The focus of this pioneering research was on two genera of South American sauropods: the Brazilian Uberabatitan and the Argentine Neuquensaurus. These dinosaurs, approximately the size of modern-day elephants, stood apart from the typical enormous sauropods by their relatively smaller stature—though an adult Uberabatitan could still grow up to an impressive 26 meters in length, making it the largest dinosaur ever discovered in Brazil. This paradox of their size and locomotion capabilities became the central question: Could these titans truly maintain an upright, bipedal posture, and if so, under what conditions?

Researchers led by Julian Silva Júnior, a postdoctoral scholar in engineering biomechanics at São Paulo State University, approached this question by digitally reconstructing the femur bones of seven sauropod specimens from various evolutionary lineages and sizes. These digital models were based on fossilized bones housed in prominent natural history museums worldwide. By applying a rigorous engineering tool called finite element analysis (FEA), the team simulated forces acting on the femurs—both external forces such as gravity and internal forces exerted by musculature—to estimate the mechanical stress during bipedal standing.

Finite element analysis, a methodology widely employed in engineering fields for designing resilient bridges and airplanes, breaks complex structures into smaller elements that can be individually analyzed. Through this computational framework, the researchers virtually subjected the dinosaur femurs to the weight and postural demands that standing on two legs would require. Two distinct scenarios were modeled: an extrinsic case focusing on gravitational forces, and an intrinsic case examining muscle forces acting on the femur. The combined data illuminated the biomechanical feasibility of sustained bipedal posture in these prehistoric giants.

The outcomes were revelatory. Among the specimens analyzed, the juvenile Uberabatitan ribeiroi and Neuquensaurus australis—the two South American genera examined—exhibited femoral structures that endured notably less stress compared to their more massive counterparts. These dinosaurs had developed more robust femurs capable of better dissipating the mechanical loads arising from their body weight during bipedal standing. This contrasted with larger sauropods, which, despite possessing enormous muscles and femurs, appeared less adapted to prolonged upright stances due to excessive femoral stress.

This biomechanical insight lends compelling support to the hypothesis that younger, smaller individuals within these species were the primary practitioners of bipedal behavior. Adult Uberabatitans, by contrast, may have found such postures uncomfortable or challenging to maintain, restricting their bipedal activity to shorter bouts or specific functional contexts. This allometric constraint highlights how growth and ontogeny influenced locomotive abilities in these dinosaurs, demonstrating a nuanced evolutionary interplay between size, skeletal strength, and behavior.

Beyond pure biomechanics, the study suggests multiple ecological and reproductive advantages conferred by this bipedality. Raising themselves on hind legs would have granted these sauropods access to foliage and leaves situated at extreme heights—resources unavailable to purely quadrupedal herbivores. Furthermore, adopting an upright posture could have served as a defensive display, magnifying their intimidating presence to deter predators. Mating rituals may also have benefited, allowing males to mount and signal dominance or attractiveness through postural exhibition, although these behavioral aspects warrant further fossil and biomechanical correlation.

However, the researchers caution that their models did not incorporate all biological factors present in living organisms. For instance, cartilage, which cushions and distributes load across joints, was not included in the simulations due to its absence in the available fossil specimens. The role of the tail, potentially used as a prop in a tripodal stance for enhanced stability, was also not directly modeled. These omissions suggest that the actual biomechanical stresses experienced by these dinosaurs could have been mitigated somewhat by soft tissue dynamics, making sustained bipedality even more plausible.

Nevertheless, the strength of the study lies in its comparative approach. By examining diverse sauropod lineages and consistently applying the computational analysis, the authors provide a robust framework to infer behavioral and anatomical evolution millions of years ago. This method reveals how evolutionary pressures shaped bone robustness and locomotive strategies differently across species and growth stages and underscores the importance of biomechanical modeling in paleobiological research.

This research was supported by the São Paulo Research Foundation (FAPESP) and conducted through an international collaboration among Brazilian, German, and Argentine institutions. It exemplifies the integration of paleontology with advanced engineering techniques to push the boundaries of what we know about extinct megafauna. Such interdisciplinary approaches are vital for reconstructing the life histories of creatures that vanished long before humans walked the Earth.

Ultimately, the ability of these sauropods to rise on their hind legs redefines our understanding of dinosaur ecology during the Late Cretaceous period. It challenges the traditional view of sauropods as exclusively quadrupedal behemoths and opens new avenues for exploring their behavioral repertoire, feeding ecology, and evolutionary adaptations. This study not only enriches the fossil narrative but also demonstrates how modern technology breathes new life into ancient bones, transforming static remnants into dynamic stories of survival and innovation.

Subject of Research:

Biomechanics and postural analysis of sauropod dinosaurs through computational modeling.

Article Title:

Standing giants: a digital biomechanical model for bipedal postures in sauropod dinosaurs

News Publication Date:

August 1, 2025

Web References:

• Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP): www.fapesp.br/en
• FAPESP News Agency: www.agencia.fapesp.br/en

References:

• Published article in the journal Palaeontology, DOI: 10.1111/pala.70019

Image Credits:

Guilherme Gehr

Research recently published in Nature reveals that Spicomellus afer possessed a remarkable tail weapon that predates any other known ankylosaur by over 30 million years. Even more astonishingly, this species sported an elaborate bony collar wrapped with spikes extending up to a meter in length from either side of its neck. Such armor had never before been observed in any extinct or extant vertebrate, making Spicomellus a truly exceptional subject for understanding dinosaurian defense and display mechanisms.

Previously regarded primarily through a single rib bone upon its first description in 2021, the discovery of additional fossilized remains has opened a window into this creature’s extraordinary morphology. Its ribs were enveloped and fused with formidable spikes, an evolutionary novelty that nobody could have anticipated. These osteological structures were not mere superficial adornments; they were integral components of the skeleton, manifesting in an unprecedented fusion that highlighted the complex integration of defensive features in early ankylosaurs.

The neck collar of Spicomellus was encircled by a ring of elongated spikes, measuring up to 87 centimeters from base to tip. Researchers propose that these neck spikes formed a defensive barrier as well as a visual display apparatus, potentially crucial for intraspecific communication related to mating rituals or hierarchical dominance. This array of spiked ornamentation situates Spicomellus apart from later ankylosaurs, whose armor typically served more conservative defensive functions instead of extravagant display.

Prof. Susannah Maidment of the Natural History Museum in London and the University of Birmingham, who co-led the study, emphasized the evolutionary implications of this find. According to Prof. Maidment, the complexity of Spicomellus’ armor contradicts prior notions that ankylosaurs developed elaborate protective features only after the Jurassic. Instead, the evidence compels a reconsideration of the timeline and pathways through which armor evolved within this group, underscoring Africa’s critical role in dinosaur evolutionary history.

The morphology of Spicomellus is so unprecedented that it defies comparison with any known animal, living or extinct. Its body was adorned with diverse plates and spikes, including massive, upward-projecting spikes over the hips and a medley of blade-like, paired long spikes along the shoulders, which may have functioned both for intimidation and protection. This morphological complexity illustrates an evolutionary experimentation with integumentary structures distinct from those of later ankylosaurs.

Despite its status as the oldest known ankylosaur, the peculiar armor of Spicomellus was not inherited by subsequent generations of the clade. Later ankylosaurs replaced such extravagant adaptations with simpler, more functionally defensive armor, likely in response to shifting ecological pressures. This suggests that as predatory threats evolved—especially in the Cretaceous, with the rise of larger carnivorous dinosaurs, crocodyliforms, and other formidable predators—the selective regime favored practical defense over ostentatious displays.

Intriguingly, the fossilized vertebrae from the tail of Spicomellus display early evidence of fused tail bones forming a rigid “handle,” a characteristic anatomical feature requisite for wielding a club-like weapon. This “handle” strongly implies the presence of a tail club, a sophisticated defensive instrument previously known only from ankylosaurs of the much later Cretaceous period, appearing some 30 million years after Spicomellus. This temporal disparity pushes back the origins of ankylosaur tail weaponry by tens of millions of years, fundamentally altering evolutionary timelines.

The coexistence of the elaborate spiked collar and a tail club analog in Spicomellus reveals that many hallmark ankylosaur adaptations were already established in the Middle Jurassic. Such a combination of features probably conferred dual advantages: active defense against predators through tail strikes and passive deterrence or display via armor arrays. This multifaceted defense strategy reflects a sophisticated level of evolutionary innovation that underscores the ecological challenges faced by early ankylosaurs.

These groundbreaking findings also underscore the crucial importance of Africa’s vertebrate fossil record—a region historically underrepresented in dinosaur paleontology. The Moroccan deposits yielding Spicomellus expose a hidden chapter about dinosaur distribution and diversification in Gondwana during the Jurassic, offering rich insights into biogeographic and evolutionary processes. This discovery highlights not only the potential for new finds but also the imperative role of interdisciplinary and international collaboration in paleontology.

One cannot overlook the broader scientific and cultural impact of such discoveries. As researchers decode the baffling anatomical features of Spicomellus, this enigmatic creature captivates the public imagination, fueling interest in evolutionary biology and deep-time ecosystems. By revealing how dramatically real dinosaur forms could deviate from traditional popular depictions, it challenges assumptions and invites ongoing inquiry into fossil diversity and the evolution of vertebrate armor.

In collaboration with Moroccan institutions, the preparation and study of the Spicomellus afer fossils were conducted with cutting-edge scientific tools at the Department of Geology of the Dhar El Mahraz Faculty of Sciences in Fez. The support from the University of Birmingham’s Research England International Strategy and Partnership Fund highlights the vital role of strategic investment in scientific infrastructure for fossil preservation and analysis, allowing rare specimens to be cataloged with precision and studied over extended periods.

Professor Driss Ouarhache, leader of the Moroccan research team, noted that these findings represent a significant breakthrough for Moroccan science, illustrating the untapped paleontological wealth of the region. The continuous exploration of these fossil-rich sediments promises to yield further discoveries that could illuminate not only ankylosaur evolution but also broader patterns of Middle Jurassic terrestrial ecosystems across Gondwana.

This transformative study, titled “Extreme armour in the world’s oldest ankylosaur,” fundamentally reshapes our understanding of early dinosaur armor evolution. It suggests a previously unrecognized diversity of morphological strategies incorporated into ankylosaur biology at an unexpectedly early stage. The Spicomellus fossils serve both as a testament to evolutionary innovation and as a catalyst for ongoing research into the origins and trajectories of dinosaur defense mechanisms, emphasizing the dynamic interplay between anatomy, environment, and survival strategies in deep time.

Subject of Research: Ankylosaur dinosaur armor evolution and paleobiology
Article Title: Extreme armour in the world’s oldest ankylosaur
News Publication Date: 27-Aug-2025
Web References: https://doi.org/10.1038/s41586-025-09453-6
Image Credits: Matthew Dempsey
Keywords: Dinosaurs, Dinosaur fossils, Prehistoric archaeology