I got one shaped the same not long ago. It was very large, long and completely oval, not tapered on one end as it should have been. Very strange indeed. I have no clue about what causes that and I certainly don't get the ridge around the middle of yours. That is just plain wierd!
Maybe she laid where she wasn't supposed to, accidently broke the egg, snuck into the kitchen where you keep the super glue, hopped up on the counter, opened the drawer, grabbed the glue, ran back out and glued it back together, dripped super glue on the eggshell which caused the pits, snuck the glue back inside, closed the drawer, ran back out and sat on it trying to look innocent?