# The body mass-maximum speed relationship and the athletic capability of giant proboscideans and sauropods

## TL;DR

This paper estimates the maximum speeds of large extinct animals like proboscideans and sauropods, finding that their immense size likely limited their movement to slow, steady gaits.

## Contribution

The study introduces a method to estimate maximum speeds of large fossil animals using body mass-speed relationships and applies it to proboscideans and sauropods.

## Key findings

- Larger proboscideans had calculated maximum speeds overlapping with those of living proboscideans.
- Maximum speeds for large sauropods were estimated at 10 km/h or lower due to their immense size and structure.
- The findings align with fossil trackway evidence suggesting sauropods moved in a single, steady gait.

## Abstract

Estimating the maximum speed capability (athletic capability) of very large fossil animals is challenging. While large animals have limbs favoring longer stride lengths and higher speeds, their body mass imposes limitations on bones, joints, available forces, and physiology, resulting in the fastest animals not being the largest. Here we use the well-known relationship between body mass and potential maximum speed to calculate upper limits for the athletic capability of fossil giant proboscideans and sauropods. First, we assess the reliability of two different fits to maximum speed data for mammals. Subsequently, we analyze masses and speeds of live proboscideans, finding they consistently move below the lower bounds predicted by model fits. Finally, we propose maximum speed for representative fossil proboscideans and sauropods. Although calculated maximum speeds for larger proboscideans are comparatively lower, there is substantial overlap with those observed in live proboscideans. For the largest sauropods approaching or exceeding 50 Tn our calculated maximum speeds are around 10 km/h or lower. These findings suggest that immense body size and graviportal structure of sauropods were key factors likely restricting their locomotion to a single, steady gait, consistent with fossil trackway evidence.

The online version contains supplementary material available at 10.1038/s41598-025-32536-3.