With their heads covered in rows of curved spines, the traditional Selkirkia worms could easily be confused with the sharp-toothed sandworms that inhabit the deserts of Arrakis in “Dune: Part Two.”
During the Cambrian Explosion more than 500 million years ago, these strange worms — living in long, conical tubes — were amongst probably the most common predators on the seafloor.
“If you were a little invertebrate that came across them, it would be your worst nightmare,” said Karma Nanglu, a paleontologist at Harvard. “It’s like being swallowed by a conveyor belt full of fangs and teeth.”
Fortunately for would-be spice collectors, these voracious worms disappeared a whole bunch of millions of years ago. But recently analyzed fossils from Morocco show that these fierce predators, measuring only an inch or two long, survived much longer than previously thought.
In an article published today within the magazine Biology lettersDr. Nanglu’s team described a brand new species of Selkirkia worm that lived for 25 million years after this group of tube-dwellers was thought to be extinct.
The newly described tube worms were discovered while Dr. Nanglu and his colleagues were reviewing fossils held within the collections of the Museum of Comparative Zoology at Harvard University. The fossils come from the Fezouata Formation in Morocco, a deposit dating to the Early Ordovician period, which began about 488 million years ago and lasted for nearly 45 million years. It was a dynamic era when Cambrian remnants got here into contact with evolutionary newcomers corresponding to sea scorpions and horseshoe crabs.
The Fezouata Formation offers an in depth picture of this ecological transformation. The site is well-known for the stays of sea creatures corresponding to trilobites, which are sometimes preserved in rusty shades of red and orange. Some of the preserved creatures even retain delicate soft tissue features that rarely fossilize. Most research on the Fezouata fossils has focused on these extraordinary finds, ignoring the vast amount of what Dr. Nanglu calls “fossil bycatch” – smaller stays and fragments also present in the Fezouata rocks.
As the team combed through the museum specimens, they noticed several fire fossils in the shape of tapered tubes that looked like elongated ice cream cones. The annular texture of these tubes, measuring just an inch long, was almost an identical to Selkirkia fossils from much older Cambrian deposits corresponding to the Burgess Shale.
“We don’t expect this guy to be around anymore,” Dr. Nanglu said. “That’s 25 million years out of line.”
Closer evaluation confirmed that the tubes belonged to a brand new species of Selkirkia worm. They gave the brand new animal the species name tsering, which comes from a Tibetan word meaning “long life.” The latest species not only expands the time record of Selkirkia worms, but in addition confirms that they lived in environments closer to the South Pole, where Morocco was positioned in the course of the Ordovician period.
According to Jean-Bernard Caron, a paleontologist on the Royal Ontario Museum in Toronto who was not involved in the brand new paper, the invention highlights that some Cambrian creatures were in a position to survive even after the explosion in diversity in the course of the Ordovician era.
“This new study adds to a growing body of evidence that many members of Cambrian societies continued to thrive in the following Ordovician period and were not rapidly replaced, as previous evolutionary models might have suggested,” he said.
According to Dr. Caron, the brand new worm’s morphology “appears remarkably unchanged compared to its Cambrian counterpart.” This suggests that Selkirkia worms have experienced little evolutionary change over the 40 million years they’ve spent devouring other seafloor inhabitants.
However, their tubular body form eventually emerged from evolutionary fashion amongst closely related worms referred to as priapulids, or penis-shaped worms. There is currently just one genus of priapulids within the tube, which builds its tubes from lumps of plant debris, reasonably than secreting material from its own body as Selkirkia worms did.
Dr. Nanglu assumes that the creation of such a tube was a robust protection in the course of the Cambrian, when fewer large predators roamed open waters. However, as free-swimming predators bred in the course of the Ordovician, the stiff tubes can have ultimately made these worms more susceptible targets. As a result, these worms were in a position to abandon their tubes and adopt more lively means of escape, corresponding to burrowing.
While the ecological costs of producing these tubes were likely covered by the Selkirkia worms in the long term, the brand new discovery proves that the worms have successfully outlived many of the odd Cambrian wonders. According to Dr. Nanglu, their presence also suggests that sometimes reality really is stranger than fiction, even in relation to big screen doppelgangers.
“It’s like the sandworm from Dune building a giant house around itself,” Dr. Nanglu said. “No matter how wild the thing you see on the screen is, I guarantee there is something in nature, even if it has been extinct for a long time, that is much wilder.”
