The new study, published in the open-access journal PLOS One on September 9, 2026, was conducted by David Varricchio of Montana State University and Heath Caldwell of North Carolina State University. Together, they examined a remarkably complete growth series of pelvic and hindlimb fossils drawn from animals that lived roughly 75 to 78 million years ago, during the late Cretaceous period, when the region they inhabited was a lush coastal plain bordering an inland seaway.

Troodontids were among the most distinctive dinosaurs of their era: small to medium-sized predators with long, slender legs, unusually large brains and eyes for reptiles, and bodies covered in feathers. Their closest relatives include the dromaeosaurids—the famed “raptors”—and their lineage sits tantalizingly close to the origin of birds. Yet despite their scientific importance, troodontids have long remained shadowy figures in the North American fossil record, known primarily from isolated teeth, fragmentary bones, and the occasional egg clutch.

That scarcity of material has created a persistent problem. The genus Troodon was established in 1856 on the basis of a single tooth, which has served as the type specimen—the anatomical benchmark against which all other members of the species must be judged—ever since. Teeth are notoriously poor anchors for species-level classification among closely related theropod dinosaurs, whose dentition can be remarkably similar across different genera. As a result, the very validity of the Troodon genus has been questioned repeatedly over the decades, with some researchers arguing the name should be abandoned entirely.

The Montana fossils change that calculus dramatically. The material analyzed by Varricchio and Caldwell comes from the upper member of the Two Medicine Formation, a geologically rich sedimentary sequence that has previously yielded eggs, nests, embryos, and adult skeletal remains attributed to a single troodontid population. Because the assemblage spans the full ontogenetic range—from embryonic individuals still inside their eggs to skeletally mature adults—the researchers could, for the first time, reconstruct how the species’ hip and leg bones changed shape, texture, and proportion throughout an individual’s life.

Among the most informative patterns documented in the study is a systematic shift in limb proportions. The ratio of femur length to tibia length, the researchers found, was consistently higher in adult specimens than in juveniles. In practical terms, this means that as these animals matured, their lower leg bones grew proportionally longer relative to their thigh bones—a developmental trajectory familiar from many fast-running animals, both extinct and modern. Such a shift suggests that young troodontids may have moved differently from adults, potentially relying on different locomotor strategies while their bodies were still developing.

Equally significant was the observation that many of these developmental changes occurred at consistent growth stages across multiple individuals. That consistency implies a strong genetic or intrinsic developmental program, relatively insulated from environmental noise. In paleontology, where distinguishing true species differences from individual or environmental variation is a constant challenge, this kind of reproducibility is gold: it demonstrates that the observed anatomical features are stable, species-level characteristics rather than artifacts of habitat, diet, or climate fluctuation.

The study also confirmed two other biological insights. First, adults of the species varied distinctly in body size, hinting at a level of individual variation—or perhaps sexual dimorphism—that future researchers will need to account for when assessing fragmentary troodontid remains. Second, in line with earlier research, the analysis suggests that foot injuries and pathologies may have been remarkably common in the species. Whether these stemmed from high-activity lifestyles, aggressive behavior, nesting-related stress, or something else entirely remains an open question, but the recurrence of foot problems across individuals adds an intriguing dimension to reconstructions of troodontid daily life.

Beyond the biological findings, the study carries a significant taxonomic proposal. Varricchio and Caldwell argue that a specific subset of the remains—a collection of pelvic and hindlimb fossils representing both juveniles and adults—should be formally designated as the type specimen of T. formosus, displacing the original single tooth that has anchored the species since the nineteenth century. Such a move would give the species a robust, diagnosable skeletal foundation and could go a long way toward securing the validity of the Troodon genus itself. However, the authors caution that this reassignment is not yet settled. The proposal depends on a decision currently pending before the International Commission on Zoological Nomenclature, the body that adjudicates disputes over scientific names. Until that ruling is issued, the tooth retains its official status.

For paleontologists who study small theropod dinosaurs, the implications extend well beyond taxonomy. Growth series of this quality are vanishingly rare in the fossil record, particularly for animals as small and lightly built as troodontids, whose delicate bones are less likely to survive fossilization than those of their larger cousins. Having a well-sampled embryonic-to-adult sequence of pelvic and hindlimb anatomy provides a reference framework that other researchers can use to identify isolated bones, assess growth stage in new discoveries, and test hypotheses about growth rates, locomotion, and life history across the broader troodontid family.

Future work is already being contemplated. The authors note that further research could illuminate how Troodon walked and ran—questions that depend critically on precisely the kind of limb-proportion and joint-architecture data this study provides. Understanding the biomechanics of an animal with proportionally long lower legs and a bird-like skeletal plan could offer fresh insights into the evolutionary transition toward the avian body plan and the range of ecological roles small feathered predators occupied in late Cretaceous ecosystems.

The research also underscores the continuing scientific value of long-term, careful fieldwork in well-studied formations like the Two Medicine. The fossils analyzed in this study were not the product of a single spectacular discovery but of accumulated collecting across decades, in an area where the same troodontid population left behind eggs, embryos, juveniles, and adults in close geological proximity. It is precisely this kind of cumulative evidence that allows paleontologists to move beyond naming new species and toward reconstructing the lives of animals that have been extinct for 75 million years.

As the authors themselves put it, the analysis of these bones “provided an unprecedented opportunity for understanding the biology of a historically enigmatic group of animals and will serve as a valuable resource for paleontologists for years to come.” Whether or not the International Commission approves the proposed type-specimen change, the study stands as a landmark in the rehabilitation of a dinosaur that science has known longest by its teeth—and is only now beginning to know by its bones.

The crux of this pivotal research lies in its intriguing discovery of collagen remnants preserved in an Edmontosaurus hip bone. This duck-billed dinosaur, which roamed the Earth during the Late Cretaceous period, has provided a unique opportunity for researchers to examine fossil integrity at a molecular level. The 22-kilogram sacrum of the Edmontosaurus, excavated from the Upper Cretaceous strata of South Dakota’s Hell Creek Formation, is an extraordinary specimen characterized by its exceptional preservation state. This context is critical, as it allows for rigorous analytical techniques to be employed without concern of contamination or degradation typically associated with less well-preserved fossils.

One of the central innovations of this study involved state-of-the-art mass spectrometry paired with an array of complementary analysis techniques. The researchers implemented protein sequencing protocols to meticulously identify and characterize the bone collagen within the fossil. This multifaceted approach facilitated the unveiling of preserved organic materials that many had deemed impossible to locate within fossils of such antiquity. The implications of these findings challenge the previously accepted paradigm of fossilization and raise a myriad of questions regarding the preservation mechanisms that allow for collagen, a protein integral to bone structure, to remain intact over geologic time.

The research, published in the prestigious journal Analytical Chemistry, shows unequivocally that organic biomolecules such as collagen can survive fossilization processes, thus refuting the long-standing hypothesis that organic findings in fossils stem solely from post-exhumation contamination. Significant findings from the study suggest that scientists must recalibrate their understanding of fossil integrity. According to Professor Steve Taylor, the chair of the Mass Spectrometry Research Group at the University of Liverpool, the research extends beyond theoretical implications. It invites the scientific community to revisit archival materials, specifically cross-polarized light microscopy images collected over the past century.

These historical images may reveal intact remnants of bone collagen within various fossil specimens, fueling further enzymatic analyses. This revitalization of previously collected data points to the notion that many fossils could harbor hidden organic treasures, paving the way for future research avenues. This insight serves as a reminder that previously dormant lines of inquiry may benefit from a fresh analytical lens, potentially unlocking connections among dinosaur species that remain unexamined.

Compounding the significance of this study is the collaborative nature of the research. A diverse array of experts collaborated, transcending traditional disciplinary boundaries. For instance, researchers from UCLA contributed their expertise through the application of tandem mass spectrometry, allowing for the accurate identification and quantification of hydroxyproline, an amino acid that specifically indicates the presence of collagen in osteological materials. This cross-institutional collaboration highlights the growing trend within the scientific community to leverage diverse skill sets for cohesive research efforts.

Furthermore, the University of Liverpool’s Materials Innovation Factory provided critical analytical support, ensuring the robustness of the data collected. Specialists from the Centre for Proteome Research at the same university further validated the findings through extensive identification of collagen fragments. This consortium of intellectual talent not only emphasizes the interdisciplinary nature of modern scientific inquiry but also illustrates how pooled knowledge can propel research into uncharted territories.

The consequences of these revelations are substantial. By demonstrating the survival of organic molecules like collagen, this research opens a veritable treasure chest of possibilities in understanding the evolutionary biology of ancient species. The biochemical preservation of fossils provides tangible links to the past, potentially reshaping narratives around species development and the ecological dynamics of ancient ecosystems. This newfound understanding can lead researchers to refine models concerning the biology and behavior of dinosaurs, offering deeper insight into the evolutionary pathways that shaped life on Earth millions of years ago.

Moreover, unraveling the mysteries surrounding how proteins have persisted over such extended periods introduces an unprecedented level of curiosity regarding biochemical pathways and structural resilience. The enigma of protein longevity invites rigorous investigation into the environmental contexts that support organic retention in fossilized remains. This realization compels paleobiologists and chemists to expand their frameworks of fossilization and consider various factors that may contribute to the preservation or degradation of biological materials.

Ultimately, the study presents a paradigm shift within paleontology. It invites the scientific community to reevaluate the criteria by which fossils are classified and studied. The inclusion of organic material within the analysis of fossils requires a more nuanced understanding of fossil biology and the geochemical environments affecting such remnants. The exploration of these concepts not only enhances our grasp of ancient life but also impacts modern biological and chemical research, indicating that past journeys can illuminate future pathways.

This remarkable intersection of paleontology and biochemistry serves to reignite public fascination with the ancient past. The prospect of reexamining storied fossils under a new lens invites intrigue among both scientists and enthusiasts alike. As more discoveries surface, the enduring legacy of fossils as windows into life on Earth will continue to enrich our understanding of both history and science. Thus, the findings surrounding the Edmontosaurus fossil herald a new chapter not just in paleontology but in the broader quest to forge connections across the annals of time.

Through this revitalized lens, scientists are armed with tools that can potentially reshape our understanding of vertebrate evolution and the historical framework of biodiversity on Earth. This study serves as a blueprint for future inquiries into the organic facets of fossils. Eager researchers will undoubtedly seek out, analyze, and dissect fossil specimens, shedding light on the captivating tales encapsulated within their very structure.

The thrilling yet complex interplay between fossil chemistry and biology invites further exploration and enriches the narrative tapestry of life’s history on Earth, suggesting that with each layer of the past we peel back, we may gain insight into the undeniable interconnectedness of all life forms through time.

Subject of Research: Preservation of organic molecules in Mesozoic fossils
Article Title: Evidence for Endogenous Collagen in Edmontosaurus Fossil Bone
News Publication Date: 17-Jan-2025
Web References: Analytical Chemistry DOI
References: Publication in Analytical Chemistry
Image Credits: Credit: University of Liverpool

Keywords

1. Dinosaur fossils
2. Collagen
3. Mass spectrometry
4. Dinosaurs
5. Fossilization
6. Biochemical processes
7. Amino acid sequences
8. Chemical analysis
9. Image analysis