Scientists have named a new species of therizinosaur based on fragmentary remains found on the Japanese island of Hokkaido. The dinosaur has been named Paralitherizinosaurus japonicus, it is the first recovered from Asian marine deposits and the third example of a therizinosaur to be found in Japan.

The fossil material, recovered from the lower Campanian Osoushinai Formation near to the town of Nakagawa in the Hokkaido Prefecture, was previously identified as a maniraptoran theropod dinosaur, possibly therizinosaur, but its taxonomic status remained uncertain. A group of scientists including Yoshitsugu Kobayashi and Anthony R. Fiorillo from the Hokkaido University Museum re-examined the fossils and erected a new taxon confirming the fossil material did represent a Late Cretaceous member of the Therizinosauridae.

Evolution of Claw Shape in the Therizinosauridae

Writing in the academic journal “Scientific Reports”, the researchers reassessed the fossil material consisting of a single vertebra plus bones and claws (unguals) from the right hand. As well as concluding that the fossils represent a therizinosaur, they confirmed that it is the geologically youngest therizinosaur known from Japan described to date.

Important Implications for Claw (Ungual) Evolution in the Therizinosauridae

The scientists compared the shape of the hand claws from Paralitherizinosaurus japonicus with the claws from geologically older therizinosaurs and they postulated that that primitive therizinosaurs had claws with generalist functionalities and that the claws of more derived, later therizinosaurs such as P. japonicus were more suited to the hook-and-pull feeding function. Hook-and-pull feeding involves the use of the claws to help gather vegetation and bring it closer to the mouth.

What’s in a Name?

The fossils were found in a concretion associated with the Campanian-aged Osoushinai Formation of the Yezo Group on Hokkaido Island. The Yezo Group mostly consists of marine deposits and many vertebrate fossils such as plesiosaurs, sharks, mosasaurs and turtles have been discovered. Fragmentary dinosaur fossils are also associated with these strata including hadrosaurids, an armoured dinosaur (nodosaurid) and a potential tyrannosaur. A therizinosaur taxon can now be added to this Late Cretaceous dinosaur biota.

To view replicas of feathered theropods including therizinosaurus (whilst stocks last): PNSO Age of Dinosaurs Figures.

The discovery of the bones and claw elements in marine deposits helped to inspire this dinosaur’s scientific name. The genus name translates as “scythe reptile by the sea”, whilst the species name honours Japan.

The scientific paper: “New therizinosaurid dinosaur from the marine Osoushinai Formation (Upper Cretaceous, Japan) provides insight for function and evolution of therizinosaur claws” by Yoshitsugu Kobayashi, Ryuji Takasaki, Anthony R. Fiorillo, Tsogtbaatar Chinzorig and Yoshinori Hikida published in Scientific Reports.

Fragmentary bones excavated from Santa Cruz Province, Patagonia (Argentina), have revealed the presence of a super-sized megaraptorid theropod in the Late Cretaceous (Maastrichtian faunal stage). The new dinosaur, named Maip macrothorax is estimated to have been at least 9.5 metres long. It represents the biggest member of the Megaraptoridae described to date and its discovery lends support to the theory that these types of dinosaurs were not members of the Allosauria clade, but they were coelurosaurs and therefore related to the dinosaur lineage that gave rise to the birds.

Silhouette of Maip macrothorax showing the preserved bones in white (A). Reconstruction of the thoracic cavity of Maip (B) at the level of dorsal vertebra 6 (D6). Drawing of the excavation of Maip showing the original disposition of the bones (C). Abbreviations: a, axis; c, coracoid; ind, indeterminate bone; g, gastralia; r, rib; v, vertebrae. Picture credit: Rolando et al. Note scale bar in (A) = 1 metre, and (B,C) 50 cm.

Picture credit: Rolando et al

The fossil material was collected from exposures of the Chorrillo Formation approximately eighteen miles southwest of the city of El Calafate (southwestern Santa Cruz Province, Patagonia, Argentina).

The “Shadow of the Death” which “Kills with Cold Wind”

The Megaraptora clade are mostly known from fragmentary and very incomplete specimens. The fossils of Maip macrothorax (pronounced my-eep mac-row-thor-ax), although representing only a small portion of the overall skeleton, consist of a single cervical vertebra (C2 the axis), several dorsal vertebrae, ribs, the left coracoid, a partial toe bone, fragments of the scapula and caudal vertebrae.

By studying these bones the researchers, that included Alexis M. Aranciaga Rolando from the Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (Buenos Aires, Argentina) and Makoto Manabe from the National Museum of Nature and Science (Japan), postulate that the Megaraptora are not archaic members of the Allosauroidea but members of the Coelurosauria clade, that group of theropods more closely related to birds than they are to other members of the Avetheropoda lineage.

Maip macrothorax

The genus name is from the native Aónikenk people of Patagonia (known as the Tehuelche in western culture). Maip is an evil spirit said to roam the Andes and its name means “the shadow of death” which “kills with cold wind”. The specific name derives from the Latin for big thorax. The rib bones indicate that this dinosaur was deep chested with a large thoracic cavity more than 1.2 metres in width.

The second neck bone of Maip macrothorax (axis – C2) shown in lateral (A), anterior (B), posterior (C) and dorsal (D) with accompanying line drawings. Note scale bar = 5 cm. Picture credit: Rolando et al.

Picture credit: Rolando et al

The researchers propose that with the extinction of the carcharodontosaurids, many of which were apex predators on the southern continents, the megaraptorids evolved becoming larger, heavier and more robust, eventually filling the niche of top predator in many parts of the Southern Hemisphere during the Late Cretaceous.

Evolutionary trends of the Megaraptora. Evolutionary trends of Megaraptora. Temporal scale and bars depicting currently known temporal distributions of Megaraptora and Carcharodontosauridae (A). Time-calibrated phylogeny of megaraptoran taxa (B), showing most relevant genera from Asia (black bars), Australia (red bars) and South America (blue bars). Main synapomorphies supporting each node are indicated by arrows. Tree topology follows the results of the present work. Curve showing the increasing in average body size of megaraptorans during Barremian faunal stage through to the Maastrichtian (C). Picture credit: Rolando et al.

Picture credit: Rolando et al

The Rise of the Megaraptorids

Around 94 million years ago (Cenomanian faunal stage of the Late Cretaceous), there was a global extinction event which led to the demise of the Carcharodontosauridae. As far as Everything Dinosaur team members are aware, there are no reliable fossil records for the presence of carcharodontosaurids in South America beyond the Turonian faunal stage (the stage that followed the Cenomanian). An absence of apex predators permitted the megaraptorids and the abelisaurids to evolve to fill this niche in the Southern Hemisphere, whilst the tyrannosaurids become bigger and occupied the apex predator role in Asia and North America.

Maip macrothorax estimated at around 9.5 metres in length, lived some sixteen million years after the next largest megaraptorid (Aerosteon – A. riocoloradense). The body size of megaraptorids during the Early Cretaceous when the carcharodontosaurids still roamed seems to have been limited to around six metres in length, suggesting that these theropods were secondary predators. However, with the extinction of the carcharodontosaurids, body size in the Megaraptoridae increased and by the very end of the Cretaceous (Maastrichtian faunal stage), a body length in excess of ten metres seems plausible.

To read the Everything Dinosaur blog post that reported the discovery of these bones in 2020: Scientists Discover Giant Megaraptor.

Helping to Resolve the Phylogeny of these Enigmatic Theropods

Although the bones only represent a small part of the total skeleton and no cranial material has been identified, Maip macrothorax is the most informative megaraptoran known from the Maastrichtian stage. Phylogenetic analysis has placed this new taxon together with other South American megaraptorans in a monophyletic clade (they shared a single, common ancestor), whereas Australian and Asian members constitute successive stem groups.

A leggy, Late Cretaceous carnivore (Murusraptor).  Picture credit: Jan Slovak (University of Alberta).

Picture credit: Jan Sovak (University of Alberta).

For models and replicas of theropods and other prehistoric animals: Wild Safari Prehistoric World Models and Figures.

The researchers propose that the South American megaraptorids differ from more basal megaraptorans such as Fukuiraptor from Japan and Australovenator from Queensland, Australia in several anatomical features and the South American lineage evolved into much bigger, more robust and powerful predators.

The scientific paper: “A large Megaraptoridae (Theropoda: Coelurosauria) from Upper Cretaceous (Maastrichtian) of Patagonia, Argentina” by Alexis M. Aranciaga Rolando, Matias J. Motta, Federico L. Agnolín, Makoto Manabe, Takanobu Tsuihiji and Fernando E. Novas published in Scientific Reports.

The Everything Dinosaur website: Dinosaur Toys.

A scientific paper has just been published describing the fossilised remains of a juvenile titanosaur from the Winton Formation of Queensland, Australia. The specimen has been assigned to the Diamantinasaurus taxon (D. matildae) and it represents the smallest sauropod described from fossils found in Australia to date.

About Ten Percent of the Skeleton Recovered

The fossils were discovered on Elderslie Station land which lies some 35 miles northwest of the town of Winton (Queensland). Landowners noticed fragments of a femur and dorsal ribs exposed on the surface (2012). Staff from the Australian Age of Dinosaurs Museum along with volunteers excavated the site and found the remainder of the fossil material representing about 10% of the total skeleton about a metre below the surface.

The postcranial material consists of cervical ribs, three incomplete dorsal vertebrae, sacral vertebrae and limb bones.

A Young Titanosaur from the Late Cretaceous

Although age estimates for the Winton Formation vary, it has been informally divided into lower and upper members, with the Diamantinasaurus material coming from the “upper” portion which is regarded as Cenomanian to potentially the lowermost Turonian stages of the Late Cretaceous (approximately 95-89 million years ago).

The study of the juvenile titanosaur was led by Museum Research Associate Samantha Rigby who is undertaking a Master of Science (Research) at Swinburne University of Technology (Victoria, Australia), under the supervision of Dr Stephen Poropat who was one of the co-authors of the scientific paper published in the Journal of Vertebrate Palaeontology. Each bone from the specimen was scanned to create three-dimensional models to digitally compare them with other sauropod remains.

This comparison suggests the small specimen belongs to the Diamantinasaurus taxon though with juvenile characteristics, vertebrae which are unfused, minimal muscle scarring on the bones, smooth bone texture and marked proportional bone size differences when compared to adult titanosaur material.

Allometric Growth

The fossil specimen (AODF 663) nicknamed “Oliver” is only the third specimen to be referred to the taxon Diamantinasaurus matildae. D. matildae was formally named and described in 2009: A Trio of New Dinosaurs from Down Under. The research team found that the bones of this small titanosaur grew allometrically, meaning that its bones changed shape and different parts of its body grew at different rates.

The limb bones are also narrower in width when compared to other Diamantinasaurus limb bones from older individuals. This suggests that as this titanosaur grew its limb bones became thicker and more robust to help support its enormous bulk.

A Juvenile Diamantinasaurus

Fossils of juvenile titanosaurs are rare and it is hoped that “Oliver” will provide important insights into the ontogeny of titanosaurs.

Everything Dinosaur acknowledges the assistance of a media release from the Australian Age of Dinosaurs Museum in the compilation of this article.

The scientific paper: “A juvenile Diamantinasaurus matildae (Dinosauria: Titanosauria) from the Upper Cretaceous Winton Formation of Queensland, Australia, with implications for sauropod ontogeny” by Samantha L. Rigby, Stephen F. Poropat, Philip D. Mannion, Adele H. Pentland, Trish Sloan, Steven J. Rumbold, Carlin B. Webster and David A. Elliott published in the Journal of Vertebrate Paleontology.

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Researchers have described two beautifully preserved skulls of juvenile Gorgosaurus dinosaurs (G. libratus). The articulated specimens have enabled the scientists to build up a comprehensive picture of how these tyrannosaurids changed as they grew. Gorgosaurus and the much bigger, later tyrannosaurid T. rex exhibit similar changes in their skulls as they grow. This study will help palaeontologists to decipher tyrannosaur material and to determine the identity of previously misidentified specimens. It should also provide more evidence to help resolve the Nanotyrannus/T. rex debate.

Skulls of the two new juvenile Gorgosaurus libratus specimens in lateral view. A, TMP 2009.12.14; B, TMP 2016.14.1. Note scale bar equals 10 cm. Picture credit: Voris et al.

Picture credit: Voris et al

Gorgosaurus libratus

Named and described in 1914 (Lambe), Gorgosaurus is known from dozens of fossil specimens found in the upper Campanian Dinosaur Park Formation of Alberta and Judith River Formation of Montana. It is one of the best sampled and researched of all the Late Cretaceous tyrannosaurs, but juvenile material is rare. The recent discovery of additional juvenile Gorgosaurus libratus specimens from the Dinosaur Park Formation, including two well-preserved skeletons with articulated skulls, provided researchers which include Jared Voris and Darla Zelenitsky (University of Calgary), along with collaborators from the University of Ohio, the University of Alberta and the Royal Tyrrell Museum, an opportunity to develop a map outlining how this dinosaur changed as it grew and matured.

Illustrations of juvenile (left) and adult (right) skulls of Gorgosaurus in lateral (top) and dorsal views (bottom). Arrows and numbers indicate ontogenetically invariant autapomorphies of Albertosaurinae and Gorgosaurus as per emended diagnosis. Juvenile illustration based on TMP 2016.14.1 (lateral) and TMP 2009.12.14 (dorsal), adult illustration based on UALVP 10. Picture credit: Voris et al.

Picture credit: Voris et al

Sorting out Daspletosaurus Specimens

The research team, which also included Professor Phil Currie (University of Alberta), found that although the skulls of tyrannosaurs changed dramatically as they grew, several taxonomically informative traits remain present regardless of the age of the animal. This means that palaeontologists can use this information to determine which taxon is represented by juvenile fossil material.

Thanks to this research, two specimens previously identified as examples of immature Daspletosaurus individuals (coeval with Gorgosaurus) are instead confirmed as Gorgosaurus.

Left dentaries in lateral view of A, small juvenile (TMP 1994.12.155); B, juvenile (TMP 2016.14.1); C, subadult (TMP 1991.36.500); D, young adult (ROM 1247); and E, adult (TMP 1967.9.164) specimens of Gorgosaurus libratus. Note the development of the autapomorphic dorsoventral expansion in the posterior region of the bone through ontogeny. Scale bar equals 10 cm. Picture credit: Voris et al.

Picture credit: Voris et al

Comparisons with Tyrannosaurus rex

The team also found that both Gorgosaurus and T. rex underwent similar anatomical changes over their lifespans, but at different times. The changes started later in Tyrannosaurus rex and occurred over a longer time interval, resulting in a larger size and longer lifespan for T. rex when compared to Gorgosaurus.

Comparison of the growth series of Gorgosaurus libratus (top) and Tyrannosaurus rex (bottom), demonstrating similar ontogenetic stages (and morphologies) occurring at similar relative size (percent of largest specimen skull length) but different body sizes and biological ages. Picture credit: Voris et al.

Picture credit: Voris et al

Implications for Nanotyrannus

Having identified a series of anatomical traits that can be relied upon to permit palaeontologists to confidently assign juvenile tyrannosaur skull fossils to a specific taxon, this allows some specimens considered small or “dwarf” forms such as Nanotyrannus (N. lancensis) to be revisited. Some of these specimens may have been misidentified, since key characteristics may not have developed in young individuals before death, but this new data set would allow closer scrutiny of the fossil material.

The new for 2021 PNSO Nanotyrannus dinosaur model.

The picture (above) shows a model of a Nanotyrannus by PNSO.

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The scientific paper: “Two exceptionally preserved juvenile specimens of Gorgosaurus libratus (Tyrannosauridae, Albertosaurinae) provide new insight into the timing of ontogenetic changes in tyrannosaurids” by Jared T. Voris, Darla K. Zelenitsky, François Therrien, Ryan C. Ridgely, Philip J. Currie and Lawrence M. Witmer published in the Journal of Vertebrate Paleontology.

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An assessment of the Mill Canyon dinosaur track site north of Moab in Grand County, Utah by Bureau of Land Management regional palaeontologist Brent Breithaupt confirms that damage was caused to the Early Cretaceous tracks and trace fossils by a construction crew, but the damage is described as “minor”.

Trace fossils (dinosaur footprints) preserved at Moab (Utah). Picture credit: Bureau of Land Management.

Picture credit: Bureau of Land Management

Essential Repairs and Maintenance at an Important Fossil Site

The site, which covers approximately 2.3 acres contains over 200 tracks and other trace fossils recording activity around a body of water at an Early Cretaceous lake (approximately 112 million years ago). A construction crew had been employed to undertake repairs and improvements to the site including the replacement of boardwalks. Members of the public became aware of the maintenance work and reported possible damage to the fossils caused by the construction crew.

Everything Dinosaur published a blog article on reports of the damage caused by Bureau of Land Management contractors: Dinosaur Tracksite Damaged and having had concerns raised about damage to the site, it was decided to conduct an assessment of the area in order to find the best way to protect the fossils whilst still permitting public access.

This Damage to the Track Site Should Not Have Occurred

The assessment concluded that the overall damage was minor. Even so, Brent Breithaupt wrote in the report that:

“This damage should not have occurred”.

The regional palaeontologist added, that if the project had not been stopped:

“It is likely that much greater damage would have occurred with increased construction activities”.

As the Bureau of Land Management failed to consult palaeontologists on the maintenance plans, crews did not know which areas of the site to avoid. The incident was described in the report as “unfortunate” and the damage “could have been avoided”.

At least six different dinosaur tracks have been deciphered at Moab (Utah). Picture credit: Bureau of Land Management.

After the report was released, the Bureau of Land Management has confirmed that an additional environmental assessment would be undertaken, the public would be consulted and palaeontologists involved in future work at the location to supervise activities. The Bureau of Land Management reported that it “remains committed to protecting plant and animal fossils on our public lands”.

The Everything Dinosaur website: Dinosaur Toys.