Newly identified softshell turtle lived alongside T. rex and Triceratops
Date:
March 11, 2022
Source:
University of Pennsylvania
Summary:
Scientists describe the find of a new softshell turtle from the
end of the Cretaceous Period.
FULL STORY ==========================================================================
A newly described softshell turtle that lived in North Dakota 66.5
million years ago at the end of the Cretaceous Period, just before the end-Cretaceous mass extinction,is oneof the earliest known species of
the genus, according to new research shared in the journal Cretaceous
Research.
========================================================================== Hutchemys walkerorum lived during a period when large and
well-known dinosaurs also roamed Earth, including Tyrannosaurus
rexand Triceratops. The find adds important information to scientists' understanding of softshell turtles more broadly, including the potential effects of the end-Cretaceous mass extinction, which took place in this
same time period, on their evolution.
Steven Jasinski, who recently completed his Ph.D. in Penn's Department of
Earth and Environmental Sciences in the School of Arts & Sciences, led
the research, collaborating with advisor Peter Dodson of the School of Veterinary Medicine and Penn Arts & Sciences. The research team included
Andrew Heckert and Ciara Sailar of Appalachian State University and
Asher Lichtig and Spencer Lucas of the New Mexico Museum of Natural
History and Science.
Hutchemys walkerorum belongs to a particular group of softshell turtles in
the Trionychidae family called plastomenines. These turtles are similar
to the softshell turtles that exist today, although the plastron of plastomenine turtles -- the bones covering their stomach and abdominal
area -- are more strongly sutured together and often larger and more
robust than in other softshell turtles.
Plastomenines lived during the Cretaceous and Paleogene periods, around
80 million to 50 million years ago. Members of this group first appear
in the fossil record during the Late Cretaceous, and a single species
continues into the Eocene Epoch, 50 million years ago, but they are at
their peak diversity before and after the Cretaceous-Paleogene boundary.
"Until recently we didn't understand these softshell turtles very well,"
says Jasinski. "However, we are starting to get more information on
this extinct group of turtles and further understanding their evolution, including how they dealt with the mass extinction." The fossil specimen
of the new species, a partial carapace -- the bones that cover the back
and what people think of as a turtle's "shell" -- was discovered in
1975 in southwestern North Dakota. A field crew from Appalachian State University led by Frank K. McKinney and John E. Callahan collected the specimen, along with a specimen of Triceratops, that summer. The fossil
turtle specimen remained at Appalachian State until 2013, when Heckert discussed it with Jasinski, a master's student at East Tennessee State University at the time.
========================================================================== Research started in earnest around that time and continued as Jasinski was
at Penn for his doctoral studies. Based on the structure of the specimen,
he and colleagues determined this fossil belonged to a genus of turtles
from the American West known as Hutchemys. Hutchemys walkerorum represents
one of the rare occurrences of these turtles prior to the mass extinction
event that brought the Age of Dinosaurs to an end. It also represents
the easternmost occurrence of the genus during the Cretaceous Period.
"With this study we gain further insight into winners and losers during
the cataclysm that ended the Age of Dinosaurs," says Dodson. "The mighty dinosaurs fell, and the lowly turtle survived." A phylogenetic analysis, comparing the new species with other known trionychids, or softshell
turtles, gave the scientists a better understanding of the group's
evolutionary relationships. Their analysis placed Hutchemys walkerorum
with other known species of Hutchemys and several other turtles in a
distinct group of derived plastomenines, which they named Plastomenini. In addition, the researchers found a group of early trionychids, placing
them in a newly established subfamily, Kuhnemydinae. Kuhnemydines are
fossil species from Asia, and the team's analysis suggests the family Trionychidae originated in Asia before migrating to North America sometime
in the Late Cretaceous.
The researchers' investigations also led them to another new
classification in the Trionychidae family, a subfamily they named
Chitrainae. This group encompasses modern softshell turtles, including
the narrow-headed and giant softshell turtles found in southern Asia.
The species name walkerorum honors Greg and Susan Walker, whose
philanthropy created The Greg and Susan Walker Endowment in 2006. Under
the terms of that gift, students in the Department of Earth and
Environmental Science (EES) may apply for funds to undertake research
projects for which no other source of support is immediately available.
==========================================================================
"The Greg and Susan Walker Endowment awards research support, typically
for projects costing up to $5,000, in response to proposals submitted to
the endowment through the Department of Earth and Environmental Science,"
says Robert Giegengack, professor emeritus.
"The professors and advisors who approve the endowment do an awesome job
in helping the students thrive," says Joan Buccilli, an administrator
in the EES department who assists students seeking support. "However,
I really do feel I have the best job, getting to navigate through their
awards with them and getting to see firsthand how excited they are and
what they have accomplished." Jasinski was awarded Walker Research
Grant funds for this project as well as others describing new species of dinosaurs, turtles, dogs, and investigations of dinosaurs and carnivorous mammals. "The Walkers' generous support helped me get the most out of my
time while at Penn," says Jasinski, "and I know they were vital to the
research of other students as well. This was one of the major reasons we
wanted to name this new species in their honor." Hermann Pfefferkorn, professor emeritus, says, "Research funds like the one established by the Walkers allow both undergrad and graduate students to pursue research
that is not funded by the grants of their professors. This means that
their creativity can bear fruits very early in their career. In this
way they learn to be scientists in their own right."
========================================================================== Story Source: Materials provided by University_of_Pennsylvania. Note:
Content may be edited for style and length.
========================================================================== Related Multimedia:
* Fossils_and_artist's_impression_of_the_softshell_turtle ========================================================================== Journal Reference:
1. Steven E. Jasinski, Andrew B. Heckert, Ciara Sailar, Asher
J. Lichtig,
Spencer G. Lucas, Peter Dodson. A softshell turtle (Testudines:
Trionychidae: Plastomeninae) from the uppermost Cretaceous
(Maastrichtian) Hell Creek Formation, North Dakota, USA, with
implications for the evolutionary relationships of plastomenines
and other trionychids. Cretaceous Research, 2022; 135: 105172 DOI:
10.1016/ j.cretres.2022.105172 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/03/220311095330.htm
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