The following is a reprint from Uncle John's Bathroom Reader Plunges Into the Universe. Why should dinosaurs have all the fun? Here are a few prehistoric critters that are every bit as bizarre as the strangest of the dinos: Opabinia Artist's rendering of Opabinia. Image: ArthurWeasley [Wikipedia] Opabinia regalis fossil from the Burgess shale on display at the Smithsonian in Washington DC. Image: Jstuby [Wikipedia] It might be a distant cousin of shrimp salad or it might be unrelated to anything alive today. Although it looked like something out of a science fiction movie, this weird four-inch-long animal lived in the sea that covered what is now Canada about 530 million years ago. Instead of legs, it had 14 pairs of oarlike gills used for swimming. But the real strangeness was saved for the head. It had five eyes - two pairs on stalks and another sitting in the middle of the top of the head. In front of all these eyes was a long flexible nozzle with a claw at the end. Scientists think the claw captured food and carried it to the mouth. Hallucigenia Hallucigenia fossil. Photo: Smithsonian National Museum of Natural History This appropriately named little beast bears no resemblance to any animal alive or dead. Like Opabinia, it lived in Canada about 530 million years ago. Hallucigenia is so bizarre that scientists are uncertain which end is the front and which side is up. The most-accepted version shows a wormlike body supported by seven pairs of spines. Along the top of the body were seven long tentacles with two-pronged tips. One end had a bulbous feature that looked a bit like a head but with no sign of eyes or mouth. At the other end was a long tube that curved up over the "back," which may have been a mouth or an anus. Carpoids Bundenbach Carpoid fossil. Photo: Fossil Museum Virtually all animals have some kind of symmetry - either bilateral like humans where your right hand is the mirror image of your left hand, or radial like a starfish, which looks the same no matter which arm is pointing up. But carpoids were completely asymmetrical. This distant relation of the sand dollar lived in the oceans of the Northern Hemisphere from 500 to about 350 million years ago. It looked something like a misshapen armored tadpole, with a bulging body covered with stony plates and a long, segmented tail that it used for swimming. Some scientists think that carpoids may have been the ancestors of vertebrates. Conodonts Various conodonts. Image: USGS For more than a century scientists kept finding microscopic, teethlike objects in marine rocks dating from 510 to 210 million years ago. They looked like tiny, cone-shaped teeth or combs, but there was no sign of a jaw or any other bit of skeleton associated with them. There were quite a few theories about what class of animal these conodonts belonged to, but it wasn't until about 20 years ago that a fossil of the whole animal was found. In appearance it was not spectacular. It was long and thin like a worm, but it had eyes and a low dorsal fin, and the teeth were located in the mouth. Many scientists now believe that the conodont may be one of the earliest-known vertebrates. Ostracoderms Some of the earliest vertebrates were armored, jawless fish that were most common between 430 and 370 million years ago. These fish had skeletons made of cartilage, but their bodies were covered with plates of bone, so it could be said that they were wearing their skeletons on the outside. Ostracoderms could be up to 3 feet (1 m) long, but most were under a foot. Their heads were usually covered by a semicircular shield with two small holes for eyes. The rest of the body was surrounded by articulated plates that allowed the animal to swim slowly by moving its tail from side to side. These animals preferred a quiet environment like a lagoon where they could drift along the bottom, straining edible particles out of the mud. Diplocaulus Diplocaulus magnicornis. Image: ArthurWeasley [Wikipedia] This 3-foot (1 m) long amphibian lived in what is now Texas about 270 million years ago. In most respects it looked like a large salamander, but its head made it unique. The skull was shaped like a boomerang with two small eyes in the front corners and the wings on either side. Scientists are not sure why Diplocaulus's head is such an odd shape, but they think it was either to make the animal swim better near the bottom of the lakes and streams it lived in - or the wide head made it more difficult for predators to swallow. Lystrosaurus Lystrosaurus georgi. Image: Dmitry Bogdanov [Wikipedia] Before the age of the dinosaurs, there were a lot of strange-looking reptiles, but few odder than Lystrosaurus. This 3-foot-long plant-eater had a squat body and splayed legs like a lizard, but its muzzle was shortened a bit like that of a bulldog. As if this wasn't attractive enough, from the corners of its mouth hung two long tusks. The eyes and nostrils were set high up, making some scientists think that the animal had lived the way hippos do now, but recent findings show that Lystrosaurus could also have lived in arid environments that were common about 230 million years ago. Ambulocetus [YouTube Link] Halfway between the land-dwelling ancestors of whales and the modern marine mammals, Ambulocetus lived in what is now Pakistan about 50 million years ago. This 12-foot-long animal looked a bit like a cross between an otter and an alligator. It had a large head with long jaws and pointed teeth designed for catching and holding fish like an alligator, but the body was more like that of an otter. Scientists think it swam by moving its tail up and down like a modern whale rather than from side to side like a fish. Phorusrhacos About 20 million years ago, South America was an island continent with its own unique forms of birds and mammals. Because no large mammalian predators had evolved there, the top carnivore was a bird - Phorusrhacos. These flightless birds stood up to 10 feet (3 m) tall and had a head the size of that of a horse. Although they couldn't fly, they were very fast runners. They could run down their prey, catch it with their powerful talons, and tear it apart with their long, hooked beaks. These frightening birds survived until about 3 million years ago, when a land bridge formed between North and South America, allowing modern carnivores to invade South America and give Phorusrhacos a little carnivorish competition. (Image: Drawing of Phorusrhacos by Charles R. Knight [wikipedia]) Diprotodon Diprotodon optatum. Image: Dmitry Bogdanov [Wikipedia] Diprotodon australis in the British Museum of Natural History. Before humans arrived in Australia about 40,000 years ago, marsupials were larger and more varied than they are today. The largest of all was the Diprotodon, which was about the size of a hippopotamus. It looked like a gigantic wombat (one of those furry, bearlike things), and it ate leaves and grass. It wasn't a fast runner, but it was too large for any of the native predators to tackle until humans came along. (We're not pointing fingers or anything, but the Diprotodon became extinct suspiciously soon after the first humans arrived. Coincidence?) Glyptodon Glyptodon asper in Naturhistorisches Museum Wien. Image: Arent [Wikipedia] The most heavily armored mammal of all time has to have been the Glyptodon. About the size of a VW Beetle, this distant relation of the armadillo roamed the plains of South American until 15,000 years ago. The first humans in that part of the world encountered these strange beasts and incorporated them into their legends. Glyptodon resembled a turtle with patches of fur except that the high, rounded shell was made of many small plates of bone. It had a long tail with a ball at the end of it like the mace of a medieval knight. Moropus Moropus elatus, on display at the National Museum of Natural History. Image: Claire H. [Wikipedia] When scientists first discovered the Moropus, they couldn't believe that the horselike head and body belonged with the long claws and massive feet found nearby. This 10-foot-long distant relative of the horse looked like a mixed-up bag of spare parts. The head and neck looked like a stunted giraffe, but the body was more like that of a bear. The front legs were quite a bit longer than the back legs, and all four feet were armed with long claws. Some scientists believe that Moropus fed by rearing up on its hind legs and pulling down branches so it could strip off the leaves with its long tongue. This animal lived in tropical Asia until about 12,000 years ago. Mammuthus Woolly Mammoth at the Royal BC Museum in Victoria, British Columbia. Image: Tracy O [Wikipedia] Everyone knows what a woolly mammoth looked like - a big hairy elephant with long, curling tusks. Everyone also knows that they died out at the end of the last ice age, about 10,000 years ago. Guess again. For one thing, the last mammoths weren't very mammoth; they were about the size of a buffalo. They lived on Wrangel Island, off the northern coast of Siberia, and survived after other mammoths became extinct. Scientists believe that the dwarf mammoths were still around about 4,000 years ago, after the pyramids were built!