Science, Tech, Math › Animals & Nature Prehistoric Shark Pictures and Profiles Share Flipboard Email Print Animals & Nature Dinosaurs Carnivores Basics Paleontologists Dinosaurs & Birds Herbivores Marine Reptiles Prehistoric Mammals Amphibians Birds Habitat Profiles Mammals Reptiles Wildlife Conservation Insects Marine Life Forestry Evolution View More By Bob Strauss Science Writer B.S., Cornell University Bob Strauss is a science writer and the author of several books, including "The Big Book of What, How and Why" and "A Field Guide to the Dinosaurs of North America." our editorial process Bob Strauss Updated March 17, 2017 01 of 16 These Sharks Were the Apex Predators of the Prehistoric Oceans The first prehistoric sharks evolved 420 million years ago--and their hungry, big-toothed descendants have persisted down to the present day. On the following slides, you'll find pictures and detailed profiles of over a dozen prehistoric sharks, ranging from Cladoselache to Xenacanthus. 02 of 16 Cladoselache Cladoselache (Nobu Tamura). Name: Cladoselache (Greek for "branch-toothed shark"); pronounced CLAY-doe-SELL-ah-kee Habitat: Oceans worldwide Historical Period: Late Devonian (370 million years ago) Size and Weight: About six feet long and 25-50 pounds Diet: Marine animals Distinguishing Characteristics: Slender build; lack of scales or claspers Cladoselache is one of those prehistoric sharks that's more famous for what it didn't have than for what it did. Specifically, this Devonian shark was almost completely devoid of scales, except on specific parts of its body, and it also lacked the "claspers" that the vast majority of sharks (both prehistoric and modern) use to impregnate females. As you may have guessed, paleontologists are still trying to puzzle out exactly how Cladoselache reproduced! Another odd thing about Cladoselache was its teeth--which weren't sharp and tearing like those of most sharks, but smooth and blunt, an indication that this creature swallowed fish whole after grasping them in its muscular jaws. Unlike most sharks of the Devonian period, Cladoselache has yielded some exceptionally well-preserved fossils (many of them unearthed from a geological deposit near Cleveland), some of which bear imprints of recent meals as well as internal organs. 03 of 16 Cretoxyrhina Cretoxyrhina chasing Protostega (Alain Beneteau). The awkwardly named Cretoxyrhina surged in popularity after an enterprising paleontologist dubbed it the "Ginsu Shark." (If you're of a certain age, you may remember the late-night TV commercials for Ginsu knives, which slice through tin cans and tomatoes with equal ease.) See an in-depth profile of Cretoxyrhina 04 of 16 Diablodontus Diablodontus. Wikimedia Commons Name: Diablodontus (Spanish/Greek for "devil tooth"); pronounced dee-AB-low-DON-tuss Habit: Shores of western North America Historical Period: Late Permian (260 million years ago) Size and Weight: About 3-4 feet long and 100 pounds Distinguishing Characteristics: Moderate size; sharp teeth; spikes on head Diet: Fish and marine organisms When you name a new genus of prehistoric shark, it helps to come up with something memorable, and Diablodontus ("devil tooth") certainly fits the bill. However, you may be disappointed to learn that this late Permian shark only measured about four feet long, max, and looked like a guppy compared to later examples of the breed like Megalodon and Cretoxyrhina. A close relative of the relatively unimaginatively named Hybodus, Diablodontus was distinguished by the paired spikes on its head, which likely served some sexual function (and may, secondarily, have intimidated larger predators). This shark was discovered in the Kaibab Formation of Arizona, which was submerged deep underwater 250 million or so years ago when it was part of the supercontinent Laurasia. 05 of 16 Edestus Edestus. Dmitri Bogdanov Name: Edestus (Greek derivation uncertain); pronounced eh-DESS-tuss Habitat: Oceans worldwide Historical Period: Late Carboniferous (300 million years ago) Size and Weight: Up to 20 feet long and 1-2 tons Diet: Fish Distinguishing Characteristics: Large size; continuously growing teeth As is the case with many prehistoric sharks, Edestus is known mainly by its teeth, which have persisted in the fossil record much more reliably than its soft, cartilaginous skeleton. This late Carboniferous predator is represented by five species, the largest of which, Edestus giganteus, was about the size of a modern Great White Shark. The most notable thing about Edestus, though, is that it continually grew but did not shed its teeth, so that old, worn-out rows of choppers protruded out from its mouth in an almost comical fashion--making it difficult to figure out exactly what kind of prey Edestus subsisted on, or even how it managed to bite and swallow! 06 of 16 Falcatus Falcatus (Wikimedia Commons). Name: Falcatus; pronounced fal-CAT-us Habitat: Shallow seas of North America Historical Period: Early Carboniferous (350-320 million years ago) Size and Weight: About one feet long and one pound Diet: Small aquatic animals Distinguishing Characteristics: Small size; disproportionately large eyes A close relative of Stethacanthus, which lived a few million years earlier, the tiny prehistoric shark Falcatus is known from numerous fossil remains from Missouri, dating from the Carboniferous period. Besides its small size, this early shark was distinguished by its large eyes (the better for hunting prey deep underwater) and symmetrical tail, which hints that it was an accomplished swimmer. Also, the abundant fossil evidence has revealed striking evidence of sexual dimorphism--Falcatus males had narrow, sickle-shaped spines jutting out of the tops of their heads, which presumably attracted females for mating purposes. 07 of 16 Helicoprion Helicoprion. Eduardo Camarga Some paleontologists think Helicoprion's bizarre tooth coil was used to grind away the shells of swallowed mollusks, while others (perhaps influenced by the movie Alien) believe this shark unfurled the coil explosively, spearing any unfortunate creatures in its path. See an in-depth profile of Helicoprion 08 of 16 Hybodus Hybodus. Wikimedia Commons Hybodus was more solidly built than other prehistoric sharks. Part of the reason so many Hybodus fossils have been discovered is that this shark's cartilage was tough and calcified, which gave it a valuable edge in the struggle for undersea survival. See an in-depth profile of Hybodus 09 of 16 Ischyrhiza An Ischyrhiza tooth. Fossils of New Jersey Name: Ischyrhiza (Greek for "root fish"); pronounced ISS-kee-REE-zah Habitat: Oceans worldwide Historical Period: Cretaceous (144-65 million years ago) Size and Weight: About seven feet long and 200 pounds Diet: Small marine organisms Distinguishing Characteristics: Slender build; long, saw-like snout One of the most common fossil sharks of the Western Interior Sea--the shallow body of water that covered much of the western United States during the Cretaceous period--Ischyrhiza was an ancestor of modern saw-toothed sharks, though its front teeth were less securely attached to its snout (which is why they're so widely available as collector's items). Unlike most other sharks, ancient or modern, Ischyrhiza fed not on fish, but on the worms and crustaceans it rousted up from the sea floor with its long, toothed snout. 10 of 16 Megalodon Megalodon. Wikimedia Commons The 70-foot-long, 50-ton Megalodon was by far the biggest shark in history, a true apex predator that counted everything in the ocean as part of its ongoing dinner buffet--including whales, squids, fish, dolphins, and its fellow prehistoric sharks. See 10 Facts About Megalodon 11 of 16 Orthacanthus Orthacanthus (Wikimedia Commons). Name: Orthacanthus (Greek for "vertical spike"); pronounced ORTH-ah-CAN-thuss Habitat: Shallow seas of Eurasia and North America Historical Period: Devonian-Triassic (400-260 million years ago) Size and Weight: About 10 feet long and 100 pounds Diet: Marine animals Distinguishing Characteristics: Long, slender body; sharp spine jutting out from head For a prehistoric shark that managed to persist for almost 150 million years--from the early Devonian to the middle Permian period--not a whole lot is known about Orthacanthus other than its unique anatomy. This early marine predator had a long, sleek, hydrodynamic body, with a dorsal (top) fin that ran almost the entire length of its back, as well as a strange, vertically oriented spine that jutted out from the back of its head. There's been some speculation that Orthacanthus feasted on large prehistoric amphibians (Eryops being cited as a likely example) as well as fish, but proof for this is somewhat lacking. 12 of 16 Otodus Otodus. Nobu Tamura The huge, sharp, triangular teeth of Otodus point to this prehistoric shark having attained adult sizes of 30 or 40 feet, though we know frustratingly little else about this genus other than that it likely fed on whales and other sharks, along with smaller fish. See an in-depth profile of Otodus 13 of 16 Ptychodus Ptychodus. Dmitri Bogdanov Ptychodus was a true oddball among prehistoric sharks--a 30-foot-long behemoth whose jaws were studded not with sharp, triangular teeth but thousands of flat molars, the only purpose of which could have been to grind mollusks and other invertebrates into paste. See an in-depth profile of Ptychodus 14 of 16 Squalicorax Squalicorax (Wikimedia Commons). The teeth of Squalicorax--large, sharp and triangular--tell an amazing story: this prehistoric shark enjoyed a worldwide distribution, and it preyed on all kinds of marine animals, as well as any terrestrial creatures unlucky enough to fall into the water. See an in-depth profile of Squalicorax 15 of 16 Stethacanthus Stethacanthus (Alain Beneteau). What set Stethacanthus apart from other prehistoric sharks was the strange protrusion--often described as an "ironing board"--that jutted out from the backs of the males. This may have been a docking mechanism that attached males securely to females during the act of mating. See an in-depth profile of Stethacanthus 16 of 16 Xenacanthus Xenacanthus. Wikimedia Commons Name: Xenacanthus (Greek for "foreign spike"); pronounced ZEE-nah-CAN-thuss Habitat: Oceans worldwide Historical Period: Late Carboniferous-Early Permian (310-290 million years ago) Size and Weight: About two feet long and 5-10 pounds Diet: Marine animals Distinguishing Characteristics: Slender, eel-shaped body; spine jutting from back of head As prehistoric sharks go, Xenacanthus was the runt of the aquatic litter--the numerous species of this genus measured only about two feet long, and had a very un-shark-like body plan more reminiscent of an eel. The most distinctive thing about Xenacanthus was the single spike protruding from the back of its skull, which some paleontologists speculate carried poison--not to paralyze its prey, but to deter larger predators. For a prehistoric shark, Xenacanthus is very well represented in the fossil record, because its jaws and cranium were made of solid bone rather than easily degraded cartilage, as in other sharks.