A newly published scientific paper highlights the uniqueness and diversity of Australian theropods.  The research, published in the Journal of Vertebrate Paleontology identifies the world’s oldest known megaraptorid.  In addition, the study provides the first evidence of the presence of carcharodontosaurs in Australia.  These fossil discoveries are rewriting the evolutionary history of theropod dinosaurs.  Furthermore, they highlight a unique predator hierarchy in Australia during the Early Cretaceous.

The research was led by Museums Victoria Research Institute and Monash University PhD student Jake Kotevski. The scientists describe five new theropod specimens. Three tibiae, and a fossil consisting of two articulated caudal vertebrae with haemal arches, from the upper Strzelecki Group. In addition, the study includes a single tibia from the slightly younger Eumeralla Formation.

Unenlagiinae left tibia (front). Carcharodontosauria left tibia (middle) and Megaraptoridae right tibia (rear). New research highlights the diversity of Early Cretaceous Australian theropods. Picture credit: Nadir Kinani/Museums Victoria.

Picture credit: Nadir Kinani/Museums Victoria

Describing the Theropod Fossils

The five specimens included in the study are:

• Articulated Megaraptoridae caudal vertebrae (NMV P257414) – from upper Strzelecki Group exposures from the Twin Reefs locality.
• A partial right tibia (Megaraptoridae) specimen number NMV P257415 also from upper Strzelecki Group exposures at the Twin Reefs locality.
• Carcharodontosauria indet. left tibia (NMV P186143). A fragmentary fossil collected from the Lesley’s Lair site by Patricia Vickers-Rich in 1988 (upper Strzelecki Group).
• NMV P221042 a Carcharodontosauria indet. right tibia from the Point Lewis locality of the Eumeralla Formation.
• NMV P257601 a crushed left tibia assigned to Unenlagiinae indet. This fossil was found at Eagles Nest, near Inverloch, (upper Strzelecki Group).

For context, the upper Strzelecki Group deposits are dated from 121.4 to 118 million years ago.  Whilst the geologically younger Eumeralla Formation dates from 113 to 108 million years ago.

Fragmentary fossil material found in Australia has been assigned to the Megaraptoridae family previously.  However, these megaraptorid fossils from the upper Strzelecki Group are several million years older.  As such, they are the oldest assigned Megaraptoridae fossil material known to science.  Previously, Everything Dinosaur has reported on the discovery of Australian megaraptor fossil material that dates from approximately 110 million years ago.

To read more about this research: Australian Theropod Bone Challenges Gondwana Break-up Theory.

Megaraptoridae right tibia. Picture credit: Nadir Kinani/Museums Victoria.

Picture credit: Nadir Kinani/Museums Victoria

A Fresh Perspective on Australian Theropods

These newly described theropod fossils offer insights into Victoria’s dinosaur dominated, Early Cretaceous ecosystem.  The fossils suggest that the apex predators were megaraptorids.  In contrast, the coeval carcharodontosaurs were much smaller and lighter.  For example, the partial tibia and articulated caudal vertebrae indicate the presence of megaraptorids that were around six to seven metres in length.  The fossils assigned to carcharodontosaurs indicate much smaller theropods.  A size estimate for the carcharodontosaurs of two to four metres in length has been proposed.

One of the authors of the study, PhD student Jake Kotevski commented:

“The discovery of carcharodontosaurs in Australia is ground-breaking. It’s fascinating to see how Victoria’s predator hierarchy diverged from South America, where carcharodontosaurs reached Tyrannosaurus rex-like sizes up to 13 metres, towering over megaraptorids. Here, the roles were reversed, highlighting the uniqueness of Australia’s Cretaceous ecosystem.”

Two Megaraptoridae caudal (tail) vertebrae and haemal arches. Picture credit: Nadir Kinani/Museums Victoria.

Picture credit: Nadir Kinani/Museums Victoria

Numerous small ornithopods are known from the Early Cretaceous of Victoria.  However, sauropod remains are absent.  This may have favoured the evolution of smaller, cursorial predators such as megaraptors.  Whereas, in South America large carcharodontosaurs were the apex predators.  They probably hunted the abundant sauropods.  This suggests the composition of the herbivorous dinosaurs in each region led to different theropods dominating the ecosystem.

To read a blog post from 2019 about the discovery of a new ornithopod from Victoria: A New Early Cretaceous Ornithopod from Australia is Described (Galleonosaurus).

Evidence of Faunal Interchange

Co-author Dr Thomas Rich (Museums Victoria) added:

“The findings not only expand Australia’s theropod fossil record but offer compelling evidence of faunal interchange between Australia and South America through Antarctica during the Early Cretaceous. The findings also challenge previous assumptions about body-size hierarchies in Gondwanan predator ecosystems highlighting Victoria’s unique Cretaceous fauna.”

Specimen number NMV P257601 has been referred to the Unenlagiinae.  Their taxonomic position within the Theropoda remains controversial.  For example, some palaeontologists consider unenlagiines to be a subfamily of the Dromaeosauridae.  However, other scientists consider, these small, long-snouted dinosaurs as a separate family (Unenlagiidae). Most unenlagiine fossil remains have been found in South America. Historically, Australia had limited evidence for their presence.  Nevertheless, the crushed tibia (NMV P257601) provides further robust evidence for a faunal interchange between South America and Australia across Antarctica.

Jake Kotevski (left) holding Unenlagiinae left tibia and Tim Ziegler (right) holding Megaraptoridae right tibia. Picture credit: Nadir Kinani/Museums Victoria.

Picture credit: Nadir Kinani/Museums Victoria

The Importance of Museum Collections

Co-author Tim Ziegler (Museums Victoria) highlighted the importance of access to museum collections to foster scientific breakthroughs.

He stated:

“Museum collections are crucial to advancing our understanding of prehistoric life. Specimens preserved in the State Collection for decades – unidentifiable until now – are providing new insights into the evolution of dinosaur ecosystems.”

Three of the fossils, uncovered between 2022 and 2023, were first identified by Museums Victoria volunteer Melissa Lowery. This discovery highlights the essential contributions of community members working alongside seasoned researchers to further our understanding of Australia’s Cretaceous past.

An aerial view of Twin Reefs, Bunurong Coastal Reserve (Victoria), the area where some of the dinosaur fossils were found. Picture credit John Broomfield/Museums Victoria.

Picture credit: John Broomfield/Museums Victoria

Everything Dinosaur acknowledges the assistance of a media release from Museums Victoria in the compilation of this article.

The scientific paper: “Evolutionary and paleobiogeographic implications of new carcharodontosaurian, megaraptorid, and unenlagiine theropod remains from the upper Lower Cretaceous of Victoria, southeast Australia” by Jake Kotevski, Ruairidh J. Duncan, Tim Ziegler, Joseph J. Bevitt, Patricia Vickers-Rich, Thomas H. Rich, Alistair R. Evans and Stephen F. Poropat published in the Journal of Vertebrate Paleontology.

The award-winning Everything Dinosaur website: Prehistoric Animal Models.

A scientific paper was published earlier this week that announced two new Hateg Basin sauropod taxa.  These dinosaurs were named Petrustitan hungaricus and Uriash kadici.  At least four sauropod taxa are known from the Hateg Basin.  However, as the sediments in this region cover several million years, it is likely that these four taxa were not contemporaneous.  It is also likely that additional sauropod genera are represented in the fossil deposits.

To read Everything Dinosaur’s earlier blog post about this new study: New Hateg Basin Sauropods are Described.

We have been asked to provide a little more information on the largest of these four sauropod taxa. As this area consisted of a series of large islands at the end of the Cretaceous, it was thought that the dinosaur fauna in this region consisted mostly of dwarf forms.  However, this idea of the Hateg Basin dinosaur fauna representing examples of “island dwarfism” has been challenged.  For example, the newly described U. kadici is thought to amongst the biggest European Late Cretaceous sauropods know to science.

The Hateg Basin Sauropod Fauna – A Complex Picture

The first sauropod to be named and described from this region of western Romania was Magyarosaurus. The German palaeontologist Friedrich von Huene erected this genus in 1932.  He assigned three species to this genus.

1. Magyarosaurus dacus – now recognised as the only valid species.
2. The nomen dubium Magyarosaurus transsylvanicus – a nomen dubium with assigned fossil material thought to represent more than one species of sauropod.
3. Magyarosaurus hungaricus – renamed in 2025 as Petrustitan hungaricus (Verónica Díez Díaz et al).

It is likely that the substantial number of fossils, often isolated and fragmentary remains found in western Romania represent several more, as yet undescribed sauropod taxa.

The Wild Past Magyarosaurus dinosaur model, a replica of this dwarf titanosaur taxon. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

The picture shows a model of the dwarf titanosaur Magyarosaurus sent to Everything Dinosaur by Wild Past.

To view the range of Wild Past models and figures in stock: Wild Past Prehistoric Animal Figures.

Uriash kadici – A Giant Amongst Hateg Basin Sauropods

The second, newly described Hateg Basin sauropod is an outlier in terms of size.  Whilst three of the four Hateg Basin sauropod taxa described to date were relatively small, Uriash kadici was much larger. Size estimates vary but it could have had a body length of around twelve metres.

Mike from Everything Dinosaur explained that three of the four known Hateg Basin sauropod taxa were relatively small.  Although size estimates vary, it is possible to compare these four taxa and to produce a scale drawing.

• Magyarosaurus dacus – 3 metres (<1 tonne).
• Paludititan nalatzensis – 6 metres (2 tonnes).
• Petrustitan hungaricus – 6-7 metres (2 tonnes+).
• Uriash kadici – 12 metres (5-8 tonnes).

Comparing the size of Hateg Island sauropods. Uriash kadici is the biggest taxon described to date. Picture credit: Everything Dinosaur from Brian Cooley/Dan Horatiu Popa/Hateg County UNESCO Global Geopark.

Picture credit: Everything Dinosaur from Brian Cooley/Dan Horatiu Popa/Hateg County UNESCO Global Geopark

Uriash kadici is the largest titanosaurian taxon described to date from the Hateg Basin.  It is larger than most of the other Late Cretaceous European titanosaurs.  Its size is only surpassed by Abditosaurus (A. kuehnei).  Abditosaurus fossils come from southern Pyrenees of Spain.  It was formally described in 2022 (Vila et al).  Abditosaurus is thought to have measured around seventeen metres long.

To read a blog post about this dinosaur: Abditosaurus – The First New Dinosaur of 2022.

What’s in a Name?

The genus name comes from the Romanian word ‘uriaș’ (pronounced ‘uriash’). It refers to gigantic humanoid characters from Romanian folklore. The species name honours Ottokár Kadić (1876–1957), a geologist and palaeontologist of the Royal Geological Survey of Hungary and discoverer of several continental vertebrate-bearing fossil localities in the north-western Hateg Basin, including the type locality of Uriash.

Mike from Everything Dinosaur explained that the recent study focusing on the Hateg Basin sauropods had expanded knowledge about European titanosaurs.  However, much remains to be discovered.  New fossil quarries will be opened, and new material will help to fill in the gaps and provide palaeontologists with a better understanding of Late Cretaceous sauropod evolution.

Visit the award-winning Everything Dinosaur website: Dinosaur Toys and Models.

Two new species of Hateg Basin sauropods have been identified.  Their fossils come from the Upper Cretaceous deposits of the Hateg Basin in western Romania.  The discovery of these new taxa can help palaeontologists to better understand dinosaur populations across the planet prior to the end-Cretaceous extinction event. The study led by Verónica Díez Díaz from the Museum für Naturkunde Berlin (Germany) demonstrates how important Europe’s fossils are when it comes to providing a more complete picture of dinosaur extinction.

Scientists from the University College London and the University of Bucharest collaborated in this research.

Hateg Basin Sauropods

The researchers report two new sauropod taxa from the Hateg Basin.  They have been named Petrustitan hungaricus and Uriash kadici. During the Late Cretaceous, much of the Europe was covered by water. However, an archipelago existed in what is known today as eastern Europe. The largest island (Hateg Island) was approximately 120 miles (200 km) from the nearest landmass. Size estimates vary, but it has been suggested that by the very end of the Cretaceous (Maastrichtian faunal stage), Hateg Island covered an area of around thirty thousand square miles. It was roughly the size of the Japanese island Hokkaido.

The archipelago was home to several different sauropod taxa.  The diversity of sauropods in the Late Cretaceous of Europe is much greater than previously thought.  Fifteen years ago, only five sauropod species were known from the Late Cretaceous of Europe.  Today, at least eleven taxa have been identified.  In contrast, only a single sauropod species is known from the Late Cretaceous of America (Alamosaurus sanjuanensis).

Commenting on the significance of this new study into Hateg Basin sauropods, corresponding author Verónica Díez Díaz (Museum für Naturkunde Berlin) stated:

“The extraordinary diversity in a small geographical area like Hațeg Island surprises us. Sauropods of different sizes lived side by side here: from giants over 10 metres long and weighing eight tonnes to dwarfs of just 2.5 metres and weighing less than a tonne. This provides exciting insights into the environmental conditions and the coexistence of different species.”

The researchers propose the presence of three additional, but only partly contemporaneous taxa in the Hateg Basin. These are Paludititan nalatzensis, Petrustitan (‘Magyarosaurus’) hungaricus and the much larger Uriash kadici. U. kadici is amongst the biggest known sauropods of the Late Cretaceous European Archipelago. Picture credit: Brian Cooley/Dan Horatiu Popa/Hațeg County UNESCO Global Geopark.

Picture credit: Brian Cooley/Dan Horatiu Popa/Hațeg County UNESCO Global Geopark

Giants and Dwarf Sauropods

Traditionally, the fauna of Hateg Island was thought to consist mainly of smaller relatives of dinosaur genera found on larger landmasses.  It had been assumed that the dinosaurs of Hateg Island became smaller due to the limited amount of resources on the island.  This biological phenomenon is known as island dwarfism (insular dwarfism).  This idea was postulated by the famous 20th Century polymath Baron Franz Nopcsa von Felső-Szilvás. He argued that the limited resources such as food, water and space on islands would result in a reduction of the size of animals that lived there. These island dwelling populations would become smaller over many generations when compared to their continental counterparts.

For example, the ornithopod Tethyshadros (T. insularis) was once thought to be a dwarf hadrosauroid.  However, subsequent analysis indicates that it was around twenty-five percent larger than previously thought.

To read more about this 2021 study: Sizing up Tethyshadros.

The biota of the Hateg Basin seems to be much more complicated and diverse.  For instance, whilst a number of Hateg Basin sauropods are relatively small, the newly described Uriash kadici may have been more than eleven metres in length.

Co-author Zoltán Csiki-Sava (University of Bucharest) added:

“Local evolution was more complex than expected and shows that not all species reduced their size.”

European Dinosaurs Linked to Gondwanan Lineages

This study also highlights the links between European dinosaur taxa and their relatives in Asia, Africa and South America.  The team’s findings strengthen the hypothesis that Late Cretaceous European titanosaurs belonged to Gondwanan lineages that invaded the former area during the Barremian–Albian faunal stages of the Early Cretaceous.  Paul Upchurch (University College London) explained that Gondwanan sauropods migrated into Europe over land bridges that existed in the Early Cretaceous.  However, sauropods were probably very capable swimmers and may have traversed distances in excess of three hundred miles (500 kilometres) to reach distant islands.

Co-author Philip Mannion (University College London) commented:

“Some of these dinosaurs were descendants of earlier faunas, while others arrived in the region late.”

Why were Large Hateg Island Sauropods Present?

The researchers interpret the presence of body-size disparity as either evidence that large-bodied taxa were ecologically excluded from body-size reduction by competition with small-bodied titanosaurs, or that dwarfing occurred stratigraphically earlier among several lineages and the small-bodied titanosaurs on Hațeg Island are the descendants of existing dwarfed ancestors. In addition, the team report that they found no indication of a body size-related titanosaurian turnover in the uppermost Cretaceous of the Transylvanian area.

Everything Dinosaur acknowledges the assistance of a media release from the Museum für Naturkunde Berlin in the compilation of this article.

The scientific paper: “Revision of Romanian sauropod dinosaurs reveals high titanosaur diversity and body-size disparity on the latest Cretaceous Haţeg Island, with implications for titanosaurian biogeography” by Verónica Díez Díaz, Philip D. Mannion, Zoltán Csiki-Sava and Paul Upchurch published in the Journal of Systematic Palaeontology.

The award-winning Everything Dinosaur website: Prehistoric Animal Models and Toys.