Oldest Dinosaur in North America Discovered

For over a century, paleontologists have grappled with the question of how and when dinosaurs first emerged and began to spread across Earth’s continents, an inquiry marked by limited fossil evidence and the challenges posed by Earth’s shifting tectonic plates. While the traditional narrative maintained that dinosaurs originated in the southern half of the ancient supercontinent Pangea, which was called Gondwana, and then later spread to the northern hemisphere’s Laurasia, a recent discovery has forced scientists to rethink this view.

In a study that could significantly alter paleontological understanding, University of Wisconsin–Madison paleontologists unveiled a surprising and important fossil find that suggests dinosaurs existed in Laurasia much earlier than previously believed. The discovery, made by the UW–Madison team in 2013, challenges traditional theories with evidence that North America—part of Laurasia—hosted dinosaur species as early as 230 million years ago.

The fossilized remains, found in present-day Wyoming, were carefully examined and analyzed for nearly a decade before being formally identified as belonging to a new dinosaur species. This dinosaur, named Ahvaytum bahndooiveche, is now recognized as the oldest known Laurasian dinosaur—an unexpected revelation since previous research focused on older, Gondwanan dinosaurs as the precursors to the northern species. With fossils that date back to around 230 million years ago, Ahvaytum bahndooiveche pushes the timeline for dinosaur diversification in the northern hemisphere much further back than researchers had once estimated.

The researchers’ efforts to properly categorize these fossils highlight the often painstaking work involved in studying ancient creatures. While Ahvaytum represents just a fragmentary specimen—since complete dinosaur fossils from this period are exceedingly rare—careful reconstruction from bones recovered from Wyoming’s Popo Agie Formation enabled scientists to form a solid understanding of its significance. The well-preserved fossils, including parts of the animal’s legs, provided enough evidence to confirm that Ahvaytum bahndooiveche was a very early relative of the sauropods, the herbivorous group known for species like the towering titanosaurs.

In terms of its physical characteristics, Ahvaytum bahndooiveche was relatively small compared to its much larger descendants. Estimated to be around the size of a chicken but with an exceptionally long tail, this early dinosaur’s size contrasts with the iconic image of giants like the sauropods that would follow. The lack of skull material means the exact diet of Ahvaytum remains unclear, although related early dinosaurs were generally omnivorous, feeding on both plants and smaller animals.

The environment in which Ahvaytum bahndooiveche lived may have contributed to its unique position in dinosaur history. Paleontologists believe this dinosaur thrived during a pivotal climatic event—the Carnian Pluvial Episode. Spanning from around 234 to 232 million years ago, the Carnian Pluvial Episode was marked by global temperature shifts and increased rainfall, creating wetter conditions than in previous periods. These conditions likely turned expansive desert regions into more hospitable environments, nurturing early dinosaurs’ growth and diversity. Ahvaytum lived during or shortly after this event, which helped trigger a new phase of dinosaur evolution.

The team of researchers led by Dave Lovelace, along with graduate student Aaron Kufner, performed high-precision radiometric dating on the sedimentary rock layers containing the fossils. The resulting data revealed that Ahvaytum lived about 230 million years ago, in an epoch when Laurasia’s climate was undergoing significant changes. The careful dating process, combined with fossilized footprints discovered in slightly older layers, suggests that dinosaurs or their close relatives were present in the region a few million years earlier than Ahvaytum.

This groundbreaking discovery adds significant new evidence to paleontological debates on dinosaur distribution and evolution. The researchers hope that their findings will inspire a more nuanced understanding of when and how dinosaurs first emerged in the northern hemisphere and their subsequent diversification across the planet.

Beyond the scientific implications, the Ahvaytum bahndooiveche discovery represents a milestone in how scientists collaborate with local Indigenous communities. The name “Ahvaytum bahndooiveche,” meaning “long ago dinosaur” in the Shoshone language, was chosen through a collaborative effort between the research team and the Eastern Shoshone Tribe, whose ancestral land encompasses the area where the fossils were found. Tribal elders and middle school students helped name the species, establishing a unique cultural link that has brought a renewed focus on making paleontological research more inclusive.

Amanda LeClair-Diaz, a member of both the Eastern Shoshone and Northern Arapaho Tribes, was instrumental in facilitating this process. She coordinated with tribal elders and the local school district to ensure that the name reflected cultural significance and that Indigenous voices were incorporated into the scientific process. This initiative marks an important step toward addressing the imbalance that often characterizes research conducted in Indigenous lands, where communities have historically been excluded from decision-making and benefits.

Through this partnership, Dr. Lovelace and his team are not only expanding our understanding of dinosaur history but also engaging in responsible research practices. The scientists involved in the discovery are mindful of their role in respecting and honoring the land and people of the area. LeClair-Diaz emphasized how the collaboration between the researchers and the Shoshone community breaks from the traditional one-sided model of scientific inquiry, moving toward a more reciprocal relationship between scientists and Indigenous peoples.

As Ahvaytum bahndooiveche gains recognition for its remarkable age and cultural significance, it reminds the scientific community that many questions about ancient life remain unanswered. Paleontologists, with their meticulous research and collaboration with local populations, are not only filling in gaps about our planet’s prehistory but are also redefining the way we approach these discoveries.

This discovery thus contributes to the ever-evolving field of paleontology, shedding light on a time in Earth’s history when life was beginning to take its first steps into the vastness of the planet, creating a new world of animals and ecosystems. With continuing advancements in technology, fossil analysis, and interdisciplinary research, it is likely that more revelations will emerge about the mysterious origins and early days of dinosaurs on our planet. But in Ahvaytum bahndooiveche, the early dinosaurs of Laurasia have already shown us how valuable each new fossil find is in piecing together a more complete picture of our Earth’s distant past.

Reference: David Lovelace et al, Rethinking dinosaur origins: oldest known equatorial dinosaur-bearing assemblage (mid-late Carnian Popo Agie FM, WY, USA), Zoological Journal of the Linnean Society (2024). DOI: 10.1093/zoolinnean/zlae153. academic.oup.com/zoolinnean/ar … 03/1/zlae153/7942678