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10 Terrific Facts About Trilobites

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For nearly 300 million years, these ancient mariners dotted our ocean floors—surviving, thriving, and fossilizing beneath the waves.

1. OVER 20,000 SPECIES ARE CURRENTLY KNOWN.

Every single continent has yielded trilobite remains. The biggest species (Isotelus rex) was some 28 inches long, while the smallest measured less than a millimeter from end to end. Some sported defensive spines, while others had smooth, rounded shells. And whereas certain trilobites came with disproportionately large eyes, many deep-sea species were blind.

2. TRILOBITES FIRST APPEARED AROUND 540 MILLION YEARS AGO.

Their debut roughly coincided with the dawn of the Cambrian period. During this game-changing chapter in Earth’s history, multi-celled organisms went through an apparent explosion in diversity, or at least an explosion in life forms that leave fossils. New creatures—including a barrage of mollusks and arthropods—seem to have evolved at an unprecedented rate.

The Cambrian also saw trilobites become the most common and diverse animals on the planet. However, trilobites began to decline when the period ended some 500 million years ago. Though the invertebrates stuck around for another 240 million years, they’d never again be so successful.

3. MANY WOULD CURL UP INTO LITTLE BALLS FOR PROTECTION.

When danger struck, some trilobites could ball themselves up like underwater pill bugs, with their rear end flexed under their head. Specimens dating as far back as the late Cambrian have been found in this defensive position. 

4. AT FIRST, SCIENTISTS DIDN’T KNOW WHAT TO MAKE OF THEM.

Fæ, Wikimedia // Public domain

In a 1679 letter, Welsh linguist and naturalist Edward Lhuyd misidentified one as “the sceleton [sic] of some Flat-fish.” Bishop Charles Lyttleton came a little closer to the mark in 1750 when he wrote London’s Royal Society about a “petrified Ins[e]ct” that he’d dug up a year before. While trilobites were, in fact, arthropods, the creatures appear to have been more closely akin to crustaceans and/or chelicerates (i.e. arachnids and horseshoe crabs) than insects.

5. MOST TRILOBITE FOSSILS ARE ACTUALLY MOLTED EXOSKELETONS.

ellenm1,Wikimedia // CC BY 2.0

Over the course of its life, a trilobite outgrew many shells. During the molting process, these discarded husks would often get preserved for posterity. One trilobite could therefore leave behind several trilobite-shaped fossils. Specimens that represent the actual creature—as opposed to its shuffled-off shell—are comparatively rare

6. THREE STATES HAVE MADE A TRILOBITE THEIR OFFICIAL FOSSIL.

JMCC1, Wikimedia // CC BY-SA 3.0 

In 1985, Ohio chose the entire Isotelus genus and Wisconsin went with Calymene celebra. Three years later, Pennsylvania picked Phacops rana after an elementary school class lobbied for its appointment.

 7. TRILOBITES GATHERED FOOD IN A VARIETY OF WAYS.

Generally speaking, early trilobites seem to have hunted down aquatic worms and eaten them alive. It’s been theorized that a few other species evolved to eat plankton or algae—with some making use of a filter-feeding mechanism.

8. TRILOBITES WERE WIPED OUT BY THE BIGGEST EXTINCTION IN HISTORY.

NASA/JPL-Caltech/UCLA (WISE),Wikimedia Commons

Some call it the "Great Dying”—250 million years ago, 90 percent of all species on earth suddenly perished. Possible causes include everything from increased volcanic activity to exploding supernovas. Regardless, the event—also known as the Permian Extinction—killed off a number of insects, sharks, armored fish, mammal-like creatures, and countless other organisms. Trilobites, however, are by far the most famous lineage to have met their end this way.  

9. NATIVE AMERICANS USED THEM AS AMULETS.

Long before Europeans first set foot on the continent, the Pahvant Ute people, from what is now called Utah, gathered Cambrian trilobites. Believing that the fossils harbored special powers, the natives carried them around as protective charms. These odd, petrified critters were given the name “Timpe-Konitza-Pachuee,” or “little water bug living in a house of stone.”

10. ONE CHINESE TRILOBITE WAS NAMED AFTER A STAR WARS CHARACTER.

Dwergenpaartje, Wikimedia // CC BY-SA 3.0

Around the start of the last decade, paleontologist Samuel Turvey happened upon several new species of trilobites while exploring in China. He gave one new invertebrate the genus name Han, which it shares with China’s biggest ethnic group. When the time came to pick species names, Turvey couldn’t resist bolstering his Star Wars cred, and named one particular trilobite Han solo. (It helped that Han solo was the only species in the genus.)

All photos courtesy of iStock unless otherwise noted. 

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Animals
This Octopus Species in Northern Australia Can Hunt on Dry Land
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YouTube

Most octopuses live in the ocean—but in northern Australia, a small, shallow-water species takes to land in search of food. Abdopus aculeatus is the only octopus that’s specially adapted to walk on dry ground. Using its long, sucker-lined arms, the slimy sea creature pulls itself along the shoreline as it searches tide pools for crabs.

Witness Abdopus aculeatus in action by watching BBC Earth’s video below.

[h/t BBC Earth]

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Weather Watch
Rising Temperatures Are Killing Off African Wild Dogs
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Over the last few decades, images of fluffy white harp seals, polar bears, and penguins have become shorthand for climate change's creeping destruction of our planet. But the poles aren't the only ecosystems in danger. A new study published in the Journal of Animal Ecology finds that rising temperatures near the equator are making it much harder for African wild dogs to survive.

"When people think about climate change affecting wildlife, they mostly think about polar bears," lead researcher Rosie Woodroffe of the Zoological Society of London told The Guardian. "But wild dogs are adapted to the heat—surely they'd be fine."

To find out, Woodroffe and her colleagues analyzed data from packs of African wild dogs (Lycaon pictus) in Kenya, Botswana, and Zimbabwe. The dog packs have been under scientist surveillance for years—some since the late 1980s—and at least one dog per pack is fitted with a radio collar.

The researchers overlaid information about local weather and temperature with data on the dogs' hunting habits, the size of each litter of pups, and how many pups from each litter survived.

These dogs are creatures of habit. Adults rise early and leave the den for a morning hunt. They range over their large territories, chasing antelopes. At midday, when the Sun is highest, they return to their pups with food. They may go out again in the evening as the temperature drops.

But like the polar bears' glaciers, the dogs' environment is gradually heating up. All three countries saw a temperature increase of about 1.8°F over the study period. This may not sound like much, but for the dogs, it was plenty. Between 1989 and 2012, the number of pups per litter in Botswana surviving to their first birthday dropped from 5.1 to 3.3. Dog packs in Zimbabwe saw a 14 percent decrease in pup survival; in Kenya, the rate declined by 31 percent.

"It's really scary," Woodroffe said.

"If you are an animal who makes your living by running around really fast, obviously you are going to get hot. But there are not enough hours in the day anymore that are cool enough to do that. It is possible that some of these big areas will become too hot for wild dogs to exist."

Woodroffe and her colleagues were not anticipating such clear-cut results. "It is shocking and surprising that even right on the equator these effects are being seen," she said. "It illustrates the global impact of climate change." 

[h/t The Guardian]

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