Siphusauctum lloydguntheri was a strange animal that lived half a billion years ago

Siphusauctum lloydguntheri (Photo courtesy Julien Kimmig | KU News Service)
Siphusauctum lloydguntheri (Photo courtesy Julien Kimmig | KU News Service)

An article published in the “Journal of Paleontology” describes the identification of an animal that lived in the Middle Cambrian, between 513 and 501 million years ago. Named Siphusauctum lloydguntheri, it was studied thanks to a specimen discovered years ago in Utah. According to the researchers who studied it, it’s the oldest stalked filter feeder discovered in North America.

The specimen of Siphusauctum lloydguntheri was discovered in what is called Spence Shale, an area where the conditions were very favorable to fossilization, even of soft tissue. It was found by fossil hunter Lloyd Gunther, who donated it to the University of Kansas’ Biodiversity Institute along with thousands of other fossils.

The favorable conditions of the Spence Shale allowed to discover extraordinary fossils that provided a lot of information about organisms that lived in the Cambrian period. Often they were very different from the ones existing today so they can be difficult to classify into existing taxonomic groups.

In the case of Siphusauctum lloydguntheri there’s a classification problem too. This animal had a body that looked like a tulip with a sort of stem it used to anchor to sediments and an upper part, called a calyx, which had everything from the digestive tract to the feeding mechanism. It lived in soft sediments, anchored in the sediment, filtering food particles. Julien Kimmig, the article’s first author, called it pretty primitive and weird, adjectives that are often associated with organisms of that period.

In 2012, another animal with similar characteristics was identified in the Burgess Shale, one of the world’s most famous fossil deposits. It was called Siphusauctum gregarium but in this case more than a thousand specimens were discovered. However, that didn’t make its classification any easier and its affinities are so dubious that at that time the researchers decided to create a whole new taxonomic family called Siphusauctidae.

The researchers who studied the specimen of Siphusauctum lloydguntheri noticed similarities with Siphusauctum gregarium but thought that there were such differences that it was a different species though part of the same genus. The name of the new species was chosen after the specimen’s discoverer and donor.

Having only one specimen that might be incomplete it’s complex for researchers to provide certainty even on its characteristics. This is a common problem with many Cambrian organisms, intriguing for their strange shapes but exactly for that reason sometimes difficult to study.

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