These can lead to new traits, such as altered coloration, new susceptibility to disease or protection from it, or different shaped features (such as legs, antennae, toes or internal organs). In living organisms, the evolution usually involves random changes to genes that will then be passed along to an individual’s offspring. The newer type is not necessarily more “advanced,” just better adapted to the conditions in which it developed.Įvolve To change gradually over generations, or a long period of time. These changes usually result in a new type of organism better suited for its environment than the earlier type. A second line of so-called bird-hipped, or ornithischian dinosaurs, led to a widely differing group of animals that included the stegosaurs and duckbilled dinosaurs.Įvolution A process by which species undergo changes over time, usually through genetic variation and natural selection. rex and the lumbering four-footed Apatosaurus (once known as brontosaurus). The lizard-hipped line became saurichians, such as two-footed theropods like T. Their descendants eventually split into two lines. All descended from egg-laying reptiles known as archosaurs. These ancient reptiles lived from about 250 million years ago to roughly 65 million years ago. Used as an adjective, the term would be cranial.ĭinosaur A term that means terrible lizard. Still, he told Science News that Caldwell’s team makes “a good case for these fossils being related to snakes.” In fact, he adds: “These fossils are the best candidates we’ve seen yet for early snake relatives.” Power Words (for more about Power Words, click here)Ĭranium The part of the skull that protects the brain. He’s a paleontologist at the University of Bath in England. “With only bits of skeleton to work with, it’s easy to make a mistake,” cautions Nicholas Longrich. (The researchers assume that they had four legs because snake species that lived tens of millions of years later had hind legs.) But even looking only at head fossils can help scientists answer questions about how life has changed over vast periods of time. That means they know little about what the rest of the body looked like. That helped them hold fast to wriggling prey.Ĭaldwell and his team based their study only on skull fossils. Indeed, Caldwell notes: “Snakes have very mobile skulls.” Besides being flexible, the ancient skulls - like in modern snakes - had teeth that curved backwards. Skull shape, and not the legless body, was the feature that gave snakes an early survival edge, the new study suggests. However, they already had developed their special skulls. Those ancient animals most likely still had four small legs, Caldwell told Science News. All were between 143 million and 167 million years old. The researchers found four new species of snakes. So for 10 years his team searched other museum collections. That discovery made him wonder if other ancient snakes had been overlooked in fossil collections. At one point he came across snake bones from the Jurassic Period. This project began while he was examining lizard fossils from England. He has been working on the new analysis of ancient snakes for more than a decade. Michael Caldwell is a paleontologist at the University of Alberta in Canada. But the new study’s authors now “challenge this,” he says, “and present a new head-first hypothesis.” “It allows constriction, an ancient predation strategy.” A highly mobile skull would have come later, he told Science News. Scientists who study snakes had assumed “the long body evolved first,” he notes. A paleontologist at the Senckenberg Museum in Frankfurt, Germany, he did not work on the new study. Indeed, the new findings challenge a common assumption about how snakes evolved, says Krister Smith.
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