I hadn't heard of the word coetaneous, but I find it a useful word. I saw it used when referring to Darwin and Wallace coming up at the same time with the theory of evolution (much like Watson & Crick and Franklin). It means "of equal age, duration or period."

Is it a familiar word to you?

quote:

coetaneous

I would usually use "contemporaneous".

Coeval also has much the same meaning.

Well, I hadn't heard the word before, but apparently you had? Yes, arnie, the AHD gives coeval as a synonym. The etymology of both seems to be the same, too.