For many years, ancient marine animals called hyoliths were evolutionary mysteries on where they would belong in the Tree of Life, until recent discovery of new features about the strange-shelled creatures were found.
Hyoliths lived some 500 million years ago during the Cambrian period, and they were only discovered 175 years ago, according to Science News. They look like mollusks or clams, but with tentacles called helen near their mouths, which propped them up on the seafloor. Their soft bodies were encased by two shells that resembled an ice cream cone, with a cone-shaped shell on the bottom, and another rounder shell on top.
Since their discovery, paleontologists were unsure how to classify them.Some scientists thought that hyoliths were related to mollusks, but others thought that hyoliths deserved their own branch. But newly discovered hyolith fossils have helped to classify where these marine creatures should be categorized in the Tree of Life, Live Science reported.
The hyolith fossils are well-preserved that there is still soft tissue intact. The main discovery that helped settle the debate on what these ancient creatures are really like is a band of tissue at the opening of the shell. This meant that about 12 to 16 tentacles protruded from that opening. That band of tissue identified hyoliths as lophophores.
The living lophophores of today such as brachiopods with shells that have a top and a bottom and horseshoe worms with tentacles that capture food particles share some similar characteristics with the hyoliths. Based on the fossils, the ancient marine creatures did not move around much and were filter feeders.
Joseph Moysiuk, an invertebrate paleontologist from the University of Toronto, said that discovery of the hyolith fossils suggested they are a cousin of the brachiopods and added a new branch to the Tree of Life.
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