A century later, researchers describe the second opavinide ever discovered.

Artistic reconstruction of Utaurora comosa from the Wheeler, Utah, USA (Cambrian: Drumian). Credit: F. Artwork by Anthony

In his book Great life, The late Stephen Jay Gould, a former professor of bioevolutionary biology at Harvard University, popularized “strange wonders” stalk arthropods. Opabinia When Anomalocaris, Discovered in the Cambrian Burgess Shale, it has become an icon of popular culture. “Cambrian horror” Anomalocaris —With a radial mouth and thorny gripping appendages — radiodontas with many relatives, fifth OpabiniaWith a distinctive frontal snout, it remains the only opavinide ever discovered. In other words, until now.

An international team of researchers led by Harvard University has confirmed that specimens that were previously considered radiodonta are actually opavinides.New research Bulletin of the Royal Society B Use a new and robust phylogenetic approach to confirm Utaurora Comosa The second opavinide to be discovered so far, the first in more than a century.

Utaurora ComosaWas discovered in the Middle Cambrian Wheeler Pagestone Formation, 500 million years ago in Utah, and was first described as a radiodonta in 2008. Stephen Patz, a former postdoc at the Institute for Biodiversity (OEB) at Harvard University, first encountered specimens at the Institute for Biodiversity and the Museum of Natural History at the University of Kansas when he was a graduate student. Pates is studying the diversity of radiodontas and felt that this specimen did not fit exactly into the true radiodontas. Pates joined the laboratory of senior author Javier Ortega-Hernández at OEB and collaborated with Jo Wolfe, a postdoctoral fellow at OEB to study the relationship between fossils and living arthropods., Decide where Utaurora Great for the tree of life.

Opabiniids are the first group with a backward-looking mouth. The grooves between their dorsal segments are precursors of systemic segmentation, and their outer swimming flaps are precursors of appendages. Utaurora With radiodonta the meantime Uta Urora’s Poor anterior structure and eye preservation —Opabinia Was best recognized from the anterior snout and five eyes, with fully observed serrated spines paired with intersegmental grooves and tails along the back.

With limited morphological observations, Pates and Wolfe compared using phylogenetic analysis Utaurora There are 43 fossils and 11 live taxa of arthropods, radiodontas, and other panarthropodas.

A century later, an international team of researchers describes the second opavinide ever discovered.

Utaurora comosa (Cambrian: Drumian) from the Wheeler, Utah, USA. The only known specimen of holotype registered in the Department of Invertebrate Paleontology, Institute of Biodiversity, University of Kansas. Credit: S. Pates

“initial Phylogenetic analysis Showed that it is most closely related Opabinia“Wolf said. “We performed more tests to investigate the results using different models of evolution. data set To visualize the different kinds of relationships this fossil might have. “

Not like Opabinia, Found in the Cambrian Burgess Shale in British Columbia, Canada. Utaurora Discovered in Utah, still Cambrian, but millions of years younger Opabinia.. “this means Opabinia It wasn’t just opabinide, Opabinia It wasn’t as unique as I expected. “

When Utaurora was first described as radiodonta in 2008, scientists thought that opaviniids and radiodonta formed a monophyletic group called “dinocarids.” However, over the last 10 to 15 years, scientists have discovered more than 10 species of radiodontas, and have been able to confirm that opabinides and radiodontas are slightly different.

“We also have more phylogenetic tools to investigate our results,” Patz said. “Based solely on form, you Utaurora A strange radiodonta, also to revive the concept of “dinocarid”.But our phylogenetic datasets and analyzes are supported Uta Urora 68% of the trees obtained by analyzing the data contain opabinide, but only 0.04% for radiodontas. “

“”Great life And the description of these fossils occurred before the current evolutionary paradigm.Similarities between Opabinia When Anomalocaris “These animals were found to represent an extinct stage of evolution associated with modern arthropods,” Wolff said. There are more tools than qualitative comparisons of morphological features for a clearer placement in the tree of life. ”

A fifth fossil 520 million years ago reveals the origin of arthropods

For more information:
The new opabinide diversifies the most bizarre wonders of a group of eukaryotic stems, Bulletin of the Royal Society B: Biological Science (2022). DOI: 10.1098 / rspb.2021.2093.. rspb.royalsocietypublishing.or…. 1098 / rspb.2021.2093

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A century later, researchers describe the second opavinide ever discovered.

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