Dinosaurs Dominate Earth for 160 Million Years Not Because of Their Size But Due to Their Specialized Stance and Locomotion [Study]

Dinosaurs are archosaurs, a larger group of reptiles that roamed the Earth after first appearing 251 million years ago, near the beginning of the Triassic Period. These prehistoric giant animals dominated the land for more than 140 years and over 160 million years in some parts of the world, according to the National History Museum (NHM). Even in contemporary times, paleontological evidence shows that dinosaurs were on the top of the food chain.

Scientists have long thought that the large size of some terrestrial dinosaurs, including the tyrannosaurus rex, and their intense predatory instincts made them a force to be reckoned with. Before the extinction of all non-avian dinosaurs 66 million years ago, the fearsome archosaurs ate almost anything, including mammals reptiles, and plants, as well as animal carcasses and even other dinosaurs.

Now, a new study led by researchers from the United Kingdom found that the "specialized stance" and "locomotion" of dinosaurs and not their size allowed them to dominate our planet for 160 million years. Some species having four or two legs, allowed them to move faster and become more agile than their competitors during that time, the researchers have found. These features provided an advantage for the dinosaurs.

Dinosaur Dominance for 160 Million Years

In the new scientific paper published in the journal Royal Society Open Science on February 7, researchers from the University of Bristol in England found that dinosaur dominance is based on their speed and dynamic mobility, based on findings among the world's first dinosaurs. The archosaurs triumphed during the Triassic while life is still recovering following the Permian-Triassic mass extinction.

To determine why dinosaurs not only survived for a long time (before the Chicxulub asteroid) 66 million years ago but also rose in the food web, the authors of the study explored the evolution of locomotion in Archosauromorpha, a clade of diapsid reptiles. It consists of all reptiles that are more related to archosaurs than lepidosaurs, which includes the order Squamata where lizards, snakes, and other reptiles belong.

Dinosaur Locomotion

The University of Bristol team applied geometric morphometrics on the shapes of limb bones. They also examined limb ratios to measure bipedality and cursoriality metrics. The team found that dinosaurs, pterosaurs, and their relatives had more variable limb form and limb ratios compared with any other group. This new evidence suggests a wider range of locomotory modes.

In a news release by the University of Bristol on February 7, the researchers found that dinosaurs and their close relatives, either bipedal (two-footed) or quadrupedal (four-footed), had limbs that evolved for running with different styles. The unique structure and power of dinosaur locomotion entailed that their close competitors, called Pseudosuchia, were outmatched since the Triassic Period.

According to the NHM, dinosaurs had an upright stance, which resembles a standing position, as opposed to lizards and crocodiles which have a sprawling stance, which looks like a crouching position.