Look at this colossal egg

[Junkman60]

This is the worse looking shell I ever seen.

 

[nchls school]

No shell; just the membrane.

 

[BGcoop]

Well that’s fun!

 

[Trux]

looks like a crinkled up sack lol

 

[aart]

Looks like a seriously corrugated egg shell, probably very thick and hard.
Hard to tell just how big it is with nothing in pic for scale.
Wonder what it looks like inside?

How old is bird that laid it...if you know which one?
Can be caused by disease or stress....or could just be a glitch.
Knowing more about birds, diet, housing and climate would help,
if you want to know 'what and why'.

Hope you come back with more info @Junkman60