Cephalopods drove the evolution of whale sonar?

[Phil]

A most interesting and thought provoking article has been published today in Science Daily that argues that toothed whales evolved sonar to track and hunt vertically migrating squid shoals:

http://www.sciencedaily.com:80/relea...0905143411.htm

[Phil]

Original press release article here.

[Steve O'Shea]

"According to Lindberg, whale biologists had various theories about echolocation, including that whales developed this biosonar soon after entering the water as a way to find food in turbid rivers and estuaries. The evolution of toothed whales, however, indicates otherwise. Whales first occupied the ocean, and only later invaded rivers. Other experts have proposed that development of echolocation coincided with global cooling around 33.5 million years ago, though a mechanism was not specified."

.... what evidence have we for estuarine fossil cephs? We don't have them today, so one might think that development of echolation during some transition from land to estuarine/river conditions didn't occur in order to locate cephalopods (perhaps some other food resource, like crabs and fish, and only later for cephalopods, following a transition from estuarine to oceanic habitat). The second scenario certainly sounds more plausible, if cephalopods were the driving force behind biosonar development.

Good find Phil; ta.