A new scientific paper on the Early Cretaceous tyrannosauroid Eotyrannus lengi has been published. It is confirmed as a valid genus and the phylogenetic assessment places the enigmatic Megaraptora clade within the Tyrannosauroidea superfamily.

First named and scientifically described back in 2001 (Hutt et al), Eotyrannus is helping to provide significant insights into the early evolution of tyrannosauroids as well as potentially redefining how enigmatic “megaraptors” such as Australovenator, Megaraptor and the recently described Maip macrothorax fit within the Theropoda.

The Carnivorous Dinosaurs of the Wessex Formation

Since the first fossils of Eotyrannus were found (1997), this theropod has attracted a lot of scientific interest. It is one of numerous carnivorous dinosaurs associated with the Wessex Formation (part of the Wealden Supergroup), indeed, back in 2021 we blogged about two new members of the Baryonychinae named and described from fossil remains found on the Isle of Wight (Wessex Formation). Last month, we wrote about an even bigger predator, an as yet, unnamed spinosaurid known as the “White Rock spinosaurid”.

For the article on the recently described baryonychids Ceratosuchops inferodios and Riparovenator milnerae: Two New Spinosaurids from the Isle of Wight.

To read about the Isle of Wight “White Rock spinosaurid”: Super-sized Isle of Wight Carnivorous Dinosaur.

The newly published paper provides further information on Eotyrannus autapomorphies (characteristic traits) that help to distinguish it from the often, fragmentary remains of other theropods associated with the Wessex Formation.

Deciphering the Fossil Evidence

Many of the fossil bones associated with the Eotyrannus genus remain entombed in their concrete-like matrix. Anatomical traits helping to define and classify this dinosaur are only beginning to emerge and there is a substantial amount of further preparation work required to permit a comprehensive analysis.

However, by combining all the new data since the formal description, the authors (Darren Naish and Andrea Cau) were able to produce a new skeletal reconstruction. The maxilla is confirmed as being quite rectangular in shape. Eotyrannus did not have the long, narrow snout (longirostrine) as seen in other early tyrannosauroids such as Dilong and Xiongguanlong from the Early Cretaceous of China. This suggests that longirostry evolved several times within the Tyrannosauroidea, perhaps in response to adaptations to permit these theropods to exploit a particular predatory niche.

Where do the Megaraptora Fit?

The scientific paper also incorporated a revised phylogenetic analysis of Eotyrannus. No significant support was found for Eotyrannus having a close evolutionary relationship to Juratyrant (J. langhami), known from the Late Jurassic of Dorset or indeed to the Late Jurassic early tyrannosauroid Stokesosaurus (S. clevelandi) from the western United States.

Instead, it is grouped with gracile, mid-sized tyrannosauroids that represent a more derived state than proceratosaurids, stokesosaurs and Juratyrant.

If megaraptoran dinosaurs are tyrannosauroids and therefore coelurosaurs, then this challenges long-held views on Theropoda classification and suggests that after the Early Cretaceous most of the hypercarnivore niches within dinosaur dominated ecosystems were increasingly occupied by coelurosaurs. It also suggests that tyrannosauroids were much more diverse and widespread during the Cretaceous than previously thought.

Eotyrannus remains a fascinating dinosaur, a genus that has led to new insights into the evolution and radiation of the Theropoda. It offers a tantalising glimpse into the ecology represented by the Wessex Formation deposits and how a mid-sized theropod co-existed with other, larger members of the ever-widening collection of Wessex Formation meat-eating dinosaurs.

Everything Dinosaur Helping to Fund Research

The authors wanted to make their paper available to everyone. To do this they set up a GoFundMe campaign to cover publishing costs. Everything Dinosaur assisted with the funding.

A spokesperson from Everything Dinosaur stated:

“We were happy to support this excellent paper and we helped to make such studies possible. Your purchases from Everything Dinosaur genuinely help science”.

The scientific paper: “The osteology and affinities of Eotyrannus lengi, a tyrannosauroid theropod from the Wealden Supergroup of southern England” by Darren Naish and Andrea Cau published in PeerJ.

A new giant, Late Cretaceous predatory dinosaur has been named based on fossils found in Argentina. The dinosaur, assigned to the Carcharodontosauridae has been named Meraxes gigas and its fossilised remains represent the most complete carcharodontosaurid specimen found to date in the Southern Hemisphere.

The giant, South American predatory dinosaur Giganotosaurus which featured in the latest instalment of the “Jurassic Park/Jurassic World” movie franchise is just one of a poorly known group of theropod dinosaurs that were the apex predators in many terrestrial environments during the Cretaceous. Although, most dinosaur fans can name many carcharodontosaurids, these meat-eaters remain enigmatic and most genera have been described based on fragmentary remains. All that has changed with the publication of a scientific paper describing Meraxes gigas from the Upper Cretaceous Huincul Formation of northern Patagonia (Argentina).

A Giant Predator with Short Arms

Writing in the scientific journal “Current Biology” the researchers who include Juan Canale (Universidad Nacional de Río Negro, Argentina), suggest that M. gigas was around eleven metres long and weighed around four tonnes (estimated 4.26 tonnes). The skull bones, which represent one of the most complete large theropod skulls ever found, indicate a skull length of 1.27 metres, but its arms were disproportionately small. Like other Cretaceous apex predators, the tyrannosaurs and the abelisaurids, this dinosaur had very short arms. Arms so short that they could not reach its own mouth.

Lead author Juan Canale commented:

“I’m convinced that those proportionally tiny arms had some sort of function. The skeleton shows large muscle insertions and fully developed pectoral girdles, so the arm had strong muscles. They may have used the arms for reproductive behaviour such as holding the female during mating or support themselves to stand back up after a break or a fall.”

The fossils found in Huincul Formation exposures (late Cenomanian to Turonian) in Las Campanas Canyon some 14 miles southwest of Villa El Chocón, (Neuquén Province, Argentina), also include an almost complete right arm (j, in the image above). This limb, one of the most complete of any derived carcharodontosaurid described to date, is comparatively short and provides evidence to support the idea that many carcharodontosaurids had reduced forelimbs similar to those observed in abelisaurids such as Carnotaurus and most famously in Tyrannosaurus rex.

The researchers propose that forelimb reduction among three lineages of large-bodied predators is an example of convergent evolution, whereby not closely related organisms evolve the same traits. The fossils of Meraxes gigas show a remarkable degree of parallelism between latest-diverging tyrannosaurids and carcharodontosaurids.

Helping to Define the Size of Giganotosaurus (G. carolinii)

Meraxes has the most complete cranium of any Carcharodontosaurinae, with a total skull length estimated at 1.27 metres which is comparable to the most complete specimen of Acrocanthosaurus (A. atokensis) with a skull size of 1.23 metres. Giganotosaurus has the next most complete skull among carcharodontosaurids, but it is missing part of the maxilla and several other bones, so estimating its total length has been problematical. Although the head of Meraxes was not as wide as the head of Giganotosaurus, the cranium of Meraxes is sufficiently similar to G. carolinii to permit an estimate for the length of the Giganotosaurus skull to be made. Based on this comparison, the skull of the largest Giganotosaurus specimen would have been around 1.62 metres long, making it one of the longest theropod skulls known to science.

The discovery of yet another super-sized carcharodontosaurid from Argentina demonstrates the high diversity of these theropods shortly before their extinction. Parallels can be drawn between the diversity of South American carcharodontosaurids and tyrannosaurs known from the Campanian faunal stage in western North America.

There are no reliable records of carcharodontosaurids in South America beyond the end of the Turonian stage of the Late Cretaceous, this great clade of theropods are believed to have become extinct around 90 million years ago.

To read a related article about another South American theropod with reduced forelimbs and fingers like a T. rex: Gualicho Sticks Two Fingers up at T. rex.

What’s in a Name

The genus name (Meraxes) is named after a female dragon from the Song of Ice and Fire series of books by George R. R. Martin, upon which the hugely successful television series “Game of Thrones” was based. The species name (gigas) comes from the Greek meaning giant.

The scientific paper: “New giant carnivorous dinosaur reveals convergent evolutionary trends in theropod arm reduction” by Juan I. Canale, Sebastián Apesteguía, Pablo A. Gallina, Jonathan Mitchell, Nathan D. Smith, Thomas M. Cullen, Akiko Shinya, Alejandro Haluza, Federico A. Gianechini and Peter J. Makovicky published in Current Biology.

Palaeontologists in New Zealand have started a consultation process in a bid to appoint a fossil emblem for New Zealand. Everything Dinosaur has come across media reports that palaeontologists at the University of Otago (South Island, New Zealand), are beginning a project to identify a fossil emblem for the country. Once a shortlist of candidate fossils has been compiled, the winner will be decided by a public vote.

Many Australian states, have fossil emblems, for example, back in January (2022), team members at Everything Dinosaur covered the announcement that the giant amphibian Koolasuchus (K. cleelandi) had been appointed the fossil emblem of Victoria. Now it seems that New Zealand wants to have a fossil emblem too.

To read the Koolasuchus story: Koolasuchus Becomes the State Fossil of Victoria.

The holotype specimen of Kairuku waewaeroa (WM 2006/1/1). Line drawing of specimen (A), photograph of the holotype in ventral view (B) and (C) scale comparison with the largest extant penguin species the Emperor Penguin (Aptenodytes forsteri. Note scale bar for (B) equals 4 cm. Picture credit: Giovanardi et al.

Picture credit: Giovanardi et al

Penguins, Plesiosaurs, Trilobites, Dolphins and Giant Prehistoric Birds

New Zealand might not be the first country one thinks about when considering the fossil record. However, several important and unique fossil discoveries have been made on Aotearoa (the Māori name for the country).

The campaign is being led by Dr Nic Rawlence (University of Otago palaeogenetics laboratory), he has suggested some of the country’s giant penguins (Kairuku waewaeroa, Kumimanu biceae, Crossvallia waiparensis), or perhaps one of the early cetaceans or an example of a primitive pinniped (Eomonachus belegaerensis), fossils of which come from the western side of North Island (Taranaki area).

Eomonachus belegaerensis an ancient seal from New Zealand. Picture credit: Jaime Bran/ Te Papa Museum.

Picture credit: Picture credit: Jaime Bran/Te Papa Museum

In 2002, the Late Cretaceous plesiosaur Kaiwhekea katiki was formally named and described. The seven-metre-long specimen was excavated from a single, large concretion found at Shag Point, Otago (Katiki Formation). It is one of the most complete plesiosaur specimens known from the Southern Hemisphere.

There are also more recent inhabitants of New Zealand to consider, such as the giant South Island Moa Dinornis robustus, as well as many important invertebrate fossils that date from the Palaeozoic but, our personal choice would be the enormous Haast’s eagle (Hieraaetus moorei), the largest eagle known to science. This huge predator occupied the niche filled by mammalian carnivores in other ecosystems. With a body weight in excess of 15 kilograms and a wingspan of around 3 metres, Haast’s eagle was a formidable and terrifying predator.

Haast’s eagle attacks a moa. This eagle is the largest eagle known to science and it only recently went extinct (500-600 years ago). Picture credit: University of Otago/John Megahan.

Picture credit: University of Otago/John Megahan

Only Recently Extinct

Unlike the trilobites, plesiosaurs, penguins and ancient marine mammals, Haast’s eagle died out relatively recently, not long after the first Māori settlers came to New Zealand.

It has not been decided yet whether a single fossil specimen should become the national emblem, or whether there would be two emblems designated, one for South Island and one for North Island.

A shortlist is due to be announced in the near future and then a public vote will decide on the winner(s).

If New Zealand appoints a fossil emblem, then perhaps the UK or the countries that make up the United Kingdom could consider having fossil emblems too.

Any suggestions?

If you have any suggestions about fossil emblems, feel free to email Everything Dinosaur: Contact Everything Dinosaur.

A cross-sectional analysis of a pterosaur wing bone has helped palaeontologists to work out the ages and growth stages of flying reptiles from the Early Cretaceous Jiufotang Formation of China. This research suggests that the Jehol tapejarid biota represents a migratory area for these pterosaurs.

Writing in the academic journal “Scientific Reports”, researchers from Shandong University of Science and Technology (China) in collaboration with the University of Birmingham, took a tiny cross section of bone from the left forelimb of a pterosaur specimen assigned to the genus Sinopterus. Detailed analysis of the bone structure revealed that the fossil came from an immature individual at a late juvenile stage prior to reaching sexual maturity. This is the first time that histological data about the growth stages of Jehol tapejarids has been undertaken and based on this study, the largest skeletally immature tapejarid individuals recorded from the Jiufotang Formation might have reached sexual maturity.

The Jehol tapejarid Sinopterus (specimen number SDUST-V1014). Photograph (a) and line drawing (b) of the wing skeleton as well as enlarged images of the deltopectoral crest (c) and pneumatic foramen on the distal end of the wing metacarpal (d). Arrow points to the thin-section sample position on the first wing phalanx. Note scale bar for a and b = 20 mm. Picture credit: Zhou et al.

Picture credit: Zhou et al

At Least a Year Old

Microscopic analysis of the internal structure of the bone revealed the presence of one line of arrested growth (LAG) suggesting that this specimen was over a year old when it died. Palaeontologists have proposed that pterosaurs had a remarkably fast growth rate in their first three years and the postulated size of the pterosaur based on SDUST-V1014 fits with this hypothesis.

The Jehol biota relating to the Pterosauria is dominated by immature individuals and skeletally mature adults are exceptionally rare. The researchers postulate that this ecosystem was not home to the adults, that they may have lived apart from juveniles and immature animals. Perhaps this part of northern China was on a migratory route for these types of flying reptiles.

The Early Cretaceous Jehol biota with emphasis on mammaliamorphs. Picture credit: Chuang Zhao.

Picture credit: Chuang Zhao

Improving Our Knowledge of Tapejarid Anatomy

Although crushed, the forelimb bones reveal helpful morphological information clarifying the anatomy of Jehol tapejarids and the researchers suggest that this improved understanding could lead to a revision of the taxa associated with the Jiufotang Formation.

In addition, this histological analysis permits comparison with other pterosaur growth rates and the researchers conclude that the size gap between sexual and skeletal maturity in tapejarids was very similar to that observed in the not very closely related Pteranodon genus (Ornithocheiroidea).

To read a related article published in 2021 that examines the significance of a headless Sinopterus specimen (S. dongi) and its role in helping to define juvenile tapejarids: Headless Pterosaur Helps to Define an Entire Genus.

The scientific paper: “A new wing skeleton of the Jehol tapejarid Sinopterus and its implications for ontogeny and paleoecology of the Tapejaridae” by Chang-Fu Zhou, Dongxiang Yu, Ziheng Zhu and Brian Andres published in scientific reports.

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