The scientists developed a detailed 3D model of the only known fossilized specimen in the world of a creature called Drakozoon. The specimen was found by one of the team approximately 6 years ago in the Herefordshire Lagerstätte, one of England's richest deposits of soft-bodied fossils. Drakozoon lived in the ocean during the Silurian Period, 444 to 416 million years ago, and today's model hints at how it lived.
The research reveals that Drakozoon was a cone-shaped, blob-like creature with a hood and it probably had a leathery exterior skin. It appears to have survived in the ocean by attaching itself to hard surfaces such as rock. It was approximately 3 millimeters long, and used filament-bearing tentacles to catch and eat organic particles in seawater. It pulled its hood down over its body for protection against predators, pulling it back again to expose its tentacles when danger passed.
Drakozoon. Credit: Imperial College London
Dr. Mark Sutton, from the Department of Earth Science and Engineering at Imperial College London, said, "Excitingly, our 3D model brings back to life a creature that until recently no one knew even existed, and provides us with a window into the life of Drakozoon. We think this tiny blob of jelly survived by clinging onto rocks and hard shelled creatures, making a living by plucking microscopic morsels out of seawater. By looking at this primitive creature, we also get one tantalising step closer to understanding what the earliest creatures on Earth looked like."
Scientists have debated what the first relatives of all creatures on Earth may have resembled and how their bodies evolved. Some think the creatures had repeated units, similar to a caterpillar with its many segments and legs, while others think that their bodies were structured in more free-form ways, similar to slugs. In the new model, the researchers say that Drakozoon had eight deep ridges on either side of its body and they suggest that these deep ridges are the genetic remnants from a time when Drakozoon had a body made of repeated units, supporting the theory that the earliest creatures on Earth were also made of repeated units.
The study shows that Drakozoon was an early member of a major group of invertebrate species called lophophorates. The best known lophophorates are the brachiopods, a type of spineless shellfish that are some of the most common fossils from the Silurian Period. The team found their Drakozoon specimen clinging onto the fossilised shell of a brachiopod.
The researchers created their 3D model by physically slicing a fossil into 200 pieces. These pieces were individually photographed and the images were fed into a computer, which generated the 3D model for analysis by the scientists.
The researchers say it is very rare to find ancient soft bodied creatures intact because they normally decompose before they can be preserved in sediment. The soft bodied Drakozoon was perfectly preserved because it lived in an area that was covered in volcanic ash, following a volcanic eruption that instantly entombed it and other creatures living with it, keeping it intact for 425 million years.
Funded by Natural Environment Research Council.
Citation: M. D. Sutton, D. E. G. Briggs, David J. Siveter and Derek J. Siveter, 'A soft-bodied lophophorate from the Silurian of England', Biology Letters, doi:10.1098/rsbl.2010.0540