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Transcript of Whale Evolution
Odontocetes (toothed whales)
Mysticetes (Baleen whales)
Today on Earth there are 78 known species of whales that have evolved from the suborders of Odontocetes and Mysticetes. (The
are just two historic examples of each subspecies that made way for modern whales).
"Whale Evolution." PBS. PBS, 2001. Web. 31 Jan. 2014. <http://www.pbs.org/wgbh/evolution/library/03/4/l_034_05.html>.
Berkeley Edu. "The Evolution of Whales." The Evolution of Whales. N.p., 2001. Web. 31 Jan. 2014. <http://evolution.berkeley.edu/evolibrary/article/evograms_03>.
"The First Whale: Pakicetus." AMNH. American Museum of Natural History, n.d. Web. 31 Jan. 2014. <http://www.amnh.org/explore/news-blogs/on-exhibit-posts/the-first-whale-pakicetus>.
"How Did Whales Evolve?" Smithsonian. Smithsonian Museum, n.d. Web. 31 Jan. 2014. <http://www.smithsonianmag.com/science-nature/how-did-whales-evolve-73276956/>.
"Evolution of Whales Animation." Smithsonian Ocean Portal. N.p., n.d. Web. 31 Jan. 2014. <http://ocean.si.edu/ocean-videos/evolution-whales-animation>.
Parry, Wynne. "How Whales' Ancestors Left Land Behind." LiveScience. TechMedia Network, 20 Mar. 2013. Web. 31 Jan. 2014. <http://www.livescience.com/28075-how-whales-ancestors-left-land.html>.
Gill, Victoria. "Fossil Shows Huge Mouth Evolution." BBC News. BBC, 17 Aug. 2011. Web. 31 Jan. 2014. <http://www.bbc.co.uk/nature/14551193>.
Turner, Alan. National Geographic Prehistoric Illustrated by Mauricio Antón.illustrated by Mauricio Antón. National Geographic Prehistoric Geographic: n.p., 2004. Print.
BBC. "Ambulocetus." BBC News. BBC, 2014. Web. 01 Feb. 2014. <http://www.bbc.co.uk/nature/life/Ambulocetus>.
Princeton Edu. "Rodhocetus." Princeton University. Princeton, n.d. Web. 01 Feb. 2014. <http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Rodhocetus.html>.
Museum of New Zealand. "Evolution." - Whales Tohorā. Museum of New Zealand, n.d. Web. 01 Feb. 2014. <http://collections.tepapa.govt.nz/exhibitions/whales/segment.aspx?irn=161>.
"Basilosaurus." BBC News. BBC, 2014. Web. 01 Feb. 2014. <http://www.bbc.co.uk/nature/life/Basilosaurus>.
Melbourne Museum. "Janjucetus – an Early Baleen Whale." 600 Million Years. Melbourne Museum, n.d. Web. 01 Feb. 2014. <http://museumvictoria.com.au/melbournemuseum/discoverycentre/600-million-years/timeline/tertiary/janjucetus/>.
Britannica. "Llanocetus Denticrenatus (fossil Mammal)." Encyclopedia Britannica Online. Encyclopedia Britannica, n.d. Web. 01 Feb. 2014. <http://www.britannica.com/EBchecked/topic/1928287/Llanocetus-denticrenatus>.
"Ocean Giants Going Aquatic: Cetacean Evolution." PBS. PBS, n.d. Web. 03 Feb. 2014.
Here is a link to the overview of the evolution of whales from the Smithsonian Museum:
was a wolf-like creature with hooves. They lived both on land and in the water. They were carnivores and occasionally ate fish. The first fossils of the
were found in Pakistan. They had whale like features in the head and the body. Their ear structure showed that they were well adapted to hearing under shallow water, while also having a skeleton adapted to movement on land. Their legs were better suited for walking than swimming. They had nostrils far-forward on their heads, so when they swam it was easy to lift part of their head out of the water. They lived in freshwater environments along the banks of streams.
The first records of the
were found in Northern Pakistan along (what used to be) shallow coastal seas and brackish rivers, where they would feed. At this point in time, it was more equipped for aquatic life due to its webbed feet. Its back feet were used to propel itself forward whilst in the water. From the
developed internal ears, which worked by picking up vibrations through the jawbone. Similarly to the
it had forward nostrils.
hind legs were very useful for making powerful strokes while swimming. They had paddle-like hind feet to create powerful strokes. Their strong tail helped control the direction, like a rudder. It had differentiated teeth which were helpful in catching prey. The ear bones were internal (like the ear bones of the
). This organism was more aquatic than earlier species.
lived in tropical seas. The need for fur was no longer evident. The smooth skin aided the blubber in the streamlined body, allowing it to glide through the water. The hind legs of the
were much less useful than those of the
. Rather than their legs assisting them in their swimming, the large and quite flat tail propelled them through the water.
retained the hind limb bones of its ancestors, but they were not visible from the outside (vestigal structure). Their teeth were useful for catching slippery ocean prey, so this shows that they were purely an aquatic mammal. They continued to have internal ears like modern whales and developed horizontal tail flukes, allowing it to swim easily. They lived in warm, shallow seas between Africa, Europe, and North America. The first fossil record was discovered in Louisiana. The
developed front flippers, which were much more efficient for its aquatic life style.
were completely aquatic. Their nostrils (blowhole) were further back on the skull, towards the top of their head, so coming up for air was much easier. They began to be able to hear better under water with their internal ears, that could now handle the pressure of deeper environments. Like the
they also had paddle-like flippers as forelimbs, while they had vestigial hind-limbs. The pelvis was detached from the spine, which freed up the tail for greater movements. They too had horizontal tail flukes allowing for a powerful stroke. The
inhabited nearly all the oceans.
Here we see the split between the Mysticetes (Baleen whales) and the Odontocetes (toothed whales).
is a prehistoric example of baleen whale. The skull bones show that it was a primitive baleen whale. They used a filter system for feeding. The combination of teeth and baleen kept the plankton and krill in, while allowing water to escape. More primitive baleen whales had both teeth and baleen. Later the evolutionary selection of only baleen was made. The L
shows an important evolutionary link between ancient whales and the modern Blue Whale.
Although Baleen whales are toothless, as an embryo they develop tooth buds. In baleen whales the tooth buds degrade, while in tooth whales they continue to develop. The filtering system of baleen whales developed due to the decrease in ocean temperatures. From the decrease in temperatures the nutrients from the environment were up welled, which caused an increase in plankton and krill. The small organisms were not easily caught by teeth, so brush like teeth (baleen) developed to take advantage of this new food supply. Baleen is made out of keratin, which is the main component of hair and nails. Baleen continuously grows from the whale's palate, allowing it to be fixed if damaged. The baleen whales are much larger than toothed whales because they need very large heads to carry long baleen plates.
In the picture above you can see that the baleen whales tended to be much larger than the toothed whales. While Baleen whales developed to take advantage of the smaller prey, toothed whales continued to feed off of larger preys like fish and squids. Modern toothed whales use echolocation to find their prey. Echolocation allows a whale to produce a sound and navigate from the echo of that sound. The noses of modern toothed whales are longer than those of baleen. Their noses are very useful in echolocation. By being able to use echolocation the toothed whales don't have to rely on sight to find prey. Toothed whales also developed only one nostril (blowhole) on the top of the head rather than two .
Here is an example of a primitive baleen whale:
Here is an example of a primitive toothed whale:
had long jaws, that were toothless in the front, with small pointed teeth along the sides. At this point echolocation was not developed yet.
Ally Leffler, Grace Spurlock, Jessica Asuquo