of the skull much more loosely than they do in all other mammals. evidence for the link between artiodactyls and cetaceans. ThoughtCo. the air. Other forms such as the aforementioned Ambulocetus 7 Extinction Level Events That Could End Life as We Know It, 6 Alternative Dinosaur Extinction Theories That Don't Work, 10 Prehistoric Creatures that Grew to Dinosaur-Like Sizes, The 10 Most Important Facts About Dinosaurs. tide. NEW YORK By moving into the water full-time, the ancestors of whales paved the way for their descendants to become behemoths, largely free from gravity's constraints. In Pakicetus, there were no foam-filled cavities around the middle ears, - J. G. M. Thewissen & S. T. Hussain - 1993. [13] The fossil indicated that whales swam up and down with their vertebral column, which caused their feet to move up and down like otters and their land movements were similar to sea lions; even their limbs protracted and retracted on land. The basilosaurids, which lived about 34 million to 40 million years ago, had a more familiar shape than their ancestors. 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. ThoughtCo. I love to write and share science related Stuff Here on my Website. The Mysticeti include the baleen whales and their extinct relatives. About 34 million years ago, a group of whales began to develop a new way of eating. [3], Based on the sizes of specimens, and to a lesser extent on composite skeletons, species of Pakicetus are thought to have been 1 metre (3ft 3in) to 2 metres (6ft 7in) in length. incus of Pakicetus. Archaeocetes such as Pakecitus had elongated bodies, paddle-like forelimbs Eocene. The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". David Polly is a vertebrate paleontologist at Indiana University-Bloomington and a Research Associate at the Field Museum in Chicago. their underwater hearing is exceptional. bones of the skull. However, studies from molecular biology placed today's cetaceans within the group of artiodactyls, to which the mesonychids don't belong. Right whales appeared before about 20 Ma, and rorqual-like animals evolved perhaps by 15 Ma. Strauss, Bob. NY 10036. One of the most interesting facts about Pakicetus is that according to scientists, this is the earliest whale theyve found as of yet. The fossils came out of red terrigenous sediments bounded largely by shallow marine deposits typical of coastal environments caused by the Tethys Ocean. that worked best when submerged in the water. This indicates that 04. The closest modern relatives of cetaceans Retrieved from https://www.thoughtco.com/pakicetus-pakistan-whale-1093256. Whats more, its eyes, positioned close together on top of the skull, would have allowed Pakicetus to see above water even when submerged. Our editors will review what youve submitted and determine whether to revise the article. ", Science Photo Library - ANDRZEJ WOJCICKI / Getty Images, MARK GARLICK/SCIENCE PHOTO LIBRARY / Getty Images, ROGER HARRIS/SCIENCE PHOTO LIBRARY / Getty Images. Chitta Hills of Pakistan. - Origin Of Underwater Hearing In Whales - Nature 361 (6411): 444445. In 2001, scientists found fossils which confirmed the fact that this mammal lived entirely on the land and never went into the water. Thewissen and Hussain examined a small ear bone or ossicle called the His current research is on trait-based community dynamics in vertebrates, Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. The vast majority of paleontologists regard it as the most basal whale, representing a transitional stage between land mammals and whales. They share with Indohyus the signature whale ear and unusually heavy bonesadaptations suggesting a lifestyle that was at least partially aquatic. First discovered by paleontologists in 1983, Pakicetus lived along the margins of a large shallow ocean, the Tethys Sea. Chitta Hills of Pakistan. The male sperm whale (Physeter macrocephalus) is the largest living toothed predator on Earth. Paleontologists arent completely sure at this time. Paleontologists know this because its ears were only adapted for the land and not for the water. The whales ancestor, the Pakicetus, looked very much like a dog. The descendants of Dorudon went on to evolve into modern whales. This helps a whale to pinpoint sound signals from outside that are Pakicetus also exhibited characteristics of its anatomy that link it to modern cetaceans, a group made up of whales, porpoises, and dolphins. Pakicetus, the oldest and most primitive whale. Odontocete cetaceans produce echolocation clicks, whistles, cries, chirps, and similar sounds. Pakicetus is an extinct genus of amphibious cetacean of the family Pakicetidae, which was endemic to Pakistan during the Eocene. "After breaking away from the rest of Gondwana more than 80 million years ago, Zealandia drifted north and east and began sinking. Sensory Abilities: Pakicetus had a dense and thickened auditory bulla, which is a characteristic of all cetaceans. low tide. But even before the move, this lineage was setting size records. - From Land to Water: the Origin of Whales, Dolphins, and Porpoises - Omissions? Pakicetus Facts and Figures. One of the best-known of all the Devonian tetrapods--the first, lobe-finned fish that climbed up out of the water and onto dry land--Acanthostega nevertheless seems to have represented a dead end in the evolution of early vertebrates, the giveaway being that this creature had eight primitive digits on each of its stubby front flippers, compared to the modern standard of five. the water after fish. In this scenario it could have focused its Like the modern well-known An adult blue whale can grow to a massive 30m long and weigh more than 180,000kg thats about the same as 40 elephants, 30 Tyrannosaurus Rex or 2,670 average-sized men. Why? Odontocetes: There are two families of odontocetes distinguished by the shape of their teeth: the porpoises (with spade-like teeth) and dolphins (with round teeth). Due (2021, August 31). These bristly baleen plates filter, sift, sieve or trap the whales favourite prey from seawater inside their mouths. Please refer to the appropriate style manual or other sources if you have any questions. It lived on land, on the edge of lakes and riverbanks in what is now Pakistan and India. Chemical information from some of these wolf-sized meat-eaters show that they ate fish. In contrast, the origin of cetaceans, which includes whales, began as four-legged land animals who actively used locomotion and were great runners as a result.[14]. and that in a modern cetacean. Fossils or organisms that show the intermediate states between an ancestral form and that of its descendants are referred to as transitional forms. (In the case of narwhals, one tooth becomes a modified tusk.). They had flatter skulls and feeding filters in their mouths. Fossil representation: Several individuals of Such muscles are consistent with webbed feet that were used for aquatic locomotion. 2001 wrote that "Pakicetids were terrestrial mammals, no more amphibious than a tapir. P. This cookie is set by GDPR Cookie Consent plugin. If you happened to stumble across the small, dog-sized Pakicetus 50 million years ago, you'd never have guessed that its descendants would one day include giant sperm whales and gray whales. Length: Around 30 million years ago, these lineages split and evolved into the more than 80 species living today. Its name means Pakistan whale.. 40.4 to 33.9 million years ago Dorudon (spear-tooth) is a genus of extinct basilosaurid ancient whales that lived alongside Basilosaurus 40.4 to 33.9 million years ago in the Eocene. Hussain - 2009. about 54 million years ago, Pakicetus lived mainly in shallow coastal waters, Baleen is made out of keratin, the same protein that makes up our fingernails and hair. Pakicetus is an extinct genus of amphibious cetacean of the family Pakicetidae, which was endemic to Pakistan during the Eocene, about 50 million years ago. As in most land mammals, the nose was at the tip of the snout. Only time will tell. These cookies track visitors across websites and collect information to provide customized ads. Pakicetus attocki lived on the margins of a large shallow ocean around 50 million years ago. Species: P. inachus (type), While it's virtually unknown for a single environmental disaster (such as an oil spill or fracking project) to render an entire species extinct, constant exposure to pollution can render plants and animals more susceptible to the other dangers, including starvation, loss of habitat, and disease. Its also a massive sound generator that helps the whale navigate. One of the most dramatic examples of a modern extinction is the passenger pigeon. Formally known as "Whales: Giants of the Deep," this exhibition traveled to New York from New Zealand, where it was developed by the Museum of New Zealand Te Papa Tongarewa. That's because environmental and evolutionary changes had whittled away at this class of creatures. Nov. 2, 2020 A new species of extinct lizard, Kopidosaurus perplexus, has just been described. While it's unusual for disease alone to wipe out a given speciesthe groundwork has to be laid first by starvation, loss of habitat, and/or lack of genetic diversitythe introduction of a particularly lethal virus or bacterium at an inopportune moment can wreak havoc. Performance cookies are used to understand and analyze the key performance indexes of the website which helps in delivering a better user experience for the visitors. In 2001, scientists found fossils which confirmed the fact that this mammal lived entirely on the land and never went into the water. of the fossil site indicates that it was a coastal region at the time, the skull has brought the second hunting theory of lurking in the water Within the exhibition, skeletons of fossil whales show visitors how the whale lineage evolved from land mammals to fully aquatic whales. adaptation in animals that spend a lot of time in the water. This The animal was given the name Pakicetus. the position of the malleus in Pakicetus was between that in a land mammal Because whales and dolphins use sound to locate food and communicate, are therefore ungulates, especially the even-toed forms pigs, cattle, Size: Between 1 and 2 meters long. and as such possibly had many estuaries and islands. Pakicetus Thus the hearing mechanism of Pakicetus is the only known intermediate between that of land mammals and aquatic cetaceans. During the Eocene, Pakistan was an independent island-continent off the coastal region of Eurasia, and therefore an ideal habitat for the evolution and diversification of the Pakicetidae. They originated in Asia and came into North America. between the equivalent bone in modern cetaceans and that in modern artiodactyls. For example, imagine that scientists find a way to permanently eliminate malaria by exterminating every mosquito on Earth. This, of course, was the disaster that wiped out the . developed for hearing in halfway stage. What is the Venus-Jupiter conjunction and how can you view it? It was a mammal that would only go near the water to grab fish. (It was modified by the American Museum of Natural History.) Updates? Phonetic: Pa-kee-see-tuss. Dorudon has a long, narrow snout, and almost certainly lacked the bulbous melon that forms the spherical bulge on the facial profile of modern toothed whales. While every effort has been made to follow citation style rules, there may be some discrepancies. Their hips and legs were on the way out. Rodhocetus fossilized remains were found during a 1992 excavation in northern Pakistan. Pakicetus had a long snout; a typical complement of teeth that included incisors, canines, premolars, and molars; a distinct and flexible neck; and a very long and robust tail. insulates them from background noise conducted through the bones of the point for your own research. It's likely that many of the Earth's mass extinctionsnot only the K-T extinction, but also the much more severe Permian-Triassic extinctionwere caused by such impact events, and astronomers are constantly on the lookout for comets or meteors that could spell the end of human civilization. Paleontologists know this because its ears were only adapted for the land and not for the water. They also succumbed to a lack of food and predation by early humans. It is the most ancient of presently-known direct ancestors of modern-day whales that lived approximately 48 mln years ago and adjusted to . It certainly doesnt look like the start of some of the largest aquatic mammals ever to live on Earth. Pakicetus is an extinct genus of amphibious cetacean of the family Pakicetidae, which was endemic to Pakistan during the Eocene, about 50 million years ago. Whales evolved during the Eocene in the warm, shallow tropical Tethys Sea, which lay sandwiched between the mainland of Asia and Europe to the north and Africa, Arabia, Madagascar, and the Indian subcontinent to the south. This website uses cookies to improve your experience while you navigate through the website. The ears of whales have many other distinctive features. The whales massive bulbous head is about one-third of the animals length. Like all other cetaceans, Pakicetus had a thickened skull bone known as the auditory bulla, which was specialized for underwater hearing. [16], Last edited on 26 February 2023, at 14:47, "A new Eocene archaeocete (Mammalia, Cetacea) from India and the time of origin of whales", "Fossil Evidence for the Origin of Aquatic Locomotion in Archaeocete Whales", "A life spent chasing down how whales evolved", "Origin of Whales in Epicontinental Remnant Seas: New Evidence from the Early Eocene of Pakistan", 10.1666/0094-8373(2003)029<0429:LTIEWE>2.0.CO;2, "Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls", "From Land to Water: the Origin of Whales, Dolphins, and Porpoises", https://en.wikipedia.org/w/index.php?title=Pakicetus&oldid=1141735500, This page was last edited on 26 February 2023, at 14:47. 50 million years ago Hippos likely evolved from a group of anthracotheres about 15 million years ago, the first whales evolved over 50 million years ago, and the ancestor of both these groups was terrestrial. These spherules are believed to have come from the impact itself. tide that would have had passable land bridges at low tide. By Graduated from ENSAT (national agronomic school of Toulouse) in plant sciences in 2018, I pursued a CIFRE doctorate under contract with SunAgri and INRAE in Avignon between 2019 and 2022. About Pakicetus It was a mammal that would only go near the water to grab fish. Dinopedia is a FANDOM Lifestyle Community. These cookies ensure basic functionalities and security features of the website, anonymously. From the shape of the fossil ossicles, the two scientists deduced that and small or nonexistent hindlimbs. Cetacea) from the West - 1980. or Odontoceti, and the filter-feeding baleen whales, or Mysticeti. of the chain of three ossicles in the middle-ear cavity is at a similar free for your own study and research purposes, but please dont been envisioned by some as a wolf sized predator that would dive into In addition, it still retained many other features of terrestrial mammals, including an auditory system that was better for hearing in air than in water, a dentition not unlike that of its closest terrestrial relatives, such as the mesonychids, and functional feet capable of locomotion on land. Species: Pakicetus had a long snout; a typical complement of teeth that included incisors, canines, premolars, and molars; a distinct and flexible neck; and a very long and robust tail. attocki , P. calcis, P. chittas. the bones surrounding the inner and middle ears fit into the other bones with other animals such as Ambulocetus, - Pakicetus inachus, A New Archaeocete (Mammalia, "But if you think about it, some of the other relatives like pigs and peccaries are pretty ferocious and will eat just about anything. The later descendants of Pakicetus were fully aquatic. Is there a database for insurance claims? [15] Speculation is that many major marine banks flourished with the presence of this prehistoric whale. may have cut off some areas of the coast, creating islands at high Wynne was a reporter at The Stamford Advocate. Why Did the Saber-Tooth Tiger (Smilodon) Go Extinct?With their enormous, deadly-sharp canines, saber-toothed carnivores are well known to many people as frig. known, is a member of the now extinct Archaeoceti suborder of toothed whales. It does not store any personal data. The stalk of the silphium plant was used to . Thewissen and Hussain say primitive whales were probably amphibians, Extinction is the death of all members of a species of plants, animals, or other organisms. to wait for the [3] In 2001, fossils of ancient whales were found that featured an ankle bone, the astragalus, with a "double pulley" shape characteristic of artiodactyls. When the landmass was eventually lifted back up it brought with it a bounty of marine sediments . attention upon prey that had become trapped in tidal pools at low New York, evolving into a body that could provide efficient aquatic movement, The teeth also suggest that Pakicetus had herbivorous and omnivorous ancestors. Commercial Photography: How To Get The Right Shots And Be Successful, Nikon Coolpix P510 Review: Helps You Take Cool Snaps, 15 Tips, Tricks and Shortcuts for your Android Marshmallow, Technological Advancements: How Technology Has Changed Our Lives (In A Bad Way), 15 Tips, Tricks and Shortcuts for your Android Lollipop, Awe-Inspiring Android Apps Fabulous Five, IM Graphics Plugin Review: You Dont Need A Graphic Designer, 20 Best free fitness apps for Android devices. The large tail of Pakicetus is possibly a specialization for aquatic locomotion, although exactly how is unclear. www.prehistoric-wildlife.com. Description This four-footed land mammal named Pakicetus, living some 50 million years ago in what we know as Pakistan today, bears the title of "first whale." "Pakicetus Facts and Figures." (Image credit: Museum of New Zealand Te Papa Tongarewa, 2008). Kas region, Pakistan. ThoughtCo, Aug. 31, 2021, thoughtco.com/reasons-animals-go-extinct-3889931. way it may be that these marine adaptations are not just driven by Philip Gingerich, Pakicetus has been envisioned by some as a wolf sized predator that would dive into the water after fish. But their ancestors of more than The current theory suggests that they went extinct about 40,000 years ago, not long after Homo sapiens arrived on the continent from Africa. In fact, in some cases it is arguable that some species of proboscideans never went extinct, but merely . seal, it probably needed to return to the shore to breed. https://www.thoughtco.com/reasons-animals-go-extinct-3889931 (accessed March 5, 2023). They are Though modern cetaceans have the same basic hearing apparatus as all They occur in a wide variety of habitats from fresh water rivers to the deep parts of the ocean. In the past two years, J. Thewissen of Duke University Medical School 3 Which land animal is the closest cousin to dolphins? These cookies help provide information on metrics the number of visitors, bounce rate, traffic source, etc. By clicking Accept All, you consent to the use of ALL the cookies. Early-Middle Eocene Kuldana Formation of Kohat (Pakistan) - This is the reason it's much healthier to marry a complete stranger than your first cousin, since, otherwise, you run the risk of "inbreeding" undesirable genetic traits, like susceptibility to fatal diseases. The climate of the early Eocene Epoch (56 million to 40 million years ago) was the warmest of the Cenozoic Era, nearly 10 C (18 F) warmer than the global average of the present day. The fossil remains of L. denticrenatus have been dated to 34 million years ago. Why Did Crocodiles Survive the K/T Extinction? The cookies is used to store the user consent for the cookies in the category "Necessary". about 50 million years ago Pakicetus is an extinct genus of amphibious cetacean of the family Pakicetidae, which was endemic to Pakistan during the Eocene, about 50 million years ago. The discovery of a more complete skeleton in 2001 prompted a reconsideration, and today Pakicetus is deemed to have been fully terrestrial; in the words of one paleontologist, "no more amphibious than a tapir." According to new dating of fossils from Java, Indonesia, H. erectus persisted in this region until around 108,000 to 117,000 years ago. Pakicetus lived. Its ear structure is more They are thought to derive from a group Name: But of course, it was definitely not a dog- or even related to dogs. The "first whale," a creature whose lifestyle (living on land but eating fish from the nearby sea) represented the early stage of this transition into the water, was a wolf-size fish eater that lived about 50 million years ago on the edges of the ancient Tethys Sea, according to the exhibit. Learn about the mass extinction event 66 million years ago and the evidence for what ended the age of the dinosaurs. This is the first thing most people associate with the word "extinction," and not without reason, since we all know that a meteor impact on the Yucatn Peninsula in Mexico caused the disappearance of the dinosaurs 65 million years ago. 1906 Dorudon was discovered in 1906 by Charles William Andrews, who described Prozeuglodon atrox (=Proto-Basilosaurus) based on a nearly complete skull, a dentary, and three associated vertebrae presented to him by the Geological Museum of Cairo. It hunted small land animals and freshwater fish, and could even hear underwater. "Imagine your hip bones just started to float off your body that is what that is," he said. Dimensions: length - 1,8 m, weight - 30 - 90 kg. Time Period: Follow us @livescience, Facebook& Google+. Unlike modern Donald Russell and their colleagues came to broadly the same conclusion "[7], However, Thewissen et al. This cookie is set by GDPR Cookie Consent plugin. You need to look no further than the end of the last Ice Age, about 11,000 years ago, when various megafauna mammals were unable to adapt to quickly warming temperatures. to its transitional nature, it is hard to say with certainty how Assortments of limestone, dolomite, stone mud and other varieties of different coloured sands have been predicted to be a favourable habitat for Pakicetus. Pakicetus "Top 10 Reasons Why Animals and Plants Go Extinct." may well be the oldest known ancestor to modern whales, hippopotamus The . Functional cookies help to perform certain functionalities like sharing the content of the website on social media platforms, collect feedbacks, and other third-party features. (2020, August 27). Original article on LiveScience.com. While most struggles for survival transpire over eons, sometimes the contest is quicker, bloodier, and more one-sided. The problem is that people tend to give sole causes while the real reasons are usually far more complex. In these and other features of its hearing apparatus, Pakicetus was Pakicetus fossils, which include many broken teeth, skulls, and skeletons, were found in the Kuldana Formation in Pakistan, a site that was located near the northern edge of the Tethys Sea during the Eocene. Dorudon lived in warm seas around the world. That's when an immense asteroid slammed into what is now the Yucatan Peninsula, triggering one of the worst extinction crises of all time. about 30 million years ago Fossil Record Fossils indicate that the earliest known baleen whales lived about 30 million years ago. So how did they come to be so specialized for life in the sea? Nowadays, there are two varieties of whale. Strauss, Bob. Further reading In 2001, scientists found fossils which confirmed the fact that this mammal lived entirely on the land and never went into the water. Analysis Witness the crisis currently facing the world's amphibians, which are falling prey to chytridiomycosis, a fungal infection that ravages the skin of frogs, toads, and salamanders, and causes death within a few weeks, not to mention the Black Death that wiped out a third of Europe's population during the Middle Ages. The ear bones of Pakicetus provide further These species went extinct at the same time as mammoths, as the ice age was ending. Top 10 Reasons Why Animals and Plants Go Extinct. of extinct land-based ungulate mammals called the mesonychid condylarths, Humans have only occupied the Earth for the last 50,000 or so years, so it's unfair to blame the bulk of the world's extinctions on Homo sapiens. The baleen of the bowhead whale can be be 4 metres long. What did the first whales look like? Although it had the body of a land animal, its head had the distinctive long skull shape of a whales. A typical representative: Pakicetus inachus Gingerich & Russell, 1981. What they have in Common. Visit our corporate site (opens in new tab). The first fossil, a skull fragment of P. inachus, was found in 1981 in Pakistan. Thus, Pakicetus represents a transitional taxon between extinct land mammals and modern cetaceans. Live Science is part of Future US Inc, an international media group and leading digital publisher. Just like Indohyus, limb bones of pakicetids are osteosclerotic, also suggestive of aquatic habitat"[8] (since heavy bones provide ballast). the ancestors of modern ungulates. Vibrations "Top 10 Reasons Why Animals and Plants Go Extinct." What are the five methods of dispute resolution? But the new discovery suggests that our species. aquatic lifestyle. Evidence suggests an asteroid impact was the main culprit. But opting out of some of these cookies may affect your browsing experience. Subsequent fossils of Pakicetus were also found in Pakistan, hence the generic name Pakicetus. and along Mass starvation is the quick, one-way, surefire route to extinctionespecially since hunger-weakened populations are much more prone to disease and predationand the effect on the food chain can be disastrous. Only those of Mystacodon selenensis, which date to approximately 36 million years ago, are older in the mysticete lineage. Until the early 1800s, billions of passenger pigeons darkened the skies of the United States in spectacular migratory flocks. Pakicetus It was only over the course of the Eocene epoch that the descendants of Pakicetus began to evolve toward a semi-aquatic, and then fully aquatic, lifestyle, complete with flippers and thick, insulating layers of fat. [2] It was a wolf-like animal, [3] about 1 metre (3 ft 3 in) to 2 metres (6 ft 7 in) long, [4] and lived in and around water where it ate fish and other small animals. Let us know if you have suggestions to improve this article (requires login). At first glance, that may seem like good news for us humans, but just think of the domino effect as all the creatures that feed on mosquitoes (like bats and frogs) go extinct, and all the animals that feed on bats and frogs, and so on down the food chain. They also claim that its orientation relative to the malleus the second Molecular studies If you knew nothing about this mammal other than what youve seen in Pakicetus pictures, then you might never guess that it was one of the earliest whales found. By most reckonings, since the beginning of life on Earth, a whopping 99.9% of all species have gone extinct. https://prehistoric-wiki.fandom.com/wiki/Pakicetus, https://www.amnh.org/explore/news-blogs/on-exhibit-posts/the-first-whale-pakicetus, https://www.britannica.com/animal/Pakicetus, https://teara.govt.nz/en/diagram/4690/pakicetus-whale-and-dolphin-ancestor, https://www.researchgate.net/figure/A-gradual-evolution-of-whale-traits-a-Pakicetus-the-terrestrial-Pakistan-whale_fig1_257767769. discovered fossil ear bones and lower jaw bones of Pakicetus in the Kala Often, reasons for extinction, especially of prehistoric mammals, fall into many categories such as human involvement or climate change. They say that in shape and proportions it is intermediate - Journal of Vertebrate Paleontology Carnivore Ear bones from Pakicetus show a feature that is unique to whales, placing it as the earliest known member of the modern whale lineage . to allow for this. It thus lacked the fat pad, and sounds reached its eardrum following the external auditory meatus as in terrestrial mammals. Strauss, Bob. We also use third-party cookies that help us analyze and understand how you use this website. About Pakicetus It was a mammal that would only go near the water to grab fish. Pakicetus (Pakistan whale). Mysticete cetaceans produce lowfrequency moans, grunts, and thumps, and at least one species produces cries and chirps. Unlike the hippos ancestor, whale ancestors moved to the sea and evolved into swimming creatures over a period of about 8 million years. Formation of northern Pakistan. ancestors of the modern cetacean groups the toothed whales and dolphins, Usually, determining which is the "better adapted" species takes thousands, and sometimes millions, of years. The exhibit also explores whale biology, and includes a life-size replica of a blue whale heart. Why did the descendants of Pakicetus eventually begin moving into the water and evolving into whales? 25 (11): 235246 - Philip D. Gingerich & Donald E. Russell - For instance, no one would have thought that prehistoric mammals were better adapted than dinosaurs until the K-T extinction changed the playing field. Once a species starts dwindling in numbers, there's a smaller pool of available mates and often a corresponding lack of genetic diversity.