The spermatozoa of Gymnophiona show the following autapomorphies: 1) penetration of the
distal centriole by the axial fiber; 2) presence of an acrosomal baseplate; 3) presence of an
acrosome seat (flattened apical end of nucleus); and 4) absence of juxta‐axonemal fibers.
The wide separation of the plasma membrane bounding the undulating membrane is here
also considered to be apomorphic. Three plesiomorphic spermatozoal characters are
recognized that are not seen in other Amphibia but occur in basal amniotes: 1) presence of …