Whale Evoloution Essay

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Whales (Cetaceans) are known to be descendants of land mammals due to several physical characteristics such as bones in their flippers which resemble the forelimbs of land mammals, vertical movement of their spines which also resembles a running land animal, also because they breathe air – obviously gills were formed for this in order for the whale as we know it today to stay under water without taking a breath for quite some time. Many ancient and modern whales have “evolutionary baggage” making their ancestry, such as reduced hind legs. Some whales still use their pelvic bones – for reproductive purposes. There is also some genetic evidence that scientists have found to relate the modern day whale to a walking, land mammal. In 1978, Palaeontologist Phil Gingerich discovered a 52 million year old skull in Pakistan that resembled fossils of creodonts – wolf sized carnivores that lived between 60 and 37 million years ago. But the skull also had some characteristics in common with the Archaeocetes, the oldest known whales. One of the most obvious was the structure of the inner ear. These new bones found proved to have features that were between terrestrial mammals and the earliest “true Whale”. In whales, the ear structure is modified in order for the whale to hear underwater. In the pakicetus, the ear is intermediate between that of terrestrial and fully aquatic animals. Early Whales: Pakicetus: Early Eocene (55 to 49 million years ago) Pakicetus was known only from a skull up until 2001. This was linked to the modern day whale via a component of the skull unique to whales. This was the way in which the inner ear bones are structured. Only living and fossil whales have their ears structured in this way. Pakicetus was about the size of a wolf and was originally adapted for underwater hearing and wading. Although the Pakicetus had many features of a land mammal,

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