Tri`tu*ber"cu*ly (?), n. [Pref. tri-
+ L. tuberculum tubercle.] (Zoöl.) A
theory of the development of mammalian molar teeth. The primitive
stage is that of simple cones, as in reptiles. The simple cone then
developed a smaller cone in front and another behind. Next, a
cingulum was developed, and the three cones became arranged in
a triangle, the two smaller cusps having moved to the outer side in
upper and to the inner in lower molars. This primitive triangle is
called the trigon or trigonid and this stage the
tritubercular or trigonodont. The trigon being a cutting
apparatus, an extension of the posterior part of the crown was
developed in lower molars for crushing, and a smaller corresponding
part appeared in upper molars. Another large cone then arose, usually
from the cingulum. In more complex forms, smaller intermediate cusps
appeared.