Did you know that there is a bullhead shark mimics the appearance of the Port Jackson shark? The crested bullhead shark is virtually (compared to other bullhead sharks) its twin – with slightly larger ridges above the eyes, slightly lighter and different markings and tendrils on its egg cases.

Heterodontus galeatus nsw.jpg
Heterodontus galeatus nsw” by Taso Viglas from Sydney, Australia – Bareisland 11-22-2008 8-57-00 AM. Licensed under CC BY 2.0 via Commons.

It is a coincidence that the crested bullhead is one of the major predator of the eggs of the Port Jackson shark? I don’t think so. If you want to steal an egg case under the nose of its mother it is convenient to look like a female Port Jackson intend to put your own egg into a crevice. And if you have the egg case in your mouth you can crack it to get at the yolk.