Chuck Bednar for redOrbit.com – @BednarChuck
An in-depth analysis of fossils, genes, and the anatomy of 73 different species of snakes and lizards has discovered that slithering serpents first evolved on land, not in the sea, and were actually nocturnal predators that had tiny hindlimbs, complete with ankles and toes.
The analysis, conducted by a team led by Yale University researchers and detailed in a paper published Wednesday in the journal BMC Evolutionary Biology, concluded that the creatures most likely emerged from the warm, forested ecosystems of the Southern Hemisphere around 128 million years ago, helping settle a longstanding debate about their origins.
While snakes are incredibly diverse, with more than 3,400 species currently living in an array of different types of habitats, the secrets of their evolution and the appearance of their ancestors had long remained a mystery, lead author Allison Hsiang, a postgraduate associate in the university’s department of geology and geophysics, explained in a statement.
Hsiang said that the study marks the first time experts have thoroughly tested the hypotheses of snake origins using high-tech methods, and that thanks to their efforts, she and her fellow authors were able to generate what they call “first comprehensive reconstruction” of an ancestral snake.
Painting a detailed picture of the ancestor of modern snakes
The researchers identified the similarities and differences between different snake species, and used this information to create a family tree and highlight the primary traits that were part of the evolutionary history of these creatures. They concluded that snakes likely originated on land in the middle Early Cretaceous period (approximately 128.5 million years ago).
“The cutting-edge methods we applied include a new method of determining the evolutionary interrelationships of living and extinct organisms by simultaneously analyzing large genomic, anatomical, and fossil datasets to yield an evolutionary tree depicting the relationships among modern and fossil snakes,” Daniel J. Field, a Ph. D. Candidate at Yale’s Department of Geology and Geophysics and one of the authors of the new study, told redOrbit via email.
“Once this family tree was obtained, we used it as the basis for a second set of computational analyses aimed at inferring the most likely ancestral condition of the extinct primordial snake ancestor – was it nocturnal or diurnal? Terrestrial or aquatic in its habits? Did it live in the northern or the southern hemisphere? And when in earth history did it likely live?” he said.
“From those analyses, we were able to determine some interesting and surprising features about the earliest snakes. For example, we determined that the earliest snakes likely retained small hind limbs, complete with ankles and toes,” Field added. “We also concluded that these snakes were likely nocturnal, and they would have been incapable of constricting their prey like some snakes do today. These snakes would have lived on land, and, like many living snakes, would likely have been nocturnal in their habits.”
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