A Glimpse into the Past:Unraveling 66 Million Years of Mammalian Diversity.

**The Importance of Historical Context in Understanding the Present**:

Alex Shupinski is shown in Bighorn Basin in Wyoming, where she collected Cenozoic era fossils.

To truly comprehend the present, delving into the past offers invaluable insights. Groundbreaking research from the University of Nebraska–Lincoln has shed light on the fossil record dating back 66 million years, tracking changes in mammalian ecosystems and species diversity across North America. This extensive study, led by Alex Shupinski, who recently earned her doctorate, alongside co-author Kate Lyons, an associate professor in the School of Biological Sciences, provides a comprehensive view of how species diversity evolved throughout the first 65 million years of the Cenozoic era, up until the advent of humans.

**The Influence of Climate and Environmental Shifts**:

The study not only reveals patterns in species diversity but also explores how climate and other environmental factors, such as shifting landscapes, have influenced animal life on the continent. Shupinski’s work, conducted in Wyoming’s Bighorn Basin where she collected Cenozoic era fossils, offers a detailed look at the relationship between mammals and their changing environments.

Published in the *Proceedings of the Royal Society B*, the findings highlight how mammals bounced back after the last mass extinction event that wiped out non-avian dinosaurs. Shupinski explained the significance of these environmental changes: “Beginning 66 million years ago, we transition from a completely sub-tropical environment across North America to grasslands, then to a frozen savanna, and finally, the Ice Age. Our study shows how species evolved through these diverse ecological, environmental, and climatic shifts, allowing us to make comparisons across different events and spatial scales.”

**A Deep Dive into the Cenozoic Era's Fossil Record**:

The researchers meticulously divided the fossil record of the Cenozoic era into million-year segments, applying three indices of functional diversity. This approach quantifies changes in community structures using mammalian traits, providing insights into mammalian communities at both local and continental scales.

A remarkable discovery was that, for the majority of the Cenozoic era, local and continental measures of functional diversity varied significantly. However, in the first 10 million years following the extinction of non-avian dinosaurs, all measures of functional diversity—both locally and continentally—showed a simultaneous increase.

Shupinski found this convergence particularly intriguing: “It was fascinating to observe that, for most of the Cenozoic, functional diversity was decoupled across time and spatial scales, except during this one period. For 10 million years, all the measures changed in the same direction. Then, around 56 million years ago, a significant wave of mammalian immigration from other continents triggered a divergence in functional diversity.”

**A Close Examination of Ancient Mammals**:

In her research, Kate Lyons, an associate professor, examines a *Coryphodon radians* specimen, a pantodont dating back about 12 million years after the extinction of non-avian dinosaurs. This fossil, housed at the Smithsonian Institution, provides a window into the evolutionary shifts that occurred in mammalian communities following the dinosaurs' demise.

Lyons explains the complexity of these changes: “Communities are evolving at different times, at varying rates, and in different directions. Locally, we might observe an increase in the diversity of roles within communities, while on a continental scale, this diversity could be decreasing.” This observation underscores the intricate nature of species adaptation and diversification over millions of years.

**Environmental Shifts and Their Impact on Mammalian Evolution**:

Lyons attributes some of the shifts in mammalian species to environmental changes, such as periods of cooling and warming or the transition from heavily forested areas to grasslands. However, she notes that these environmental changes, while significant, did not reach the level of disruption caused by the mass extinction of dinosaurs. This distinction is crucial in understanding the resilience and adaptability of mammalian species in the face of environmental stressors.

Lyons further highlights the potential implications of these findings for modern conservation efforts: “This research could help identify areas or communities that are under particular stress. We may be entering a sixth mass extinction event, and if that’s the case, we might expect to see certain communities responding similarly to those after the extinction of non-avian dinosaurs.”

**Applying Historical Insights to Modern Conservation**:

The field of conservation paleobiology benefits greatly from tracking long-term changes in ecosystems, as it helps both scientists and the public grasp the ongoing biodiversity crises. This study offers a comprehensive analysis of the mammalian age and provides a glimpse into possible future scenarios.

Shupinski emphasizes the practical applications of this research: “If we observe similar responses in the functional diversity of modern community structures, it could serve as a valuable conservation tool. We could identify communities that are experiencing the most significant disturbances and are at the highest risk of losing their ecological services and functions.”

**Collaborative Research Efforts**:

This study is a collaborative effort, with contributions from Peter Wagner, a professor of Earth and Atmospheric Sciences at Nebraska, and Felisa Smith from the University of New Mexico, Albuquerque. Their combined expertise has yielded a deeper understanding of how past environmental changes have shaped the evolution of mammalian communities and what this might mean for the future of biodiversity on our planet.