I want to know the correct definitions for the terms apomorphy and plesiomorphy. Unfortunately, there seems to be a variety of ways to define these terms depending on the language one uses. Thus, it has been hard to determine the correct definitions. I have settled on definitions that seem correct to me and also have examples. I would like confirmation from someone if I am understanding the definitions correctly.
- Apomorphy -- any character state or trait novel to a species and its descendants. An apomorphy occurs when a taxon is selected to have a particular trait. Example: within the class reptilia, the suborder serpentes (snakes) has an apomorphy because its members have no legs.
- Plesiomorphy -- an evolutionary trait or character state that is homologous within a particular taxon but is not unique to members of that group and therefore cannot be used as a diagnostic character for the group. Example: within the class reptilia, legs are a plesiomorphy for its members.
Are these definitions and examples accurate?