An international team of scientists have unearthed the remains of Africa’s oldest dinosaur skeleton. The fossils represent a sauropodomorph, which has been named Mbiresaurus raathi. The fossils were excavated from Pebbly Arkose Formation exposures in Mashonaland Central Province, Zimbabwe. This basal sauropodomorph and the associated vertebrate fauna discovered to date is helping scientists to better understand the dispersal and distribution of early dinosaurs and their contemporaries.

Mbiresaurus raathi

The research team led by palaeontologists from Virginia Tech in collaboration with colleagues from the Natural History Museum of Zimbabwe, the Universidade de São Paulo, (São Paulo, Brazil) and the Chipembele Wildlife Education Centre, (Mfuwe, Zambia) have explored the extensive Upper Triassic sandstone exposures of the Pebbly Arkose Formation. As well as finding the nearly complete and articulated sauropodomorph specimen (M. raathi), the team have been documenting the vertebrate fauna associated with these 230-million-year-old deposits.

The first evidence of Africa’s oldest dinosaur known to science was found during fieldwork in 2017. Two years later, the team returned to excavate more of the specimen and to work on the fossilised remains of an as yet, unnamed theropod dinosaur discovered nearby.

The holotype (NHMZ 2222) consists of a considerable portion of the entire skeleton including skull material. A second specimen (NHMZ 2547), representing a larger individual was discovered in close proximity to the holotype. The research team estimate that Mbiresaurus was around two metres in length and weighed approximately 25 kilograms.

Commenting on the significance of this dinosaur discovery, field team member Christopher Griffin, who graduated in 2020 with a PhD in geosciences from the Virginia Tech College of Science, stated:

“The discovery of Mbiresaurus raathi fills in a critical geographic gap in the fossil record of the oldest dinosaurs and shows the power of hypothesis-driven fieldwork for testing predictions about the ancient past.”

Documenting the Early Dinosauria

South America is regarded by many palaeontologists as the cradle of dinosaur evolution. As far as scientists are able to deduce; based on the fossil record, the dinosaur dynasty began with the evolution of small, agile meat-eaters in South America. However, as landmasses at the time mostly consisted of a single, super-sized continent (Pangaea), it is perfectly feasible to propose that the Dinosauria arose elsewhere and spread across Pangaea.

Dr Griffin added:

“These are Africa’s oldest-known definitive dinosaurs, roughly equivalent in age to the oldest dinosaurs found anywhere in the world. The oldest known dinosaurs, from roughly 230 million years ago, the Carnian Stage of the Late Triassic, are extremely rare and have been recovered from only a few places worldwide, mainly northern Argentina, southern Brazil, and India.”

Sterling Nesbitt, an associate professor at the Department of Geosciences at Virginia Tech and co-author of the scientific paper published this week in the journal “Nature”, explained that basal sauropodomorphs such as Mbiresaurus demonstrate how the early evolutionary history of the Dinosauria is being rewritten with every new discovery.

An Ancient Triassic Biota

The Carnian-aged fossils are providing scientists with evidence of a diverse reptilian biota which co-existed with the earliest dinosaurs. The fieldwork has revealed evidence of cynodonts, aetosaurs (armoured archosaurs more closely related to crocodylians than to the archosaur lineage that led to the birds and the dinosaurs), and rhynchosaurs.

The team also unearthed fossilised remains of an as yet, unnamed theropod dinosaur (herrerasaurid). These archaic animals are similar to the biota associated with contemporaneous deposits found in South America and India.

What’s in a Name?

The genus name Mbiresaurus is from the local Shona language for the name of the district “Mbire” where the fossils were found and from the Greek for lizard. The species name honours palaeontologist Michael Raath for his pioneering work studying vertebrate fossils found in Zimbabwe. The research team conclude that Mbiresaurus was probably bipedal and from an analysis of its small, serrated teeth, it was probably herbivorous although omnivory cannot be ruled out.

A New Theory on the Early Dispersal of the Dinosauria

The researchers have postulated a new theory on dinosaur dispersal. As Africa was once part of the colossal super-continent Pangaea, the distribution and dispersal of the Dinosauria was constrained by climatic conditions across the landmass.

The central portion of Pangaea was dominated by extremely arid environments. These deserts acted as a barrier, the earliest dinosaurs were restricted to southern Pangaea. Only later in their evolutionary history, during a period of climate change resulting in a much wetter climate (Carnian Pluvial Event) did the Dinosauria disperse worldwide.

The research team deliberately targeted Zimbabwe for fieldwork as the northern part of the country would have been located at roughly the same latitude as southern Brazil and India during the Late Triassic.

They conclude that the distribution of the first dinosaurs is correlated with palaeolatitude-linked climatic barriers, and dinosaurian dispersal to the rest of the super-continent was delayed until these barriers were removed. The distribution of the earliest members of the Dinosauria remained restricted by the climatic conditions that prevailed in southern Pangaea.

An Exciting Development for Palaeontology in Zimbabwe

The discovery of a nearly complete specimen of one of the earliest dinosaurs known to science provides a major boost to the Natural History Museum of Zimbabwe and demonstrates that palaeontologists from southern Africa have a major role to play in obtaining evidence about early dinosaur evolution.

Michel Zondo, a curator and fossil preparator at the Natural History Museum of Zimbabwe commented:

“The discovery of the Mbiresaurus is an exciting and special find for Zimbabwe and the entire palaeontological field. The fact that the Mbiresaurus skeleton is almost complete, makes it a perfect reference material for further finds. It is the first sauropodomorph find of its size from Zimbabwe, otherwise most of our sauropodomorph finds from here are usually of medium- to large-sized animals.”

Everything Dinosaur acknowledges the assistance of a media release from Virginia Tech in the compilation of this article.

The scientific paper: “Africa’s oldest dinosaurs reveal early suppression of dinosaur distribution” by Christopher T. Griffin, Brenen M. Wynd, Darlington Munyikwa, Tim J. Broderick, Michel Zondo, Stephen Tolan, Max C. Langer, Sterling J. Nesbitt and Hazel R. Taruvinga published in Nature.

An international team of researchers have uncovered the remains of a huge mosasaur, one that was adapted to hypercarnivory and was an apex predator in the shallow seas of North Africa around 66 million years ago. In addition, the scientists have unearthed remains of other marine vertebrates that shared this giant’s habitat. Acid damage on the bones suggest that these animals were prey and ingested by mosasaurids potentially this new leviathan named Thalassotitan atrox.

Thalassotitan atrox

Late Cretaceous Marine Giant

The remains of this Late Cretaceous marine giant, including a 1.4-metre-long-skull were excavated from the Upper Cretaceous, phosphatic beds of the Ouled Abdoun Basin (northern Morocco). High sea levels created a shallow, tropical sea that teemed with life in North Africa and at the very end of the Cretaceous, approximately 66 million years ago (Maastrichtian faunal stage of the Cretaceous), the 9-metre-long Thalassotitan was the apex marine predator.

A Contemporary of Tyrannosaurus rex

Thalassotitan atrox was a mosasaur, which are extinct members of the largest order of reptiles the Squamata. As such, Thalassotitan was more closely related to snakes and lizards than it was to archosaurs such as crocodilians and the Dinosauria. However, it was a contemporary of Tyrannosaurus rex and like T. rex it was a hypercarnivore, attacking and feeding upon other large vertebrates.

An Apex Predator

The massive jaws and robust, conical teeth suggest that Thalassotitan was an apex predator, filling a similar environmental nice as Orcas (Orcinus orca) and the Great White shark (Carcharodon carcharias) in extant marine ecosystems. The research team, who included Dr Nick Longrich, Senior Lecturer from the Milner Centre for Evolution at the University of Bath and lead author on the study, published in the journal Cretaceous Research, postulate that the acid-etched fossilised bones of other vertebrates found in the same deposit might represent prey ingested by mosasaurids, likely Thalassotitan.

Thalassotitan’s large teeth are often broken and show extensive signs of wear, with some teeth in the jaws worn down to the root. Piscivory (fish-eating) would not have caused this damage, the scientists conclude that this is evidence to support the theory that Thalassotitan was an apex predator.

Dr Longrich commented:

“Thalassotitan was an amazing, terrifying animal. Imagine a Komodo Dragon crossed with a great white shark crossed with a T. rex crossed with a killer whale.”

Thalassotitan’s Potential Victims

The scientists comment that possible remains of Thalassotitan’s victims may have been found. Fossils from the same beds show damage from acid, perhaps evidence of their partial digestion in the stomach of Thalassotitan before the bones and teeth were regurgitated. Fossils with this particular damage include large predatory fish, a sea turtle, a half-metre-long elasmosaurid (plesiosaur) skull, and jaws and skulls of at least three different mosasaur species.

Dr Longrich explained the significance of the acid etched fossil bones and teeth stating:

“It’s circumstantial evidence. We can’t say for certain which species of animal ate all these other mosasaurs. But we have the bones of marine reptiles killed and eaten by a large predator and in the same location, we find Thalassotitan, a species that fits the profile of the killer – it’s a mosasaur specialised to prey on other marine reptiles. That’s probably not a coincidence.”

Mosasaurids Not in Decline Immediately Prior to their Extinction

The discovery of T. atrox along with the other dozen or so mosasaurid genera identified from fossils found in the Ouled Abdoun Basin suggests that mosasaurs continued to diversify and fill new niches until their extinction at the end of the Cretaceous. These marine lizards probably filled ecological niches vacated by the recently extinct ichthyosaurs and they may have out-competed plesiosaurs. The mosasaurs were probably not in decline prior to the end-Cretaceous extinction event.

Co-author of the scientific paper, Professor Nour-Eddine Jalil (Muséum National D’Histoire Naturelle, Paris), added:

“The phosphate fossils of Morocco offer an unparalleled window on the paleobiodiversity at the end of Cretaceous. They tell us how life was rich and diversified just before the end of the ‘dinosaur era’, where animals had to specialise to have a place in their ecosystems. Thalassotitan completes the picture by taking on the role of the megapredator at the top of the food chain.”

A Threat to Other Marine Animals and to Other Thalassotitans

Extensive pathology associated with the fossilised remains of Thalassotitan indicate that these large mosasaurs sustained injuries as a result of combat. Injuries not only sustained through predation but also during intra-specific combat – fights with members of their own species. The skull and jaws show signs of injury. Other mosasaur fossils have similar pathology, but in Thalassotitan these wounds were exceptionally common, suggesting frequent, intense fights over feeding grounds or mates.

Merciless Sea Monster

Although not the largest mosasaurid described to date, specimens from the Tylosaurus and Hainosaurus genera indicate body lengths in excess of twelve metres, Thalassotitan was a formidable predator, and this is emphasised by the binomial scientific name chosen by the research team. The genus name is from the Greek for “sea monster” or “sea titan” and the species name means “cruel or merciless”

Phylogenetic analysis recovers Thalassotitan as a close relative of Prognathodon currii and P. saturator within the Mosasauridae tribe the Prognathodontini. Prognathodon is represented by numerous species all known from the end of the Cretaceous (Campanian to Maastrichtian faunal stages). Prognathodon species are characterised by very robust skulls, with powerful jaws.

More Discoveries Waiting to be Made

Dr Longrich and his colleagues stressed the importance of the prehistoric animal fossils from the Upper Cretaceous of Morocco and hinted that further exciting discoveries are likely to be made.

He stated:

“There’s so much more to be done. Morocco has one of the richest and most diverse marine faunas known from the Cretaceous. We’re just getting started understanding the diversity and the biology of the mosasaurs.”

The extensive, Upper Cretaceous phosphate beds of the Ouled Abdoun Basin have proved palaeontologists with more than a dozen species of mosasaurid to study. Many of these mosasaurs show anatomical adaptations that permitted them to exploit different niches in the ecosystem (niche partitioning). For example, Gavialimimus (G. almaghribensis) had a long, narrow jaw lined with interlocking teeth suggesting that this mosasaur specialised in hunting small fish. In contrast the recently described Pluridens serpentis had disproportionately small eyes, suggesting that this mosasaurid either hunted at depth or within murky water.

To read Everything Dinosaur’s article about P. serpentis: Giant Moroccan Mosasaurid Pluridens serpentis.

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

The scientific paper: “Thalassotitan atrox, a giant predatory mosasaurid (Squamata) from the Upper Maastrichtian Phosphates of Morocco” by Nicholas R. Longrich, Nour-Eddine Jalil, Fatima Khaldoune, Oussama Khadiri Yazami, Xabier Pereda-Suberbiola, and Nathalie Bardet published in Cretaceous Research.

For models and replicas of mosasaurs and other marine reptiles: CollectA Scale Prehistoric Animal Models.