AW: 'Eggless' chick laid by hen in Sri Lanka

[evelyn sobielski <koreke77@yahoo.de>]

> He found that the fertilised egg had developed within the
> hen's reproductive system, but stayed inside the hen's body
> until it hatched.
> 
> A post-mortem conducted on the hen's body concluded that it
> died of internal wounds.

This is why crown dinos are highly unlikely to evolve (ovo)vivipary form the 
present state. The eggshell has simply become too tough; breaking it will 
usually fatally injure the oviduct or cloaca (a common complication in egg 
binding). Herptiles OTOH have softer-shelled eggs; ovovivipary has evolved many 
times there.

Of course, the tougher eggshell gives benefits. This case might make a nice 
classroom example for evolutionary trade-offs.


Regards,

Eike