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Evolution Of Cetaceans
The evolution of cetaceans is thought to have begun in the Indian subcontinent from even-toed ungulates (Artiodactyla) 50 million years ago (mya) and to have proceeded over a period of at least 15 million years. Cetaceans are fully aquatic mammals belonging to the order Artiodactyla and branched off from other artiodactyls around 50 Year#Abbreviations yr and ya, mya. Cetaceans are thought to have evolved during the Eocene (56-34 mya), the second epoch of the present-extending Cenozoic Era. Molecular and morphological analyses suggest Cetacea share a relatively recent closest common ancestor with hippopotamus, hippopotamuses and that they are sister groups. Being mammals, they surface to breathe air; they have five finger bones (even-toed) in their fins; they nurse their young; and, despite their fully aquatic life style, they retain many skeletal features from their terrestrial ancestors.Thewissen, J. G. M., L. N. Cooper, J. C. George, and S. Bajpai. 2009. From land to wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Cetaceans
Cetacea (; , ) is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel themselves through the water with powerful up-and-down movements of their tail, which ends in a paddle-like fluke, using their flipper-shaped forelimbs to steer. While the majority of cetaceans live in marine environments, a small number reside solely in brackish water, brackish or fresh water. Having a cosmopolitan distribution, they can be found in some rivers and all of Earth's oceans, and many species migrate throughout vast ranges with the changing of the seasons. Cetaceans are famous for cetacean intelligence, their high intelligence, complex social behaviour, and the enormous size of some of the group's members. For example, the blue whale reaches a maximum confirmed length of and a weight of 173 tonne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Animal Echolocation
Echolocation, also called bio sonar, is a biological active sonar used by several animal groups, both in the air and underwater. Echolocating animals emit calls and listen to the Echo (phenomenon) , echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects. Echolocation is used for animal navigation , navigation, foraging, and predation, hunting prey. Echolocation calls can be Frequency modulation, frequency modulated (FM, varying in pitch during the call) or constant frequency (CF). FM offers precise range discrimination to localize the prey, at the cost of reduced operational range. CF allows both the prey's velocity and its movements to be detected by means of the Doppler effect. FM may be best for close, cluttered environments, while CF may be better in open environments or for hunting while perched. Echolocating animals include mammals, especially odontocetes (toothed whales) and some bat species, and, using s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Maiacetus
''Maiacetus'' ("mother whale") is a genus of early cetacean from the Habib Rahi Formation of Pakistan. Paleobiology The genus contains a single species, ''Maiacetus inuus'', first described in 2009 on the basis of two specimens, including a specimen which has been interpreted as a pregnant female and her fetus. This represents the first description of a fetal skeleton of an archaeocete. The position of the fetus (head-first) suggests that the animal gave birth on land."Earliest whales gave birth on land" '''', 3 February 2009 Modern whales generally give birth tail first, while land mammals give birth head first. That the ''Maiacetus'' sh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Remingtonocetus
''Remingtonocetus'' is an extinct genus of early cetacean freshwater aquatic mammals of the family (biology), family Remingtonocetidae endemic to the coastline of the ancient Tethys Ocean during the Eocene. It was named after naturalist Remington Kellogg. History of discovery named ''Protocetus harudiensis'' based on a partial skeleton, the type specimen found in the Lutetian shallow subtidal mudstone in the Harudi Formation, India. renamed it ''Remingtononocetus harudiensis'' due to morphological differences from ''Protocetus''. ''Remingtonocetus domandaensis'' was named by based on a partial skeleton found in a Lutetian coastal shale in the Domanda Formation of Pakistan. ''Remingtonocetus'' is larger, has a broader Rostrum (anatomy), rostrum, and longer premolars than ''Andrewsiphius''. It is smaller than, has more gracile premolars and molars than ''Dalanistes''. ''R. harudiensis'' differs from ''R. domandaensis'' in molar morphology. Description ''Remingtonocetus'' was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Remingtonocetidae
Remingtonocetidae is a diverse family of early aquatic mammals of the order Cetacea. The family is named after paleocetologist Remington Kellogg. Description Remingtonocetids have long and narrow skulls with the external nare openings located on the front of the skull. Their frontal shields are narrow and their orbits small. Their mouth has a convex palate and an incompletely fused mandibular symphysis. The dental formula is . The anterior teeth are flattened mediolaterally, making them appear shark-like. In the postcranial skeleton, the cervical vertebrae are relatively long and the sacrum is composed of four vertebrae of which at least three are fused. The acetabular notch is narrow or closed and on the femoral head the fovea is absent. Cranial fossils are common but dental remains are rare. The postcrania morphology is based entirely on a single specimen of '' Kutchicetus'' which was small and had a long and muscular back and tail. Perhaps remintonocetids swam like ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Kutchicetus
''Kutchicetus'' is an extinct genus of early whale of the family Remingtonocetidae that lived during Early-Middle Eocene (Lutetian and Ypresian) in what is now the coastal border of Pakistan and India (, paleocoordinates ). It is closely related to ''Andrewsiphius'' with which it was synonymized by . proposed a new clade, Andrewsiphiinae, for the two species. Later authors, however, still accept both as separate genera. ''Kutchicetus'' is smaller than other remingtonocetids, and probably is the smallest Eocene cetacean. With its extremely narrow snout, it resembles ''Remingtonocetus'' and '' Dalanistes'', but its strong tail distinguishes it from both ''Remingtonocetus'' and ''Andrewsiphius''. Its limbs were short. ''Kutchicetus''' vertebral formula is 7, 15, 8, 4, 20–25. Its four fused sacral vertebrae were probably articulated to the hip bone and the numerous tail vertebrae were robust and elongated in contrast to its short and relatively gracile limb bones. This m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Ambulocetidae
Ambulocetidae is a family of early cetaceans from Pakistan. The genus ''Ambulocetus'', after which the family is named, is by far the most complete and well-known ambulocetid genus due to the excavation of an 80% complete specimen of ''Ambulocetus natans''. The other two genera in the family, '' Gandakasia'' and '' Himalayacetus'', are known only from teeth and mandibular fragments. Retaining large hindlimbs, it was once thought that they could walk on land—indeed, their name means "walking whales"—, but recent research suggests they may have been fully aquatic like modern cetaceans, though the research has some limits that cast doubt on this conclusion. Description The most basal of marine cetaceans, ambulocetids lived in shallow near-shore environments such as estuaries and bays, but were still dependent on fresh water during some stage of their life. Some of the characteristics related to sound transmission found in the lower jaws of modern whales that were absent in pak ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Ambulocetus
''Ambulocetus'' (Latin ''ambulare'' "to walk" + ''cetus'' "whale") is a genus of early Semiaquatic, amphibious cetacean from the Kuldana Formation in Pakistan, roughly 48 or 47 million years ago during the Early Eocene (Lutetian). It contains one species, ''Ambulocetus natans'' (Latin ''natans'' "swimming"), known solely from a near-complete skeleton. ''Ambulocetus'' is among the best-studied of Eocene cetaceans, and serves as an instrumental find in the study of evolution of cetaceans, cetacean evolution and their transition from land to sea, as it was the first cetacean discovered to preserve a suite of adaptations consistent with an amphibious lifestyle. ''Ambulocetus'' is classified in the group Archaeoceti—the ancient forerunners of modern cetaceans whose members span the transition from land to sea—and in the family (biology), family Ambulocetidae, which includes ''Himalayacetus'' and ''Gandakasia'' (also from the Eocene of the Indian subcontinent). ''Ambulocetus'' ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Pakicetidae
Pakicetidae ("Pakistani whales") is an extinct family of early whales that lived during the Early Eocene in Pakistan. Unlike modern cetaceans, they had well-developed limbs and were capable of walking. The species included were fox to wolf-sized. Description described the first pakicetid, '' Ichthyolestes'', but at the time they did not recognize it as a cetacean, identifying it, instead, it as a fish-eating mesonychid. Robert West was the first to identify pakicetids as cetaceans in 1980 and, after discovering a braincase, Phillip Gingerich and Donald Russell described the genus ''Pakicetus'' in 1981. During the following two decades, more research resulted in additional pakicetid cranial material and by 2001 postcranial material for the family had been described. Though all parts of pakicetid postcrania are known, no complete skeleton from a single individual has been recovered. The pakicetid goldmine is the "H-GSP Locality 62" site in the Kala Chitta Hills where fossils fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Pakicetus
''Pakicetus'' (meaning 'whale from Pakistan') is an extinct genus of amphibious cetacean of the family Pakicetidae, which was endemic to the Indian Subcontinent during the Ypresian (early Eocene) period, about 50 million years ago. It was a wolf-like mammal, about long, and lived in and around water where it ate fish and other animals. The name Pakicetus comes from the fact that the first fossils of this extinct amphibious whale were discovered in Pakistan. The vast majority of paleontologists regard it as the most basal whale, representing a transitional stage between land mammals and whales. It belongs to the even-toed ungulates with the closest living non-cetacean relative being the hippopotamus. Description Based on the sizes of specimens, and to a lesser extent on composite skeletons, species of ''Pakicetus'' are thought to have been to in length. ''Pakicetus'' looked very different from modern cetaceans, and its body shape more resembled those of land-dwelling h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Raoellidae
Raoellidae, previously grouped within Helohyidae, are an extinct family of semiaquatic digitigrade artiodactyls in the clade Whippomorpha. Fossils of Raoellids are found in Eocene strata of South Asia and Southeast Asia. An exceptionally complete skeleton of ''Indohyus,'' the best preserved Raoellid, from Kashmir suggests that Raoellids are the " missing link" sister group to whales (Cetacea). All other Artiodactyla are relatives of these two groups. δO18 values and osteosclerotic bones indicate that the raccoon-like ''Indohyus'' was habitually aquatic. However, it is still unclear if ''Indohyus'' primarily fed on land or in water. It is hypothesized that cetaceans evolved from ancestors similar to Raoellids and later fully adapted to aquatic life. Taxonomy *'' Rajouria'' **''Rajouria gunnelli'' *'' Haqueina?'' **''Haqueina haquei'' **''Haqueina haichinensis'' *''Indohyus'' **''Indohyus indirae'' **''Indohyus major?'' *'' Kunmunella'' **''Kunmunella kalakotensis'' **''Kunmunella ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Indohyus
''Indohyus'' (Meaning "India's pig" from the Greek words ''Indos'', "from India" and ''hûs'', "pig") is an extinct genus of artiodactyl known from Eocene fossils in Asia. This small chevrotain-like animal found in the Himalayas is among the closest known non-cetacean relatives of whales. Discovery The fossils were discovered among rocks that had been collected in 1971 in Kashmir by the Indian geologist A. Ranga Rao who found a few teeth and parts of a jawbone; when he died, however, many rocks had yet to be broken open. Ranga Rao's widow gave the rocks to Hans Thewissen, who was working on them. When his technician accidentally broke one of the skulls they had found, Thewissen recognised the ear structure of the auditory bulla, formed from the ectotympanic bone in a shape which is highly distinctive, found only in the skulls of cetaceans both living and extinct, including '' Pakicetus''. Paleobiology About the size of a fox, this omnivorous pig-like creature shared some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
