Lingyuanosaurus sihedangensis – A New Species of Therizinosaur is Announced

Scientists from the Chinese Academy of Sciences in collaboration with the University of Alberta, have announced the discovery of a new Therizinosaur based on fragmentary fossils from the Lower Cretaceous Jehol Group of Liaoning Province (north-eastern China).   This is the third Therizinosaur to have been named from the Jehol Group, joining Jianchangosaurus and Beipiaosaurus.  These dinosaurs are approximately the same size, the researchers have put forward a number of theories to help explain why three similar-sized members of the Therizinosauridae could have potentially co-existed without directly competing.

The dinosaur has been named Lingyuanosaurus sihedangensis (pronounced: ling-you-an-oh-sore-us), the genus name honours the city of Lingyuan, whilst the trivial epithet refers to the town of Sihedang where the fossils were discovered.

Fossil Material Ascribed to Lingyuanosaurus sihedangensis Prior to Complete Preparation

Lingyuanosaurus fossil material.

Picture Credit: Scientific Reports

The picture above shows some of the fossils used to name and describe this new species of dinosaur.  Top left (a), limb bones consisting of a right femur and left tibia, whereas, (b) contains ribs, part of the right humerus and the ischium.  Slab (c) consists of claw bones (manual unguals) and ribs, whilst (d), shows the right ankle bone (astragalus) and the left ilium.  Note the scale bar equals 5 cm.

An Intermediate Position within the Therizinosauria

Described from a single, disarticulated but associated partial skeleton, the exact age of the fossils is disputed.  The fossil-bearing strata at Sihedang have been assigned to the Yixian Formation in some studies but to the younger Jiufotang Formation in others.  A phylogenetic analysis carried out by the authors places Lingyuanosaurus in an intermediate position within Therizinosauria.  It has been placed between the early-branching Therizinosaurs such as Falcarius, Jianchangosaurus, and Beipiaosaurus and the late-branching ones such as Alxasaurus and Therizinosaurus.  Lingyuanosaurus sheds additional light on the evolution of major Therizinosaurian characteristics, including the distinctive pelvic girdle and hindlimb morphology seen in this group.

A Drawing of a Typical Therizinosaur

A drawing of a typical Therizinosaur.

Picture Credit: Everything Dinosaur

Where Did Lingyuanosaurus Fit into the Jehol Biota?

Measuring around two metres in length, this is the third similar-sized Therizinosaur to be assigned to this Early Cretaceous biota of northern China.  The presence of three very similar types of dinosaur in the Jehol Group is unusual.  Unless the region was particularly rich in resources, these dinosaurs could have been in direct competition with each other.  The researchers put forward several possible explanations as to why three similar Therizinosaurs have been identified.

• Firstly, the beds in which these Therizinosaurs (Jianchangosaurus, Lingyuanosaurus and Beipiaosaurus), have been found are not precisely dated.  The Yixian and the Jiufotang Formations were deposited over a span of at least 8 million years.  It is possibly that these three dinosaurs could have been separated from each other by a considerable period of time, hundreds of thousands or even millions of years.
• Secondly, these three species are known from different parts of Liaoning Province.  Whereas, Jianchangosaurus and Lingyuanosaurus were found at sites just a few miles apart, Beipiaosaurus heralds from more than 200 miles further north.   There is some, albeit limited, evidence to suggest that during the Early Cretaceous the deposition of the Jehol Group occurred in multiple small basins, suggesting that the three Jehol Therizinosaurs might have been separated by geographic barriers even if they were mutually contemporaneous.
• Thirdly, if these three Therizinosaurs did live at the same time, in the same habitat, they might have occupied different niches in the ecosystem.  The teeth of Jianchangosaurus are different (although the holotype represents a juvenile, so comparison with fully grown animals can be problematic), this suggests that Jianchangosaurus might have fed on different types of vegetation compared to Lingyuanosaurus and Beipiaosaurus.  In addition, the ratio of limb bones in Beipiaosaurus is different to the other two dinosaurs, it might have been relatively slow in comparison with Jianchangosaurus and Lingyuanosaurus and therefore it could have had a more limited range.

Claw Fossils (Manual Unguals) – Lingyuanosaurus sihedangensis

Claw fossils of Lingyuanosaurus (manual unguals).

Picture Credit: Scientific Reports

The scientific paper: “A New Transitional Therizinosaurian Theropod from the Early Cretaceous Jehol Biota of China” by Xi Yao, Chun-Chi Liao, Corwin Sullivan and Xing Xu published in Scientific Reports

Lambeosaurine Reported from the Liscomb Bonebed (Alaska)

The first fossil evidence of a lambeosaurine duck-billed dinosaur has been reported from the Liscomb Bonebed (Prince Creek Formation) of Alaska.  Part of the top of a skull, a bone called the supraoccipital (it forms part of the braincase), has been found during field work on the famous Alaskan fossil site on the banks of the Colville River.  This discovery demonstrates that both lambeosaurine and hadrosaurine dinosaurs lived in the high Arctic during the Late Cretaceous.  It also suggests that the crested lambeosaurines may have preferred inland environments, whilst their cousins, the hadrosaurines dominated the ecosystem in coastal and low-lying, near shore environments.

Evidence to Indicate that Lambeosaurines Lived in the Arctic During the Late Cretaceous

Hadrosaurines and lambeosaurines co-existed in low-lying, coastal areas of the Late Cretaceous of Alaska.

Picture Credit: Masato Hattori

Writing in the on-line, academic journal “Scientific Reports”, researchers from Hokkaido University (Japan) and the Perot Museum of Nature and Science (Dallas, Texas), confirm the discovery of a skull bone associated with a lambeosaurine (crested duck-billed dinosaur) in the hadrosaurine dominated Liscomb Bonebed, a site that has to date, yielded some 6,000 dinosaur bones.  The fossils exposed on the banks of the Colville River in a region of Alaska known as the North Slope, represent one of the most important Maastrichtian-aged dinosaur fossil sites in the world.  It has provided evidence of a high latitude Late Cretaceous dinosaur dominated ecosystem.  The bonebed is described as a monodominant, multitaxic unit as although 98.5% of all the fossils found represent just one species – the hadrosaurine Edmontosaurus* other types of dinosaur including three Theropods have been identified from fossils found at this site too.  The supraoccipital confirms the presence of lambeosaurines at this location as well, although, based on the ratio of hadrosaurine to lambeosaurine fossils found, crested duck-billed dinosaurs probably only made up a tiny portion of the entire plant-eating dinosaur community.

Views of the Single Skull Bone (Supraoccipital) Identified as Lambeosaurine

Lambeosaurine supraoccipital (DMNH 2014-12-266) from the Liscomb Bonebed (a) dorsal view, (b) ventral view, (c) left lateral view, (d) posterior view, (e) anterior view and (f) right lateral view.  Note scale bar = 2 cm.  The dorsal (a) and posterior views (d) show the two, prominent bumps (squamosal bosses) that helps to identify this bone as lambeosaurine material.  Abbreviation sqb = squamosal bosses.

Picture Credit: Scientific Reports

The newly described supraoccipital differs from those of hadrosaurines as it has large, prominent bumps towards the back of the bone (squamosal bosses).  It is also a different shape when compared to supraoccipital bones associated with members of the Hadrosaurinae such as Edmontosaurus.  For example, it is proportionally shorter in length (when measured from the front to the back of the bone – anterior to posterior).

Lambeosaurine and Hadrosaurine

The dinosaur family known as the Hadrosauridae is split into two main, but closely related lineages, the Lambeosaurinae and the Hadrosaurinae.  Traditionally, these two groups have been distinguished by their skulls, lambeosaurines having hollow crested skull crests, whilst the hadrosaurines lack bony crests.  This assessment might prove too simplistic, but for the time being, the general classification of Hadrosaurs into these two sister lineages remains the consensus.

Classifying the Hadrosauridae (Duck-billed Dinosaurs)

Tracing the Evolution of Duck-billed Dinosaurs.  Two distinct but sister lineages are recognised the non-crested Hadrosaurinae and the hollow crested Lambeosaurinae.

Picture Credit: Everything Dinosaur

Co-author of the scientific paper, Dr Anthony Fiorillo (Perot Museum of Nature and Science) stated:

“This first definitive evidence of a crested hadrosaur in the Cretaceous Arctic tells us that we still have much to learn about the biodiversity and the biologically productive environments of the ancient north and that the story these fossils tell us is continually evolving.”

Field Team Members Excavating Part of the Liscomb Bonebed on the Banks of the Colville River (Alaska)

Field team members excavating the Liscomb Bonebed.

Picture Credit: Dr Anthony Fiorillo (Perot Museum of Nature and Science)

A Link Between the Lambeosaurines of North America and Asia

The single fossil bone might not be sufficient to erect a new genus of lambeosaurine dinosaur, but the discovery is extremely significant as it links the dinosaur biota of the most northerly portions of North America to dinosaur faunas from the Late Cretaceous of northern Asia.  For example, Nipponosaurus (N. sachalinensis) from the North Pacific island of Sakhalin, is also a lambeosaurine.

Commenting on the connection between Arctic dinosaur faunas and those of the North Pacific, co-author Ryuji Takasaki (Hokkaido University) said:

“This new discovery illustrates the geographic link between lambeosaurines of North America and the Far East.  Hopefully, further work in Alaska will reveal how closely the dinosaurs of Asia and North America are connected.”

Known Geographical Distribution of Lambeosaurine Dinosaurs in the Late Cretaceous

Palaeogeographical records of lambeosaurines during the Late Cretaceous.  The red star represents the Liscomb lambeosaurine fossil find.

Picture Credit: Scientific Reports

Hadrosaurines and Lambeosaurines Had Different Habitat Preferences

The Liscomb Bonebed might be dominated by fossil material assigned to the Hadrosaurinae, but the discovery of a single fossil bone indicates the presence of lambeosaurines.  This site is representative of a coastal, near-shore environment and it differs from the lambeosaurine dominant structures of localities in Russia and China interpreted as inland environments.  The researchers postulate that crested duck-billed dinosaurs (lambeosaurines), preferred inland habitats, whilst the non-crested duck-bills (hadrosaurines), favoured coastal habitats.   Different habitat preferences might have been a strategy to avoid excessive competition between these two groups of closely related dinosaurs.

Lambeosaurine and Hadrosaurine Habitats (Inferred from the Liscomb Bonebed)

Hadrosaurines (grey) may have preferred lowland coastal habitats whilst the lambeosaurines (black) may have dominated faunal ecosystems further inland.

Picture Credit: Scientific Reports

Note: Edmontosaurus*

Things are never that straight forward in vertebrate palaeontology.  In 2015, a new taxon of hadrosaurine was erected based on the Liscomb duck-billed dinosaur bones.  The new species was named Ugrunaaluk kuukpikensis and although it was believed to be closely related to Edmontosaurus, it was established as a separate taxon.  However, in 2017 subsequent analysis challenged this conclusion.  Ugrunaaluk had been erected based on the study of fossil bones from immature individuals of various growth stages.  The hadrosaurine bones from the Liscomb Bonebed overwhelmingly represent the remains of juveniles.  The establishment of a unique duck-billed dinosaur taxon for northern Alaska remains controversial.  Many palaeontologists now consider Ugrunaaluk to be nomen dubium (not a valid genus).

To read Everything Dinosaur’s 2015 article about Ugrunaaluk kuukpikensis: Alaska’s Latest Dinosaur Ugrunaaluk kuukpikensis

The scientific paper: “The First Definite Lambeosaurine Bone From the Liscomb Bonebed of the Upper Cretaceous Prince Creek Formation, Alaska, United States” by Ryuji Takasaki, Anthony R. Fiorillo, Yoshitsugu Kobayashi, Ronald S. Tykoski and Paul J. McCarthy published in Scientific Reports.