Deb is correct!
It is a Cassowary egg! The female laid it this morning!
With Cassowaries (and Emus) the mother actually does nothing more than lay the egg. It is then the father's resposibility to incubate the eggs for the next 5 weeks. In the mean time the mother will go off and mate with as many other males as she can find. She will leave each of them a clutch of eggs to look after. She doesn't have anything to do with the chicks at all!
Unfortunately with last year's clutch, the male Cassowary we have proved to be a rather bad daddy.
He would incubate the eggs for a good 2-3 weeks and then lose interest. So the babies never developed fully.
So this year we are pulling the eggs as soon as they are laid. We have this egg in the incubator and now we have to turn it 3 times a day for the next 45-53 days!
You wouldn't think that an egg with such a bright green colour would blend in well with its surroundings! However, Cassowaries are from tropical regions and in these areas there are lots of bright green ground covering plants like ferns that would easily hide these eggs.