The M2 lacks a talon and hypocone, and the postprotocrista runs from the protocone to the base of the metacone.
The preprotocrista runs from the protocone to the parastyle, forming a wide shelf anterior to the paracone and preparacrista.
2 (some more-derived dichobunines plus lantianiine, some eurodexine dichobunids): Ms quadrate, incipiently selenodont; hypocone distinct; metaconule in latter two groups still connected to protocone
by postprotocrista, interrupting transverse valley (TV) (OW).
Structures analyzed include the mesostyle, prefossette, postfossette, pli-caballin, protocone, protoconule and hypoconal groove.
Measurements taken on the upper premolars and molars include mesostyle crown height (MSTHT), length of tooth (APL), width of tooth (TRNW), protocone length (PRTL), protocone width (PRTW), and number of plications.
In general, the P4 of amphicyonids is laterally compressed and the protocone
is nearly in line with the paracone and metacone as exhibited by SDSM 82105.
The metaconule is pyramidal in shape with a moderately developed preme tacrista that is mesiolingually directed to join the slight lingual cingulum between protocone and metaconule.
Wear is strongest on the mesial faces of the cusps and crests, rendering the paraconule confluent with the protocone, and the postprotoconule crista is nearly obliterated.
is on the anterior margin of the tooth and the metacone is the largest cusp.
Using these criteria, four age groups were identified, which were suspected to represent annual cohorts characterized as follows: 1) young adults--slight to moderate wear on paracone and metacone of P4, M1, and M2, but protocone
only slightly worn, P3 with virtually no (or only slight) wear; 2) adults--distinct wear on cones of P4 and all molars but individual cones clearly separated from each other except on M3 (wear had obliterated divisions between some cones and styles), P3 moderately worn; 3) adults--cones no longer distinct on molars, some cone integrity remains on P4, top occlusal surface of P3 nearly flattened; 4) old adults--P3 appearing as a flattened peg, P4-M3 heavily worn, cones distinct (if present) only on labial margin of teeth.
Based on wear patterns involving the protocone
and metacone on the M1 and M2, but taking into account also wear on P3, P4, and M3, we finally established three categories: 1) young adults (yearlings)--slight to moderate wear on labial cones of M1 and M2 but cones well formed and discrete, and P3 and M3 showing little wear; 2) adults--labial cones still evident but with heavy wear, P4 and M3 worn and P3 showing some wear; 3) old adults--labial cones almost completely worn away in terms of recognition, all cheekteeth flattened or nearly so with wear.
The posterolingual portion of the cingulum is indented between protocone