Filling within the hyperlinks of the evolutionary chain with a fossil document of a ”snake with 4 legs” connecting lizards and early snakes could be a dream come true for paleontologists. But a specimen previously thought to suit the invoice will not be the lacking piece of the puzzle, in keeping with a brand new Journal of Systematic Palaeontology examine 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,” mentioned Caldwell, lead writer of the examine and professor within the departments of organic 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 hyperlink found?
In a paper printed within the journal Science in 2015, a workforce of researchers reported the invention of what was believed to be an instance of the primary identified 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,” mentioned Caldwell.
Caldwell defined that the brand new examine of Tetrapodophis revealed quite a few mischaracterizations of the anatomy and morphology of the specimen—traits that originally gave the impression to be shared most carefully with snakes, suggesting this is perhaps the long-sought-after snake with 4 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 amplectus is not in fact a snake and was misclassified,” mentioned 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 famous, had been hiding within 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,” mentioned Caldwell. “The original study only described the skull and overlooked the natural mould, which preserved several features that make it clear that Tetrapodophis did not have the skull of a snake—not even of a primitive one.”
A controversial specimen
Although Tetrapodophis might not be the snake with 4 legs that paleontologists prize, it nonetheless has a lot to show us, mentioned examine coauthor Tiago Simões, a former U of A Ph.D. pupil, Harvard post- doctoral fellow and Brazilian paleontologist, who identified a number of the options that make it distinctive.
“One of the greatest challenges of studying Tetrapodophis is that it is one of the smallest fossil squamates ever found,” mentioned Simões. “It is comparable to the smallest squamates alive today that also have reduced limbs.”
An extra problem to finding out the Tetrapodophis is entry 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,” mentioned Simões.
“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.”
The examine, “Tetrapodophis amplectus is not a snake: Reassessment of the osteology, phylogeny and functional morphology of an Early Cretaceous dolichosaurid lizard,” was printed within the Journal of Systematic Palaeontology.
Michael W. Caldwell et al, Tetrapodophis amplectus will not be a snake: re-assessment of the osteology, phylogeny and purposeful morphology of an Early Cretaceous dolichosaurid lizard, Journal of Systematic Palaeontology (2021). DOI: 10.1080/14772019.2021.1983044
Taylor & Francis
Paleontologists debunk fossil considered lacking hyperlink between lizards and first snakes (2021, November 18)
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