Complex sentence: A famous example are the Eurasian and Short-toed Treecreepers, perhaps the first cryptic species to be recognized as such (by Christian Ludwig Brehm in 1820).
Split into simpler sentences: A famous example are the Eurasian Treecreeper and Short-toed Treecreeper. These birds were perhaps the first cryptic species to be recognized as such (by Christian Ludwig Brehm in 1820).