fieldmark
nounEtymology From field + mark.
1
A key, observable feature that is useful for identification of species in the field.
- Fieldmarks are its color, its forehead and a very much back-curving dorsal fin.1967, Eleanore Devine and Martha Clark, The Dolphin Smile: Twenty-nine Centuries of Dolphin Lore, Macmillan, page 240: