Researchers have announced the discovery of a new species of Late Cretaceous armoured dinosaur from fragmentary fossils found in North Patagonia, (Río Negro Province, Argentina). It may represent an entirely new and previously unknown branch of the armoured dinosaur family tree from South America (Gondwana). Named Jakapil kaniukura (pronounced Jack-a-pil can-nee-ook-your-rah), it is the first definitive thyreophoran species from the Patagonia of Argentina and it might have been a biped with short, stumpy arms reminiscent of the abelisaurid theropod dinosaurs.

Fossils from the “La Buitrera Paleontological Area” (LBPA)

Writing in the academic journal “Scientific Reports”, researchers from the Universidad Maimónides (Buenos Aires, Argentina) in collaboration with a colleague from the Universidad del País Vasco/Euskal Herriko Unibertsitatea (Bilbao, Spain), report the discovery of a fragmentary, disarticulated skeleton representing a sub-adult animal, from the upper beds of the Candeleros Formation (early Late Cretaceous 94-97 million years ago). The sandstone exposures represent aeolian (wind borne) sand dunes indicating an arid to semi-arid palaeoenvironment in what is now termed the “La Buitrera Paleontological Area” (LBPA). The holotype (MPCA-PV-371), consists of skull elements including bones from the jaw, rib fragments, bones from the shoulders, two partial upper arm bones (humeri), a possible partial right ulna and other assorted fragmentary limb bones. Fifteen partial teeth were also recovered along with numerous osteoderms (dermal armour).

The sub-adult animal is estimated to have had a body length of less than 1.5 metres, perhaps weighing around 4.5 to 7 kilograms.

Commenting on the significance of this fossil discovery, lead author of the paper Facundo Riguetti (Universidad Maimónides), stated:

“Our finding is important for several reasons. On the one hand, Jakapil expands the fossil record known in the region and allows us to know a little better the prehistoric ecosystem of our land, and specifically of the ancient Kokorkom desert, today northern Patagonia.”

The PhD student went onto add:

“Moreover, this new species represents a lineage of thyreophoran dinosaurs previously unknown in South America. The Thyreophora originated about two hundred million years ago and evolved rapidly into several species distributed throughout the world. However, of these early thyreophorans, the lineage represented by Jakapil was the only one that persisted until at least a hundred million years ago.”

A Survivor from an Ancient Armoured Dinosaur Line

Phylogenetic analysis recovers Jakapil kaniukura either as a basal member of the Thyreophora or a stem ankylosaur, closely related to Scelidosaurus, fossils of which are associated with the Lower Jurassic Charmouth Mudstone Formation of Dorset, England. Its discovery suggests that early thyreophorans had a much broader geographic distribution than previously thought and that an ancient lineage persisted into the early Late Cretaceous.

A Bipedal Armoured Dinosaur

Evolutionary trends observed in armoured dinosaurs suggest a transition between small, cursorial, light-weight species to much larger, heavily armoured quadrupedal forms epitomised by the likes of Stegosaurus in the Late Jurassic and Ankylosaurus and Edmontonia in the Late Cretaceous. The relative dimensions of the forelimb and hind limb bear a greater resemblance to those of bipedal theropods and basal ornithischian dinosaurs than they do to members of the Thyreophora.

The reduced nature of the upper arm, indicated by the fragmentary humeri resembles the arm bones of abelisaurids – famous for their tiny, almost vestigial front limbs.

Etymology

The genus name is from the northern Tehuelchean language meaning “shield bearer”, whilst the species name is derived from the Mapudungun language for “crest” (kaniu) and “stone” (kura) which references the diagnostic bony crest on the lower jaw.

The researchers, including co-author Sebastián Apesteguía (Universidad Maimónides) speculate that Jakapil, if it was a biped, resembled Scutellosaurus, which is known from the Early Jurassic of Arizona. However, they caution against defining this little armoured dinosaur as bipedal. They observe that it still retains some anatomical characteristics associated with a quadrupedal stance and they comment that more complete limb bones are required to make a more accurate assessment of its locomotion.

Everything Dinosaur acknowledges the assistance of a media release from the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) in the compilation of this article.

The scientific paper: “A new Cretaceous thyreophoran from Patagonia supports a South American lineage of armoured dinosaurs” by Facundo J. Riguetti, Sebastián Apesteguía and Xabier Pereda-Suberbiola published in Scientific Reports.

Plesiosaur fossils found in strata associated with a 100-million-year-old river system prove that some plesiosaurs, traditionally thought to be marine animals, may have lived in freshwater. These long-necked, piscivores co-existed with the giant dinosaur Spinosaurus (S. aegyptiacus).

Freshwater Plesiosaurs

Scientists from the University of Bath and University of Portsmouth in the UK, and Université Hassan II (Morocco), have reported evidence small plesiosaurs from Kem Kem Group deposits in Morocco.

The fossils include bones and teeth from three-metre-long adults and an arm bone (humerus) from a 1.5- metre-long juvenile. They hint that these creatures routinely lived and fed in freshwater, alongside frogs, crocodiles, turtles, fish, and the huge aquatic dinosaur Spinosaurus.

When is a “Marine Reptile” a Marine Reptile?

The Plesiosauria clade was a long-lived and widely distributed group of marine reptiles. Most fossils, which date from the Upper Triassic to the end of the Cretaceous (Maastrichtian faunal stage), are associated with marine deposits, but a few specimens have been found in strata associated with brackish and freshwater environments. The researchers report plesiosaurs from river deposits of the Kem Kem Group. The numerous shed teeth show heavy wear similar to that observed in in the teeth of coeval spinosaurids. Contemporary plesiosaur fossils from the Bahariya Formation of Egypt have been identified as examples of the Polycotylidae plesiosaur family. The Kem Kem fossils probably represent leptocleidid plesiosaurs. Most Leptocleididae fossils come from shallow nearshore, brackish or freshwater palaeoenvironments suggesting that these small-bodied plesiosaurs were adapted to shallow, low-salinity environments.

As the fossil plesiosaur teeth show the same signs of wear as the teeth of Spinosaurus, the researchers imply that the plesiosaurs were eating the same food – chipping their teeth on the armoured fish that lived in the river. This indicates that they spent a lot of time in the river, rather than being occasional visitors.

As other types of Mesozoic marine reptile (mosasaurids and the crocodile-like teleosaurids), are thought to have inhabited (at least some of the time), freshwater environments, this suggests that so-called “marine reptiles” may have thrived in non-marine habitats.

Co-author of the scientific paper, Dr Nick Longrich (University of Bath Milner Centre for Evolution), commented:

“It’s scrappy stuff, but isolated bones actually tell us a lot about ancient ecosystems and animals in them. They’re so much more common than skeletons, they give you more information to work with. The bones and teeth were found scattered and in different localities, not as a skeleton. So, each bone and each tooth is a different animal. We have over a dozen animals in this collection.”

Diverse and Varied Kem Kem Group Freshwater Fauna

While extant marine mammals like whales and dolphins wander up rivers, either to feed or because they are lost, the number of plesiosaur fossils in the river deposits suggest that is unlikely. The team identified cervical, dorsal and caudal vertebrae, lots of teeth and the humerus from a juvenile. The researchers postulate that the plesiosaurs were able to tolerate fresh and salt water, like some whales, such as the beluga whale (Delphinapterus leucas).

Co-author Dr Samir Zouhri said:

“This is another sensational discovery that adds to the many discoveries we have made in the Kem Kem over the past fifteen years of work in this region of Morocco. Kem Kem was truly an incredible biodiversity hotspot in the Cretaceous.”

Plesiosaurs – Freshwater Incursions

The researchers compiled a list of all the geological formations that have shown evidence for the presence of members of the Plesiosauria clade in brackish or freshwater. Having collated this information, they re-examined the data identifying the different types of plesiosaur associated with the deposit.

As a result, a map documenting the incidences of freshwater incursions by different plesiosaur types was produced.

For the key to the geological formations see the end of this article.

Co-author David Martill (University of Portsmouth) exclaimed:

“What amazes me is that the ancient Moroccan river contained so many carnivores all living alongside each other. This was no place to go for a swim.”

Key to the Geological Formations Featured in the Plesiosaur Map

Geographic distribution of non-marine Plesiosauria Formations: 1, Dinosaur Park Formation (Campanian); (2), Horseshoe Canyon Formation (Campanian – Maastrichtian); 3, Isachsen Fm. (Late Aptian); 4, Strand Fiord Formation (Turonian – Coniacian); 5, Great Estuarine Group (Bathonian); 6, La Colonia Formation (Upper Campanian – Lower Maastrichtian); 7, Wadhurst Clay Formation (Valanginian); 8, Tunbridge Wells Sands Formation (Upper Valanginian); 9, Wessex Formation (Barremian); 10, Upper Weald Clay Formation (Barremian); 11, Vectis Formation (Barremian – Aptian); 12, Obernkirchen Sandstone (Late Berriasian);
13, Bükerberg Formation (Berriasian); 14, Kem Kem beds (Cenomanian – Albian?); 15, Chenini Formation (Albian); 16, Bahariya Formation (Cenomanian), 17, Sunday River Formation (Valanginian); 18, Lianmugin Formation (Upper Aptian); 19, Xinhe Formation (Middle Jurassic); 20, Ziliujing Formation (Toarcian); 21, Xintiangou Formation (Middle Jurassic), 22, Xiashaximiao Formation (Middle Jurassic); 23, Shezi Formation (Upper Triassic); 24, Razorback Beds (Sinemurian); 25, Evergreen Formation (Pliensbachian – Toarcian); 26, Griman Creek Formation (Albian); 27, Eumeralla Formation (Aptian) 28; Wonthaggi Formation (Valanginian – Aptian), 29 Eumeralla Formation (Upper Aptian – Lower Albian). Note that some formations contain more than one occurrence.

Everything Dinosaur acknowledges the assistance of a media release from the University of Bath in the compilation of this article.

The scientific paper: “Plesiosaurs from the fluvial Kem Kem Group (mid-Cretaceous) of eastern Morocco and a review of non-marine plesiosaurs” by Georgina Bunker, David M. Martill, Roy Smith, Samir Zouhri and Nick Longrich.

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.