Riccardo Levi-Setti: Experimental physicist and trilobite expert

Steve Koppes (USA)

Although he is an experimental physicist who discovered new elementary particles in the early 1950s and invented the high-resolution scanning ion microprobe, Riccardo Levi-Setti also is known in paleontological circles for co-discovering a giant trilobite subspecies and for his book, Trilobites.

Decades ago, as a diversion, Levi-Setti began to collect and study these bug-like marine creatures, which went extinct 250 million years ago. A Professor Emeritus in Physics at the University of Chicago, Levi-Setti unearthed the first specimen of Paradoxides davidis trapezopyge in 1974, while he and his Swedish colleague, Jan Bergström, were digging for Cambrian trilobites in the Manuels River gorge of eastern Newfoundland.

Bergström, a professor emeritus at the Swedish Museum of Natural History in Stockholm, lauded Levi-Setti as one of a small minority of trilobite collectors who publishes jointly with professional palaeontologists. As Bergström said:

Riccardo’s contributions on trilobite vision, in particular, represent a very important addition to our understanding of trilobite function. I guess that, in the long run, some intelligent palaeontologist would have come up with the same thing, but who knows when – and if?”

Since his early discoveries, Levi-Setti has organised many Moroccan expeditions, which he used to collect more specimens to complete the illustrations for a new trilobite book, this time in colour.

He has analysed trilobite vision on specimens from Bohemia, France, as well as Great Britain, the United States and Morocco. Along with co-author, Euan Clarkson of the University of Edinburgh in Scotland, he described the optics of trilobite eyes in 1975. Writing in the journal Nature, they noted the similarity of certain trilobite lenses to lenses designed in the seveteenth century by philosopher and scientist, René Descartes, and physicist and astronomer, Christiaan Huygens. Clarkson and Levi-Setti concluded that the design of these trilobite eyes evolved to increase the concentration of light in their dark oceanic environments.

As he said:

These findings show that Darwinian survival of the fittest leads to the optimization of many animal functions, in this case vision, up to the limits imposed by the laws of physics. In trilobite vision, this optimization had already been achieved around 450 million years ago.”

The lens-bearing visual surface of the giant trilobites of Newfoundland’s Manuels River gorge has been lost to the fossil record. Nevertheless, the locality ranks among Levi-Setti’s favourite trilobite hunting grounds. As he recalled:

When I first started digging there, the locality was a gorgeous river gorge with forest all the way down to the river.”

Further digging revealed that the locality held beautifully preserved, foot-long trilobites.

Unfortunately, the gorge had become a dumping ground for old cars, refrigerators and other refuse. In 1978, Levi-Setti contacted the chairman of the geology department at Memorial University in Newfoundland to recommend that something be done to preserve the locality. The provincial government obliged. Years later, a cleaned-up Manuels River Linear Park offered miles of scenic nature trails for visitors to enjoy.

However, the Manuels River Natural Heritage Society banned all digging, so Levi-Setti had to curtail his work there. That changed in 2008, when the society asked him for permission to reproduce the trilobite photograph that adorns the cover of his book. Levi-Setti asked if it might be possible for him to resume his work at Manuels River. The society’s governing board then rapidly and unanimously approved his request.

When Levi-Setti resumed his Manuels River excavations, during his two-week stay, a Memorial University palaeontology student provided assistance, as did members of the society’s governing board. “It was absolutely wonderful,” said a delighted Levi-Setti. Plans are afoot to build a museum that highlights the scientific importance of the Manuels River, whose fossils are preserved without a trace of the distortions that plague some fossil beds. “The rocks there have been beautifully preserved horizontally, just the way they were deposited. It’s fantastic,” Levi-Setti said.

One of the most prolific forms of life in the sea during their heyday, trilobites provide valuable evolutionary data. For example, some trilobite lineages beautifully illustrate the concept of punctuated equilibria advanced by palaeontologists, Niles Eldredge and Stephen Jay Gould, in evolutionary biology. According to this concept, evolution proceeds in rapid and dramatic steps between long periods of biological stability.

However, trilobites are important to Levi-Setti for personal as well as scientific reasons, as he recounts in his book. Having fought with the Italian resistance against the Nazis during World War II, working with trilobites evokes a time before life had conquered land and humans had yet to invent genocide.

As Levi-Setti wrote in Trilobites:

It is time travel and, at the same time, an addictive treasure hunt” .

Jan Bergström passed away in 2012 and Riccardo Levi-Setti in 2018.

Reference

Trilobites by Riccardo Levi-Setti, published by The University of Chicago Press.