500-million-year-old fossil represents rare discovery of ancient animal
in North America

Date:
September 9, 2021
Source:
University of Missouri-Columbia
Summary:
Many scientists consider the 'Cambrian explosion' -- which occurred
about 530-540 million years ago -- as the first major appearance
of many of the world's animal groups in the fossil record. Like
adding pieces to a giant jigsaw puzzle, each discovery dating from
this time period has added another piece to the evolutionary
map of modern animals. Now, researchers have found a rare,
500-million-year-old 'worm-like' fossil called a palaeoscolecid,
which is an uncommon fossil group in North America. The researchers
believe this find, from an area in western Utah, can help scientists
better understand how diverse the Earth's animals were during the
Cambrian explosion.



FULL STORY ==========================================================================
Many scientists consider the "Cambrian explosion" -- which occurred about
530- 540 million years ago -- as the first major appearance of many of
the world's animal groups in the fossil record. Like adding pieces to a
giant jigsaw puzzle, each discovery dating from this time period has added another piece to the evolutionary map of modern animals. Now, researchers
at the University of Missouri have found a rare, 500-million-year-old "worm-like" fossil called a palaeoscolecid, which is an uncommon fossil
group in North America. The researchers believe this find, from an area
in western Utah, can help scientists better understand how diverse the
Earth's animals were during the Cambrian explosion.


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Jim Schiffbauer, an associate professor of geological sciences in the MU College of Arts and Science and one of the study's co-authors, said that
while this fossil has the same anatomical organization as modern worms,
it doesn't exactly match with anything 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 perfectly fit
with annelids, priapulids, or any other types of organism on the planet
today that we would generally call a "worm." But palaeoscolecids have
the same general body plan, which in the history of life has been an
incredibly successful body plan. So, this is a pretty cool addition
because it expands the number of worm-like things that we know about
from 500 million years ago in North America and adds to our global
occurrences and diversity of the palaeoscolecids." At the time, this palaeoscolecid was likely living on an ocean floor, said Wade Leibach,
an MU graduate teaching assistant in the College of Arts and Science,
and lead author on the study.

"It is the first known palaeoscolecid discovery in a certain rock
formation - - the Marjum Formation of western Utah -- and that's important because this represents one of only a few palaeoscolecid taxa in North America," Leibach said. "Other examples of this type of fossil have
been previously found in much higher abundance on other continents,
such as Asia, so we believe this find can help us better understand how
we view prehistoric environments and ecologies, such as why different
types of organisms are underrepresented or overrepresented in the fossil record. So, this discovery can be viewed from not only the perspective of
its significance in North American paleontology, but also broader trends
in evolution, paleogeography and paleoecology." Leibach, who switched
his major from biology to geology after volunteering to work with the invertebrate paleontology collections at the University of Kansas,
began this project as an undergraduate student by analyzing a box of
about a dozen fossils in the collections of the KU Biodiversity Institute.

Initially, Leibach and one of his co-authors, Anna Whitaker, who was
a graduate student at KU at the time and now is at the University of Toronto-Mississauga, analyzed each fossil using a light microscope,
which identified at least one of the fossils to be a palaeoscolecid.

Leibach worked with Julien Kimmig, who was at the KU Biodiversity
Institute at the time 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 analyses provided by sophisticated microscopy equipment located at the MU X-ray Microanalysis Core, which is directed by Schiffbauer. Using the core facility at MU, Leibach focused his analysis
on the indentations left in the fossil by the ancient animal's microscopic plates, which are characteristic of the palaeoscolecids.

"These very small mineralized plates are usually nanometers-to-micrometers
in size, so we needed the assistance 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 to the genus and species levels," Leibach said.

Leibach said the team found a couple reasons about why this particular
fossil may be found in limited quantities in North America as compared
to other parts of the world. They are:
* Geochemical limitations or different environments that may be more
predisposed to preserving these types of organisms.

* Ecological competition, which may have driven 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 the novel "Dune" by Frank Herbert, which is inhabited by a
species of armored worm and the collector of the specimens Arvid Aase.

The study, "First palaeoscolecid from the Cambrian (Miaolingian, Drumian) Marjum Formation of western Utah," was published in Acta Palaeontologica Polonica, an international quarterly journal which publishes papers from
all areas of paleontology. Funding was provided by a National Science Foundation CAREER grant (1652351), a National Science Foundation Earth
Sciences Instrumentation and Facilities grant (1636643), a University of
Kansas Undergraduate Research grant, a student research grant provided
by the South- Central Section of the Geological Society of America, and
the J. Ortega- Herna'ndez Laboratory for Invertebrate Palaeobiology at
Harvard University. The study's authors would like to thank Arvid Aase
and Thomas T. Johnson for donating the specimens analyzed in the study.The
new taxon is named Arrakiscolex aasei after the fictional planet Arrakis
in the novel "Dune" by Frank Herbert, which is inhabited by a species
of armored worm and the collector of the specimens Arvid Aase.

========================================================================== Story Source: Materials provided by University_of_Missouri-Columbia. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Wade Leibach, Rudy Lerosey-Aubril, Anna Whitaker, James Schiffbauer,
Julien Kimmig. First palaeoscolecid from the Cambrian (Miaolingian,
Drumian) Marjum Formation of western Utah. Acta Palaeontologica
Polonica, 2021; 66 DOI: 10.4202/app.00875.2021 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210909124042.htm

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