These Are The Oldest Fossilized Muscles, and They Are Rewriting Prehistory

Haootia quadriformis: do you even lift?

Aug 27 2014, 9:00am

Image: Jack Matthews.

Recently, paleontologists have been turning up all kinds of odd beastlings, many of them dating back 500 million years or more. First, there was the exquisitely preserved brain of a Cambrian predator, then the plant-like fractal animals known as rangeomorphs, and now, researchers based out of Cambridge University have discovered the earliest evidence of muscular formation in the fossil record.

The ancient muscles belonged to Haootia quadriformis, an oceanic animal that lived about 560 million years ago in the Ediacaran period. The find is especially significant because the previous world's-oldest-muscles record-holders were from the early Cambrian period, at least 20 million years later. In this way, Haootia quadriformis, has challenged the conventional evolutionary timeline of the emergence of animals.

"In recent decades, discoveries of preserved trackways and chemical evidence in older rocks, as well as molecular comparisons, have indirectly suggested that animals may have a much earlier origin than previously thought," explained lead author Alex Liu in a statement.

"The problem is that although animals are now widely expected to have been present before the Cambrian Explosion, very few of the fossils found in older rocks possess features that can be used to convincingly identify them as animals," he said.

"Instead, we study aspects of their ecology, feeding or reproduction, in order to understand what they might have been."

Haootia quadriformis, on the other hand, has set itself apart from all other Ediacaran fossils with its distinctly animalian features. It is among the earliest cnidarians, a group that now includes coral, jellyfish, and anemones.

While cnidarians don't exactly have ripped bods, they do sport fibrous bundles of muscular tissue. Haootia quadriforma's musculature is arranged in a distinctive four-fold symmetrical pattern similar to its modern relatives. Liu and his colleagues published their analysis of the animal's characteristics today, in the Proceedings of the Royal Society B.

Like most primordial lifeforms, Haootia quadriformis may as well have come from another planet (and given how different Earth was 560 million years ago, it arguably did). According to an artistic recreation, it looked like a flailing, disembodied heart rooted to the seafloor like a rangeomorph.

The Haootia quadriformis. Image: Martin Brasier. 

But in spite of its alien appearance, the Haootia quadriformis was flexing its muscles before it was cool. Twenty million years after this particular fossilized individual died, the Cambrian explosion would rapidly expand the diversity of animal life across the planet. Muscle tissue would become abundant, and some animals would bulk up into hulking predators by feeding on it. It's fair to say the adaptation has come in handy, and we owe it all to pioneering Ediacaran oddities like Haootia quadriformis.