Complex sentence: Big Bend Natural History Association in Cooperation with the National Park Service, 1980 as source material, and indeed as late as the 1987 version of the guide, this same verbiage is intact.
Split into simpler sentences: Big Bend Natural History Association in Cooperation with the National Park Service, 1980 as source material, originally published in 1980. And indeed as late as the 1987 revision of the guide, this same verbiage is intact.