The Evolution of Whales

http://www.edwardtbabinski.us/whales/evolution_of_whales/The Whale's Tale - research on whale evolutionOnly 24 years after Charles Darwin rewrote the book of life with his theory of natural selection, a fellow

Victorian scientist named William Flower trained this powerful new idea on one of the toughest problems inzoology: the whale. Natural historians had long before recognized that whales are mammals, but that wasabout as far as they had come in understanding the origins of cetaceans. How evolution had managed tocraft such a unique beast presented a mystery as vast as the creature itself.In 1883, Flower offered an idea that--on the face of it--seemed positively daft. The legless leviathans, he

suggested, had evolved from mammals known as ungulates, a group whose best-known characteristic is aset of hoofed feet. In other words, dolphins, porpoises, humpbacks, orcas, and all other whales are closekin of cows, horses, pigs, and related barnyard stock.More than a century after Flower raised his audacious hypothesis, it no longer stirs even a whiff of

controversy. Dozens of scientific studies over the past 3 decades have convinced biologists that cetaceansare the progeny of hoofed mammals. Yet the whale's story is far from finished.

Whales Closest Living Relative and AncestorsBack To The Sea

The earliest known representatives of whales walked on land and were carnivores with fur and hooves.Their successors in the Eocene, likely evolved into squat and heavy-headed species, pursued anamphibious life in shallow water. Within ten million years these species' bodies were adapted to life in theocean.Which animals were the ancestors of whales?

Past discoveries of whale fossils have lent to the belief that long-extinct ungulates, called mesonychids,were ancestors or relatives of whales. Molecular data from DNA samples, indicate whales arose fromartiodactyls, which include hippos, not mesonychids, and that hippos are in fact the closest living relativesto whales. Discoveries of ankle bones on early whales, lend credibility to the artiodactyllink. There now isalso morphological support for the hippo link.

Pakicetid fossils described in 2001 were important in determining what whales were related to. Thesefossils confirmed what was already suggested by scientists studying the DNA of modern whales: thatwhales' closest relatives are even-toed ungulates (artiodactyls, such as pig, hippo, camel, deer, andcows)."

Pakicetus50 million years ago. SEEPIC.

A Common MisconceptionPakicetus is a Middle Eocene arch~eocete from Pakistan; it is currently the earliest known well-preserved

cetacean. Until 2001, pakicetus was known only from its skull, but recent finds in Pakistan have producedspecimens that show very primitive characters in both the skull and the rest of the skeleton. These animalshad relatively well developed limbs, but were aquatic."Pakicetids did not look like whales at all, and resembled land mammals. However, the skulls of pakicetidshave an ear region that is highly unusual in shape, and only resembles that of modern and fossil whales.These features are diagnostic for cetaceans, they are found in all cetaceans, and in no other animals.These features are the main reason why pakicetids are considered whales. In many other features,pakicetids are also similar to some whales, but those features are not shared by all whales. An example ofthe latter is the dentition. Pakicetid teeth look a lot like those of fossil whales, but are unlike those ofmodern whales. Pakicetids did not live in the sea. The rocks in which their fossils are preserved indicate

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that the bones were buried in a shallow stream, and that the climate was hot and dry. It is likely thatpakicetids waded in these streams. Their bones are unusually thick, possibly an adaptation to make theanimal heavier counteracting the buoyancy ofthe water."Pakicetus SkullsThe author of the article in National Geographic Magazine, Evolution of Whales, discusses at length aboutwitnessing humpback whales leaping near their boat, and comments "I wondered what the crews onwhaling ships thought when they would occasionally haul aboard a fully grown adult with miniature legssticking out from its flanks. Whether they knew it or not, they were looking at testimony to the origin ofthese mysterious marine giants."

Over 80 species are classified as whales, or as taxonomists prefer to call them, cetaceans, which originatesfrom the Greek ketos for sea monster. Cetaceans are divided into two groups, the Mysticetes (baleen

whales) which use comblike plates on the roofs of their mouths to strain food from the water. Some ofthese are the Blue whales, fin whales, bowheads, and most of the other large whales belong to this line,along with some smaller whales such as the minke whale and pygmy right whale.

Odontocetes, the toothed whales, include belugas, narwhals, sperm whales, pilot whales, and beakedwhales, including dolphins and porpoises. Killer whales are the largest members of the dolphin family.The early Eocene epoch, which lasted from 55 million years ago to around 34 million years ago, is oftencalled the dawn of the age of mammals, and when whales had their first known beginnings.Paleontologists can now trace the origins of whales through a series of fossil discoveries.

Blue whales, the largest of the cetaceans, are larger than any known dinosaur dimension, measuring up toas much as 100 feet, and weigh a third of a million pounds.

The author of National Geographic's Evolution of Whales, comments about his visit with Thewissen, in

which he is handed the skull of one of the oldest known whales. "At first glance I thought he had handedme the head of a coyote." Remains of Pakicetus were discovered in the Himalayan foothills sediment.Judging by surrounding sediment, the creature lived as a land-dweller, among marsupials and squirrel­sized primates, our very early human ancestors.

The remains of Pakicetus are closely linked to river channels, which suggest the creature spent part timearound and perhaps in water. Subtle clues in the anatomy of Pakicetus cause scientists to declare thecreature an early whale. A combination of• cusps on the molars teeth,• One of the middle ear bones (the tympanic) which contains an s-shaped fold, as well as the• positioning of other middle ear bones inside the skull.These traits are absent in other known mammals, but are a signature of all later whales.

Middle ear bone (the incus) from a 50-million year old Pakicetid"Beautifully Intermediate" says Dr. Thewissen, "It's structure helps answer how a land mammal's ear adapted tounderwater sound." a middle ear bone from a 50-million year old Pakicetid.

The Tympanic"One particularly baffling fossil was the back part of a 50-million-year-old skull. It was about the size of acoyote's and had a high ridge running like a mohawk over the top of its head, where muscles could attachand give the mammal a powerful bite. When Gingrich looked underneath the skull, he saw ear bones. Theywere two shells shaped like a pair of grapes and were anchored to the skull by bones in the shape of an S.For a paleontologist like Gingerich, these ear bones were a shock. Only the ear bones of whales have sucha structure; no other vertebrate possesses them." ,

Around a million years after Pakicetus appeared, another relative emerged. Ambulocetus natans wasdiscovered in Pakistan in 1994, by Dr. J.G.M. 'Hans' Thewissen. Ambulocetus natans means "the walking,

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swimming whale". Ambulocetus had thick, splayed-out legs, four-toed feet and a small hoof at the end ofeach toe. The creature possessed sharp teeth and was roughly the size of a large sea lion. Ambulocetusmay have been an ambush-hunter, similar to the hunting style of modern crocodiles.

In a painting by Carl Buell, Ambulocetus, a 45 million year old whale, still retained the legs of its ancestors. It mayhave lived like an alligator, basking on land and ambushing in the water. SEEPIC.

Dr. Thewissen examining the Pelvis of AmbulocetusAmbulocetus natans, the 49 million year old "walking, swimming whale" discovered in Pakistan by Thewissen and teamin 1992, and described in 1994-1996, is currently the oldest known saltwater cetacean. "With long hind legs andhands, but the teeth and ears of a more modern whale, this animal was on the fence between land and sea."

49 million years ago. SEEPIC.Ambulocetus

Around 42-45 million earlier Kutch was border to a river delta, periodically filled by waters from the IndianOcean. It was a place filled with sharks, rays, bony fish, crocodiles and turtles, and also early whales.Some of the early whales found in this region have been lndocetus, Rodhocetus, Andrewsiphius andKutchicetus. These early whales were no bigger than about 5 to 15 feet long and resembled large-headed,snaggle-toothed, web-footed sea lions or walruses and, similar to these modern species, may havereturned to land to mate, birth, and moving about on short hind legs. However, recent analyses on oXygenisotopes in their teeth indicated they no longer needed to drink fresh water like Pakicetus. These particularsuccessors of Ambulocetus had made significant metabolic change toward becoming true marine mammals.

Nasal Drift in Early WhalesWhales breathed with more ease when they no longer had to lift a snout above water. The nostrilsmigrated upward toward the top of their head, as ancient whales spent more time immersed in the water.Blowholes help to distinguish modern forms of whales. While toothed whales generally have one hole,baleens are split into two. SEEPIC.Fig 1. PakicetusFig 2. Rodhocetus nostrils were higher on the skull, intermediate between its ancestors and modern

whales.

Fig 3. A modern gray whale can emerge from the water, inhale and resubmerge without stopping or tiltingits snout to breathe.

The spinal column of these creatures became more flexible and powerful, with the dwindling of rear limbsand hip bones. Their necks shortened, allowing the creatures to swim through the water with less drag andarms became like rudders. Having less need for outer ears, some were picking up sound underwater,through their lower jawbones, transmitted to the inner ear by specialized fat pads. With each new speciesof whale, they became more streamlined and ventured farther from shore. This transition took place in lessthan ten million years. According to Thewissen, "Whales underwent the most dramatic and completetransformation of any mammal. The early stages were so poorly known 15 years ago that creationists heldup whales as proof that species couldn't possibly have come through natural selection. Now whales areone of the better examples-of evolution."

The author describes prying a partial skull from the rubble, and Bajpai identifies the fragment as belongingto Remingtonocetus, by its long, narrow jaws. "We assume they were snapping up fish, like the moderngharial crocodile does with its needle-like snout," he said. "It is a specialization that appears several timesamong later cetaceans, including. modern river dolphins." SEEPIC.

Around 40 million years ago, ancient whales spread out from the Tethys Sea, which is considered thecradle of whale evolution, a group known as Dorudontines arose. These creatures could still bend theirflippers at the elbow, and their nostrils had transitioned only partially up the snout to the top of the head.For the most part they were fully-fledged fluked cetaceans who gave birth at sea and may have been the

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group who gave rise to modern whales.

The author of Evolution of Whales interviews Paleontologist James Goedert about he and his wife's twentyyears searching for remains of the early whales. The two have primarily been searching for fossils in theepoch following the Eocene, the Oligocene, from 34 million to 24 million years ago. "When we began,there were archaeocetes, or ancient whales, and then there were recognizable baleen and toothed whales.What came in between? The Oligocene, and it was pretty much a big blank. If you find a whale from thistime period, chances are its a new species or even a whole new family. And when I do find one, there's nofeeling like it." The Goederts' work has produced the oldest odontocete, several of the earlier mysticetes,and the Northern Pacific's oldest whale. The author journeys with Goedert into an area which containsfossils of the early whales. Geological forces had compressed bottom sediments of the early ocean intostone, then later they were thrust up on the continent's edge to be eroded by rainstorms and waves. Thework to recover fossilized remains was already done.

The author comes across a fossil, to which Goedert says "You're looking at a very primitive true toothedwhale." It was a link between ancient whales which carried a mixture of teeth shapes, legacy to their dayson land, and odontocetes (the division with sperm whales, dolphins and their kin), whose teeth are moreuniform, like spear tips or pegs. A more important observation in the transitional animal were in thearchitecture of the skull. Beginnings of special sacs off the main nasal passage for moving air back andforth to create sound vibrations and a lens of fatty tissue, or the melon, in the whale's forehead, used for

focusing outgoing sounds and thinned portions in the area of the lower jaw, which aided in reception ofsound vibration. Combined, they provided the ability to successfully navigate and find prey throughecholocation, especially successful for toothed whales, odontocetes.

Evolution of EcholocationDiscoveries in fossil finds of early whales demonstrate that whales acquired underwater hearing, as were

other traits, in stages. Pakicetus lacks the fat pad extending to the middle ear which modern Cetacea have.Later whales acquired the fat pad and jawbone adapted for reception of sound. However, the melon,evolved only in odontocetes, or toothed whales. In Basilosaurus, sounds transmitted to the middle ear asvibration from the lower jaw. Odontocetes (toothed whales) echolocate, the melon directs sound outwardand the lower jaw works as a receptor.

Researchers Discover Clues to Whale EvolutionA team of international scientists, including Hans Thewissen, an anatomist and paleontologist at the

Northeastern Ohio University, has discovered that the inner ear of whales evolved much more quickly thanexpected, allowing the animals to become fully aquatic early in their evolution. The team's research,funded by the (NSF), shows that the semicircular canals, the organ responsible for balance and located inthe inner ear, was adapted to aquatic life approximately 45 million years ago.Cetaceans (whales, dolphins and porpoises) have unique semicircular canals that allow them to be. highly

acrobatic swimmers without becoming dizzy. By investigating this organ in ancient fossils, the researchersfound that early whales acquired this special trait quickly and early on in their evolution. This was adefining event that likely resulted in their total independence of life on land."The early evolutionary development of small semicircular canals by cetaceans opened an entirely newmammalian niche for habitation and contributed to the broad diversity of marine living habits that we seein whales today, "The evolutionary acquisition of such specialized organs or abilities (like the brain andupright walking habit of man) provide mechanisms by which highly evolved organisms dominate in certainenvironments."

The researchers found that in living cetaceans the semicircular canals are much smaller than in any other

mammal of the same body size. In fact, the semicircular canal1 of the huge blue whale are smaller thanthose of humans. In general, cetaceans are more acrobatic than similarly sized land animals (imagine anelephant making the jumps of a similar-sized whale). This could be the result of the small canals, becausethe small size makes the canals less sensitive, preventing the animal from becoming dizzy (i.e.experiencing vertigo).

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Rodhocetus

46.5 million years ago. SEEPIC.

Fossil of whale that walked on land found in PakistanFossils of a 46-million-year-old whale that walked on four legs on land, but swam with the undulating, up­

and-down tail motion of a modern whale, have been discovered in Pakistan by paleontologist Philip D.Gingerich and researchers from the Geological Survey of Pakistan.Named Rodhocetus kasrani, the whale provides important information about structural and behavioral

changes that occurred 40 to 50 million years ago as whales made the transition from land-dwelling toocean-dwelling mammals."Rodhocetus is the first early whale found with a complete thoracic, lumbar and sacral vertebral column,"said Gingerich. "It retains primitive features seen in land mammals, but also exhibits derived characteristicsfound only in later ocean-dwelling species. It is an excellent candidate for a direct ancestor of modernwhales." In other words, it has a flexible backbone for ungulating.With its pointed snout, sharp teeth, short legs and robust tail, Rodhocetus may have looked somethinglike a 10-foot-long crocodile with fur. According to Gingerich, it is the oldest whale ever found with theflexible back and heavily muscled tail needed for efficient swimming. "This shows that tail swimmingsimilar to that of modern whales evolved early in cetacean history. Rodhocetus' fossilized remains werefound during a 1992 excavation in northern Pakistan. The excavation site is now a rocky, mountainousdesert, but 50 million years ago, it was located beneath the southern edge of an immense, ancient oceancalled the Tethys Sea."Whales are a classic example of fundamental changes being driven by evolution,"Gingerich said. "Over a 10-miliion-year period, whales gradually adapted in ways that allowed them tospend longer periods in the water and catch more fish." Since good swimmers were more likely to live andreproduce, physical changes that improved swimming ability were more likely to be passed on to latergenerations.

Protocetus

45 million years ago. SEEPIC.

Protocetus"Protocetids for which most of the skeleton is known had large feet which they used in swimming, similar

to Ambulocetus. However, it is possible that other protocetids had a tailfluke. Unlike remingtonocetids andambulocetids, protocetids had large eyes that were laterally placed in the head under a large bonyextension of the frontal bone (the supraorb'ital plate).First whales to disperse widely across the world's oceansProtocetids are a heterogeneous group of whales that lived in the Eocene, from approximately 48 to 35

million years ago. Protocetids postdate pakicetids and ambulocetids and predate most basilosaurids anddorudontids. In Pakistan and India, protocetids are found in combination with remingtonocetids.Protocetids were the first whales to-leave the Indian Subcontinent and disperse to all shallow (sub )tropicaloceans of the world. In addition to Indo-Pakistan, they are also known from Africa and the east coast ofNorth America.

Remingtonocetid Kutchicetus43-46 million years ago. SEEPIC.

"Remingtonocetids are fossil whales that lived in South Asia, approximately from 49-43 million years ago.Their heads were very different from other whales. Their eyes were small, their snout long, and they hadears that transmitted sound similarly to those of modern whales. Remingtonocetids had long fore- and hindlimbs. The reconstruction of Kutchicetus is based on the bones,. It was a small animal, no bigger than ariver otter."

Evolution of Whale Hearing Unfolds in Fossil Record

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An international team of scientists has traced the evolution of hearing in modern cetaceans (whales,dolphins and porpoises). "This study of the early evolution of whales demonstrates the changes that tookplace in whales' outer and middle ears, required for the transition from a land-based to a marine-basedexistence. The ear is the most important sense organ for modern toothed whales, say scientists, becausethese whales locate their prey using echolocation. Directional hearing is critical: A blind such whale couldfind food without much trouble; a deaf one would starve. The study documents how hearing in thesewhales evolved. The research is based on cetacean fossils representing four groups of early whales. Theearliest cetaceans, pakicetids (those that swam in ancient seas 50 million years ago), used the same soundtransmission system as did land mammals, and so had poor underwater hearing. More recent cetaceans,remingtonocetids and protocetids (those that lived 43-46 million years ago), retained the land-mammalsystem, but also developed a new sound transmission system. "The fossils document the ways in whichcetacean hearing has changed, starting with ear fossils of whales' land ancestors and ending with the earof near-modern looking whales," said Hans Thewissen. The newer system was similar to that of modernwhales. The later whales could hear better in water than pakicetids could, and could also hear in air, buthearing in both media was compromised by the existence of two systems. With the advent ofbasilosauroids (approximately 40 million years ago), the old land-mammal ear disappeared, and themodern cetacean sound transmission system began its development.

Durodon

37 million years ago. SEEPIC.

Basilosaurids and DorudontidsBasilosaurids and dorudontids lived in the late Eocene, approximately 35 and 41 million years ago. They

are mainly known from the eastern United States and from Egypt, but were probably worldwide in theirdistribution. Basilosaurids were enormous (possibly up to 60 feet long) and had long snake-like bodies.They had a tailfluke, but they probably swam using sinuous movements with their bodies. it is not clearwhether that was the main propulsive organ. Fossilized stomach contents in one Basilosaurus indicatesthat it ate fish, including sharks. Dorudontids are closely related to basilosaurids but were proportionallymore like dolphins. They probably swam using their fluke. Both basilosaurids and dorudontids hadcomplete hindlimbs, that included a mobile knee and several toes. However these extremities were tiny, sosmall that they were certainly not important in aquatic propulsion.

DorudonDorudon was a genus of ancient cetacean that lived alongside Basilosaurus 40 to 36 million years ago, in

the Eocene. They were about 5 metre long and were most likely carnivorous, feeding on small fish andmollusks. Dorudontids lived in warm seas around the world, fossils have been found in North America aswell as in Egypt. Dorudontids were originally believed to be baby Basilosaurs as they were so similar, buthave since been shown to be a different species with the discovery of Dorudon babies. Although they lookvery much like modern whales, basilosauridsand dorudontids lacked the 'melon organ' that allows theirdescendants to sing and use ultrasound as effectively as modern whales.

Basilosaurus

37 million years ago. SEEPIC.Aetiocetus

24-26 million years ago. SEEPIC.

Nasal Drift in Whales: Aetiocetus an IntermediateTransitional FormsFossils or organisms that show the intermediate states between an ancestral form and that of its

descendants are referred to as transitional forms. There are nwmerous examples of transitional forms inthe fossil record, providing an abundance of evidence for change over time. Pakicetus is described as anearly ancestor to modern whales. Although pakicetids were land mammals, it is clear that they are relatedto whales and dolphins based on a number of specializations of the ear, relating to hearing. The skullshown here displays nostrils at the front of the skull. A skull of the beluga whale that roams the seas today

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has its nostrils placed at the top of its skull. It would appear from these two specimens that the position ofthe nostril has changed over time and thus we would expect to see intermediate forms.

Baleen whales have toothed ancestors Toothed whales have full sets of teeth throughout their lives.

Baleen whales, however, only possess teeth in the early fetal stage and lose them before birth. Thepossession of teeth in fetal baleen whales provides evidence of common ancestry with toothed whales andother mammals. In addition, fossil evidence indicates that the late Oligocene whale Aetiocetus (left), fromOregon, which is considered to be the earliest example of baleen whales, also bore a full set of teeth.

Squalodon16 million years ago. SEEPIC.Early Echolocation

A picture of the squalodon skullPublic display at the Smithsonian Museum of Natural History in Washington DC. SEEPIC.

Squalodon calvertensis, long-snouted shark toothed whaleSqualodons lived from the early-middle Oligocene into the middle Miocene, roughly 33 to 14 million years

ago. The squalodon genus belongs to the Odontocete Order, the toothed whales. Specifically it belongs tothe Squalodontidae superfamily. This superfamily is named after the shark squallus, since its' cheek teethsuperficially resemble the teeth of a squallus shark; hence the name "shark toothed whale". TheSqualodontidae superfamily contains three different groups of medium-sized (roughly 3 meters in length)shark toothed whales. They are the short-snouted shark toothed whales (prososqualodon), the medium­snouted shark toothed whales (phoberodon), and the long-snouted shark toothed whales. This last groupcontains the genus squalodon. Finally, squalodon skulls show evidence for the first appearance ofecholocation.

EcholocationSeawater is eight hundred times denser than air and transmits sound more efficiently as a medium. Sound

travels almost 5.5 times further in water than in air and cetaceans use their watery world to produce a

variety of vocalizations, clicks, whistles, and calls. The resident populations of orcas in this region havedeveloped their own unique dialect, or form of language. Toothed whales echolocate by producing a seriesof clicks that are emitted at various frequencies. These sound pulses are emitted through the whale'smelon-shaped forehead, reflect off objects, and are retrieved through their lower jaw which has a foam­like construction. Whales "read" the reflected sound similar to the way we read reflected light with our

eyes. Baleen whales use low frequencies to communicate, sometimes over long distances. Marinemammals utilize a wide variety of physical behaviors to communicate. They use subtle or dynamic displaysto signal others, herd prey, issue a warning, or to help dislodge parasites.

Encephalization is defined as the-amount of brain mass exceeding that related to an animal's total bodymass. Quantifying an animal's encephalization has been argued to be directly related to that animal's levelof intelligence. In fact, as early as 1871, Charles Darwin wrote in his book' The Descent of Man': "No one,I presume, doubts that the large proportion which the size olman's brain bears to his body, compared to thesame proportion in the gorilla or orang, is closely connected with his mental powers."

Origin and Evolution of Large Brains in Toothed WhalesAnother major hypothesis regarding the high encephalization in toothed whales focuses on the neural

processing needs associated with either echolocation per se or its elaboration into a complex perceptualsystem in the sub-order Odontoceti (Jerison, 1986; Ridgway, 1986; Oelschlager, 1990). Results here showan increase in encephalization at the origin of Odontoceti that J11aybe related to the emergence andelaboration of the ability to process high-frequency acoustic information associated with echolocation.

Cetotherium15 million years ago. SEEPIC.

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Mysticeti - Baleen whalesAll living mysticetes are large filter-feeders although the exact means by which baleens are used vary

among species (gulp-feeding for balaenopterids, skim-feeding for balaenids, and bottom ploughing foreschrichtiids).The morphological modifications linked to filter-feeding are:

• Loss of functional teeth (vestigial teeth are lost before birth),• Development of large body size and head,• Shortening of the neck,• Expanded maxillae (on which the epithelially-derived baleen plates develop),• Mandibular rami only attached to each other by a ligament (at the symphysis).

Questions Remain On Whale Evolution• At what point did whales evolve extra myoglobin in their muscles, to store oxygen for long dives?• When did Humpbacks begin singing? Since changes in physiology are not always associated with

apparent shifts in anatomy, they are harder to determine.

The family tree belonging to whales is far from finished. Many branches contain gaps, that await to befilled in. Scientists have known since the 1880's whales and ruminants possess multichambered stomachsand similarities in a folding pattern on the cortex of the brain. Modern analysts have discovered matcheson proteins and amino acids, shared between whales and artiodactyls, hoofed animals with an evennumber of toes, including ruminants, pigs and hippos. Ankle bones discovered by Philip Gingerich andcolleagues described in a 2001 of Science, point to artiodactyl origins, as does the systematic analysis ofpakicetid cetaceans by Thewissen and co-workers from 2001. Norihiro Okada, Institute of Technology,Japan, in fact believes hippos are the closest living relatives of whales. Okada and colleagues discoveredunique genetic markers shared only by whales and hippos, which indicates common ancestry. Heconcludes, "It is the solution to a problem that has continued more than a century." If the conclusion ofOkada is correct, that would mean whales descended from a group of early artiodactyls calledanthracotheres, modestly sized creatures with piglike appearance and four hoofed toes on both feet, justas hippos have today. These creatures were common in Eurasia during the age of mammals, theanthracotheres lead to the rise of a number of marsh-dwelling forms.

Ambulocetus SEEPIC.

Basilosauruswith well developed hind limbs, thOugh reduced in size. SEEPIC.

Sperm whales retain hind limb atavisms.Losing their LegsPakicetuswalked on land and waded in water, but Ambulocetus was more aquatic. It's pelvis was fused to itsbackbone, which allowed it to support its weight on land, while webbed feet gave it additional power underwaterwhen it would swim, perhaps undulating its spine like an otter. Basilosaurus,snakelike and possessingshrunken legs,emerged on the scene some ten million years later. Some evidence indicates the reduced limbs may have been usedin copulation. Today, hind rudiments are small and internal, acting as an anchor for genitalia muscles.The animalsstill retain genetic codes, for longer limbs. On occasion a whale may be born with a limb or two sprouted, known asan atavism.

The author of Evolution of Whales comments on his conversation with Lawrence Barnes, and recollection ofa Pliocene dolphin, with blunt nose and squarish head, and long tusks resemble a mollusk eating walrus.This fossil provoked him to wonder just how many varieties of whales had existed since the most ancientspecies. Barnes confessed never adding them up, and suggested to try doing so. Left with the file cardindex, representing all identified cetacean species, around 1000 were counted. Barnes response was, "Myguess is that represents ten percent of what's out there waiting to be dug up." Jim Goedert would say tokeep looking, the world holds more miracles -- big, small, new and old -- than can be imagined.

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