This Is What Earth's First Large Animals Looked Like

Artist's impression of rangeomorph (no, it's not a plant). Jennifer Hoyal Cuthill

These things might look like a pot plant you’d see in the dentist’s waiting room, but they’re actually one of the first large animals on planet Earth.

Known as rangeomorphs, these alien-like animals could grow up to two meters (6.6 feet) in height. Researchers from the University of Cambridge and the Tokyo Institute of Technology have recently been studying their fossils and believe they became one of the first animals through their ability to “shapeshift.” The study was recently reported in the journal Nature Ecology and Evolution.

These creatures lived in the oceans during the Ediacaran period, between 635 and 541 million years ago. It’s hard to tell how they behaved exactly as they’re not like anything on Earth. In fact, they’re so dissimilar, It’s even hard to link with any modern group of animal.

"What we wanted to know is why these large organisms appeared at this particular point in Earth's history," Dr Jennifer Hoyal Cuthill of Cambridge's Department of Earth Sciences and Tokyo Tech's Earth-Life Science Institute, the paper's first author, said in a statement.

"They show up in the fossil record with a bang, at very large size. We wondered, was this simply a coincidence or a direct result of changes in ocean chemistry?"

A fossil of a rangeomorph. J Hoyal Cuthill

The researchers analyzed numerous rangeomorphs fossils from Canada, the UK, and Australia using micro-CT scanning and photographic measurements. They then plugged this information into computer modeling software.

According to this analysis, the animal displays the earliest evidence for nutrient-dependent growth in the fossil record. It’s believed this animal had “ecophenotypic plasticity,” a phenomenon whereby nutrients can dictate the body size and shape of an organism.

The rise of the rangeomorphs also coincided with an ice age, known as the Gaskiers glaciation, which changed the ocean’s chemistry dramatically. This saw a sudden increase in oxygen and other nutrients, making it easier to be a large organism.

"During the Ediacaran, there seem to have been major changes in the Earth's oceans, which may have triggered growth, so that life on Earth suddenly starts getting much bigger," added Dr Cuthill.

"It's probably too early to conclude exactly which geochemical changes in the Ediacaran oceans were responsible for the shift to large body sizes, but there are strong contenders, especially increased oxygen, which animals need for respiration."

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