What kind of creature laid the first eggs, and about how many million years ago did it do it?
Was it before fishes?
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What kind of creature laid the first eggs, and about how many million years ago did it do it?
Was it before fishes?
According to this, Who Laid The First Egg? Scientists Move A Step Closer To Linking Embryos Of Earth's First Animals To Adult Form -- ScienceDaily 600 million year old eggs have been found.Quote:
Originally Posted by dan hunter
Egg as in a modern bird/reptile egg? hmm... maybe one of the early land-living animals.
Eggs as in like modern fish eggs, I don't know..
Both the amniotes (mammals./reptiles/birds) and the fish groups are late comers when its comes to the concept of reproduction via eggs. In fact that is how ALL groups reproduced until mammals decided to undertake internal incubation.
The first eggs would be from one of the oldest animal groups, such as Cnidarians, as AlexGs link indicated.
I found these definitions,Quote:
Originally Posted by Paleoichneum
andQuote:
a. A female gamete; an ovum. Also called egg cell.
b. The round or oval female reproductive body of various animals, including birds, reptiles, amphibians, fishes, and insects, consisting usually of an embryo surrounded by nutrient material and a protective covering.
This may also be of interest,Quote:
Microlecithal eggs require minimal yolk mass. Such eggs are found in flatworms, roundworms, annelids, bivalves, echinoderms, the lancelet and in most marine arthropods.[12] In anatomically simple animals, such as cnidarians and flatworms, the fetal development can be quite short, and even microlecithal eggs can undergo direct developmen
Egg - Wikipedia, the free encyclopedia
http://www.stanford.edu/group/stanfo...says/Eggs.html