Fossils document how dinosaurs gave rise to birds

Everyone knows that dinosaurs are extinct. As children, many of us gazed in awe at the fossils of these magnificent beasts. As adults, a lot of us still do! Except that dinosaurs aren't extinct, at least based on the most recent interpretations of the fossil record and analyses of DNA. The collective evidence points to a conclusion …

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Manatees that walked on land

Manatees and the dugong, known collectively as sirenians, are herbivorous, aquatic mammals that are generally restricted to shallow, tropical waters. Like whales, sirenians have reduced the amount of hair on their bodies, have forelimbs shaped into flippers, lack external hindlimbs and have a paddle-like tail. Despite their overall similarities, the DNA of sirenians is much more similar to that …

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The earliest platypuses: bigger and toothier

Platypuses are strange creatures, even to evolutionary biologists. They have hair, webbed feet, a beaver-like tail, and duck-like bills with which they can sense electrical currents, they lay eggs, and the males possess venom glands on their hind limbs. When a drawing and a pelt of the animal were first sent to British scientists at the end of the …

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How the ankylosaurs got their club-like tails

Ankylosaurs were a group of herbivorous dinosaurs that were covered with bony armor composed of osteoderms (bones formed in their skin), much like the mammalian glyptodonts. Many of the ankylosaurs had osteoderms flanking the tips of their tails, making a club-like structure that may have been used to ward off predators or compete for females. A recent paper [1] …

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How the turtle got its shell

Turtles are unique among reptiles in that they have a large shell, composed of a carapace on their back and a plastron on their belly. This shell largely develops from fused ribs and bones derived from the skin. Since turtles presumably evolved from a lizard-like ancestor to become the distinctively shelled creatures we know of today, we might …

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Way back when snakes had legs

As I recently discussed, snakes are genetically nested within lizards. One of the major evolutionary implications of this fact is that snakes used to have legs. Just this week, researchers [1] heralded the discovery of a major fossil, helping to bridge the putative transition from legged-lizard ancestors to modern legless snakes. Tetrapodophis 125-113 million years ago …

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A bat with claws

Bats are unique among mammals in that they are capable of powered flight. While we do not have evidence of flightless bats, we do have fossils of bats with primitive features. The oldest known species* is Onychonycteris finneyi, which Nancy Simmons and colleagues discovered in Wyoming rocks that date to approximately 52.5 million years ago [1]. If you've ever …

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When whales walked: Fossils document the rise of the largest animals on earth

Whales provide some of the best evidence that evolution has occurred, with DNA, development, biogeography, and the fossil record all telling the same story: that whales once walked on land. Now before you start imaging a humpback whale or a bottlenose dolphin with legs, let me back up and clarify. Whales, as we now know …

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Transitional fossils: Are there any, really?

Perhaps the most damning criticism of Charles Darwin's theory of evolution by natural selection was based on fossils. If organisms evolve such that their descendants adopt radically different forms than their ancestors, why don't we see evidence of this in the fossil record? As if on cue, two years after Darwin outlined his theory in …

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