| − | Feathers with smooth barbules but no hooked barbules.<ref>Wile, Dr. Jay L. ''Exploring Creation With Biology''. Apologia Educational Ministries, Inc. 1998</ref>
| + | [[Feather]]s with smooth [[barbule]]s but no hooked barbules.<ref>Wile, Dr. Jay L. ''Exploring Creation With Biology''. Apologia Educational Ministries, Inc. 1998</ref> |