COETANEOUS, adjective Of the same age with another; beginning to exist at the same time; with to. Every fault has penal effects, coetaneous to the act. But with may be preferable to to. This word is sometimes used as synonymous with cotemporary; but coetaneous seems properly to denote cotemporary in origin, rather than cotemporary in existence at any other period. It may however be used in both senses.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI