squalodon

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Squalodon.
This was a 10ft long toothed whale that lived during the Oligocene epoch. Its name means “shark tooth”, obviously describing the incredibly shark-like nature of its rear teeth, most notably the flat and serrated shape. No modern whales have dentition like this- all toothed whales have conical teeth that are usually blunted from use, as did most Oligocene-Holocene whales. Their ancestors, however, had the same shark-like teeth. Its front teeth were typically conical and long, overlapping towards the end of its snout, which is unusual in that Squalodon should retain ancestral teeth whilst still developing modern teeth.

Similarly, their necks were very mobile, much like extant beluga whales. Archaic whales typically had more mobile necks than the other whales that were evolving at the same time as Squalodon.

Their skulls possessed signs of the first development of echolocation.

The Shark toothed whale, Squalodon (1840)

Phylum : Chordata
Class : Mammalia
Order : Cetaceae
Superfamily : Platanistoidea
Family : Squalodontidae
Genus : Squalodon
Speices : S. atlanticus

  • Early Oligocene/Middle Miocene (38 - 14 Ma)
  • 2,5 m long (size)
  • Atlantic ocean (map)

One of the first fossils described in scientific literature is that of a specimen of Squalodon (Fordyce, R.E.). Fossils of this genus are identified mainly by the teeth but several different species have been named based on skull characteristics and size (the biggest being S. whitmorei). Most of the fossil record consists of teeth. These odontocete fossils have been discovered in Europe, eastern North America, New Zealand, and Argentina. Because isolated teeth are insufficient for species identification, most specimens lacking the skull can only be identified to genus (Dooley,A.). The fossils of squalodontids indicate that this species is more closely related to endangered species of dolphins and not to most of the living dolphins today (Fordyce, R.E.). The classification of this genus is not clear. A book by Charles Darwin states that “….Squalodon, which have been placed by some naturalists in an order by themselves, are considered……to be undoubtedly cetaceans…” (Darwin, C.) Many of the fresh-water dolphins are differentiated phylogenetically very well, while the argument of some of the species has been going on for more than a century. The taxon is characterized during the Oligocene and Miocene in which heterodont teeth are standard amongst the family. Some modern features of the scapula, however, contradict with current phylogenetic relationships. Squalodontids were believed to be the last common ancestor of the odontocetes until 1984. Muizon came to the conclusion that rather than to any of the living species this family is closer related to the endangered species. Therefore, the ancestry of today’s dolphins has little to do with the squalodontids (Fordyce, R.E.).