Toothed whales, the odontocetes, have access to rich marine food resources down to depths of 2000 m and achieve a biomass turnover larger than that of human fisheries combined ().The key to this success is their ability to locate, track, and capture fast-moving prey underwater in complete darkness at depths of, routinely, >100 m using echolocation, a feat that critically depends on the . This eye position occurs in aquatic mammals such as hippopotamus. 2001). The only known fossils dated to the Oligocene have been found in Peru and New Zealand. 2004;430:7768. For other protocetids, a diet of smaller fish has been suggested (O'Leary and Uhen 1999). Manage cookies/Do not sell my data we use in the preference centre. The tympanic bulla, a bone which forms the floor of the middle ear cavity, was less connected to the rest of the skull as compared to more primitive whales. 2006). We thank the Alaska Eskimo Whaling Commission and the Barrow Whaling Captains Association for access to specimens and contributing to their scientific study. 2006). Gingerich PD, Smith BH, Simons EL. 1999;25:53456. Some paleontologists speculate that Basilosaurus both looked and swam like a giant eel, undulating its long, narrow, muscular body close to the water's surface. When you visit the site, Dotdash Meredith and its partners may store or retrieve information on your browser, mostly in the form of cookies. the Basilosaurid whale? Cetaceans are unrelated to other marine mammals, the sirenians (manatees and dugongs) and the pinnipeds (seals, sea lions, walruses). 25 and 26). 2007). Basilosaurid forelimbs have broad and fan-shaped scapulae attached to a humerus, radius, and ulna which are flattened into a plane to which the elbow joint was restricted, effectively making pronation and supination impossible. California Privacy Statement, de., Ray, C.E., and D.P. Basilosaurid genera are separated into four subfamilies: Dorudontinae, Basilosaurinae, Kekenodontinae, and Stromeriinae. In: Thewissen JGM, Nummela S, editors. There are several recent reviews of the evolution of odontocetes and mysticetes (Fordyce and Muizon 2001; Bianucci and Landini 2007). Structural adaptations of early archaeocete long bones. Modern representatives of artiodactyls include pigs, hippos, camels, deer, sheep, cattle, and giraffe, and, of these, hippos are thought to be the closest living relatives of cetaceans (Nikaido et al. However, shark have the eagles. 2001;21:34766. The position of the eyes, osteosclerosis of the limb bones, sedimentological data, and stable isotope data are consistent, and all suggest that pakicetids were waders in shallow freshwater. 482. It had an extremely long, slender body, and had a narrow snout lined with teeth of different shapes. The emergence of whales: evolutionary patterns in the origin of Cetacea. At the time, of course, no one knew that these petrified artifacts were actually the bones of a long-extinct prehistoric whale. The great length of the vertebral column of basilosaurids can be attributed to the increase in the number of lumbar vertebrae in the taxon but also by the increase in length of each individual vertebra. J Vert Pal. We dont have your requested question, but here is a suggested video that might help. 1st ed. Some dolphins can exceed speeds of 50 km/h, a feat accomplished by thrusting the flukes while adjusting attack angle with their flippers [].These movements are driven by robust axial musculature anchored to a relatively rigid torso consisting of numerous short . A 50-mL graduated cylinder contains 20.0 mL of water. Let's hear questions in a question they were asking that so that's a shark, whales and dolphins. So first that shark whales and the dolphins. We hope that a detailed understanding of evolutionary patterns will allow us to determine the processes that drove cetacean evolution. Oxygen in the molecules that make up the teeth comes from the drinking water and food that the animal ingests. Humans and chimpanzees share a recent common ancestor. At the same time, a long rost rum with narrow jaws develops. X-ray computed tomographic (CT) scanning has been . volume2,pages 272288 (2009)Cite this article. For example, protocetids are diverse and many of them are poorly known, and the evolution of some organ systems (e.g., vision) is poorly understood (Thewissen and Nummela 2008). 21), and Georgiacetus from North America (Hulbert et al. ______________________ The closest match, so far, of whale DNA to In: Thewissen JGM, editor. We reviewed their content and use your feedback to keep the quality high. Archaeocetes are important because they represent the earliest radiation of cetaceans and because they include the ancestors of the two modern suborders of cetaceans, the Mysticeti (baleen whales) and Odontoceti (toothed . Get 5 free video unlocks on our app with code GOMOBILE, _______________________________ Where is the nasal opening in He appears anxious and says that he is short of breath. So let's see. Write C++ statements that do the following: The scientific name is always the Genus + species. (2015). Until recently, practically nothing was known about the morphogenetic processes concealed in this metamorphosis, about what cranial structures take part in it, and about the exact way in which the cetacean skull becomes transformed during embryogeny. Such a diagram is called a cladogram. Embryos of the pantropical spotted dolphin (Stenella attenuata) covering approximately weeks 4 to 9 of embryonic development. The branching of the cetacean groups on this cladogram is consistent with most recent work (Thewissen et al. In: Thewissen JGM, editor. 13). Vestibular evidence for the evolution of aquatic behaviour in early cetaceans. Thewissen JGM, Bajpai S. Whale origins as poster child for macroevolution. This type of locomotion may be a good model for swimming in Remingtonocetus. Hyemoschus is not osteosclerotic and spends relatively little time in the water. The rete mirabile depends on countercurrent blood flow within the net (blood flowing in opposite directions.) Contr Mus Pal Univ Michigan. They appear to have lived side by side roughly 34 to 40 million years ago. Basilosaurus (a.k.a. A point of similarity among protocetids is the position and size of the eyes, which differentiates them from earlier cetaceans (Nummela et al. In the earlier embryos, the hind limbs are present, but then they disappear as embryonic development continues. (2001), Nature), Fossiliferous area of H-GSP Locality 62, the richest locality for pakicetid cetaceans. Also unlike earlier cetaceans, the nasal opening is not at the tip of the snout (Thewissen and Bajpai 2001b). Whales originated from aquatic artiodactyls in the Eocene epoch of India. Bianucci G, Landini W. Fossil history. To see earlier posts, select the Archives at the top of this page. It was Owen, therefore, who suggested the slightly comical name Zeuglodon ("yoke tooth") instead. 1990. Sequence stratigraphic control on preservation of late Eocene whales and other vertebrates at Wadi Al-Hitan, Egypt. The skeleton of A. natans (H-GSP 18507) had a large pelvis that supported the animal as it walked on land, but the tail and hind limbs were used during swimming (http://www.neoucom.edu/DEPTS/ANAT/publ.html, J.G.M. In addition, the part of pakicetid skulls behind the eyes (orbits) and the joints for the lower jaw (mandibular fossa) is very narrow (Fig. In spite of our advances in understanding of the pattern of cetacean origins, it remains unclear which process caused this pattern: Why did cetaceans enter the oceans? Privacy Strauss, Bob. Fish FE. Proc Natl Acad Sci USA. The organ of balance is located in the petrosal, a bone attached to the ectotympanic. Their molars differed greatly from those of protocetids and ambulocetids, there not being a central depression surrounded by three cusps in the upper molars (O'Leary and Uhen 1999). Eg: when we looking at the whales's anatomy, we can see that they evolved from an ancien 4 legged land mammal. 1st ed. The evolution of the blowhole in whales, which according to the fossil evidence moved from the tip to the vertex of the head, has caused some concerns amongst our creationist readers who wonder how such a feat could have taken place. Many features that are common in land mammals have changed in the evolutionary process that led to cetaceans. Modern cetaceans undulate their tails dorsally and ventrally. The changing cetacean body plan during the first ten million years of cetacean evolution. This suggests that the diet of remingtonocetids is different from that of earlier cetaceans. These Pakistani protocetids were certainly able to locomote on land, and it is likely that they used land and water in the way that modern sea lions do: hunting in water but coming ashore for mating, giving birth, and nursing. Curr Sci (New Delhi). They lived during the middle to the early late Eocene and are known from all continents, including Antarctica. Scientists have found that toothed whales can produce a vocal fry, just like Kardashian. Sound waves passed into the fat pad through the thin bone of the lower jaw and then continued to the middle and inner ear. Skeletal evidence indicates that Basilosaurus could perceive the direction of origin for underwater sounds. From Land to Water: the Origin of Whales, Dolphins, and Porpoises, https://doi.org/10.1007/s12052-009-0135-2, http://www.neoucom.edu/audience/about/departments/anatomy/AnatFaculty/media, www.neoucom.edu/DEPTS/ANAT/Thewissen/whale_origins/whales/Pakicetid.html, http://www.neoucom.edu/DEPTS/ANAT/publ.html, http://www.neoucom.edu/DEPTS/ANAT/Thewissen/whale_origins/index.html, www.neoucom.edu/DEPTS/ANAT/Thewissen/whale_origins/whales/Remi.html, https://creativecommons.org/licenses/by/2.0. Nummela S, Thewissen JGM, Bajpai S, Hussain ST, Kumar K. Eocene evolution of whale hearing. Two isotopes, forms of elements that are chemically identical but have heavier atoms because of excess neutrons in the nucleus, are common in nature: Oxygen-16 and Oxygen-18 (where the number reflects the mass of the atom). One of the first identified prehistoric whales, Basilosaurus, the "king lizard," has been a part of American culture for literally hundreds of years, especially in the southeastern U.S. Unlike earlier archaeocetes, which all had 11 teeth per half jaw (44 teeth in all), basilosaurids had lost one tooth in each upper jaw, bringing their total number to 42. 10 Facts About Basilosaurus. 1990;229:1547. We thank the Geological Survey of Pakistan for collaborating in collecting and studying Pakistani fossils and for logistic support, and Dr. S. Taseer Hussain for his leadership of the Howard University-Geological Survey of Pakistan project. Basal fully aquatic whales, the basilosaurids are worldwide known from Bartonian-Priabonian localities, indicating that this group was widely distributed during the late middle Eocene. Cour Forsch Inst Senckenberg. Dorudon was once mistaken for its much larger cousin, Basilosaurus. Modern whales and dolphins are superbly adapted for marine life, with tail flukes being a key innovation shared by all extant species. Basilosaurus was an unfamiliar, long snake like animal. 2002;417:1636. 2001a;75:4635. Embriology is a study of how creatures develope before being born or hatching from an egg. The earliest cetaceans had nasal bones (gray) and a nasal opening (black) near the tip of the snout. Thewissen JGM, Williams EM, Hussain ST. Eocene mammal faunas from northern Indo-Pakistan. 1990. Now, cetacean origin is one of the best known examples of macroevolution documented in the fossil record. J Vert Pal. Basilosaurus drazindai and Basiloterus hussaini, new Archaeoceti (Mammalia, Cetacea) from the middle Eocene Drazinda Formation, with a revised interpretation of ages of whale-bearing strata in the Khirthar Group of the Sulaiman Range, Punjab (Pakistan). We review raoellid artiodactyls, as well as the earliest families of cetaceans: pakicetids, ambulocetids, remingtonocetids, protocetids, and basilosaurids. The foramen is enormous, covering nearly the entire depth of the jaw in modern cetaceans and remingtonocetids, unlike pakicetids, where it is smaller (Fig. Good introductions to the evolutionary history of odontocetes and mysticetes have been published (Fordyce and Muizon 2001; Bianucci and Landini 2007). However, the first basilosaurid specimenBasilosaurus, whose Latin name is translated king lizardwas originally classified as a lizard when it was first described. 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. 2007). Basilosaurids occurred worldwide during most of their history, and important fossils have been recovered in Egypt and the southern United States. One hearing-related feature is the size of the mandibular foramen, a perforation of the lower jaw behind the teeth. 12). A new study finds that toothed whales can make a range of vocalizations, including some akin to human 'vocal fry,' thanks to a special nasal structure. Koch exhibited the 114-foot long skeleton in a saloon (the price of admission: 25 cents), but his scam imploded when naturalists noticed the different ages, and provenances, of Hydrarchos' teeth (specifically, a mixture of reptilian and mammalian teeth, as well as teeth belonging to both juveniles and full-grown adults). Thewissen). However, the rest of Basilosaurus hearing adaptations indicate it was fully marine, and thus any retention of adaptations for hearing airborne sound was probably vestigial. J Vert Pal. The evolutionary history of cetaceans - whales, dolphins, and porpoises - started with the rise of Archaeoceti, a paraphyletic group of stem cetaceans, in the ancient Tethys seaway during the early Eocene more than 50 million years ago (Bajpai and Gingerich 1998).The earliest archaeocetes - pakicetids, ambulocetids, remingtonocetids - were amphibious species from Eocene sediments of fluvial . In: Thewissen JGM, editor. Gingerich PD, Ul-Haq M, Khan IH, Zalmout I. Eocene stratigraphy and archaeocete whales (Mammalia, Cetacea) of Drug Lahar in the eastern Sulaiman Range, Balochistan (Pakistan). Humans and chimpanzees share a recent common ancestor. The first embryo shows forelimbs but not hind limbs (in most mammals forelimbs develop before hind limbs). [12] They were characterized by elongated distal thoracic vertebrae, lumbar, and proximal sacrococcygeal. https://doi.org/10.1007/s12052-009-0135-2, DOI: https://doi.org/10.1007/s12052-009-0135-2. In the latter case, the heat exchange is used to reduce the temperature of the testes. PubMedGoogle Scholar. Contr Mus Pal Univ Michigan. These are two species of extinct basilosaurid whales! B.T. 2006; Madar 2007; Fig. Berkeley: Univ Calif Press; 2008. p. 25786. In: Thewissen JGM, editor. Cetaceans have lungs and come to the surface to breathe air, like other mammals and unlike fish. All modern Cetacea live in water and cannot survive out of the water. Indohyus was an animal similar in size to a cat but quite different from a cat in shape. [3] While they were unable to support body weight on land, they might have assisted as claspers during copulation. 2001), and as is beautifully indicated by the presence of an astragalus with two trochleas (Fig. Gingerich PD, Arif M, Clyde WC. Llanocetus denticrenatus was discovered in the latest Eocene sediments of Seymour Island, Antarctica and current research puts it as the earliest known Mysticeti or baleen whale. As cetaceans became more aquatic, the nasal bones retracted and the nasal opening migrated to the top of the skull and became the blowhole (modified from Thewissen and Bajpai 2001b). Palaios 24:290-302. The ectotympanic of Indohyus has a thickened internal lip, a powerful indicator that Indohyus is closely related to cetaceans. amphibian-like creatures f fish share a What is comparative anatomy? Eg: there's a stage of developement when dolphins and humans are looks the same. Some toothed whales can dive over 6,000 feet deep to catch fish. Because of a shortage of forelimb fossils from other archaeocetes, it is not known if this arrangement is unique to basilosaurids, as some of the characteristics are also seen in Georgiacetus.[3]. Retrieved from https://www.thoughtco.com/facts-about-basilosaurus-king-lizard-whale-1093325. 1st ed. ThoughtCo, Feb. 16, 2021, thoughtco.com/facts-about-basilosaurus-king-lizard-whale-1093325. 2002;22:40522. However, under closer examination, scientists . One feature that is a strong indicator of this relationship is the shape of one of the bones of the ear. The phylogeny among fossil animals can be determined by coding their morphology and having a computer program determine the greatest similarities in significant characters. The marrow cavity of the femur of Ambulocetus makes up 57% of the cross section of the bone. 2001, 2007). Coen Elemans was . Thewissen). In most mammals, its walls are made of a bone called the ectotympanic, as is the case in artiodactyls and cetaceans. https://www.thoughtco.com/facts-about-basilosaurus-king-lizard-whale-1093325 (accessed March 4, 2023). Nummela S, Hussain ST, Thewissen JGM. J Vert Pal. The marrow cavity is filled with sediment (gray in this image; http://www.neoucom.edu/audience/about/departments/anatomy/AnatFaculty/media, J.G.M. A type of Basilosaurid ancient whale. Mounts of entire skeletons can be viewed at the National Museum of Natural History (Washington DC), Alabama Museum of Natural History, and National Museum of Nature and Science (Tokyo). 2001; Nummela et al. In addition, the hind limbs may have been used as claspers to help guide the long bodies of the males and females into position for mating. Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. The middle ear is filled with air in life and has a bony wall, similar in shape to a nutshell. Archaeocete whales have been found from early to middle Eocene (52-42 Ma) deposits in Africa and North America but are best known from Pakistan and India. a Outline ellipses and regression of body size (on x-axis, as 10-log in grams) against semicircular canal radius (on y-axis, as 10-log in mm) for modern land mammals (maroon) and modern cetaceans (blue). Excavation of a fossil, left foreground, in Gujarat, India. In life, the peg like front teeth were used to seize prey and the rear triangular teeth were used to dispatch and process prey. In all cetaceans, the medial wall of the ectotympanic is very thick, as indicated by the white line, and is called the involucrum. Basilosaurinae was proposed as a subfamily containing two genera: Basilosaurus and Basiloterus. Shifting continents 34 mya created large-scale changes in ocean currents and temperatures that coincided with this diversification. Strauss, Bob. Teeth consist mostly of calcium phosphate. New York: Plenum; 1998. p. 21334. The skeletons of Ambulocetus (top) and Pakicetus (bottom), J.G.M. Comparing things that are similar and different. 1994, 2001b; Fig. That this evolutionary process is repeated in a way during ontogeny became obvious through external observations on embryos and fetuses (Kukenthal 1893). 2001a). Baltimore: Johns Hopkins Univ Pr; 2007. p. 1931. Pakicetids are the earliest cetaceans and had a pelvis that was similar to most terrestrial mammals (composite of H-GSP 30395, 30213). 1995a, b; Fig. Protocetids are a diverse group, with approximately 15 genera described. (2021, February 16). It was not until 2001 that skeletons of these whales were discovered (Thewissen et al. By Robert Boessenecker (@CoastalPaleo) and Sarah Boessenecker (tetrameryx) Happy Fossil Friday! O'Leary MA, Uhen MD. Llanocetus was a large animal with a 2 meter (6.5 foot) long head and a body length of perhaps 30 feet (9.1 meters). Although not positioned at the tip of the snout like more primitive whales (e.g. Experts are tested by Chegg as specialists in their subject area. Like Kim Kardashian, whales . Eg: the nasal opening of the basilosaurid whale shows that this animal is an intermediate species between land mammal and modern whale. On the rudimentary hind limb of the great fin-whale (Balaenoptera musculus) in comparison with those of the humpback whale and the Greenland Right Whale. J Pal. The second body type among basilosaurids is shorter, as short as 4m. These basilosaurids, called dorudontines (Uhen 1998), had dolphin-shaped bodies and swam by up-and-down motions of their tail fluke. The earliest cetaceans, pakicetids, ambulocetids, and remingtonocetids are only known from India and Pakistan. Univ Michigan Pap Pal. Swimming may have been a combination of paddling with the hind limbs and dorsoventral undulations of the tail. 23) with large teeth, suggestive of a diet that includes hard elements (such as bones of large fish or other vertebrates). Similar to earlier archaeocetes and unlike most later cetaceans, basilosaurids retained a heterodont dentition, with clear morphological differences between incisors, canines, premolars, and molars (Uhen 2004). Just like Pakicetus, ambulocetids had osteosclerotic limb bones (Madar 1998). . Bajpai SB, Thewissen JGM, Kapur VV, Tiwari BN, Sahni S. Eocene and Oligocene sirenians (Mammalia) from Kachchh, India. If Basilosaurus had positive buoyancy, it would be difficult for it to dive and swim effectively. Its overall body shape is so unlike those of other whales that it was initially thought to be a marine reptile; hence the name Basilosaurus, which means king lizard. The teeth towards the back of the mouth have multiple large serration-like cusps. What would be considered the strongest evidence that two species are related to one another? Discover fascinating details about this enormous marine mammal. 2001b;293:223942. police officer relieved of duty. Terms and Conditions, Tr Ecol Evol. Diet: The skull of Basilosaurus is superficially crocodilian in shape, exhibits large jaw muscle attachment areas, and a fearsome set of teeth with canine-shaped incisors in front, and flattened, serrated triangular molars in back. 2001a;30:269319. Paleobiology. It appears most likely that Ambulocetus was an ambush predator, attacking prey that came close to it but not pursuing it over long distances. The blowhole in modern cetaceans is located between the eyes on the forehead, an adaptation for breathing while remaining submerged. Fig 1. It is called the blowhole. Google Scholar. Specimens courtesy of John Craighead George and the Barrow Whaling Captains Association, Diagram showing changes in the pelvis of Indohyus (RR 256) and cetaceans. Eg: whales and hippos evolved from a common ancestor. Anat Rec. Basilosaurids are like most mammals in that there are only three phalanges per finger, whereas in modern cetaceans this number is commonly increased. Curiously, the ribs of Basilosaurus are very dense and thickened, which is a specialization that probably allowed it to achieve slight negative buoyancy. The Bowhead whale specimens were collected under NMFS marine mammal collection permit 814-1899. Peters, S.E., Antar, M.S.M., Zalmout, I.S., and Gingerich, P.D. _______________________________ Where is the nasal opening in coat of fur. Fetus of the pantropical dolphin (LACM 94389, Stenella attenuata) with whiskers along the rostrum. The tail vertebrae are robust, suggesting that the tail was muscular. The transition from raoellid to pakicetid and thus from artiodactyl to cetacean was a remarkable event that included the wholesale rebuilding of the skull and its food-processing equipment. Their diversity was highest during the Eocene Epoch. _____________ ____________Mammals Whether the hind limbs were functional is unclear; well-formed joints and evidence of muscle attachments on the bones suggest that they may have been functional, but they also may have been completely atrophied. Nature. Age: 34-40 million years old, Eocene Epoch. Basilosaurids, however, were the first widespread truly aquatic group of whales. 2007; Thewissen et al. Whales, Dolphins, Porpoise. The tail made up as much as three-quarters of the total body length of Basilosaurus. Therefore, externally, remingtonocetids may have resembled enormous otters with long snouts (www.neoucom.edu/DEPTS/ANAT/Thewissen/whale_origins/whales/Remi.html). Model of cetacean locomotor evolution as proposed by Fish (1996). Deciphering whale origins with molecules and fossils. Developed by Carl Linnaeus who used Greek and Latin names. 2002). 2002). In the late middle Eocene, around 41 million years ago, a new kind of cetacean emerged, the first one that resembles modern cetaceans: Basilosauridae (Uhen 1998). Modern whales emerge Mysticetes and Odontocetes (33-28 mya) The ancestors of toothed and baleen whales diverged as the world's climate rapidly cooled and opened up new opportunities for basilosaurid diets. In: Thewissen JGM, editor. This wear pattern has been correlated to fish eating (O'Leary and Uhen 1999). Rodhocetus nostrils were higher on the skull, intermediate between its ancestors and modern whales. Basilosauridae is a paraphyletic family of extinct cetaceans that lived during the late middle to the early late Eocene, known from all continents. With aquatic origins for cetaceans now being known to occur within the artiodactyls, the search is on for the discovery of the terrestrial relatives of raoellids. This is consistent with the environmental evidence from the rocks that the fossils are found in. 1994;263:2102. Spoor F, Bajpai S, Hussain ST, Kumar K, Thewissen JGM. 2002;33:7390. In an if/else statement, the if part executes its statement or block if the expression is __________, and the else part executes its statement or block if the expression is __________. Only a few tail vertebrae have been discovered. (D) Pelvis and femur of the juvenile male specimen figured in C. (E) Another pelvis and femur from an adult specimen (B. mysticetus, 98B5) for comparison. "10 Facts About Basilosaurus." The hindlimbs are tiny, and the pelvis lacked any bony connection to the vertebral column (and must have floated in the muscles of the belly), indicating that these elements could not support any weight out of water. The earliest whaleswhich were thought to have evolved from terrestrial ancestors in the order Artiodactyla (a group that contains living pigs, hippopotamuses, and even-toed ungulates), most likely the raoellid artiodactyls (aquatic artiodactyls from South Asia that lived during the Eocene)had relatively long back legs and were probably amphibious in their lifestyle. have come from the common ancestor. Variation in the skeleton behind the skull is hard to assess because these bones are only known in a few species, specifically Rodhocetus and Artiocetus from Pakistan (Gingerich et al. At the end of each limb, there were four or five toes that ended in hoof, similar to that of a deer. We also thank the Department of Wildlife, North Slope Borough, and the Barrow Arctic Science Consortium for logistic support and assistance in the acquisition of specimens. Numbers are used to refer to individual specimens. Updates? Snively E, Fahlke J.M. In modern bowhead whales (pictured here is the pelvis of an adult male, B. mysticetus, 98B5), the acetabulum and obturator foramen are lost and the ilium is reduced. In hunting behavior, Ambulocetus may have been similar to a modern crocodile, and, externally, Ambulocetus may have looked like a crocodile (http://www.neoucom.edu/DEPTS/ANAT/Thewissen/whale_origins/index.html). Evolution and Development 9:278-289. In pakicetids, the eyes faced upward, whereas in Ambulocetus, they face toward the sides, although they are still located high on the skull (Nummela et al. Uhen MD. This is a clear indication that this prehistoric whale spent most of its life near the water's surface since its hollow backbone would have crumpled from the intense water pressure deep beneath the waves. Comparing things that are similar and different. Let us know if you have suggestions to improve this article (requires login). However, all modern cetaceans lack a hair coat, presumably an adaptation to reduce friction and improve locomotion. The morphology of the sense organs suggests that hearing was important for Remingtonocetus but that vision was not.
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