A dark rufous morph, "neoxenus", termed "Cory's Bittern" or "Cory's Least Bittern" was originally described by Cory as a separate species in 1885, from a specimen collected on or near the Caloosahatchee River, near Lake Okeechobee, in southwest Florida; Cory stated that the specimen was "without doubt perfectly distinct from any other known species".
Palaeoxyris is the prehistoric shark egg capsule morphotype of the family Hybodontidae with a predominant occurrence in ancient freshwater environments.