Once upon a time, we feared whales. Medieval maps of the world featured nightmarish sea beasts haunting the periphery of the known world, ready to devour adventurous sailors. But those gargantuan cetaceans have undergone a complete change of image, and nowadays we pay good money to go on boat tours for glimpses of creatures we often describe as "majestic."
Maybe those ancient cartographers were tapping into some ancestral memory. If you were to go back far enough — way back to the Eocene epoch some 40 to 50 million years ago — you would see some terrifying proto-whales lurking in the tidewaters. While it's fairly common knowledge that our early ancestors slithered out of the ocean, what's less well known is that some of them weren't impressed. These creatures took a look, said "meh," and headed back into the big blue. Mind you, that turnaround took millions of years of adaptation. The point is, a few of those refuseniks were the great-grannies and granddads of modern cetaceans (whales, dolphins and porpoises), and some of them bear a curious resemblance to medieval sea creatures. Here be monsters!
Say you've managed to get your hands on Dr. Who's Tardis time machine and decided to give it a whirl. Punching in numbers at random, you end up spinning back some 47.5 million years and landing at the seashore in prehistoric Pakistan. There you spot an enormous, horrifying creature waddling out of the water looking like a crocodile/pterodactyl hybrid.
But this is no lizard: It's an ancient mammal, which it soon proves by giving birth to a miniature version of itself. The babe comes out head-first, snapping the big teeth that line its long, predatory jaws.
While some modern whales, like orcas, have teeth, most sport baleen for sieving krill, and all of them are born tail-first. But back in the Eocene, Maiacetus inuus babies came out head-first with well-developed chompers, ready for battle. Maiacetus means "mother whale," and we know about their babies because in 2000, paleontologists found the fossil of a female M. inuus in Pakistan. Not only was the fossil intact, but there was a fetus in her belly with impressive teeth, poised to emerge snout-first.
Paleontologists also know that this early cetacean species was amphibious, stumping across the shoreline on stubby legs and paddling ominously through the shallows, still dividing its time between land and sea [source: National Science Foundation].
All is quiet at the shoreline, and water eddies around a few small rocks. But wait, are those rocks? Did they just blink? Suddenly a giant dog-rat with a snout like a steroidal wild boar darts out of the water, a fish clenched in its jaws. This, believe it or not, is an ancient whale.
Back in the 1980s, a team of paleontologists were combing through rock formations in Northern Pakistan, looking for fossils. One day, they came across the crest of a large, long skull. Unearthing it, they discovered that its brain cavity was relatively small compared to the size of the skull. It also had a developed tympanic bone for limited underwater hearing. These two features tipped them off that they had a 50-million-year-old whale on their hands. They named it Pakicetus inachus.
But unlike modern whales, P. inachus divided its time between land and sea, which might be part of the reason why it hadn't yet developed the sophisticated hearing mechanisms found in later species. Scarily, its eyes poked up and were positioned on the side of its scalp – which means it probably hunted from below like an alligator [source: Gingerich].
Bees buzz around a series of domestic hives in early 19th-century Mississippi. Wedged between the hives are the gigantic vertebrae of an ancient sea creature. So ubiquitous are these bones during this era that Mississippians and Alabamans routinely use them as furniture. They even stick them in their fireplaces to prop up logs. Curious about the strange bones, a local judge decides to send some samples to a well-known anatomist [source: Zimmer]. Believing that the fossilized vertebrae belong to a massive dinosaur, the anatomist decides to call the species "Basilosaurus," meaning "king lizard." He's right about the size but wrong about the dinosaur thing.
Basilosaurus isis was a mammal — a whale that lived about 40 million years ago. Its front legs had evolved into flippers, and it had some stubby hind feet that would've been no use on land. But at 50 feet (15 meters) in length, slithering through the water like a giant eel with terrifying rows of sharp, curved teeth for ripping sharks to pieces, it would have been one of the most dangerous predators lurking in the oceans of the late Eocene [source: Gingerich].
The sea goddess Tethys was one of the Titans who ruled the world before Zeus and his cohorts came along. This pre-Olympian deity lends her name to a prehistoric sea, the Tethys Ocean, which once divided ancient land masses. Before the Indian subcontinent slammed into Asia and crumpled up the Himalayas, the Tethys Ocean stretched from present-day Indonesia to Spain. It was warm, shallow and teeming with fish — no wonder those ancient land-roving cetaceans decided that life in the sea was the life for them!
Among those adapting to this welcoming submarine environment was a smaller version of the Basilosaurus called the Dorudon atrox. In fact, it appears that D. atrox had to keep a sharp eye out for its bigger cousin; the fossil record indicates that the Basilosaurus diet included Dorudons [source: Fahlke]. Still, at roughly 15 feet (5 meters) in length and fully equipped with razor-sharp teeth, the Dorudon was a menacing critter.
Curiously, field work uncovering the fossils of Basilosaurus, Dorudon and numerous other ancient cetaceans has established a distant but significant relationship between modern whales and hippos [source: Gingerich et al.].
Back in Herman Melville's day, when the whaling industry was at its height, the big prize was spermaceti, a mix of oil and wax found inside the heads of sperm whales. A single whale can have as much as 500 gallons (1,900 litres) of the stuff. There's still some debate about its biological purpose, but the most likely explanation is that it functions as a kind of resonator for echolocation. Modern sperm whales use echolocation to hunt for squid at incredible depths. They send out clicks, and the time interval between when they make the sound and when it bounces back allows them to quickly locate prey in the dark depths of the ocean. And while they have some lower teeth, they don't really use them much.
That's not the case when it comes to one of their Miocene ancestors, which cruised the Mediterranean region roughly 10 million years ago. Paleontologists named it Zygophyseter varolai and gave it the English common name "killer sperm whale" because it was probably very similar to modern killer whales, both in size and feeding habits. The fossil record indicates a fearsome 20-foot-long (6 meters) predator with a well-developed spermaceti organ for echolocating large, powerful prey and ripping them to shreds with big, sharp, deeply rooted teeth [source: Bianucci and Landini]. Z.varolai also had an asymmetrical cranium, which is particularly associated with high-frequency sound production and echolocation. They needed this handy attribute to find and devour those delicious swimmers who emitted high sonic frequencies [source: Fahlke et al.].
In the late '90s, a teenage surfer found a bizarre and frightening fossil embedded in limestone on an Australian beach. It was a massive skull with huge fangs and enormous eye sockets. The fossil ended up gathering dust in a museum office for more than half a decade before an expert named Erich Fitzgerald began studying it.
While some whales have teeth, others don't need them. A blue whale, for instance, takes a massive gulp of seawater and then forces it out through its huge baleen, trapping microscopic zooplankton called krill. The method works well — after all, blue whales are the biggest animals to have ever existed, so they must be doing something right.
Scientists divide modern whales into two groups: those with teeth, like orcas and right whales (Odontoceti), and those with baleen (Mysticeti). Evolutionary biologists once assumed that the two groups split up when the Mysticeti developed baleen. But Fitzgerald's examination of the fossil, which he called Janjucetus hunderi, proved that assumption wrong. That's because while J. hunderi clearly belongs to the Mysticeti subgroup, it doesn't have baleen at all. Twenty-five million years ago, this 10-foot-long (3 meters) early Mysticete scoured the seas for prey to chomp on with its big, sharp teeth [source: Fitzgerald].
Forty-five million years ago, an 8-foot-long (2 meters), 500-pound (227 kilograms) beast called Rodhocetus kasrani waddled into the water and dove, using webbed hoofs to paddle speedily out to the open sea like some nightmarish cross between a crocodile and a shark.
When orcas and dolphins catch fish, they like to swallow them whole. Their little peg-like teeth are just there to grip their prey long enough to get it down their gullets. Not so with Rodhocetus kasrani, who sported a diverse mouthful of fangs, slicers and grinders for shearing its victims into easy-to-swallow morsels. Also unlike orcas and dolphins, R. kasrani had enough legginess to locomote on land whenever that seemed like a good idea.
Different as they are from modern whales, these early cetaceans had all kinds of whale-ish traits, including something in their jaw inelegantly named a "mandibular fat pad." When we Homo sapiens dive underwater, what little sound we can hear is transmitted as vibrations in our skulls, giving us no sense of the source's location. A whale's handy fat pad aids in directional hearing — allowing predators like the gruesome Rodhocetus kasrani to get an instant fix on the whereabouts of its next meal [source: Gingerich et al.].
There you are, 50 million years ago, enjoying a hot Eocene afternoon at the seashore and watching a foxlike prehistoric rodent cool its paws in the mud at the water's edge. Suddenly, a monstrous beast explodes from the depths, seizes the hapless fox-thing in its massive jaws and disappears beneath the waves. All is quiet again. The local birds return to their business. It's as though nothing ever happened. You've just glimpsed the probable hunting methods of an Ambulocetus natans, a 400-pound (180 kilograms), 10-foot-long (3 meters) "walking whale."
Basically, an Ambulocetusnatans was a mammalian version of a crocodile but with longer hind legs to power it through the water. Like crocodiles and hippos, it had widely spaced eyes that sat near the top of the skull — ideal for lurking invisibly in the shallows until some tasty victim comes along. Paleontologists think it waddled around a bit on land but probably spent the bulk of its time in shallow coastal waters. With webbed feet and hearing mechanisms well adapted for life underwater, A. natans forms part of the important fossil record that tells us how whales inched their way from land to sea over millions of years [source: Thewissen et al.].
Seventeenth-century Italian Agostino Scilla was one of those old-school polymaths who excelled at everything. An accomplished professional painter, he was also a geologist and paleontologist. In fact, he was among the first scholars to study and document fossils. His 1670 drawing and description of a fossil from Malta was one of the first in scientific literature.
That fossil was a jaw belonging to what is now called a Squalodontid, and it included three sharp, serrated teeth. Squalodontidae, which were about 10 feet long (3 meters), are also called "shark-toothed dolphins," and their teeth are truly menacing. Modern dolphin teeth are nonthreatening little bumps that have the same shape from the front to the back of the jaw. Squalodontidae, however, had large, curved, sharp fangs in front and serrated, triangular cheek teeth for slicing their prey up into manageable chunks.
Once upon a time, paleontologists theorized that modern dolphins were descended directly from squalodons, but it now seems more likely that these sleek predators, who prowled the seas between 28 million and 15 million years ago, died out before passing on their DNA [source: Fordyce].
Your modern sperm whale may seem to be a mighty beast. After all, Moby Dick was one of them, and he sank a whaling boat. Although Melville based his great novel on a true story, he fudged some facts to make his whale scarier. The truth is that sperm whales spend most of their time diving deep while on the hunt for cephalopods like squid and octopuses. And although they have some peglike teeth, they actually use suction to hold onto their prey.
But in 2010, researchers in Peru uncovered the remains of a gigantic sperm whale dating back 12 million years to the Miocene era. Measuring more than 50 feet (15 meters) in length, its head alone was nearly 10 feet (3 meters) long, and its powerful jaws were lined with 12-inch (30.4 centimeters) teeth. Its prey? Baleen whales. The paleontologists who found this monster named it for Herman Melville, which seems fitting. After all, as one of the largest known predators to have ever existed, Leviathan melvillei was the force of nature Melville wanted Moby Dick to be [source: Urbina].
Entelodonts were frightening creatures that once patrolled throughout Eurasia, North America and Africa. HowStuffWorks looks at the now-extinct beast.
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