[Paleontology • 2015] Desmatochelys padillai • Oldest Known Marine Turtle? A New protostegid from the Lower Cretaceous of Colombia
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| Desmatochelys padillai Cadena & Parham. 2015
This is what the habitat of Desmatochelys padillai might have looked like 120 million years ago.
Illustration: Jorge Blanco || Cadena & Parham. 2015. PaleoBios. 32(1).
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Recent studies suggested that many fossil marine turtles might not be
closely related to extant marine turtles (Chelonioidea). The uncertainty
surrounding the origin and phylogenetic position of fossil marine
turtles impacts our understanding of turtle evolution and complicates
our attempts to develop and justify fossil calibrations for molecular
divergence dating. Here we present the description and phylogenetic
analysis of a new fossil marine turtle from the Lower Cretaceous (upper
Barremian-lower Aptian, >120 Ma) of Colombia that has a minimum age
that is >25 million years older than the minimum age of the
previously recognized oldest chelonioid.
This new fossil taxon, Desmatochelys padillai sp. nov.,
is represented by a nearly complete skeleton, four additional skulls
with articulated lower jaws, and two partial shells. The description of
this new taxon provides an excellent opportunity to explore unresolved
questions about the antiquity and content of Chelonioidea. We present an
updated global character-taxon matrix that includes D. padillai and marine turtles known from relatively complete specimens.
Our analysis supports D. padillai as sister taxon of D. lowi within Protostegidae, and places protostegids as the sister to Pan-Dermochelys within
Chelonioidea. However, this hypothesis is complicated by discrepancies
in the stratigraphic appearance of lineages as well as necessarily
complicated biogeographic scenarios, so we consider the phylogeny of
fossil marine turtles to be unresolved and do not recommend using D. padillai
as a fossil calibration for Chelonioidea. We also explore the
definition of “marine turtle,” as applied to fossil taxa, in light of
many littoral or partially marine-adapted fossil and extant lineages. We
conclude that whereas the term “oldest marine turtle” depends very much
on the concept of the term being applied, we can confidently say that D. padillai is the oldest, definitive, fully marine turtle known to date.
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| The skeleton of the fossilized sea turtle measures almost 2 meters.
Cadena & Parham. 2015. PaleoBios. 32(1).
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| The skeleton of Desmatochelys padillai sp. is almost completely preserved. |
Oldest Fossil Sea Turtle Discovered - The fossilized turtle is at least 120 million years old
Scientists at the Senckenberg Research Institute in Frankfurt have
described the world’s oldest fossil sea turtle known to date. The
fossilized reptile is at least 120 million years old – which makes it
about 25 million years older than the previously known oldest specimen.
The almost completely preserved skeleton from the Cretaceous, with a
length of nearly 2 meters, shows all of the characteristic traits of
modern marine turtles. The study was published today in the scientific
journal “PaleoBios.”
“Santanachelys gaffneyi is the oldest known sea turtle” – this
sentence from the online encyclopedia Wikipedia is no longer up to date.
“We described a fossil sea turtle from Colombia that is about 25
million years older,” rejoices Dr. Edwin Cadena, a scholar of the
Alexander von Humboldt foundation at the Senckenberg Research Institute.
Cadena made the unusual discovery together with his colleague from the
US, J. Parham of California State University, Fullerton.
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Desmatochelys padillai Cadena & Parham. 2015
This is what the habitat of Desmatochelys padillai might have looked like 120 million years ago.
Illustration: Jorge Blanco || Cadena & Parham. 2015. PaleoBios. 32(1).
|
“The turtle described by us as Desmatochelys padillai sp.
originates from Cretaceous sediments and is at least 120 million years
old,” says Cadena. Sea turtles descended from terrestrial and freshwater
turtles that arose approximately 230 million years ago. During the
Cretaceous period, they split into land and sea dwellers. Fossil
evidence from this time period is very sparse, however, and the exact
time of the split is difficult to verify. “This lends a special
importance to every fossil discovery that can contribute to clarifying
the phylogeny of the sea turtles,” explains the turtle expert from
Columbia.
The fossilized turtle shells and bones come from two sites near the
community of Villa de Leyva in Colombia. The fossilized remains of the
ancient reptiles were discovered and collected by hobby paleontologist
Mary Luz Parra and her brothers Juan and Freddy Parra in the year 2007.
Since then, they have been stored in the collections of the “Centro de Investigaciones Paleontológicas” in Villa Leyva and the “University of California Museum of Paleontology.”
Cadena and his colleague examined the almost complete skeleton, four
additional skulls and two partially preserved shells, and they placed
the fossils in the turtle group Chelonioidea, based on various
morphological characteristics. Turtles in this group dwell in tropical
and subtropical oceans; among their representatives are the modern
Hawksbill Turtle and the Green Sea Turtle of turtle soup fame.
“Based on the animals‘ morphology and the sediments they were found in,
we are certain that we are indeed dealing with the oldest known fossil
sea turtle,” adds Cadena in summary.
Cadena, E.A. and J.F. Parham. 2015. Oldest Known Marine Turtle? A New protostegid from the Lower Cretaceous of Colombia. PaleoBios. 32(1).
