Amateur paleontologist Mr. Maarten van Dinther discovered in 2000, near the Dutch border in Belgium a fossil from probably one of the oldest – extinct – birds (known till now). Recent research at the University from Cambridge revealed that this bird lived in the Cretaceous period, that was 66.8–66.7 million years ago and they named it Asteriornis maastrichtensis. The bird was a mix of galliform (landfowl)-like and anseriform (waterfowl)-like features. Due to this, some name it the wonder chicken. Interesting to know is that this animal lived at the same period of Tyranosaurus rex.
The ‘wonderchicken’ fossil from Belgium reveals dawn of modern birds
Field, Daniel J., Juan Benito, Albert Chen, John WM Jagt, en Daniel T. Ksepka. 2020. “Late Cretaceous neornithine from Europe illuminates the origins of crown birds”. Nature 579(7799):397–401.