Millions of years ago, a group of creatures with frondlike structures filled the ancient seas. The mysterious organisms are known as rangeomorphs and had bodies that were well-suited to the sea conditions of the Ediacaran Period 635 million to 541 million years ago.
Rangeomorphs, which could possibly be among the earliest animals that emerged on the planet, existed during a period in history when most other life forms were microscopic in size. The creatures, which measured between 10 centimeters and two meters in height, had bodies that consisted of soft branches that each has many smaller side branches that form a fractal geometric shape. Like all other organisms that thrived on a much younger Earth, however, rangeomorphs have disappeared.
Although the organisms are already extinct, a computer program developed by Jennifer Hoyal Cuthill, from the University of Cambridge, which simulate things that are observed in fossil records, allowed her and colleagues to learn how rangeomorphs lived, evolved and disappeared.
Using the computer program, Hoyal Cuthill and colleagues, whose findings were published in the journal Proceedings of the National Academy of Sciences (PNAS) on Aug.11, found that while rangeomorphs are often believed to be a "failed experiment" of evolution because they disappeared quickly after the start of the Cambrian Explosion, the period of rapid evolution marked by the emergence of most major animal groups in fossil record, their analysis showed how successful the animals were.
The organisms, for instance, were good at filling spaces, which suggests that rangeomorphs managed to survive by absorbing carbon and oxygen that are dissolved in the seawater albeit they do not appear to have any active body parts particularly feeding structures.
"They are incredibly efficient at filling space," Hoyal Cuthill said. "If I tried to come up with a better arrangement, I don't know if I could do it."
It also appeared that one of the primary causes that led to the disappearance of these organisms is their very structure. When the Cambrian Explosion began, rangeomorphs did not have any means to defend themselves against the predators that evolved during the period. The changing chemical composition of the ocean, which used to suit them during the Ediacaran Period, no longer provides the nutrients that they need to survive.
"Rangeomorphs were adaptively optimal for the low-competition, high-nutrient conditions of Ediacaran oceans," the researchers wrote. "With the Cambrian explosion in animal diversity (from 541 Ma), fundamental changes in ecological and geochemical conditions led to their extinction."
