Paleontologists debunk fossil thought to be missing link between lizards
and first snakes

Date:
November 18, 2021
Source:
Taylor & Francis Group
Summary:
Filling in the links of the evolutionary chain with a fossil record
of a 'snake with four legs' connecting lizards and early snakes
would be a dream come true for paleontologists. But a specimen
formerly thought to fit the bill is not the missing piece of the
puzzle, according to a new study.



FULL STORY ========================================================================== Filling in the links of the evolutionary chain with a fossil record of a ''snake with four legs" connecting lizards and early snakes would be a
dream come true for paleontologists. But a specimen formerly thought to
fit the bill is not the missing piece of the puzzle, according to a new
Journal of Systematic Palaeontologystudy led by University of Alberta paleontologist Michael Caldwell.


==========================================================================
"It has long been understood that snakes are members of a lineage of four- legged vertebrates that, as a result of evolutionary specializations, lost their limbs," said Caldwell, lead author of the study and professor in
the departments of biological sciences and earth and atmospheric sciences.

"Somewhere in the fossil record of ancient snakes is an ancestral form
that still had four legs. It has thus long been predicted that a snake
with four legs would be found as a fossil." Missing link discovered?
In a paper published in the journal Sciencein 2015, a team of researchers reported the discovery of what was believed to be an example of the
first known four-legged snake fossil, an animal they named Tetrapodophis amplectus.

"If correctly interpreted based on the preserved anatomy, this would be
a very important discovery," said Caldwell.



========================================================================== Caldwell explained that the new study of Tetrapodophisrevealed a number
of mischaracterizations of the anatomy and morphology of the specimen
-- traits that initially seemed to be shared most closely with snakes, suggesting this might be the long-sought-after snake with four legs.

"There are many evolutionary questions that could be answered by finding
a four-legged snake fossil, but only if it is the real deal. The major conclusion of our team is that Tetrapodophis amplectusis not in fact
a snake and was misclassified," said Caldwell. "Rather, all aspects
of its anatomy are consistent with the anatomy observed in a group of
extinct marine lizards from the Cretaceous period known as dolichosaurs."
The clues to this conclusion, Caldwell noted, were hiding in the rock
the fossil was extracted from.

"When the rock containing the specimen was split and it was discovered,
the skeleton and skull ended up on opposite sides of the slab, with a
natural mould preserving the shape of each on the opposite side," said Caldwell. "The original study only described the skull and overlooked
the natural mould, which preserved several features that make it clear
that Tetrapodophisdid not have the skull of a snake -- not even of a
primitive one." A controversial specimen Although Tetrapodophismay not
be the snake with four legs that paleontologists prize, it still has
much to teach us, said study coauthor Tiago Simo~es, a former U of A
PhD student, Harvard post- doctoral fellow and Brazilian paleontologist,
who pointed out some of the features that make it unique.



==========================================================================
"One of the greatest challenges of studying Tetrapodophisis that it is
one of the smallest fossil squamates ever found," said Simo~es. "It is comparable to the smallest squamates alive today that also have reduced
limbs." An additional challenge to studying the Tetrapodophisis access
to the specimen itself.

"There were no appropriate permits for the specimen's original removal
from Brazil and, since its original publication, it has been housed in a private collection with limited access to researchers. The situation was
met with a large backlash from the scientific community," said Simo~es.

"In our redescription of Tetrapodophis, we lay out the important legal
status of the specimen and emphasize the necessity of its repatriation
to Brazil, in accordance not only with Brazilian legislation
but also international treaties and the increasing international
effort to reduce the impact of colonialist practices in science." ========================================================================== Story Source: Materials provided by Taylor_&_Francis_Group. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Michael W. Caldwell, Tiago R. Simo~es, Alessandro Palci, Fernando F.

Garberoglio, Robert R. Reisz, Michael S. Y. Lee, Randall L. Nydam.

Tetrapodophis amplectus is not a snake: re-assessment of
the osteology, phylogeny and functional morphology of an
Early Cretaceous dolichosaurid lizard. Journal of Systematic
Palaeontology, 2021; 1 DOI: 10.1080/ 14772019.2021.1983044 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211118061612.htm

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