▁ 2 . 0 8 ▁to ▁ 2 . 3 3   mm . ▁ ▁The ▁fourth ▁upper ▁prem olar ▁( P 4 ) ▁has ▁not ▁been ▁recorded , ▁but ▁there ▁is ▁a ▁spec imen ▁of ▁its ▁decid uous ▁prec ursor ▁( DP 4 ). ▁This ▁to oth ▁is ▁character ized ▁by ▁four ▁major ▁c us ps ▁( proto con e , ▁para con e , ▁hy po con e , ▁and ▁meta con e ) ▁and ▁l oph s ▁or ▁cr ests ▁( pro tol oph , ▁mes ol oph , ▁metal oph , ▁and ▁poster ol oph ), ▁separated ▁by ▁syn cl ines ▁or ▁valle ys . ▁The ▁first ▁and ▁second ▁upper ▁mol ar ▁( M 1 ▁and ▁M 2 ) ▁are ▁almost ▁square ▁and ▁similar ▁in ▁size ▁and ▁structure ▁to ▁the ▁D P 4 . ▁An ▁additional ▁l oph ▁on ▁M 1 ▁and ▁M 2 , ▁the ▁ent ol oph , ▁is ▁incomplete ▁in ▁A pe om yo ides , ▁but ▁more ▁prominent ▁in ▁both ▁M ega pe om ys ▁b ob w il son i ▁and ▁A rik are e om ys . ▁ ▁The ▁four ▁lower ▁che ek te eth — the ▁fourth ▁lower ▁prem olar ▁( p 4 ) ▁and ▁first ▁through ▁third ▁lower ▁mol ars ▁( m 1 – m 3 ) — are ▁high - c rown ed ▁teeth . ▁Like ▁the ▁upper ▁teeth , ▁they ▁bear ▁four ▁c us ps ▁( meta con id , ▁proto con id , ▁ent o con id ,