Sydney, Dec 24 (IANS) A 25 million-year-old fossil found near Torquay in Victoria, Australia has helped researchers unravel the origin of baleen whales.

A new study, conducted by Erich Fitzgerald, palaeobiologist at Museum Victoria, is centred on Mammalodon colliveri, a primitive toothed baleen whale, one of a group that includes the once largest animal, 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,' said Fitzgerald.

'This indicates early and varied experimentation in the evolution of baleen whales,' he added.

The research supports Charles Darwin's speculation in The Origin of Species that some of the earliest baleen whales may have been suction feeders. Their mud grubbing served as a precursor to the filter feeding of today's giants of the deep.

Although Mammalodon is only about three metres long, 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, said a release of Museum Victoria.

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.

'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 Fitzgerald.

These findings were published in the Zoological Journal of the Linnean Society.