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”.

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Researchers from the Smithsonian Institute (Washington), the University of Oslo and the Ludwig Maximilian Universität (Munich), have published a paper that describes two ichthyosaur specimens from the famous Upper Jurassic Solnhofen deposits of southern Germany. The fossils, an almost complete Aegirosaurus (JME-SOS-08369) and a tail (JME-SOS183), reveal extensive soft tissue preservation, analysis of which indicates the presence of blubber in these marine reptiles.

Late Jurassic Aegirosaurus sp. (JME-SOS-08369) shown in (A) in normal light and (B) composite picture in UV light indicating location of further close-up images included in the scientific paper. Interpretative drawing (C). Note scale bar equals 20 cm. Picture credit: Delsett et al.

Picture credit: Delsett et al

These amazing fossil specimens representing marine reptiles that lived around 150 million years ago will help scientists to better understand how soft tissue can be preserved in the carcases of vertebrates deposited on the seafloor.

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Aegirosaurus

Aegirosaurus is a genus of ichthyosaur within the Ophthalmosauridae family. Its fossils are associated with the Upper Jurassic limestone deposits of Solnhofen in southern Germany. These deposits are famous for their vertebrate fossils, although ichthyosaur material is rare. Fossils ascribed to this genus have also been found in Lower Cretaceous strata in south-eastern France (Fischer et al, 2011). This discovery suggests that most Late Jurassic ichthyosaurs came through the end Jurassic extinction and continued to thrive in the Early Cretaceous.

Aegirosaurus was an active, nektonic pursuit predator, probably feeding on small fish and squid.

Picture credit: DPA

Evidence for Blubber

The nearly complete ichthyosaur skeleton (JME-SOS-08369) was excavated in 2009, whereas the second specimen involved in this study (the tail), was originally found in 1926, but not formally described. No genus has been assigned to the tail specimen, although the researchers confidently assign it to the Ophthalmosauridae.

The Late Jurassic ichthyosaur tail (specimen number JME-SOS2183) shown in (A) regular light, under ultraviolet light (B) with an interpretative line drawing (C). Note scale bar equals 10 cm. Picture credit: Delsett et al.

Picture credit: Delsett et al

Soft tissue samples were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) analysis. The analyses confirm the presence of the phosphate mineral apatite, with phosphate most likely derived from the body itself. In addition, a yellow-coloured, amorphous substance was identified, the researchers postulate that this substance represents decomposed blubber.

Skull from Late Jurassic Aegirosaurus sp. (JME-SOS-08369) with (A) interpretative drawing and (B) photograph. Note scale bar equals 5 cm. Picture credit: Delsett et al.

Picture credit: Delsett et al

Identifying Adipocere

The researchers conclude that the detailed analysis of the yellowish, amorphous substance indicates that it is adipocere. This is late-stage post-mortem decomposing fatty acids produced by microorganisms under low oxygen conditions. As adipocere is a typical breakdown product of animal blubber, it is postulated that these ichthyosaurs had blubber to help insulate them, just as many extant marine mammals do. The paper does not address any endothermic implications for this conclusion.

Understanding Ichthyosaur Taphonomy

The two ichthyosaur specimens with their extensive soft tissue preservation will help scientists to interpret the taphonomy (how fossils are preserved) of Solnhofen Archipelago vertebrates. Future research will focus on microscopical and geochemical analysis of different parts of the specimens that have the potential to reveal more information about tissue types.

In addition, the beautifully preserved fossils hold the potential for investigations into the locomotion of ophthalmosaurids, helping scientists to better understand how these marine reptiles moved through the water.

The scientific paper: “The soft tissue and skeletal anatomy of two Late Jurassic ichthyosaur specimens from the Solnhofen archipelago” by Lene L. Delsett​, Henrik Friis, Martina Kölbl-Ebert and Jørn H. Hurum published in PeerJ.

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