No Visual Difference Between Boy Dinosaurs and Girl Dinosaurs looked again at the E. regalis holotype and the paratype material which come from the Horseshoe Canyon Formation (southern Alberta, Canada).

It was the pioneering Canadian palaeontologist Lawrence Lambe who first named and described Edmontosaurus back in 1917.  The holotype (CMN 2288), the fossil specimen on which the original description of Edmontosaurus (E. regalis) is based, consists of an incomplete skull and partial skeleton.

The paratype (CMN 2289), the specimen that has proved to be most beneficial in the clarification Edmontosaurus as it shows features not seen on, or are more distinct that those found in the holotype, consists of an incomplete but partially articulated skull in addition to significant elements from the rest of the skeleton.  The researchers were able to identify a number of unique anatomical characteristics that help to distinguish E. regalis from E. annectens.

A Scale Drawing of Edmontosaurus regalis

A scale drawing of Edmontosaurus regalis. Note the colourful red comb on the top of the skull.

Picture credit: PLOS One

A “Soft, Fleshy Comb”

In the picture above, the scale drawing of Edmontosaurus is shown sporting a “soft, fleshy comb” on top of the skull.  Recent research suggests that E. regalis did indeed have a comb, a bit like a giant rooster.

Soft-tissue crests in members of the Dinosauria.

Picture credit: Julius Csotonyi

To read an article published in 2013 that suggests members of the Hadrosaurinae had soft-tissue crests: Duck-billed Dinosaur with a Comb Like a Rooster.

With a better understanding of the differences between the two species of Edmontosaurus, the team could then develop their ideas, applying them to related duck-billed dinosaurs such as the giant Shantungosaurus from the Late Cretaceous of China, enabling them to revise this part of the Hadrosaurinae family tree.

Edmontosaurus regalis Compared to Edmontosaurus annectens

Corresponding author for the paper, Dr Hai Xing has published previously, describing differences between Edmontosaurus and Shantungosaurus.  Analysis of the skull bones of Edmontosaurus enabled Dr Xing and his colleagues to add a further three distinguishing characteristics to help tell the difference between E. regalis and E. annectens, (adult specimens).  In addition, the researchers identified a unique feature of the jugal (a bone in the cheek area linking the maxilla to the eye-socket),

Views of the Holotype E. regalis Material

Close-ups of the jugal anterior process of CMN 2288 in lateral (E) and posterolateral (F) views.

Picture credit: PLOS One

Key

• en =external naris
• n =nasal bone
• j = jugal bone
• pm = premaxilla (front of the top jaw)
• m = maxilla (part of the top jaw)
• p = palatine (bone related to the palate)
• pt = pterygoid bone

The red arrow (E and F), points to the sharp, posterodorsally tilted ridge of bone that pushes into the eye-socket area.  This feature is unique to Edmontosaurus regalis.

Ugrunaaluk kuukpikensis – Nomen dubium

In 2015, a new type of flat-skulled hadrosaur was described (U. kuukpikensis), based mostly on fossils excavated from the Liscomb bonebed in the Price Creek Formation of northern Alaska.  This new dinosaur, was thought to be quite closely related to Edmontosaurus, it was assigned to the Edmontosaurini tribe, but Xing et al argue that as the description was based on fossils of juveniles and as their study sheds new light on the anatomy of Edmontosaurus, Ugrunaaluk kuukpikensis may not be a valid genus.  Instead, they suggest that the Liscomb bonebed material represents a northern occurrence of Edmontosaurus (E. regalis).

Whilst the team are quick to praise the meticulous approach of Mori, Druckenmiller and Erickson they suggest that given the relatively small size of the Ugrunaaluk fossils and the lack of overlap between these specimens and known Edmontosaurus fossils it is not credible to assert a new genus based on the evidence to date.  U. kuukpikensis becomes a Nomen dubium (dubious name).

To read about the discovery of the Alaskan duck-billed dinosaur fossils: Duck-billed Dinosaur from Alaska.

Views of the Holotype Skull Material (CMN 2288)

CMN 2288 the holotype skull fossil of E. regalis (left lateral view and dorsal view, with accompanying line drawings).

Picture credit: PLOS One

The scientific paper: “Supplementary Cranial Description of the Types of Edmontosaurus regalis (Ornithischia: Hadrosauridae), with Comments on the Phylogenetics and Biogeography of Hadrosaurinae” by Hai Xing, Jordan C. Mallon, Margaret L. Currie published in PLOS One.

Visit the Everything Dinosaur website: Everything Dinosaur.

One Step Closer to a State Dinosaur for California

California is one step closer to joining a select group of American States that have their own State dinosaur.  A vote in the “Golden State’s” legislative assembly was passed and the duck-billed dinosaur Augustynolophus morrisi is nearer to becoming the official dinosaur of the most populous State in the Union.  California already has a substantial number of State symbols, including the Leatherback Turtle (Dermochelys coriacea), the State marine reptile and the artichoke (Cynara cardunculus), California’s State vegetable.

The Hadrosaur Augustynolophus morrisi Could Become the State Dinosaur for California

Augustynolophus could become California’s State dinosaur.

Picture credit: Augustynolophus Twitter Account

Augustynolophus morrisi

Assembly member, Richard Bloom, the representative for Santa Monica, introduced a bill at the beginning of the year to make this Late Cretaceous, duck-billed dinosaur a state symbol.  The vote yesterday moved Augustynolophus nearer to becoming adopted.  Augustynolophus (pronounced August-steen-ah-pho-lus mor-riss-eye) fossils, including a fragmentary skull, have been found in the Moreno Formation, the fossils represent the most complete dinosaur discovered in California.  In fact, despite California’s size, it is the third largest State in the United States, very few dinosaurs are associated with this part of America.

We at Everything Dinosaur, think that just one other dinosaur genus Saurolophus is associated with California and these fossils, also from the Moreno Formation, may have been reassigned to Augustynolophus.

Helping to Support Learning and Educational Opportunities

The reason why lawmakers in California are keen to adopt a dinosaur as a symbol is that they hope that the dinosaur will promote learning and support educational opportunities.  California already has an official state fossil, Smilodon californicus – a sub-species of Sabre-toothed cat known from the famous La Brea Tar Pits close to the centre of Los Angeles.

Images of a Smilodon Figure (Mojo Fun Smilodon)

Various views of the Mojo Smilodon model.  Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

The picture (above) shows a Mojo Fun Smilodon figure.

To view the Mojo Fun range of prehistoric animal models: Mojo Fun Prehistoric and Extinct Models.

Twitter Account for a Dinosaur

Augustynolophus has its own Twitter account (@augustynolophus), you can follow the progress of the legislation on Twitter.  The Californian Senate have to vote and if the outcome is favourable then the Governor will have the final say.

Only seven of the fifty States that make up the USA have official State dinosaurs:

• Wyoming – Triceratops
• Texas – Paluxysaurus jonesi (Sauroposeidon)
• Oklahoma – Acrocanthosaurus atokensis
• New Jersey – Hadrosaurus foulkii
• Missouri – Hypsibema missouriensis
• Maryland – Astrodon johnstoni
• Colorado – Stegosaurus armatus

To read an article about British Columbia debating whether to introduce an official fossil for the Canadian Province: Four Contenders for the Official Fossil for Canadian Province.

To see the Everything Dinosaur website: Everything Dinosaur.

No Sexual Dimorphism in the Dinosauria

A couple of weeks ago, Everything Dinosaur reported on the publishing of a new scientific paper that set out to re-define the Dinosauria.  A new model for plotting the various branches of the dinosaur family tree has been proposed, meat-eating dinosaurs such as Tyrannosaurus rex and Velociraptor find themselves aligned with the ornithischians (bird-hipped dinosaurs), whereas iconic dinosaurs such as Diplodocus and the less iconic Herrerasaurus might just be outside of the Dinosauria altogether.  A new study has just been published that postulates that there was no sexual dimorphism within the Dinosauria.

To read more about the reclassification of the dinosaurs: Root and Branch Reform of the Dinosaur Family Tree.

That’s science, fundamental principles get challenged and in the light of new evidence, accepted thinking can be overturned.

Challenging the Idea of Sexual Dimorphism in the Dinosauria

Also, last month, Dr Jordan Mallon, palaeontologist and post-doctoral fellow of the Canadian Museum of Nature, published in the journal “Paleobiology” a fascinating article which challenges another fundamental precept of dinosaurs.  Dr Mallon argues that there is no proof that male dinosaurs looked different from females.

Many Scientific Papers Had Proposed Evidence for Sexual Dimorphism in Dinosaurs (including Stegosaurs)

Females may have had reduced plates that were more spiky.

Picture credit: Evan Siatta with additional annotation by Everything Dinosaur

The Emperor’s New Clothes Syndrome

Dr Mallon conducted a detailed statistical analysis on nine different dinosaur taxa.  Dinosaurs that have relatively well-documented fossil records, including skull material which is believed to represent animals of different ages (ontogenetic stages), dinosaurs about which sexual dimorphism has been reported, inferred or at least debated in the past.

The dinosaurs studied:

1. Coelophysis bauri
2. Coelophysis rhodesiensis
3. Stegoceras validum
4. Allosaurus fragilis
5. Stegosaurus mjosi
6. Kentrosaurus aethiopicus
7. Tyrannosaurus rex
8. Plateosaurus sp.
9. Protoceratops andrewsi

With crocodilians and many birds displaying sexual dimorphism, take alligators and the often-cited peacocks for example, as these animals are closely related to the Dinosauria, then surely dinosaurs were sexually dimorphic too?  But it could it be a case of the “Emperor’s New Clothes”?  Scientists expected to find evidence in the fossil record demonstrating differences between the boys and the girls and a large body of evidence based on the shape and size of bones has been gathered to reinforce this hypothesis – but just how valid is this idea?

An Extensive Statistical Analysis Searching for Evidence of Sexual Dimorphism

Dr Mallon set about conducting a wide-ranging, in-depth statistical analysis of sexual dimorphism in the Dinosauria, the first such investigation, as far as we, at Everything Dinosaur, are aware.   Previously published papers were re-visited including the intriguingly titled “The King’s New Clothes: A Fresh Look at Tyrannosaurus rex”, written by our chum Pete Larson, twenty years ago.  In addition, amongst the numerous papers referenced in his thought-provoking piece: “Recognising Sexual Dimorphism in the Fossil Record: Lessons from Nonavian Dinosaurs”, Dr Mallon looked at the research undertaken in 2015 by Maiorino, Farke, Kotsakis and Piras* into Protoceratops andrewsi, one of the species subjected to statistical analysis in this new study.

In the Maiorino et al paper, a number of examples of sexually dimorphic traits were listed amongst the Ceratopsia (see table below).

Sexually Dimorphic Traits within Horned Dinosaurs

A table outlining proposed sexual dimorphism in horned dinosaurs.

Table credit: L. Maiorino et al (from a paper also referenced by Dr Mallon).

Skull Measurements Not Characteristic of Sexual Dimorphism

The team concluded that anatomical traits such as the height and width of the frill and skull size thus may not be sexually dimorphic.  When careful measurements were considered, it seems that the size of the frill and skull size could not determine the boys from the girls, at least not in this Asian Late Cretaceous dinosaur.

Trying to Spot the Girls Amongst the Boys (P. andrewsi)

Using frill and skull measurements to identify sexual dimorphism in Protoceratops.

Picture credit: L. Maiorino et al

Dr Mallon concurs.  In the 2015 study, scientists measured a number of traits within a sample set of twenty-nine Protoceratops skulls.

They measured:

1 – Width of the frill.
2 – Postorbital width of the skull.
3 – Length of the frill.
4 – Width of the skull across jugals.
5 – Nasal height of the skull.
6 – Height of the frill.
7 – Length of external nares.
8 – Width of external nares.

The 2015 study could not determine two distinct clusters of measurements when the skulls were assessed.  If they had, then these two unambiguous groups would have supported the idea that Protoceratops at least, exhibited sexual dimorphism.

Protoceratops One of Nine Different Dinosaurs Incorporated within the Study

A Protoceratops exhibit on display at The Naturmuseum Senckenberg (Frankfurt, Germany). Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Why is Sexual Dimorphism in the Dinosauria Such a Big Deal?

The fossil record can only tell us so much.  For instance, inferring behaviour is extremely difficult.  Most palaeontologists now agree that many dinosaurs lived in herds (should that be flocks)?  If sexual dimorphism can be identified that it will provide critical information about the role of sexual selection in the evolution of different types of dinosaurs, as well as supporting the idea that many dinosaurs indulged in visual displays and intraspecific combat.

Dr Mallon argues that quantifiable data to support this hypothesis is often lacking.  A review of existing literature was undertaken to identify quantitative evidence for differences between the boy dinosaurs and the girls and according to this new research, the good doctor could find no evidence for sexual dimorphism in the nine taxa studied.

This contradicts many existing perceptions, but as with all science it is a question of evaluating the evidence.

Looking for Medullary Bone

Dr Mallon states that he can’t be certain that dinosaurs were not sexually dimorphic, it’s just that the available evidence precludes its detection.  A helpful start would be to positively identify females by the presence of unlaid eggs in the body cavity or medullary bone within fossil material and indeed there have been some examples already found.  However, more data is needed before we can positively distinguish the males from the females.

Things would of course be much easier, if nonavian dinosaurs were still around today.  All we would need is some volunteers willing to lift the tail of a Triceratops or probe the private parts of a Pachycephalosaurus, would anyone want to give it a try?

* The Protoceratops paper: L. Maiorino , A. A. Farke , T. Kotsakis , and P. Piras . 2015. “Males resemble Females: Re-evaluating Sexual Dimorphism in Protoceratops andrewsi (Neoceratopsia, Protoceratopsidae)”. PLoS ONE 10:e0126464. doi: 10.1371/journal.pone.0126464.

An article published in December 2016 that looks at the potential evolutionary advantage of different sized members of the same Coelophysis flock: Sizing Up Early Dinosaurs – Variation an Evolutionary Advantage.

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