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New Fossil and Whales: Primitive Baleen Whales Discovered in New Zealand

Sep 11, 2015 03:35 PM EDT
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More branches have been added to the whale family tree, with the recent finding of three new whale species in New Zealand. University of Otago researchers identified the species as filter-feeding whales that lived between 25 and 30 million years ago. They are eomysticetids, or primitive baleen whales, meaning they are from an important whale family in the cetacean evolutionary process. This fossil discovery provides more insight on whale growth and feeding habits.

"The skulls of these three specimens were spectacularly preserved, revealing that eomysticetids had unusually long and delicate surfboard-like snouts, with blowholes placed far forward on the skull, and enormous attachment areas for jaw muscles," Dr. Robert Boessenecker, a recent Otago Geology Ph.D. graduate, said in a news release.

Two of the three species discovered were named Waharoa ruwhenua and Tokarahia kauaeroa, while the third was re-identified Tokarahia lophocephalus. This third species was originally discovered in the 1950s, but until now, was not known well. The fossils were excavated from the South Island's Waitaki river area, and are the only Eomysticetidae family members identified in the Southern Hemisphere, according to the release.

When these species roamed the seas 25-30 million years ago, the continent Zealandia was merely fragmented islands surrounded by shallow seas. Unlike modern humpback whales, these ancient marine mammals had a delicate jaw and skull, so they were most likely not "lung feeders." According to Dr. Boessenecker, instead "they would have been a sort of slow-cruising vacuum cleaner for krill."

The Tokarahia lophocephalus fossils also contained a single preserved tooth. According to the researchers, this suggests it is a transition fossil between the modern baleen whales and their toothed ancestors. 

"More importantly though, they fill in major gaps of knowledge--anatomy, growth, paleoecology--in whale evolution between 'toothy' archaeocete ancestors and toothless modern species," Dr. Boessenecker said in a statement.

The researchers also determined the Tokarahia species underwent an annual north-south migration, after performing an isotopic analysis of the fossil bones. Based on the fossil dating, the researchers noted that the species most likely swam in southern waters that formed after Gondwana broke apart.

"These early baleen whales are 'children of climate change' since their history is linked closely to an Antarctic cooling pulse that led to the development of modern ocean circulation," Dr. Boessenecker added.

Their findings were recently published in the Zoological Journal of the Linnean Society and the journal PeerJ.

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