The evolution of snakes from lizards

Snake evolution legs

The diversity in cranial structure of squamates is remarkable and appears tightly linked to functional and constructional demands within specific clades of lizards or snakes 34 , 35 , 36 , 37 , 38 , 39 , suggesting that large-scale comparisons of skull shape and size across the whole of Squamata could offer a holistic framework to address the ecological origin of snakes. The study was published online today July 23 in the journal Science. The ecological origins of snakes as revealed by skull evolution. So it does look as though snake evolution began in the southern continents. Firstly, the old and worn skin is replaced; secondly, it helps get rid of parasites such as mites and ticks. Further complicating matters, snake-like amphibians called "aistopods" appear in the fossil record over million years ago, the most notable genus being Ophiderpeton; these were completely unrelated to modern snakes. Different regions of the skull are visible by black lines connecting landmark points: B, back of the skull; F, frontal; M, maxilla; N, nasal; P, parietal; PM, pre-maxilla; Q, quadrate. In complement, and to formally test the recently revived hypothesis that snake skulls evolved by heterochrony 27 , 40 , 45 , we quantified ontogenetic skull shape variation by analyzing multivariate ontogenetic trajectories in a unique data set of squamate embryos. Conflicting ecological hypotheses for early snakes, including aquatic 9 , 10 , 11 , terrestrial 12 , 13 , 14 , fossorial 15 , 16 , 17 , 18 , or even multiple habitats 19 , have been proposed based on cladistic analysis of discrete traits. The 3D-rendered skulls with species names corresponding to the observed extreme species in both positive and negative directions are shown. Three major competing hypotheses for the habitat of early snakes -- burrowing i. These patterns are often related to behavior, such as a tendency to have to flee from predators. Digital snake skulls. The percent of extant families collected at a particular branch is shown for major lineages. Palaeontology Abstract The ecological origin of snakes remains amongst the most controversial topics in evolution, with three competing hypotheses: fossorial; marine; or terrestrial.

One major challenge the group faced was to collect reptile specimens covering all major groups of lizards and snakes. The roughly million-year-old snakedubbed Tetrapodophis amplectus literally, four-legged snakelikely didn't use its feet for walking.

Why are snakes limbless

Furthermore Filipe Oliveira da Silva, the first author of the study, suggests that snake evolution and diversification was not a straightforward process but rather an interplay between natural selection and developmental processes. Other major skull shape changes present both in lizards and snakes include the shortened quadrate bone along its dorso-ventral axis at negative PC2 values, a condition also found in convergent morphologies Figs. These results show that the evolutionary path followed by snakes is more complicated than previously thought. Plain snakes usually adopt active hunting strategies, as their pattern allows them to send little information to prey about motion. The positions of sampled fossils and ontogenies are indicated by blue crosses and stars, respectively. The probe is marked at the point where it stops, removed, and compared to the subcaudal depth by laying it alongside the scales. Until recently, the biggest prehistoric snake in the fossil record was the appropriately named Gigantophis , a late Eocene monster that measured about 33 feet from head to tail and weighed as much as half a ton. Unfortunately for Gigantophis fans, this prehistoric snake has been eclipsed in the record books by an even bigger genus with an even cooler name: the South American Titanoboa, which measured over 50 feet long and conceivably weighed as much as a ton.

This close-up photo shows Tetrapodophis' rear feet. Instead, the appendages may have helped Tetrapodophis hold onto a partner while mating, or even grip unruly prey, said study co-researcher David Martill, a professor of paleobiology at the University of Portsmouth in the United Kingdom.

Image credit: Alessandro Palci An ongoing debate The question of whether modern snakes evolved from swimming or burrowing ancestors has been dangling in the mind of researchers for more than a hundred years. In a paper published Thursday in Nature Communications, the researchers explain that they came to their conclusion after comparing the shape and size of skulls belonging to species of lizards and snakes.

Thus, the study adds another dimension to the investigation of snake origins.

Snake evolution game

Image credit: Julius T. It's likely that Tetrapodophis used its long body to constrict prey , such as lizards and frogs, Martill added. Molting A snake shedding its skin. Caldwell, from the University of Alberta in Canada. Introduction A century of anatomical and phylogenetic studies have established that snakes evolved from lizards 1 , 2 , these two groups forming together one of the most-specious clades of terrestrial vertebrates—the squamate reptiles. The body scales may be smooth, keeled , or granular. A probe is inserted into the cloaca until it can go no further. Previous research has detailed two-legged snake fossils , but this is the first known snake ancestor to sport four legs, he said. Notably, a discrete area containing all fossorial lizard and snake species clearly separates from other ecologies at negative PC2 values Fig.

For clarity, only Toxicofera specimens are shown. The Giant Prehistoric Snakes of the Cenozoic Era Speaking of giant monitor lizards, some prehistoric snakes also attained gigantic sizes, though once again the fossil evidence can be frustratingly inconclusive.

snake lower classifications

It likely evolved from terrestrial-burrowing creatures, and was a transitional animal that lived during the shift from ancient lizards to modern-day snakes, he added. The new study used CT scans to create three-dimensional structures of the inner ear bones of 80 snake and lizard species, including living semi-fossorial and semi-aquatic snakes as well as a primitive fossil snake of the genus Dinilysia.

The inner surface of the old skin liquefies. Furthermore Filipe Oliveira da Silva, the first author of the study, suggests that snake evolution and diversification was not a straightforward process but rather an interplay between natural selection and developmental processes.

snakes with legs
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The ecological origins of snakes as revealed by skull evolution