Many scientists consider the “Cambrian Explosion” – which occurred around 530-540 million years ago – to be the first major appearance of many groups of the world’s animals in the fossil record. As if adding pieces to a giant jigsaw puzzle, each discovery from this period has added another piece to the evolving map of modern animals. Today, researchers at the University of Missouri have found a rare 500-million-year-old “worm-like” fossil called paleoscolecid, which is a rare fossil group in North America. Researchers believe the discovery, which came from an area in western Utah, may help scientists better understand just how diverse Earth’s animals were during the Cambrian explosion.
Jim Schiffbauer, associate professor of geological sciences at MU College of Arts and Science and one of the study’s co-authors, said that although this fossil has the same anatomical organization as modern worms, it does not exactly match to everything we see. on modern Earth.
“This group of animals are extinct, so we don’t see them, or any modern relatives, on the planet today,” Schiffbauer said. “We tend to call them ‘worm-like’ because it’s hard to say that they fit perfectly with annelids, priapulids, or any other type of organism on the planet today that we would generally call a “worm.” But the Paleoscolecids have the same general body plane, which in the history of life has been an incredibly successful body plane. So that’s a pretty cool addition as it increases the number of worm-like things. that we have known for 500 million years in North America and adds to our global occurrences and the diversity of Paleoscolecids.
At the time, this paleoscolecid likely lived on the ocean floor, said Wade Leibach, an MU graduate teaching assistant at the College of Arts and Sciences and lead author of the study.
“This is the first known finding of paleoscolecids in a certain rock formation – the Marjum formation in western Utah – and it is important because it represents one of the few taxa of paleoscolecids in North America. North, ”Leibach said. “Other examples of this type of fossil have already been found in much higher abundance on other continents, such as Asia, so we believe this finding may help us better understand how we view environments and ecologies. prehistoric times, for example why different types of organisms are under-represented or over-represented in the fossil record. Thus, this discovery can be viewed not only from the point of view of its importance in North American paleontology, but also of broader trends of evolution, paleogeography and paleoecology.
Leibach, who transitioned from biology to geology after volunteering to work with the University of Kansas’ Invertebrate Paleontology Collections, began this project as an undergraduate student analyzing a box of ‘a dozen fossils in the collections of the KU Biodiversity Institute. Initially, Leibach and one of his co-authors, Anna Whitaker, who was then a graduate student at KU and now at the University of Toronto-Mississauga, analyzed each fossil using an optical microscope, which identified at least one of the fossils to be a paleoscolecid.
Leibach worked with Julien Kimmig, who was at the time at the KU Biodiversity Institute and is now at Penn State University, to determine that in order to be able to confirm their initial findings he would need the help of additional analyzes provided by sophisticated experts. microscopy equipment located at the MU X-ray Microanalysis Core, which is led by Schiffbauer. Using MU’s central facility, Leibach focused his analysis on the imprints left in the fossil by the microscopic plaques of the ancient animal, characteristic of the Paleoscolecids.
“These very small mineralized plates typically measure nanometers to micrometers. So we needed the help of the equipment in Dr Schiffbauer’s lab to be able to study them in detail, because their size, orientation and distribution is how we classify the organism. at the genus and species level, ”said Leibach.
Leibach said the team found a few reasons why this particular fossil can be found in limited quantities in North America compared to other parts of the world. They are:
- Geochemical limitations or different environments that may be more predisposed to preserve these types of organisms.
- Ecological competition, which may have led this type of organism to be less competitive or less abundant in certain areas.
The new taxon is named Arrakiscolex aasei after the fictional planet Arrakis in Frank Herbert’s novel “Dune”, which is inhabited by an armored worm species and specimen collector Arvid Aase.
The study, “The First Paleoscolecid of the Cambrian (Miaolingian, Drumian) Marjum Formation of Western Utah,” was published in Acta Palaeontologica Polonica, an international quarterly journal that publishes articles in all areas of the study. paleontology. Funding was provided by a National Science Foundation CAREER Grant (1652351), Earth Science Instrumentation and Facilities Grant from the National Science Foundation (1636643), an undergraduate research grant from the University of Kansas, a student research grant provided by the South-Central Section of the Society of America and the J. Ortega-Hernández Laboratory of Invertebrate Paleobiology at Harvard University. The study authors would like to thank Arvid Aase and Thomas T. Johnson for donating the specimens analyzed in the study.