Ancient Crocodile Ancestor Walked on Two Legs as Adult

Ancient Crocodile Relative Walked on Two Legs as an Adult

A newly discovered fossil reveals a fascinating detail about an ancient relative of crocodiles that lived over 200 million years ago. This reptile, surprisingly, changed its gait as it matured – walking on four legs when young, but transitioning to a bipedal stance in adulthood.

Meet Sonselasuchus cedrus

The species, named Sonselasuchus cedrus, belongs to the shuvosaurid group, ancient reptiles that thrived during the Late Triassic period, approximately 225–201 million years ago.

A Striking Resemblance to Dinosaurs

Researchers found that Sonselasuchus bore a remarkable resemblance to ornithomimid dinosaurs – the fast-running dinosaurs often nicknamed “ostrich dinosaurs.” Interestingly, this similarity isn’t due to a close evolutionary relationship, but rather a case of convergent evolution, where similar body forms develop in similar environments.

The findings were published in the Journal of Vertebrate Paleontology by a team from the University of Washington Department of Biology and Burke Museum.

The Shift in Walking Style

One of the most compelling discoveries is the change in Sonselasuchus’ walking style throughout its life. Analysis of the proportions of its leg bones suggests a transformation in body shape as it grew.

Lead researcher Elliott Armour Smith explained that the change occurred due to differing growth patterns between the forelimbs and hindlimbs.

“By analyzing the proportions of skeletons from different animals, we found that the two-legged posture was likely a result of different growth patterns,” Smith stated.

He added that when young, the front and back legs of the animal were relatively balanced. “We hypothesize that Sonselasuchus had more balanced fore and hind limbs when young, but its hind limbs grew longer and stronger as it matured.”

its walking style also changed. “Essentially, we think this creature started life walking on four legs… then switched to walking on two legs as they grew up.”

This shift is a rare finding in the fossil record of ancient reptiles.

A Rich Fossil Site

The Sonselasuchus fossils were unearthed in Petrified Forest National Park, Arizona, USA. In 2014, researchers discovered approximately 950 fossils of this species at the location, part of a large-scale excavation project spanning over a decade.

Did you know?

Petrified wood, also found in abundance in Indonesia’s Banten province and Mount Halimun Salak National Park, provides insights into ancient forests and their environments. The process of petrification involves mineral-rich waters replacing organic material, preserving the cellular structure of the wood.

FAQ

What is Sonselasuchus cedrus?

It’s an ancient relative of crocodiles that lived during the Late Triassic period and exhibited a unique change in walking style as it grew.

How did Sonselasuchus change its walking style?

It transitioned from walking on four legs when young to walking on two legs as an adult, due to differing growth rates in its limbs.

Where were the fossils found?

The fossils were discovered in Petrified Forest National Park, Arizona, USA.

Explore more about ancient reptiles and fossil discoveries: Ancestors of Crocodiles Lived 240 Million Years Ago, Were Not Dinosaurs

Learn about petrified wood in Indonesia: Petrified Wood in Indonesia: Tracing Geological Chronicles and Ecological Transitions