Ice Age manatees may have called Texas home

Date:
October 1, 2020
Source:
University of Texas at Austin
Summary:
Manatees don't live year-round in Texas, but these gentle sea cows
are known to occasionally visit, swimming in for a 'summer vacation'
and returning to warmer waters for the winter. New research has
found fossil evidence for manatees along the Texas coast dating
back to the most recent ice age. The discovery raises questions
about whether manatees have been visiting for thousands of years,
or if ice age manatees once called Texas home.



FULL STORY ========================================================================== Manatees don't live year-round in Texas, but these gentle, slow-moving sea
cows are known to occasionally visit, swimming in for a "summer vacation"
from Florida and Mexico and returning to warmer waters for the winter.


========================================================================== Research led by The University of Texas at Austin has found fossil
evidence for manatees along the Texas coast dating back to the most
recent ice age. The discovery raises questions about whether manatees
have been making the visit for thousands of years, or if an ancient
population of ice age manatees once called Texas home somewhere between
11,000 and 240,000 years ago.

The findings were published in Palaeontologia Electronica.

"This was an unexpected thing for me because I don't think about
manatees being on the Texas coast today," said lead author Christopher
Bell, a professor at the UT Jackson School of Geosciences. "But they're
here. They're just not well known." The paper co-authors are Sam Houston
State University Natural History Collections curator William Godwin,
SHSU alumna Kelsey Jenkins (now a graduate student at Yale University),
and SHSU Professor Patrick Lewis.

The eight fossils described in the paper include manatee jawbones and
rib fragments from the Pleistocene, the geological epoch of the last
ice age. Most of the bones were collected from McFaddin Beach near
Port Arthur and Caplen Beach near Galveston during the past 50 years by
amateur fossil collectors who donated their finds to the SHSU collections.



==========================================================================
"We have them from one decade to another, so we know it's not from some
old manatee that washed up, and we have them from different places,"
Godwin said.

"All these lines of evidence support that manatee bones were coming up
in a constant way." The Jackson Museum of Earth History at UT holds
two of the specimens.

A lower jawbone fossil, which was donated to the SHSU collections by
amateur collector Joe Liggio, jumpstarted the research.

"I decided my collection would be better served in a museum,"
Liggio said. "The manatee jaw was one of many unidentified bones
in my collection." Manatee jawbones have a distinct S-shaped curve
that immediately caught Godwin's eye. But Godwin said he was met with skepticism when he sought other manatee fossils for comparison. He
recalls reaching out to a fossil seller who told him point-blank "there
are no Pleistocene manatees in Texas." But examination of the fossils by
Bell and Lewis proved otherwise. The bones belonged to the same species
of manatee that visits the Texas coast today, Trichechus manatus. An
upper jawbone donated by U.S. Rep. Brian Babin was found to belong to
an extinct form of the manatee, Trichechus manatus bakerorum.



==========================================================================
The age of the manatee fossils is based on their association with
better-known ice age fossils and paleo-indian artifacts that have been
found on the same beaches.

It's assumed that the cooler ice age climate would have made Texas
waters even less hospitable to manatees than they are today. But the
fact that manatees were in Texas -- whether as visitors or residents --
raises questions about the ancient environment and ancient manatees, Bell
said. Either the coastal climate was warmer than is generally thought,
or ice age manatees were more resilient to cooler temperatures than
manatees of today.

The Texas coast stretched much farther into the Gulf of Mexico and hosted
wider river outlets during the ice age than it does now, said Jackson
School Professor David Mohrig, who was not part of the research team.

"Subsurface imaging of the now flooded modern continental shelf
reveals both a greater number of coastal embayments and the presence
of significantly wider channels during ice age times," said Mohrig,
an expert on how sedimentary landscapes evolve.

If there was a population of ice age manatees in Texas, it's plausible
that they would have rode out winters in these warmer river outlets,
like how they do today in Florida and Mexico.


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


========================================================================== Journal Reference:
1. Christopher Bell, William Godwin, Kelsey Jenkins, Patrick
Lewis. First
fossil manatees in Texas: Trichechus manatus bakerorum in the
Pleistocene fauna from beach deposits along the Texas Coast of
the Gulf of Mexico.

Palaeontologia Electronica, 2020; DOI: 10.26879/1006 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201001133214.htm

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