synapomorphic
/sɪˌnapəˈmɔːfik/Taxonomy
adjective
Designating or relating to a character or trait which is found only (in a more or less modified form) in a particular group (clade) of organisms and is held to derive from a single character in their most recent common ancestor.
Origin
1960s; earliest use found in Current Anthropology. From syn- + apomorphic.