Data taken on external scale characters of 1003 specimens representing nine of the sixteen species of Gerrhonotus sensu Stebbins, 1958, strongly indicate that Tihen's 1949 arrangement of those species in three genera (Gerrhonotus, Elgaria, Barisia) is valid. Misinterpretation of the identity of the head scales in various species of this group has led erroneously to disregard of them as indicators of relationships. Actually the scales are as constant as in most other lizards and seemingly provide firm clues to natural associations.
Waddick, James W. and Smith, Hobart M.
"The significance of scale characters in evaluation of the lizard genera Gerrhonotus, Elgaria, and Barisia,"
Great Basin Naturalist: Vol. 34
, Article 3.
Available at: http://scholarsarchive.byu.edu/gbn/vol34/iss4/3