A 70-million-year-old piece of shark poop has revealed the baby predator's last meal: baby turtle.
Aug. 30, 2011 --
Evolution and natural selection have played a role in the ever-changing landscape of plants, animals, bacteria and fungi. Although species evolve as they find their niche and adapt to new opportunities, some animals have remained relatively unchanged over the course of history. These animals are known as living fossils. Compared to the animals on this list, humans are relative newcomers to this planet. Homo sapiens emerged out of Africa a mere 200,000 years ago. Many living fossils are considerably older than humans and other mammals; some have even outlasted the dinosaurs. In this slideshow, take an up-close look at animals that have persevered virtually unchanged through the ages and continue to thrive today. We begin with the platypus, an unusual egg-laying animal with fur, a bill and a venomous bite. Charles Darwin himself coined the term "living fossil" while observing the platypus. Native to eastern Australia, the animal is the only surviving example of its family, Ornithorhynchidae. This group of animals is believed to have split from mammals some 166 million years ago.
The horseshoe crab could hold the distinction of being the oldest animal species still in existence. Dating back to the Paleozoic era, the horseshoe crab existed on Earth before the dinosaurs and soldiered on through several mass extinction events. In 2008, a horseshoe crab fossil, the oldest in existence found so far, dated back to around 445 million years ago, according to a report by LiveScience.
The tadpole shrimp, Triops cancriformis, is another contender for the title of oldest living animal species. This shrimp is related to the horseshoe crab so its longevity should come as no surprise. According to a report by The Telegraph, the tadpole shrimp as it appears today is virtually identical to a fossil of a specimen that lived some 200 million years ago just as dinosaurs rose to prominence. Despite the animal's remarkable endurance, the tadpole shrimp is currently listed as an endangered species.
Once thought to be extinct in the same event that killed off the dinosaurs some 65 million years ago, the coelacanth is a lobe-finned fish that sparked a debate over whether this species represented a missing link between aquatic animals and four-legged terrestrial creatures, according to National Geographic. The animal was rediscovered in 1938 and only two species of coelacanth still exist today. In 2007, a fossilized coelacanth fin was found dating back roughly 400 million years.
Snapping turtles as we know them first walked the earth some 40 million years ago, but they have been virtually unchanged over the past 215 million years of their evolution, according to Tortoise Trust. Although not among the most endangered tortoises and turtles according to the Turtle Conservation Coalition, the snapping turtle is listed as threatened.
The more than 20 species of alligators and crocodiles living today have evolved beyond their more primitive ancestors. But the basic physical design of these reptiles has remained essentially the same for the past 320 million years or so. Alligators and crocodiles share a common ancestry, though the two groups separated from each other some 60 million years ago.
The nautilus is the most primitive cephalopod in existence, a group that includes the most complex squid and octopus. Dating back to more than half a billion years ago, the nautilus reached the high point in its evolution during the Paleozoic era about 505 million to 408 million years ago. Several species of nautilus still survive today -- relatively unchanged from their ancestral counterparts.
Goblin sharks are rare, deep-sea dwellers with a unique elongated nose that distinguishes them from other sharks. They're also ancient, and are between 112 million to 124 million years old as a species. Around 2,000 different species of fossil sharks have been discovered, according to the ReefQuest Centre for Shark Research. The earliest sharks predate the dinosaurs by more than 200 million years.
The cockroach is famous for being a survivor. These insects can survive for weeks without their heads and even withstand the fallout following a nuclear blast. Cockroaches are also an especially long-surviving animal. Roaches have thrived on Earth for some 320 million years, with an estimated 5 million to 10 million individual species ranging in shape, size and habitat. This photo shows Blaberus giganteus, one of the largest species of cockroach on Earth.
Hagfish may have had to endure a less-than-flattering name since scientists first described them in the 18th century. However, these famously ugly marine animals have existed for about half a billion years. The hagfish also represents an important evolutionary step in the development of vision. These ancient fish may have been among the earliest animals to evolve more complex, camera-like eyes as opposed to the strictly photosensitive vision possessed by more primitive species. As such, the hagfish represents a kind of missing link in the evolution of the eye.
LOS ANGELES — More than 70 million years ago, a baby shark may have bitten off more than it could digest.
A fossilized hunk of poop from an ancient baby shark has revealed the tiny predator's last meal: a baby turtle. The findings were presented here at the 73rd annual meeting of the Society of Vertebrate Paleontology.
"It's a case where a newborn shark ate a newborn turtle and died," said study co-author David Schwimmer, a paleontologist at Columbus State University in Georgia.
The 1.5-inch-long (3.8 centimeters) piece of fossilized poop, technically known as a coprolite, was found at a fossil bed near the South Carolina coastline. Between 70 million and 80 million years ago, when the poop's owner lived, the area was a tidal estuary where the ocean met inland river systems. [8 Weird Facts About Sharks]
Based on the size of the coprolite, Schwimmer and his colleagues hypothesize that the shark that ejected it was a newborn. Inside the coprolite were several tiny turtle vertebrae, each about 0.1 inches (about 3 millimeters) long, which must have come from a very young turtle.
The vertebrae suggest the turtle is a soft-shell freshwater species, whereas the shark comes from a marine environment. Based on that information, Schwimmer believes the shark may have emerged from an estuarine pupping ground, where baby sharks hatched. Once the newborn shark emerged, it devoured the unsuspecting newborn turtle.
The turtle was probably about 4 inches (10 cm) across, while the shark may not have been much bigger. The fact that the vertebrae were undigested indicates the baby predator died not long after eating, possibly because its last meal didn't sit well with the animal, Schwimmer said.
"It's possible the turtle was too much shell," Schwimmer told LiveScience. The shark "may have died from too much turtle."
Though Schwimmer hasn't determined the shark and turtle species, one possibility is that the shark may be the extinct coastal predator Squalicorax kaupi. The turtle may have been a relative to common freshwater species that are found in the region today.
This isn't the first time paleontologists have gleaned something from ancient shark poop. Other shark coprolites have revealed that sharks dealt with tapeworms even 270 million years ago, and fossilized dung from other animals can reveal their dietary habits.
More from LiveScience:
Image Gallery: Pile of Turtle Fossils Unearthed
Image Gallery: 25 Amazing Ancient Beasts
Cyclops of the Sea: Pictures of a One-Eyed Shark