It had a more streamlined body and a fully flexible rear spinal column, which could have produced the motions for the powerful beat of a horizontal tail fluke that propels modern whales. Zhai, Philip D. Gingerich, and Liezu Chen, Skull of New Mesonychid evolutionists own criteria. characters are not all clear-cut.[13] One need only compare the Given the significance evolutionists have attributed to these There were hoofed counterparts to every kind of predator we have today. Why did nikki vincent leave tvsn. What are the multiple roles of a successful introductory paragraph? Web did mesonychids swimdark blue suit brown shoes. C. Milinkovitch, Axel Meyer, and Jeffrey R. Powell, Phylogeny of Heres how paradise fought back. They went in decline at the end of the Eocene, and became extinct in the early Oligocene. The history of book bansand their changing targetsin the U.S. that the stratigraphical relationships of most of these fossils are [18] If the younger date (early Lutetian) is Some modern species, such as pigs, are omnivorous, while some prehistoric species, such as mesonychians, were carnivorous. [34], In addition, no chain of descent from archaeocetes to modern Heritage rough rider flag grips for sale. Debate has The order argues that Protocetus was completely aquatic and that its They include rhinoceroses and tapirs, the horses closest living relatives. Further studies will be required to reinforce this hypothesis, particularly since Indohyus is acting as the sole keystone between early whales and their more ancient, artiodactyl ancestors. less advanced its features; the younger the fossil the more Perhaps whales were modified from some otter-like creature, as proposed by Thomas Henry Huxley, or, as William Henry Flower speculated, maybe whale ancestors were omnivorous, hoofed, hippo-like animals which dwelt in prehistoric marshes. Earliest Whales. They had an elongated skull and triangular teeth, which are similar to whales. [4][5] However, weight estimations of P. gigantea vary from 129 to 396kg.[6]. The fossil record and the evidence from the living animals was in apparent discord, and resolution was difficult to achieve. Lutetian. anything more than fragmentary crania. Mammals, Marine Mammal Science, no. If you continue to use this site we will assume that you are happy with it. size difference between Basilosaurinae and protocetids casts doubt Bulletin of the American Museum of Natural History 132 (1966): The only hints of the former hind limbs are the vestiges of a pelvis and femur, the upper leg bone, embedded in the body wall. Mesonychidae (meaning "middle claws") is an extinct family of small to large-sized omnivorous - carnivorous mammals. How did the mesonychids swim? Anyone can read what you share. of cetaceans, International Geology Review 7 (1965): 1463. . This ordinary woman hid Anne Frankand kept her story alive, This Persian marvel was lost for millennia. Weight estimates vary, from 20 to 55kg (about 45-120lbs). The Origin of Whales or the Evolution. 1978), 585. It is simply an acknowledgement that evidence Since the hind limbs were a mere 2 feet long and the whole body was 50 feet long, the discoverers concluded that the legs could not have supported the body on land or assisted in swimming. They had an elongated skull and triangular teeth, which are similar to whales. In 2001 two different teams of paleontologists described the rare ankle bones from three different early whales Hans Thewissen and colleagues reported on Pakicetus and Ichthyolestes, and a team led by Philip Gingerich described Rodhocetus. What does Lo Debar represent in the Bible? The family Protocetidae includes the Natural History (April 1994): 12; Carl Zimmer, Back to the Sea, Editorial Team Thus, if Pakicetus is moved Writing in the current issue of the journal Nature, Dr. Philip D. Gingerich, a paleontologist at the University of Michigan at Ann Arbor, said the new species, Rodhocetus kasrani, was the earliest known transitional whale with an anatomy adapted for swimming like a whale. The hind feet of Ambulocetus, however, were clearly adapted for swimming. Mesonychids were reported in the 1980's. They found them in Asia and Europe. [6], Mesonyx specimens have been unearthed in Colorado, Wyoming, Utah and China. lm_second=a.getSeconds();lm_second=((lm_second<10)? He called it Ambulocetus. fossils in their battle with creationists, one cannot help but [RETURNTOTEXT], [11] Van Valen, (1966): 92. If we take Indohyus as a model for the sort of creature at the root of the whale family tree, then the forerunners of early whales primarily ate terrestrial plants, spent most of their time on land, but would sometimes swim in fresh bodies of water and chewed in specialized, shearing manner which would later be co-opted by their descendants to cut flesh. ((lm_year<70)?2000:1900):0)+lm_year; Planetary Science, 22 (1994): 419, 427-31. monthName[7] = 'August' Thewiseen, Jennifer Sensor, Mark Clementz, and Sunil Bajpai have just published an overview of early whale diet in Paleobiology. 46-47 million years ago transformed one or more of the species into an amphibious archaeocete. var a; Its forelimbs were equipped with fingers and small hooves. [1] The subfamily Mesonychinae, which includes Sinonyx, appears to be monophyletic: mesonychids proper. Basilosaurus isis was over 50 feet. Dissacus nor Ankalagon has been recovered. Naturalists understood the relevance of these features to whale evolution long ago. Ambulocetus, Rodhocetus, Indocetus, Protocetus, and Whales are highly-modified, once-hoofed mammals which are entirely aquatic. Even better, in 1981 paleontologists Philip Gingerich and Donald Russell found what they thought was a confirmation of Van Valens suggestion in the remains of one of the earliest whales, Pakicetus. whales [emphasis mine]); J. G. M. Thewissen, Phylogenetic As it turned out, whales were not only more closely-related to artiodactyls than to the mesonychids. All protocetids were less than ten feet long, this claim beyond a reasonable doubt. Ankalagon, the only middle Paleocene mesonychids known at that The hind feet of ambulocetus, however, were clearly adapted for swimming. Another discovery in Pakistan has now advanced the transition story three or four million years and out into deeper waters. of the skulls of Ambulocetus, Rodhocetus, and Indocetus. [archaeocete] skull appears as if it might have been derived from They were endemic to north america and eurasia during the early paleocene to the. The genus' greatest diversity is seen in North America, with P. ossifraga known from Latest Paleocene strata of Wyoming, and P. gigantea, P. intermedia, and P. gracilis known from Early Eocene strata of Wyoming. Like Pakicetus, it spent . What did mesonychids evolve into? (Eocene 2), and late (Eocene 3) subepochs. Deltatheridia, a new order of mammals. Relationships of Mysticeti and [1] It is hypothesized that some mesonychid species began [7] Mesonychidae as defined by Szaly and Gould (1966) is probably paraphyletic or polyphyletic, with Hapalodectinae and Andrewsarchinae (represented by the lone skull of Andrewsarchus) wrongly assigned to the group. All of the known fossil whales were fully-aquatic. ancestor to descendant relationships.[26] Indeed, the tremendous They were endemic to North America and Eurasia during the Early Paleocene to the Early Oligocene, and were the earliest group of large carnivorous mammals in Asia. the pakicets was one of the whales ancestors and the grey wolf was the dogs ancestor. Rose, Postcranial Skeleton of the Early Eocene Mesonychid Are flights to Gran Canaria still flying? Hind Limbs of Eocene Basilosaurus: Evidence of Feet in Whales, monthName[5] = 'June' uncertain. a series of transitional fossils, the evolutionist does not mean [36], [1] E.g., Stephen Jay Gould, Hooking Leviathan By Its Past, We use cookies to ensure that we give you the best experience on our website. Marine For Dissacusium and Yangtanglestes are so "Mesonyx and the other mesonychid mesonychians (mesonychians part IV) | ScienceBlogs", http://paleodb.org/cgi-bin/bridge.pl?a=basicTaxonInfo&taxon_no=49575, http://paleodb.org/cgi-bin/bridge.pl?a=basicTaxonInfo&taxon_no=49572, https://en.wikipedia.org/w/index.php?title=Pachyaena&oldid=1083550403, Articles with dead external links from April 2022, Creative Commons Attribution-ShareAlike License 3.0, This page was last edited on 19 April 2022, at 11:32. published in 1976. Archaeoceti are uncertain, with insufficient fossil evidence to possible to identify a single ancestral species. The sagittal crest gave expanded attachment for the temporalis muscles; Sinonyx had a powerful bite. ends, broken lines, and question marks. Simpson concluded: The current leaders in the field believe that archaeocetes However, mesonychids are now often given ordinal rank as Whether the early archaeocetes form a series or sequence of Under the discarded mesonychid hypothesis, whale ancestors were already committed carnivores that simply slid into the water, but the new picture indicated that whales underwent some major changes in diet and dentition during their early evolution. They lived 60-37 mya. [7] An additional two species Mesonyx uqbulakensis and M. nuhetingensis have been described from the early Eocene Arshanto Formation in China.[8]. Sinonyx is no longer considered ancestral to Cetacea,[7] but has convergent features to early land-dwelling whales that suggest it may have had some similar adaptations. lm_day=a.getDate();lm_day=((lm_day<10)? In that case, what is believed to have been a fully marine archaeocete discussed above), but specialists admit there is a lack of clear This evidence suggests that these creatures probably ate marine life and scavenged off of the shore (Ponzetti 2006). One branch of the ungulate family, called the mesonychids, were predators. Functional analysis of its skeleton shows. (1993): 483. known from jaws, teeth, and rather limited postcrania. The habitat they lived in was mainly on shore. The animal was given the name Pakicetus. Nature 347 (1990): 428-29. the Mammalia, in W. Patrick Luckett and Frederick S. Szalay, eds., monthName[8] = 'September' mesonychids for which postcrania have been described. likewise noted that the cited similarities in skull and dental a reconstruction of the skull of Rodhocetus kasrani, see Philip Pakicetus inachus is known from only the back portion of a skull, Its forelimbs were equipped with fingers and small hooves. Gould, is now generally classified with triisodontines rather than Its forelimbs were equipped with fingers and small hooves. Mesonychids first appeared in the early Palaeocene with the genus Dissacus. These creatures also had an inner ear, which is a characteristic. The big question of where whales had come from appeared to be solved, but then the course of the research took a left turn. [27] It has been calculated In order to investigate these mysteries, scientists turn to indirect evidence preserved on and inside the teeth themselves. A change in the way whale ancestors chewed may have preceded the transition to a carnivorous diet. bones. This evidence suggests that these creatures probably ate marine life and scavenged off of the shore (Ponzetti 2006). [3] They were probably active hunters. extraordinary claim of cetacean evolution. York: John Wiley & Sons, 1980), 329. poorly known that Zhou, et al. Lake erie salt mine ice cream; Its forelimbs were equipped with fingers and small hooves. 6 Other characters Sinonyx has in common with early whales include an ossified tympanic bulla, which improves sensitivity to high-frequency sounds and is often seen in predators that hunt small prey by sound, and an enlarged jugular foramen, which gives more room for the cranial nerves that control swallowing and the balance between athletic activity and digestion.[8]. These creatures also had an inner ear, which is a characteristic. Inside South Africas skeleton trade. Brain casts show that M. obtusidens had an unusually well-developed neocortex for an Eocene mammal. Lux* south ari atoll water villa. They may have also been scavengers, similar to hyenas. [RETURNTOTEXT], [10] Robert L. Carroll, Patterns and Processes of Vertebrate [RETURNTOTEXT], [4] Leigh Van Valen, Deltatheridia, A New Order of Mammals, J. G. M. In modern whales, they contribute mightily to the propulsive beat of the tail fluke. Gingerich dates the Ypresian-Lutetian boundary This progression of features is believed Ibid., 395. Known locations for Zygorhiza is almost exclusively the East coast of the United States, primarily in the Gulf Coast states, and many fossils have been found in Louisiana, Mississippi, and Alabama. that fits expectations is more readily received. were ancestral to modern whales, but there is no agreement on which It was about the size of a modern sea lion, weighing 600 to 700 pounds and measuring about 10 feet from snout to tail. [RETURNTOTEXT], [22] Protocetus atavus is known from a well-preserved skull and figure 19, p. 24. (Princeton: Princeton University Press, 1992), 368, 370, 372, 376; dispute remains unsettled. continue to be classified in the more technical literature as a Are Mesonychids classified under Cetacea? While a single part of the skeleton may seem like too little to influence a major debate, though, the three early whales were found to have a particular ankle bone known as the astragalus with a distinctive double-pulley shape which is characteristic of artiodactyls. To save chestnut trees, we may have to play God, Why you should add native plants to your garden, What you can do right now to advocate for the planet, Why poison ivy is an unlikely climate change winner. The pygmy hippopotamus doesnt approach its cousins five-ton heft. than is commonly appreciated. Find in Pakistan. Their anatomies retain vestiges of the four-legged land animals in their ancestry, the ones that began the bold return to the sea more than 50 million years ago. Lawrence G. Barnes and Edward Mitchell, Nevertheless, the different pattern of tooth wear in the one individual and the odd tooth shapes of some other early whales such as Andrewsiphius hints that these animals had a wider array of feeding strategies than we presently understand. Things were so frustrating that in 1976 paleontologists Jere Lipps and Edward Mitchell wondered if any fossils of the transformation would be found at all perhaps the changes happened so fast that the chances of creatures with transitional features being preserved was low. Are mesonychids classified under Cetacea? The genus likely originated from Asia and spread to Europe, and from there to North America across a land bridge in what is now the North Atlantic ocean. wastebasket group that includes all ancient toothed Cetacea that (Mammalia: Condylarthra), Journal of Paleontology 54, no. evident from the fact so many groups of mammals and even reptiles The migration of whales to the sea is a classic example of transcendental evolutionary change, along with the first fishlike animals establishing their beachhead 370 million years ago, birds becoming flying animals and early human ancestors developing upright walking. the World (London: Addison-Wesley Publishing, 1983), 123; Robert [RETURNTOTEXT], [2] The scenario is sketched in Keith Banister and Andrew Campbell, Web did mesonychids swimdark blue suit brown shoes. Priscilla shirer elijah answer key. [20] This would make Ambulocetus younger than Rodhocetus and possibly younger than Indocetus and even Protocetus. whales has been identified. This made them, by definition, mammals. 2361 (1969): 25; for application of statement to archaeocetes, see Functional analysis of its skeleton shows. [RETURNTOTEXT], [5] Frederick S. Szalay, The Hapalodectinae and a Phylogeny of the to whales, is to understate the problem. Paleobiology 2: 147-155, Thewissen, J., Sensor, J., Clementz, M., & Bajpai, S. (2011). Whereas creatures such as Bunophorus exhibited all three wear types, the molars of most early whales were dominated by Phase I tooth wear. Mesonychids were not the ancestors of whales, and hippos are now known to be the closest living relatives to whales. pronounce that the evolutionary case is now closed.[3] The [33] This is particularly revealing when one considers Natural History 85 (1945): 214. [RETURNTOTEXT], [35] Quote from Andre Wyss, Clues to the origin of whales, Aspects of Cetacean Origins: A Morphological Perspective, Journal Evolution of dental wear and diet during the origin of whales Paleobiology, 37 (4), 655-669 DOI: 10.1666/10038.1, Thewissen, J., Williams, E., Roe, L., & Hussain, S. (2001). Banister and Campbell likewise If you continue to use this site we will assume that you are happy with it. [RETURNTOTEXT], [9] Malcolm C. McKenna, Toward a Phylogenetic Classification of (1975): 1-48; P. D. Gingerich, S. M. Raza, M. Arif, M. Anwar, and Some of these creatures, Van Valen hypothesized, were mollusk eaters that caught an occasional fish, the broadened phalanges [finger and toe bones] aiding them on damp surfaces, and the resemblance between the teeth of the earliest known whales and mesonychids appeared to support this connection. 92. [1] Various described species of Pachyaena ranged in size from a coyote to a bear. formation in Pakistan. the Paleobiological Evolution of Cetacea, trans. Other change over time involved improvements in the animals' maneuverability in their new environment. Can mesonychids swim? Known locations for Zygorhiza is almost exclusively the East coast of the United States, primarily in the Gulf Coast states, and many fossils have been found in Louisiana, Mississippi, and Alabama. The habitat they lived in was mainly on shore. Their streamlined bodies, the absence of hind legs, and the . Didymoconidae (Condylarthra, Mesonychia) in Asia, With a New Genus Its forelimbs were equipped with fingers and small hooves. You Are Here: unblocked sticky ninja east london walking tour self guided did mesonychids swim. Mesonychids e.g. If Protocetus was fully But even Darwin much later could not fathom the evolutionary steps by which some land mammals had become whales. about 48 mya (Gingerichs early Lutetian date), that would push purpose of this article is to suggest that the fossil evidence for For more on our changing understanding of whale evolution, check out the chapter As Monstrous as a Whale in my first book Written in Stone. family of archaeocetes was involved. [RETURNTOTEXT], [14] Sinonyx jiashanensis can be found at Zhou, et al., 391. demonstrate close relationships. Edward Mitchell, A Phylogeny of D. Gingerich, The Whales of Tethys, Natural History (April appendicular skeleton.) M. J. Benton, ed., The Fossil Record 2 (London: Chapman & Hall, species being Dissacus saurognathus, which is Dissacus carnifex Sinonyx was about 1.5m (5ft) long, about the size of a modern grey wolf with a large elongated head, short legs, digitigrade feet adapted for running, and tiny hooves on all of its toes. Web did the mesonychids swim? from 38.6 to 35.4 mya. The animal still had four limbs for walking on land, though probably with diminished agility. and significant portions of fore and hind limbs. It was originally discovered in the 1990s and was named by Philip Gingerich in 1994. Haldane). Gingerich fossils, the degree of evolutionary advancement corresponds to the Since mammals only get two sets of teeth a milk set, which is shed, and a permanent adult set their feeding choices and strategies leave distinctive wear patterns on their teeth which can be examined for clues. To acknowledge, as Robert Carroll did recently, that [i]t is Even though Indohyus exhibited tooth wear that was similar to that seen among the earliest whales, it was not consuming the same kind of food. cms geographic adjustment factor 2021 did mesonychids swim. Its forelimbs were equipped with fingers and small hooves. rise to archaeocetes, despite the inability to identify any species Li Chuan Luei and Ting Su-Yin, The Paleogene comprised of three extinct families: Protocetidae, Remingtonocetidae, and Basilosauridae. If you continue to use this site we will assume that you are happy with it. These chemical signatures are influenced by environment and behavior and can be used to construct a general picture of an animals ecology. Home | How did the Mesonychids swim? [8] No one has nominated any of Unblocked sticky ninja east london walking tour self guided did mesonychids swim. Recently scientists determined which group of prehistoric artiodactyls gave rise to whales. "The embarrassment of past absence has been replaced by a bounty of new evidence -- and by the sweetest series of transitional fossils an evolutionist could ever hope to find.". whales Zygorhiza kochii is a species of extinct whale known from the late Eocene (around 36 million years ago) of the Gulf Coast of the United States. Dr. J. G. M. Thewissen, an anatomist and paleobiologist at Northeastern Ohio Universities College of Medicine in Rootstown, Ohio, reported the discovery in January. Mesonychids are medium-to-large-sized carnivorous mammals closely related to even-toed ungulates (pigs, camels, goats, cattle) and cetaceans (whales and dolphins) that lived in the Paleogene, evolving soon after the extinction of the dinosaurs 65 million years ago and going extinct around 30 million years ago. lm_year=a.getYear();lm_year=((lm_year<1000)? gave rise to odontocetes or mysticetes. Mammals of China, Bulletin of Carnegie Museum of Natural History 21 (1983): 1-93. 46-47 million years ago Wells, Berggren, eds., Eocene-Oligocene Climatic and Biotic Evolution These Creatures Also Had An Inner Ear, Which Is A. Cetaceans are distant descendants of a group of poorly defined mammals known as condylarths. New fossil discoveries have now revealed several of the critical evolutionary steps in the earliest history of whales. A population of mesonychids in a marshy habitat might have been enticed into the water by seafood. Gatineau park spring trails search. Mesonychidae (Mammalia, Condylarthra), American Museum Novitates It could also hunt in the sea, probably swimming by kicking its big feet. [4][5] Like other mesonychids, the toes ended in small hooves. Paleocene mesonychid known at the time. [35] As for Basilosaurus advanced its features. archaeocetes. broken skull with lower jaws. The trouble was that the fossil record of whales was so poor that no one could be sure exactly how cetaceans had evolved. were essentially contemporaries. In the case of mesonychids, the relationship to archaeocetes Gingerich, et al., (1994): 844-845. fossils in a morphological sequence and more critical of dates that Can Mesonychids swim? [1], While this was the earliest genus of mesonychid to be named (by Edward Drinker Cope in 1872) and the group is named after it, Mesonyx was one of the most derived genera of mesonychids, evolving features for active running. of African Mammals (Cambridge, MA: Harvard University Press, Its tail was long and slender, with no evidence of use for swimming. The data gleaned from the carbon isotopes indicated a curious paradox, however. from vertebrae, ribs, a tooth, and part of a second skull which as more advanced. But more importantly, if Basilosaurus did This fossil animal, named Ambulocetus natans, which means swimming walking-whale, was excavated from sediments of an ancient seabed in Pakistan. Into the water It lived in or near estuaries about 50 to 48 million years ago. In the generally accepted cladogram by Spaulding et al. (see below), what does the presence of intermediate features in not possible to identify a sequence of mesonychids leading directly See also Culotta, 16. Mesonychids were not the ancestors of whales, and hippos are now known to be the closest living relatives to whales. "I am absolutely delighted to report that our usually recalcitrant fossil record has come through in exemplary fashion," Dr. Stephen Jay Gould, a Harvard University paleontologist and essayist, wrote in this month's issue of Natural History magazine. under 48 mya. guides. Pakistan, Science 220 (1983): 403-406. a=new Date(); [2] These animals had a reduced sense of smell and likely relied on sight and hearing to find food. Gatineau park spring trails search. has not provided unequivocal evidence on whether archaeocetes gave lm_hour=a.getHours();lm_hour=((lm_hour<10)? What are the side effects of Thiazolidnedions. By 06/07/2022 ether spiritual energy 06/07/2022 ether spiritual energy The link between other ungulates and whales is thought to be mesonychids, extinct four-legged . Ungulates are typically herbivorous and many employ specialized gut bacteria to allow them to digest cellulose. 2 (1995): 402. Science 249: 154-157 (1990). Though modern Carnivora have more complex brains, their ancestors did not; Mesonyx species would have been intelligent animals for their time. They were also most diverse in Asia, where they occur in all major Paleocene faunas. These land animals were exploiting an opportunity to feed on fish in the sea.". a mesonychid type, but there is little beyond certain general Web what did the mesonychids look like? comprised of two extinct subfamilies: Dorudontinae and Basilosaurinae. The subjective nature of such comparisons is monthName[3] = 'April' The long skull had a relatively large sagittal crest above the braincase to anchor large jaw muscles and give it a powerful bite. the vast differences. Cetacea, American Zoologists 15, no. Cetaceans are among one of several groups that have transitioned from roaming all over the land to swimming in the sea. Pakicetus inachus, a new archaeocete (Mammalia, Cetacea) from the early-middle Eocene Kuldana Formation of Kohat (Pakistan). Bartonian. '0':'')+lm_minute; Although they had nothing to ponder but this skull, scientists could see that Pakicetus had teeth resembling those of mesonychids, but it was well adapted to feeding on fish in surface waters of shallow seas. Recently scientists determined which group of prehistoric artiodactyls gave rise to whales. these genera for ancestor of the archaeocetes, and thus mesonychids Still, the emerging picture is that the transition from land-to-water occurred in a mosaic fashion. Basilosaurus establish? 1 have been suggested as ancestral to whales. [RETURNTOTEXT], [6] Szalay and Gould, 169-170 lists Dissacus as the only middle P. nemegetica is known from Late Paleocene strata of Mongolia. In 1966 Leigh Van Valen proposed that whale ancestry could be drawn back to an odd group of hoofed, carnivorous mammals called mesonychids. Basilosaurus isis, on the other 3 (1981): 535. Xiaoyuan Zhou, New whale from the Eocene of Pakistan and the (1994): 807. [RETURNTOTEXT], [23] Protocetus was found in deep-neritic deposits. Press, 1990), 172. noteworthy that the skull of Pakicetus was only one-half the size 9 Views. However, no such animal has ever been found. was already on the scene at or near the time archaeocetes first Why the early whales clustered together in the tooth wear diagram is probably a result of their tooth shape. Language links are at the top of the page across from the title. Its hind legs are smaller than those . Did the Mesonychids swim? But why would animals like whales, with all the apparatus for successful living on the land and ages of experience doing it, seek such a different habitat? considered a mesonychid subfamily) and archaeocetes probably McGraw-Hill, 1993), 484. Pachyaena Pakicetus Ambulocetus Rodhocetus Basilosaurus Zygorhiza Year reported Country where found Geological age (mya) Habitat (land, fresh water, shallow sea, open ocean) Skull, teeth, ear structure types most like. terms of both morphological (primitive to advanced) and stratigraphical (lower/older to higher/younger) criteria, is Pakicetus, Sinonyx ("Chinese claw") is a genus of extinct, superficially wolf-like mesonychid mammals from the late Paleocene of China (about 56 million years ago). The Hind Feet Of Ambulocetus, However, Were Clearly Adapted For Swimming. Evolution (Cambridge: University Press, 1997), 329. but would sometimes swim in fresh bodies of water and chewed in specialized . What we can learn from Chernobyl's strays. In fact, all three families In other words, the older the fossil the 42.1 mya, the Bartonian from 42.1 to 38.6 mya, and the Priabonian 3 (1975): 824. On See, R. Ewan Fordyce and Lawrence G. Barnes, The Evolutionary History of Whales and Dolphins, Annual Review of Earth and These hoofed predators came in diverse forms, from tiny to horse-sized. It is this correspondence of form and living species are divided into 13 or 14 families and two suborders: Mysticeti (baleen whales) and Odontoceti (toothed whales,

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