An article published in the journal “Science” describes an analysis of fossils that belong to the genus Dickinsonia, perhaps the most iconic of the so-called Ediacara biota, the organisms that lived during the Ediacaran period. A team of researchers conducted a highly sophisticated examination of fossils dating back some 558 million years ago, discovering traces of cholesterol, a steroid typical of animals. The conclusion is that the organisms of the genus Dickinsonia must be animals and this could be the proof that closes decades of discussions about their nature.
Fossils of Dickinsonia have been discovered in the last 70 years in various parts of the world in sizes ranging from a few millimeters to 1.4 meters in length. Like so many other organisms of the Ediacara biota, its form so different from those of the organisms of later eras made it difficult even to catalog them taxonomically in a precise kingdom. For decades there have been discussions and even correctly establishing the number of species within the genus Dickinsonia based on the fossils found has been a source of controversy.
Normally, the fossils of Dickinsonia are imprints in sandstone beds that today can be part of cliffs and therefore difficult to reach. Exactly in a cliff near the White Sea along the northwest coast of Russia, Ilya Bobrovskiy of ANU discovered fossils that belong to this genus very well preserved. At a height between 60 and 100 meters, they required a work more of an alpinist than of a paleontologist to extract the sandstone blocks that contained them.
The work gave excellent results because the fossils contain not only imprints but parts of those organisms’ body. Most of the fossils discovered in the Ediacara hills in Australia, the ones the biota and the Ediacaran period takes their name from, are too degraded to be able to attempt an analysis through some new technology. At ANU, there’s one of the world’s most sophisticated equipment to find biomarkers but they need for the fossils examined to have kept their traces to obtain some results.
Ilya Bobrovskiy already conducted an analysis of an organism of the Ediacara biota that belongs to the genus Beltanelliformis, described in an article published in the journal “Nature Ecology & Evolution” in January 2018. In that case, the examination indicated that it was a colony of cyanobacteria.
The Dickinsonia fossils found by Ilya Bobrovskiy were suitable to the examination so he tried to look for traces of organic molecules inside some samples. The ANU equipment for the research of biomarkers indicated a clear presence of traces of substances produced by cholesterol’s decay. The materials around the parts of Dickinsonia showed traces of ergosterols and this suggests that there were green algae.
As far as we know, only animals produce cholesterol so the organisms of the genus Dickinsonia must be animals. This result confirms some of the conclusions of a research published in the journal “Paleontology” in August 2018 which claims that some organisms of the Ediacara biota were animals including those of the genus Dickinsonia. This new research, however, was based on analyzes carried out using modern technologies and not on similarities in physical characteristics, confirming that new types of analysis can be very useful in the field of paleontology.
This research offers an answer to the dilemma that for decades led to discussions about Dickinsonia and new information on the rise of animals. It says nothing about their relationships with the phyla of the animals that emerged later, in the Cambrian period. According to the research published in the journal “Nature Ecology & Evolution” in January 2018, Dickinsonia belongs to a group related to ctenophores or even belongs to that phylum. Slowly, research is offering new solutions to the mysteries of some of the strangest organisms that have ever lived on Earth.
