Over 200 million years ago, the ancestors of crocodiles were radically different from those of today. Instead of evolving in water, these reptiles swiftly roamed the dry land.
The fossil remains of an animal, named
Galahadosuchus jonesi, reveal a light body and elongated limbs, perfectly adapted for rapid running. Unlike its modern cousins, it likely moved with agility to catch prey in the arid landscapes of the Triassic, resembling more of a sprinting lizard than an aquatic predator.
Skeletal reconstruction of Galahadosuchus jonesi, with orthographic views.
Credit: Matt Dempsey
During this period, the Gloucester region in England was a plateau surrounded by hot, dry plains. Dense vegetation housed a diversity of small creatures, such as reptiles, amphibians, and early mammals, which
Galahadosuchus jonesi probably hunted by exploiting its speed.
The bones were found in rock fissures on both sides of the Bristol Channel. These natural cavities acted as traps, where animals that died on the surface were washed in and gradually covered with sediment, preserving their skeletons for hundreds of millions of years.
Scientists compared these fossils to those of a related species,
Terrestrisuchus, which also belongs to the crocodylomorph group. After a thorough anatomical study, they identified thirteen major differences, confirming it was indeed a distinct species.
Its name blends an allusion to the knight Galahad, for its upright posture, and a tribute to David Rhys Jones, a physics teacher who left a mark on the lead author of the study during his school years.
Block containing the holotype specimen of Galahadosuchus jonesi.
Credit: Bodenham The evolution of limbs in reptiles
Reptile limbs have undergone major transformations throughout evolution, influenced by their lifestyle. In modern crocodiles, the short, powerful limbs are adapted for swimming and walking near water, whereas their ancestors like
Galahadosuchus jonesi possessed long, slender limbs for running on land.
This difference is explained by environmental pressures. In open terrestrial habitats, speed is advantageous for hunting or escaping predators, favoring the development of elongated limbs. Conversely, aquatic life requires more compact limbs for efficient propulsion in water.
Comparative anatomical studies show how bones, muscles, and joints have evolved to meet these needs. For example, the structure of the pelvis and leg bones in terrestrial crocodiles indicates a more upright posture and an ability to support the body's weight during running.