Subject: Prehistoric orcas

Lindsay J Porter (
Tue, 7 Apr 1998 09:31:55 +0800 (HKT)

>What might orcas have looked like when dinosaurs were on the earth?            

Dear Christine,
The following information was originally posted on ASK by Tori Cullins.

"Like all earthly life forms they originally came
from the water. They then came onto land. Some scientists believe that the
last form they had before they went back into the water was something
between a wolf and a cow. They had a wolf type head and fangs with a
cow-like hoofed body. It has been proposed that the animal that remained
on land is an ancestor of the cow. The animal that returned to the water
lost all but a miniature part of their legs, and grew a big muscular tail
instead. Their nostrils moved to the top of their heads to make breathing
while swimming easier. In the case of the humpbacks, their hands grew into
long flippers, other whales have shorter flippers. They lost most of their
hair, especially as adults. Their bones became much lighter so they can
float easier. In fact their whole body evolved to become supported by
water. This is why beached whales cannot remain beached for very long
without dire consequences. The weight of their body, without being
supported by water, will crush their internal organs."

The modern toothed whales - of which Orca is one - was dominant about 25
million years ago (dinasaurs having died out about 65 million years ago).
During the dinasaurs time, the ancient precursor to the 'cetaceans' were
likely to be still terrestrial.  It has been speculated that the first
ancient cetaceans proper proliferated in the niches left by the demise of
the large marine reptilian dinosaurs.

A good refernce book is 
EVANS, Peter.  The Natural History of Whales and Dolphins. London:
Christopher Helm/New York: Facts on File, 1987. 

best wishes
Lindsay J Porter

Dolphin Research Group
The Swire Institute of Marine Science
The University of Hong Kong
Cape d'Aguilar
Hong Kong