Study finds giant dinosaurs evolved larger forefeet

A research team including Graduate Student Kohei Yamaguchi and Associate Professor Mugino Kubo at the Graduate School of Frontier Sciences, the University of Tokyo, together with Assistant Professor Tai Kubo at the Center for Data Science, Waseda University, analyzed fossil footprints of sauropods, the largest land animals in Earth's history, and clarified evolutionary changes over time. It was revealed that while the soles of forefeet became more circular from the Jurassic to the Cretaceous period to support weight, there were no noticeable changes in the hindfeet. Progress in research on the ecology and evolution of extinct animals is expected. The results were published in Paleobiology on June 15.

Sauropods were the largest land animals in Earth's history, with the largest species estimated to weigh 75 tons, an order of magnitude larger in body weight than large species of other taxonomic groups. For this reason, elucidating how these dinosaurs walked is considered important when considering constraints that giant body size places on locomotion.

To elucidate the evolution of foot morphology closely related to how sauropods walked, the research team focused on sauropod fossil footprints unearthed worldwide from the Early Jurassic to the Late Cretaceous period (spanning approximately 130 million years). Because fossil footprints preserve the actual locomotion of the animals that left them, they serve as direct evidence for estimating foot morphology and walking patterns of extinct animals.

Using sketches of fossil footprints collected from literature, they applied elliptic Fourier analysis for the first time. This technique extracts and describes contours of two-dimensional images enclosed by closed curves, allowing quantitative comparison of object outlines.

In addition, by analyzing a dataset consisting of measurements from 690 trackways collected from papers describing fossil footprints, they verified temporal changes in sauropod foot morphology.

As a result, it was found that the morphology of forefoot soles approached a circle more suitable for weight support toward the Cretaceous period, and larger individuals approached a circle even more closely. In contrast, no temporal change was observed in hindfoot morphology. Although the relative size of forefeet compared to hindfeet also increased over time, it was revealed that even with enlargement, the size increase in forefeet was not as large as that of hindfeet. Applying this method to other dinosaur groups is expected to lead to the elucidation of dinosaur ecology and evolution.

Yamaguchi said, "Quantitative comparison of dinosaur footprint morphology was itself a first attempt, so we had to proceed by trial and error from selecting methods to conducting analyses. In addition, comprehensive literature surveys took time. Because descriptions were written in various languages and methods differed among researchers, organizing data was also difficult. Moving forward, through large-scale trackway data and morphological analyses, I hope to contribute to estimating trackmakers, clarifying the evolution of walking styles, and understanding the effects of body size on locomotion."

Journal Information
Publication: Paleobiology
Title: Temporal changes in sauropodomorph foot morphology and graviportal adaptations under gigantism inferred from trackways
DOI: 10.1017/pab.2026.10098