The story of the discovery begins more than six decades ago. In 1963, a British expedition collected an extensive suite of synapsid fossils from Triassic deposits in what is now Tanzania. The material was eventually housed at the Natural History Museum in London, where it remained only partly studied for generations. Because many of the specimens had never been formally described, palaeontologists could not be certain what animals they represented or what they revealed about the ecosystems of the Middle Triassic, a pivotal interval in the history of life on land. Among the unstudied material was an associated skeleton belonging to a large herbivorous dicynodont, alongside a more recently discovered fragmentary skull from the same region. It was these specimens that the new research set out to resolve.

Detailed anatomical work on the skeleton and skull produced a surprise. The fossils did not belong to a local Tanzanian genus, as might have been expected, but to Dinodontosaurus, a dicynodont previously known only from South America. Further comparative study confirmed that the Tanzanian material differed from its South American relatives in ways sufficient to warrant designation as a distinct species, which the team named Dinodontosaurus isiyavamanda. The species name honours the Wamanda people, who inhabit the region of Tanzania where the fossils were found, anchoring the animal’s scientific identity to the landscape and communities connected to its discovery.

The implications of this biogeographic link extend far beyond taxonomy. The Tanzanian rocks that yielded Dinodontosaurus isiyavamanda belong to the same geological deposits that have produced fossils thought by some researchers to represent the oldest possible dinosaurs. For decades, these rocks were believed to share certain fossil genera with contemporaneous-looking sequences in South Africa, which were assigned a Middle Triassic age. If the Tanzanian deposits were equivalent to those South African beds, then any dinosaur-like fossils within them could plausibly rank among the earliest of their kind. The recognition of Dinodontosaurus in both Tanzania and South America now provides a direct correlation between the rock sequences of those two regions, indicating that they accumulated during the same span of geological time.

That correlation matters because of what recent dating work has revealed on the other side of the Atlantic. New radiometric dates from South America suggest that the early dinosaur-bearing rock sequences there are up to 10 million years younger than the comparable sequences in South Africa. Because the Tanzanian beds can now be tied to the South American sequences through their shared Dinodontosaurus faunas, the conclusion follows that the Triassic rocks of Tanzania can no longer be regarded as preserving the oldest potential dinosaur fossils. Instead, the dinosaur candidates from Tanzania are probably no older than those from South America, a shift that forces a reassessment of the timing and geography of dinosaur origins.

Hady George, a PhD student in the School of Earth Sciences at the University of Bristol and lead author of the study, emphasised the significance of the finding. He noted that the discovery marks the first confirmed record of the genus Dinodontosaurus outside South America, and that the finding links the Tanzanian and South American fossil-bearing rocks, showing that they are of equivalent age. According to George, this helps confirm that the oldest dinosaur candidates from Tanzania are probably no older than those from South America, refining the timeline of dinosaur origins. He added that forthcoming research projects will examine the remaining fossil material and explore the biomechanics and ecology of Triassic dicynodonts, work that promises to illuminate how these remarkable herbivores lived and interacted.

The new species also carries a deeply personal story of scientific patience. Nigel Larkin, a palaeontologist and Visiting Research Fellow in the School of Biological Sciences at the University of Reading and a co-author of the paper, first studied the dicynodont skeleton for his master’s thesis at University College London in 1994. Even then, he judged it to represent a species new to science, but the formal write-up languished for nearly 30 years. Larkin reflected that he was glad to have waited, because the international team assembled under George’s leadership was able to develop the story in far greater detail and depth than he could have achieved alone. He observed that techniques have improved vastly over the past three decades, allowing researchers to extract far more information from specimens using methods such as micro-CT scanning than could have been imagined in the 1990s, and that international collaboration has become far easier. As he put it, what is 30 years compared with the age of a prehistoric specimen?

The fossils themselves have spent most of their modern history in museum storage. Dr Mike Day, Curator of Non-Mammalian Tetrapods at the Natural History Museum in London, explained that the Tanzanian specimen has been in the museum’s care for over 60 years, and that its identity has now finally been brought to light. He noted that revealing Dinodontosaurus lived in both South America and eastern Africa offers a glimpse of the planet 240 million years ago, and that the discovery demonstrates how revisiting museum collections can change our understanding of the past just as much as finding new fossils in the field. His remarks underscore a growing theme in modern palaeontology: historic collections, properly curated and re-examined with contemporary methods, remain invaluable records of life on Earth and continue to yield discoveries decades after excavation.

Technically, the study rests on careful craniomandibular osteology—the detailed description of the skull and lower jaw bones—of the new species, which the authors formally diagnose as Dinodontosaurus isiyavamanda sp. nov. within the therapsid group Anomodontia. Dicynodonts are characterised by their turtle-like beaks and, in many species, tusks, and they dominated terrestrial herbivore niches through much of the Permian and Triassic periods. Because different dicynodont genera appear, vanish, and evolve at different points in the Triassic, their presence in a rock unit functions much like a fingerprint in time. Establishing that the Tanzanian Manda Beds contain the same genus as dated South American sequences therefore provides a biostratigraphic anchor that radiometric dating from South America can calibrate, tightening the chronological framework for the entire region and for the critical interval when dinosaurs first appear in the fossil record.

The discovery also opens a substantial research agenda. A large amount of the Tanzanian Dinodontosaurus material remains to be examined, particularly the postcranial skeleton—the bones beyond the skull and jaws—which has yet to receive the same level of anatomical scrutiny. Future work will investigate the anatomy of these remains and compare them directly with South American specimens, testing how the two populations relate and what their differences reveal about evolution across a vast landmass. The researchers also plan to study the biomechanics of Dinodontosaurus and related dicynodonts to better understand how multiple large herbivorous species managed to coexist in Triassic ecosystems, a question with parallels to the dynamics of modern megaherbivore communities. For now, the humble museum drawer in London has delivered a result with outsized consequences: a new species, a transcontinental correlation, and a younger, more precise window onto the dawn of the dinosaurs.

Subject of Research: A new Triassic dicynodont species from Tanzania and its implications for the age of early dinosaur-bearing rocks

Article Title: New species of 240-million-year-old prehistoric animal from Tanzania discovered

Article References: New species of 240-million-year-old prehistoric animal from Tanzania discovered. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Dinodontosaurus isiyavamanda, dicynodonts, Triassic, Tanzania, dinosaur origins, synapsids, Natural History Museum London, University of Bristol, biostratigraphy, radiometric dating, museum collections, Journal of Vertebrate Paleontology

The significance of the work lies in the unusual nature of the calibration target. Most geological dating methods are validated against other laboratory measurements, creating a chain of inference in which small errors can compound. The Vesuvius eruption is different. Because Pliny the Younger recorded his first-hand observations of the disaster in extraordinary detail, scientists know the eruption date from written history rather than from any radiometric measurement. That makes the volcanic minerals erupted in 79 CE a kind of natural standard, a sample whose true age is known independently and against which the laboratory technique can be tested and refined.

Argon-argon dating relies on the slow, steady radioactive decay of potassium-40, a naturally occurring isotope, into argon-40. Because argon is a gas that normally escapes from minerals before they crystallize, any argon-40 trapped inside a volcanic mineral must have accumulated after the rock cooled. Scientists measure the ratio of argon-40 to argon-39, a proxy isotope created in the laboratory by irradiating the sample with neutrons, which converts a stable isotope of potassium, potassium-39, into argon-39. The more argon-40 relative to argon-39, the older the sample. The technique is prized because it spans an enormous range of time, from eruptions within living memory to meteorites that formed at the dawn of the solar system, but its usefulness depends entirely on knowing the decay rate of potassium-40 with precision.

The new study, led by Paul Renne, a Berkeley professor in residence of earth and planetary science and director of the independent Berkeley Geochronology Center, analyzed eight samples of sanidine, a potassium-rich volcanic mineral, from pumice ejected during the 79 CE eruption. When the minerals were analyzed in 2025, the argon-argon method pegged their age at 1,938 years, give or take 13 years. The actual age, derived from the historical record, is 1,946 years. That result corresponds to a precision of 0.7 percent and an accuracy of 0.4 percent, a level of performance that pushes the technique firmly into the historical realm. Accuracy, in this context, refers to whether a measurement reflects the true value, while precision describes how reproducible the measurement is; the Vesuvius benchmark shows the method now excels on both counts.

Getting to that level of performance required solving problems on two fronts: the laboratory and the archive. In the laboratory, the team benefited from better samples, an improved mass spectrometer, and updated neutron irradiation techniques. The samples themselves had an interesting history. In 1998, co-author Andrea Marzoli of the University of Padua collected new, more potassium-rich pumice from Oplontis, another Roman town buried by the same eruption. Crucially, these samples came from the earliest stage of the eruption. Magma chambers beneath stratovolcanoes like Vesuvius tend to stratify, with dense iron- and magnesium-rich magma settling to the bottom while soluble elements such as potassium concentrate near the top. Because the potassium-rich magma erupts first, it ends up at the base of the ash and pumice deposits, and Marzoli’s samples came from exactly those bottom layers. The samples were then shelved and never analyzed for nearly three decades.

Several years ago, graduate students Caroline Hasler, Anthony Fuentes, and Andy Tholt, working under postdoctoral fellow Jack Carter in Renne’s laboratory, proposed retrieving the old samples and attempting to improve on a 1997 analysis of Vesuvius sanidine that had predicted sub-one-percent precision was achievable. The effort dovetailed with a larger project: a Bayesian scheme, published in 2025, to intercalibrate the two most widely used geologic clocks, argon-argon dating and uranium-lead dating, which have historically produced results that do not always agree. The 1997 Vesuvius data had been included in that intercalibration but carried little statistical weight because of its lower precision. The new measurements change that, giving the historical benchmark real authority in reconciling the two methods. Renne also credited co-author Bill Cassata with a major role in developing the analytical strategy and data analysis, describing the success as a combination of better samples, instrumental advantage, and a more concerted effort.

Before any of the laboratory work could be interpreted, however, the team had to settle a long-running dispute among historians. Some scholars have argued that the eruption occurred later in the fall of 79 CE, citing a coin found at Pompeii that they claimed could only have been minted in September of that year. Hasler compared the coin with other contemporary Roman coinage and concluded that it was likely produced before September, supporting the traditional August 24 date derived from Pliny the Younger’s account. Adopting a liberal two-month uncertainty in the eruption timeline turned out to have little effect on calibrating the dating technique itself, but it proved essential for a second major result: a sharper determination of the half-life of potassium-40.

That half-life, the time it takes for half of any given quantity of potassium-40 to decay, is the fundamental constant underlying every argon-argon date ever published. The team now reports a value of 12.044 billion years, with an uncertainty of 0.088 billion years, twice as precise as the previous value derived from nuclear physics experiments. Because the decay constant links the measured argon ratios to elapsed time, improving it tightens every argon-argon age across the entire timescale the method covers, from recent volcanic eruptions to the formation of the planets.

The practical consequences extend well beyond Vesuvius. Renne noted that more accurate and precise argon-argon dating will be invaluable in calibrating radiocarbon dating, the dominant method for attaching dates to organic materials such as wood that are younger than about 55,000 years. It will also help ground-truth uranium-lead dating of billion-year-old rocks from the earliest days of planet Earth. Geologists studying active volcanoes stand to benefit directly as well, since reconstructing the eruptive history of a volcano that still threatens dense urban areas, such as those near Mexico City, Naples, or Yogyakarta in Indonesia, depends on precisely dating its past eruptions. As Renne put it, if you want to assemble the eruptive history of a volcano in relatively recent time, precision and accuracy really count, and the study shows that kind of useful precision can now be achieved into the historical realm.

The improved clock also sharpens scientists’ ability to connect cause and effect in the deep past. Renne pointed out that better precision allows researchers to more confidently infer causal relationships between events in the geologic record, such as a meteor impact structure and a mass extinction. A decade ago, he used argon-argon dating to establish precise dates for a meteor impact, massive volcanic eruptions in India, and the dinosaur extinction, all of which occurred within a few tens of thousands of years around 66 million years ago. Those dates bolstered the idea that the impact triggered intensified volcanism, delivering a one-two punch that wiped out all non-avian dinosaurs. Looking forward, Renne said the team hopes to unify as many geologic dating methods as possible using the same Bayesian mathematics, bringing more raw observations into a single coherent framework. But argon-argon dating, he emphasized, will always remain a standard and an important calibrant. The study also establishes a new benchmark for the method’s ability to date very recent eruptions with decadal accuracy, ensuring that the eruption that destroyed Pompeii will keep contributing to science for centuries to come. The work was funded by the National Science Foundation, the Ann and Gordon Getty Foundation, and the Berkeley Geochronology Center.

Subject of Research: Recalibration of the argon-argon geologic dating method using the historically dated 79 CE Vesuvius eruption

Article Title: The eruption that destroyed Pompeii is helping scientists date Earth's history

Article References: The eruption that destroyed Pompeii is helping scientists date Earth's history. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: argon-argon dating, Vesuvius, Pompeii, geochronology, potassium-40 half-life, sanidine, radiometric dating, Pliny the Younger, Science Advances, UC Berkeley, volcanic eruption dating, uranium-lead calibration