Cambrian Fossil Gives Answers To What Early Tunicates Look Like, Its Similarities To Vertebrates

An odd fossil of a Cambrian creature, which is believed to be 500,000-years-old, helped experts obtain an answer to what early tunicates look like.

(Photo : Unsplash/Raimond Klavins)

The discovery also provided an answer to the similarities between these early tunicates and the early vertebrates, a Live Science report said.

According to Karma Nanglu, co-author of the study and a postdoctoral fellow at the Museum of Comparative Zoology at Harvard University, the fossil that was discovered belongs to the ancient species of tunicate dubbed as the Megasiphon thylakos.

Nanglu said the fossil could help researchers and even the public learn about the ecology and lifestyle of tunicates that existed a long time ago.

Its period, the Cambrian, was part of the Paleozoic era. It had produced a burst of evolution ever known wherein an incredible diversity of life had emerged.

What are tunicates

Tunicates are described as very strange creatures that come in all shapes and sizes. Early research also said these species have a wide variety of lifestyles.

An entry posted in The Harvard Gazette said an adult tunicate's basic shape was "typically barrel-like, with two siphons projecting from its body."

One of the siphons usually draws in water with food particles through suction, which then allows the animal to feed through the use of an internal basket-like filter device. Meanwhile, the other siphon expels the water.

According to experts, the two main tunicate lineages are called ascidiaceans, or also known as "sea squirts," and the appendicularians.

Most of the ascidiaceans started to look like as a tadpole and later they will morph into a barrel-shaped adults. They usually live their adult lives embedded into the seafloor.

On the other hand, the appendicularians maintain their physique as a tadpole even as they grow to adulthood. These species also swim freely in the upper waters.

Quoting Nanglu, the Discovery Magazine said the unearthed fossil of Megasiphon's morphology suggested that the ancient way of living of tunicates had involved a non-moving adult that filter fed with its large siphons.

"It's so rare to find not just a tunicate fossil, but one that provides a unique and unparalleled view into the early evolutionary origins of this enigmatic group," Nanglu said.

Nanglu pointed out that the discovered tunicate tells researchers that they were most likely to be animals that had a lava form like a tadpole.

After that, they metamorphosed into a barrel-shaped animal that had these two siphons pointing up into the water column.

Relatives of vertebrates

The tunicates can be categorized under the phylum Chordata that also includes animals being equipped with backbones.

Due to this characteristic, tunicates can be considered as the closest relatives to vertebrates, which includes human, compared to other types of invertebrates.

Their relation to vertebrates could be attributed to their look as a tadpole at the start of their lives.

Researchers said the tunicates' existence could also be critical in understanding the evolution of human beings, however, studying them is not that easy as they were "almost completely absent" in the whole range of fossil records.

The Megasiphon thylakos is the only definitive tunicate fossil with soft tissue preservation that has been unearthed as of present times.

Researchers found it as the oldest of its kind, originating from the middle Cambrian Marjum Formation in Utah.