12 Oldest Animal Species on Earth

Goblin sharks are among the most terrifying creatures to behold, and for that reason, we're glad they dwell at the bottom of the ocean and rarely stray from there. That's why humans have so infrequently laid eyes on these beasts, even though they've been on Earth for as long as we have and much longer. A live goblin shark was caught in Japan in January 2007, but it died within days. Still, scientists were able to examine the specimen and learn much about this rarely encountered living fossil. (National Geographic)

Image via REUTERS/Tokyo Sea Life Park/Handout

The only terrestrial creatures on the list, these ants may be among the oldest species still living on Earth, but they're new to human knowledge. That's because although they've been here all this time, scientists only discovered the blind, subterranean ants in 2008, the first discovery of a new ant species since 1923. Martilis heureka represented not just a new species of ant, but also a whole new genus and subfamily, a primitive, prehistoric one that existed at the very beginning of ant evolution 120 million years ago. (Science Daily)

Image via Michael Brantstetter/www.antweb.org/Wikimedia

Frilled sharks are the oldest species of shark still in existence. Given their age, they are less evolved than more "modern" sharks, and therefore their simple bodies appear like some combination of a shark and an eel. Like goblin sharks, frilled sharks live at the bottom of the ocean and so, despite being caught occasionally by accident, they're rarely encountered by humans. On the other hand, now that you see what a frilled shark looks like, we can't promise you won't be seeing them in your nightmares. (Sharkfacts)

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Image via Awashima Marine Park/Getty Images

Although tadpole shrimp have been on Earth for more than 200 million years, they are classified as an endangered species. Will they end their long run of existence before today's generations of humans? Maybe not. In 2010, scientists discovered a unique trait that gives these animals a shot at continued survival. It seems their eggs can lie dry and dormant for extremely long periods and still create new life when rehydrated. Said Dr. Larry Griffin from the Wildfowl and Wetlands Trust, "Now that we know how this curious creature survives, we have realised that there's a good chance there are more populations out there." Here's to 220 million more years. (The Telegraph U.K.)

Image via NalesnikLD/Wikimedia

"Sturgeon" is actually an umbrella term for several species that have existed for around 200 million years. But despite being so ancient, almost every species of sturgeon is now critically endangered due to that most deadly of predators: us. Sturgeon are harvested for their roe, which are prized for their use in making caviar. But sturgeon grow and mature slowly (they can live for 100 years), so over-harvesting, pollution and habitat destruction all combine to threaten their continued existence. The good news is that sturgeon are able to produce millions of eggs. The bad news is that we keep eating those eggs. (International Union for Conservation of Nature)

The oldest shrimp on Earth, these ancient creatures took the messages in their yearbooks seriously: They haven't changed. In some 200 million years on the planet, evolution hasn't altered the horseshoe shrimp a bit. We know this because we have horseshoe-shrimp fossils from that long ago, and they show an animal that is exactly the same as the ones that are still swimming around today. (Triops Guys)

Image via Visuals Unlimited, Inc./Fabio Pupin

Lampreys are creepy, eel-like parasites with circular mouth holes filled with dozens and dozens of small, sharp teeth that they use to latch onto fish hosts and suck their blood. Disturbing, right? Well, if you're hoping to get in a time machine and escape to a time when lampreys didn't exist, you'd have to go all the way back to the Palaeozoic era. In 2006, scientists studied a 360-million-year-old lamprey fossil, only to discover that it was essentially the same as the lampreys we have today. "They're very ancient, very primitive animals," said Dr. Michael Coates of the University of Chicago. (University of Chicago)

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Coelacanths used to be extinct … but then they weren't! Well, not really. But we thought they'd been extinct for millions of years until we found one in 1938. Since then, scientists have studied the very rare, endangered fish with great interest because they are so similar to the ancient fish that eventually evolved to crawl out of the water and become the first land vertebrate. In fact, just last week, a team of scientists reported the genome sequence of the coelacanth for the first time. Understanding the coelacanth's genetic blueprint can help us understand how they evolved into, well, just about everything. (Los Angeles Times)

Image via Hoberman Collection/UIG via Getty Images

Horseshoe crabs are among the most well-known of "living fossils," having remained virtually unchanged for an astonishing 445 million years on Earth. Canadian scientists found a new horseshoe-crab fossil that dated that far back in 2008. Although the creatures were already considered one of the oldest living animals on the planet, the new fossil proved that they were a full 100 million years older than we previously knew, and yet still the same today as they were all the way back then. (Science Daily)

Half a billion years. That's how long the nautilus has called our planet home, surviving all the major mass extinctions that hit the reset button on life throughout the globe. But now the nautilus is in danger of becoming extinct. Why? Because humans like cool shells. People harvest the nautilus because they prize their unique spiral shells and use them for decoration. But we've overfished them nearly to extinction. In places where a person used to be able to catch hundreds per day, now only one or two may be caught. (Phys.org)

As we get to the very oldest animals on Earth, they become more and more primitive. That's because now we're talking about a time long enough ago that land-dwelling creatures didn't exist at all. But jellyfish existed, even 505 million years ago. That makes them almost twice as old as we thought they were until recently. In 2007, researchers from the University of Kansas found new fossil evidence of jellyfish going back over half a billion years, 200 million more than the oldest know jellyfish fossils up until that point. So it's more accurate to say that jellyfish are 505 million years old at least. Who knows what evidence we may find to show they're even older than that? (Science Daily)

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It's unclear exactly how long sea sponges have been around, but they are at least old enough to be the longest-existing creatures on Earth, outside the realm of microorganisms (like bacteria). The oldest evidence of a sea sponge found was a fossil discovered just last year in a 760-million-year-old rock. This beat the previous record for oldest sea-sponge fossil, a 635-million-year-old sponge discovered in 2009. There may be still older fossils yet to find. But finding an older species is unlikely, as these simple organisms appear to be the progenitors of much more complicated life, including the first multicellular animals. (National Geographic)