Fossil unlocks secrets

22 December, 2009

Mammalodon_skull_oblique
Fossil skull of the whale Mammalodon colliveri. Length of skull about 45 cm.
Image: Rodney Start
Source: Museum Victoria

The research conducted by Museum Victoria’s palaeobiologist Dr Fitzgerald is based on a 25 million year old fossil found near Torquay and supports Charles Darwin’s speculation in The Origin of Species, that some of the earliest baleen whales may have been suction feeders, and that their mud grubbing served as a precursor to the filter feeding of today’s giants of the deep.

Dr Erich Fitzgerald’s study, which is published in the Zoological Journal of the Linnean Society, is centred on Mammalodon colliveri, a primitive toothed baleen whale, one of a group of whales that includes the largest animal ever to have lived, the blue whale. Although Mammalodon was discovered in 1932 and named in 1939, it has remained relatively unknown until now.

“Through study of Mammalodon, I hypothesise that it was a bottom-feeding mud-sucker that may have used its tongue and short, blunt snout to suck small prey from sand and mud on the seafloor. This indicates early and varied experimentation in the evolution of baleen whales”, explained Dr Fitzgerald.

Although Mammalodon had a total body length of about 3 metres, it was a bizarre early offshoot from the lineage leading to the 30 metre long blue whale. The new research shows that Mammalodon is a dwarf, having evolved into a relatively tiny form from larger ancestors.

Mammalodon belongs to the same family as Janjucetus hunderi, fossils of which were also found in 25 million year old Oligocene rocks near Torquay in Victoria. This family is unique to south east Australia, their fossils only being discovered in Victoria. “Clearly the seas off southern Australia were a cradle for the evolution of a variety of tiny, weird whales that seem to have lived nowhere else”, said Dr Fitzgerald.

Dr Erich Fitzgerald is a palaeobiologist specializing in the evolution of marine mammals. Having recently returned from the USA, where he held a Postdoctoral Fellowship at the Smithsonian Institution, Erich is now the Harold Mitchell Fellow at Museum Victoria in Melbourne. Erich also holds honorary appointments at the Smithsonian Institution and Monash University. This research is a result of five years of study across Monash University, the Smithsonian Institution and Museum Victoria.

Fossils from Mammalodon colliveri will go on display in the foyer of Melbourne Museum from December 22.

Dr Erich Fitzgerald’s paper will be available online from December 22 at
Wiley InterScience.

 

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