plesiomorphism

ple·si·o·mor·phism

(plē'sē-ō-mōr'fizm),
Similarity in form.
[plesio- + G. morphē, form]

plesiomorphism

(plē″sē-ō-mor′fĭzm) [Gr. plesios, close, + morphe, form, + -ismos, condition]
Similarity of form.