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Move over, dinosaurs!
Untold numbers of fossils representing billions of years of geologic history are preserved around the planet, and though large and heavy dinosaur bones tend to be the most visible examples, fossils can take many forms.
Fossils can represent microscopic creatures, animals with no bones at all, preserved internal organs, and traces of skin, hair and feathers. They can even offer evidence of ancient animals' behavior in impressions of footprints or burrows, or as individuals trapped in amber — snapshots of life in scenes from the distant past.
In addition to offering tantalizing glimpses of animals that went extinct millions of years ago, fossils also reveal the ancient world they inhabited. Each precious find is another tiny piece in the vast puzzle of Earth's geologic history, and helps scientists to understand how life on this planet evolved and changed over billions of years.
Here are a few examples of spectacular finds that offer a window into Earth's past, and help scientists understand the remarkable animals that lived long ago.
Oldest on EarthSlide 2 of 17
Oldest on Earth
Scientists recently unearthed the oldest fossils ever found: layered structures created by microbes 3.7 billion years ago, preserved in ancient rock in Greenland. Their discovery pushes back the earliest evidence of life on Earth by approximately 220 million years. [3.7-Billion-Year-Old Rock May Hold Earth's Oldest Fossils]
The fossils were found in metamorphic rocks that were subject to intense underground heating and pressure, so the finding will likely face scrutiny over whether the observed structures arose from natural causes or if they indeed have biological origins, according to scientists.Slide 3 of 17
Tiny "vampires"Slide 4 of 17
Microscopic fossil structures perforated by tiny, circular and half-moon-shaped holes show that even ancient microbes had predators. Discovered in Arizona's Grand Canyon, these preserved, shell-like pods that protected single-cell organisms were punctured in several places — most likely by a miniscule creature in search of a meal, according to a study published in May 2016 in the journal Proceedings of the Royal Society B.
"It would be hard to explain these very distinct holes, except through predation," according to Melanie Hopkins, an assistant curator of invertebrate paleontology at the American Museum of Natural History in New York City.
Hopkins, who was not involved in the study, told Live Science that this is the oldest known evidence of predatory behavior, dating back approximately 750 million years ago.
Study author Susannah Porter, an associate professor of paleobiology at the University of California in Santa Barbara, wrote in the study that this type of predation — which she described as "vampire-like" — is similar to that of certain amoebas alive today, which may be modern relatives of this ancient predator.Slide 5 of 17
Oldest nervous systemSlide 6 of 17
Oldest nervous system
The oldest and best-preserved nervous system to date belongs to a fossilized arthropod that looked like a shrimp in a fancy helmet.
Discovered in what is now South China, Chengjiangocaris kunmingensis lived 520 million years ago, and was described in a study published in March 2016 in the journal Proceedings of the National Academy of Sciences.
Running along the length of the ancient animal's segmented body was a visible central nerve cord, studded with nerve tissue masses arranged along its entire length. The preservation was so good that researchers were even able to detect individual nerve structures.
Fossilization typically preserves only hard structures such as bones, teeth, exoskeletons or shells. But the location where these arthropod fossils were found is well-known for conditions that are ideal for preserving soft tissue. The animal's carcass likely was buried in fine sediment and had little exposure to oxygen; this allowed the internal organs to fossilize rather than decay, and preserved them in exceptional detail.Slide 7 of 17
An intermediate pterosaurSlide 8 of 17