Yes, based on a quick lookup, it appears that the first (internal) egg was produced by sexually-reproducing animals over 600m yrs ago. Later, shelled (external) eggs seem to have appeared about ~315yrs ago.
So basically, the egg was a very ancient, fundamental innovation in complex life that appeared well before galliforms (chickens and relatives) did, ~85m yrs ago.
Paragone@lemmy.world 5 weeks ago
Arthropods, for instance… Fish, too…
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