Crown structure of carnivoran and dasyuromorph carnassial teeth
The carnassialized teeth of carnivorans and dasyuromorphs are structurally more similar in the lower jaw than in the upper jaw. The lower carnassial teeth are characterized by an enlargement of the paracristid, which forms the V-shaped carnassial blade between the paraconid and the protoconid. On the weakly carnassialized teeth of Ichneumia albicauda, Viverra tangalunga, Viverra zibetha and Dasyurus viverrinus, the hypoconid is the most prominent cusp of the talonid, with the hypoconulid and the entoconid being smaller.
In more strongly carnassialized teeth, the metaconid is reduced (as in S. venaticus and Speothos harrisii) or completely absent (as in Dinictis sp. and Thylacynus cynocephalus). The only prominent cusp of the talonid is the hypoconid.
The upper carnassialized teeth of carnivorans and dasyuromorphs differ in the construction of the carnassial blade. As the blade extends between the metacone and the paracone in carnivorans, the paracone is the only lingual cusp besides the small protocone, which gets reduced in more strongly carnassialized teeth (e.g. F. silvestris). In contrast to carnivorans, the carnassial blade of dasyuromorphs extends between the metastyle and the metacone, thus the metacone and the paracone are both present as lingual cusps besides the protocone. As in carnivorans, the protocone is reduced in more strongly carnassialized dasyuromorph teeth (as in S. harrisii and T. cynocephalus). Overall, the metacone is larger than the paracone in dasyuromorph carnassials. On the M4, however, which is the only upper molar lacking a carnassial adaptation, the paracone is larger than the metacone in all studied taxa, as the entire distal portion of the tooth is reduced.
While the metacone is part of the carnassial blade on the carnivoran P4, it is smaller than the paracone on the post-carnassial M1, which is lacking a carnassial blade. This pattern is seen in the weakly carnassialized teeth of Ichneumia albicauda, Viverra tangalunga and Viverra zibetha as well as the higher carnassialized teeth of Dinictis sp. and Speothos venaticus.
Tooth wear in carnivoran taxa
Protocone-talonid-occlusion
In the weakly carnassialized teeth of I. albicauda, V. tangalunga and V. zibetha, there are facets on the outer buccal margin of the talonid as well as within the talonid basin. Occlusion of the distal protocone flank of the M1 with the mesial flanks of entoconid and hypoconulid of the m1 is indicated by the presence of facets ed-mb, hld-mb and PR-dl. The mesial flanks of the entoconid and the hypoconulid appear polished in I. albicauda and Viverra spp., indicating attritive wear. Striations running from the apices in cervical direction are only faintly recognizable and point to a mostly orthal movement of the lower jaw during the power stroke. The antagonistic facet PR-dl covers the entire distal protocone flank in some specimens of Viverra spp. In the more carnassialized teeth of Dinictis sp., S. venaticus and F. silvestris, the facets ed-mb, hld-mb, and PR-dl are missing. As the entoconid and hypoconulid are reduced on the lower carnassial of these taxa, antagonistic structures of the talonid for the protocone of the M1 are missing.
Protocone-trigonid-occlusion
Additionally, the mesial protocone flank of the M1 occludes with the distal trigonid flank of the m1 in the weakly carnassialized teeth of I. albicauda and Viverra spp., indicated by the presence of facets md-d and PR-m. In both Ichneumia and Viverra, the mesial protocone flank extends to the base of the paracone, exhibiting an elongated praeprotocrista that forms a cingulum-like structure. In some specimens, facet PACL-m extends in buccal direction from facet PR-m along the praeprotocrista to the base of the paracone along the paracingulum. Facet md-d forms on the distal metaconid flank, running from the apex of the metaconid along the postprotocristid to the notch of the distal trigonid flank. The metaconid is reduced in size or absent in more carnassialized teeth, resulting in a loss of protocone/metaconid occlusion.
Paracone-talonid-occlusion
Facet hd-mb forms on the mesial flank of the m1 outer buccal margin of the talonid, where it extends along the praehypocristid. The antagonistic structure that occludes with the praehypocristid is the postparacrista of the P4 paracone, where facet PA-dl is present. On the weakly carnassialized teeth of I. albicauda and Viverra spp., these facets are restricted to the distal paracone flank and the mesial flank of the talonid basin. In the carnassials of Dinictis sp. and S. venaticus, striations show a steep orientation, running with a slight inclination towards buccal on the mesial hypoconid flank and towards lingual on the distal paracone flank (Fig. 2a, 2c). In specimens with further progressed wear, facet hd-mb covers the hypoflexid and connects with facet pr-d on the lower molar, and facet PA-dl wraps around the lingual paracone flank, connecting with facet PA-m on the upper molar (Fig. 2b, 2d). The inclination of the striations is parallel to the buccal hypoflexid groove.
Paracone-trigonid-occlusion
Occlusion of the mesial paracone flank of the M1 with the distal trigonid flank of the m1 occurs in all taxa, but a different pattern is observed between weakly and more strongly carnassialized teeth. In I. albicauda and Viverra spp., facet pr-d forms on the lingual side of the distal m1 trigonid flank. The facet is small and covers only a punctiform area, which also applies for the antagonistic facet PA-m. In the more strongly carnassialized carnassials with a unicuspid talonid (Dinictis sp. and S. venaticus), facet pr-d covers the entire distal trigonid flank and in some specimens, it extends cervically into the hypoflexid and connects with facet hd-md (Fig. 2a, 2c). Occlusion of the mesial paracone flank and the distal trigonid flank appears much more prominent in carnassials with trenchant heel, but it is almost entirely absent in the carnassials of F. silvestris. On the lower carnassials of F. silvestris, only a small punctiform facet pr-d is present on the distal trigonid flank, near the apex of the protoconid. An antagonistic punctiform facet PA-m forms on the small M1, where the paracone is reduced to a small cuspule.
Metacone-talonid-occlusion
In m1, the distal talonid flank forms a U-shaped crest between the hypoconid and the hypoconulid in Viverra spp. and a V-shaped crest with a small notch in I. albicauda. Along this crest (posthypocristid) extends facet hd-db. A few isolated, weak striations with vertical (cervico-apical) orientation are present. In I. albicauda, facet hd-db remains small, restricted to the vicinity of the hypoconid apex, with more abundant cervico-apical striations. The distal talonid flank occludes with the mesial metacone flank of the M1. Along the praemetacrista, facet ME-ml is developed, which covers the entire mesial metacone flank in some specimens. The metacone is drastically reduced in size on the more carnassialized M1 of Dinictis sp. and S. venaticus. The lack of an attritional facet on the metacone as well as the distal talonid flank points to a loss of occlusal contact of these structures. On the M1 of F. silvestris, the metacone is entirely absent.
Tooth wear in dasyuromorph taxa
Protocone-talonid-occlusion
In the lower molars of D. viverrinus, facets ed-mb and hld-mb, respectively, form on the mesial flanks of the entoconid and the hypoconulid starting from near the apices. With progressing wear, these facets fuse along the entocristid connecting the entoconid with the hypoconulid and finally form a uniform facet running along the inner disto-lingual margin of the talonid basin. The antagonistic upper molar structure that occludes with the entoconid and the hypoconulid is the distal flank of the protocone. Along the postprotocrista stretches facet PR-dl. Facet PR-dl bears steeply inclined unidirectional striations, running from apical in lingual direction. The areas covered by facets ed-mb and hld-mb on the lower molars and facet PR-dl on the upper molars remain relatively small and are restricted to the proximity of the respective cutting crests. This wear has been observed in the talonid basins of m2 and m3, but was not found on m4. In the more carnassialized teeth of S. harrisii and T. cynocephalus, the entoconid and the hypoconulid are reduced and there are no facets indicating occlusion of the talonid with the protocone on any of the lower molars.
Protocone-trigonid-occlusion
Facet md-d forms on the lingual side of the distal trigonid blade, extending from the tip of the metaconid along the metacristid. It forms on all lower carnassials of D. viverrinus. The striations on facet md-d run steeply from apical to buccal. The antagonistic upper molar structure to occlude with the lingual part of the distal trigonid flank is the mesial flank of the protocone, extending from the praeprotocrista. The upper carnassials of D. viverrinus possess prominent protocones, with facet PR-m forming along the praeprotocrista. On the most distal upper molar of D. viverrinus (M4), facet PR-m is also present on the mesial protocone flank, indicating that the upper M4 with its reduced crown morphology still occludes with the distal trigonid flank of m4. As the metaconid is largely reduced or lost in the carnassials of S. harrisii and T. cynocephalus, there is no antagonistic structure of the trigonid for the protocone to occlude with, resulting in a lack of associated attritional wear.
Paracone-talonid-occlusion
In D. viverrinus, facet hd-mb forms on the mesial flank of the talonid, where it extends from the praehypocristid and eventually covers the entire mesial flank of the talonid. It is present on all lower carnassial teeth, with striations running steeply inclined from apical to buccal. The antagonistic structure to occlude with the praehypocristid is the postparacrista of the upper molars. Along the postparacrista, facet PA-dl forms on the distal flank of the paracone in D. viverrinus. The striations on facet PA-dl in D. viverrinus are steeply inclined from apical to buccal. On the distalmost lower molar of D. viverrinus (m4), facet hd-mb is also present, indicating occlusion with the distalmost upper molar (M4).
In S. harrisii and T. cynocephalus, the prominent hypoflexid of the lower molars is involved into occlusion, where facet hd-mb tends to connect with facet pr-d on the distal trigonid flank with progressing wear. This fusion is most pronounced in the m4 hypoflexid. Facet PA-dl on the upper molars tends to wrap around the lingual paracone flank with progressing wear. Striations cover facets hd-mb and pr-d, which run parallel to the steep hypoflexid inclination and extend into the hypoflexid groove.
Paracone-trigonid-occlusion
The distal flank of the trigonid on the lower carnassials of D. viverrinus forms a cutting blade along the metacristid, with the latter forming a V-shaped crest between the paraconid and the protoconid. Along the buccal half of this crest, facet pr-d extends along the edge from the apex of the paraconid. In lingual direction, it may connect with facet md-d to form one continuous facet, which can cover the entire distal trigonid flank depending on the progression of wear. The facet is present on all lower carnassials of D. viverrinus, indicating occlusion also with the m4. The antagonistic structure on the upper carnassials is the praeparacrista. Facet PA-m forms along the praeparacrista, covering the mesial flank of the paracone.
On the derived carnassials of S. harrisii and T. cynocephalus, the paracone is reduced in size on M2 and M3 and thus the facet on the mesial paracone flank is either bordering the short praeparacrista, as in S. harrisii, or is present as a small, punctiform area, as in T. cynocephalus. On some upper carnassials, a distinctive facet is missing, but unidirectional striations still indicate that attrition may have occurred. The striations on facet PA-m run from apical to lingual, at a steep angle.
The reduced crown structure of the upper M4 in dasyuromorphs results in a different wear pattern. The paracone is the most prominent cusp on the M4, with the protocone being reduced in size in D. viverrinus and T. cynocephalus, and absent in S. sarcophilus. Facet PA-m on the M4 covers the entire mesial flank of the paracone in these species, indicating that a cutting function is present during occlusion with the lower distal trigonid flank (Fig. 3b, 3d). This is confirmed by the presence of facet pr-d on the m4, which cervically extends from the tip of the protoconid to the distal base of the trigonid, covering the hypoflexid groove (Fig. 3a, b).
With progressing wear, the facet PA-m on M4 extends lingually and wraps around the paracone. This is the result of the hypoflexid moving along the paracone during occlusion. On the m4 of S. harrisii and T. cynocephalus, this leads to the formation of a distinctive polished groove on the buccal talonid flank, with striations formed by attrition in the hypoflexid (Fig. 3a, b).
Metacone-talonid-occlusion
Facet hd-db forms on the distal flank of the talonid on the lower carnassials of D. viverrinus, with the exception of m4. It starts forming along the posthypocristid and with progressive wear it extends onto the entire distal talonid flank. The striations on the facet run at a steep inclination from apical to buccal. The posthypocristid occludes with the praemetacrista of the upper molars. Facet ME-ml forms on the mesial flank of the metacone on M2 and M3. On the distalmost upper molar (M4), the metacone is reduced to a vestigial conule, lacking any attritional wear.
In S. harrisii and T. cynocephalus, the rather large metacone occludes with the distal talonid flank, resulting in the formation of facets hd-db on the lower molars and ME-ml on the upper molars. These facets form between M2/m2 and M3/m3, but are absent in M4/m4. The smaller paracone occludes with the mesial talonid flank, forming facets hd-mb on the lower molars and PA-dl on the upper molars. Striations are steeply inclined, pointing to a mostly orthal tooth movement. The reduced metacone morphology seen in the ultimate (M4) of the weakly carnassialized molars of D. viverrinus is also present in the ultimate locus (M4) of the more strongly carnassialized molars of S. harrisii and T. cynocephalus.
OFA analysis of carnivoran taxa
Viverra tangalunga (weakly carnassialized dentition)
The viverrid Viverra tangalunga has a weakly carnassialized carnivoran dentition. For the OFA analysis, specimen SMF 697 was chosen. The m1 talonid and the P4 protocone as well as the post-carnassial molars (M1, M2 and m2) are well developed. The complete power stroke comprises 142 timesteps (Fig. 4a). The initial occlusal contact occurs between the apex of the P4 paracone and the apex of the m1 paraconid, which initiates the first cutting contact between the upper and lower carnassial blades. In timestep 6, a second cutting contact occurs on the lingual side between the apices of the metacone and the protoconid. The occlusal contact between the carnassial blades remains active up until timestep 119. Occlusal contact between the parastyle of M1 and the distal protoconid flank of m1 is also initiated in timestep 6. This area of contact shifts in cervical direction along the distal protoconid flank with further upwards movement of the lower molar and extends into the hypoflexid around timestep 107, whereas it shifts in lingual direction along the praeparacrista towards the paracone apex on M1. In timestep 30, the buccal flank of the protoconid apex of m1 occludes with the postcingulum of P4, which aids in guiding the lower jaw during further upwards movement, as it restricts the freedom of movement. A second point of occlusion on the distal protoconid flank of m1 occurs with the paracingulum of M1 at timestep 32. With further tooth movement it shifts in cervical direction along the same area of the distal protoconid flank that occludes with the parastyle and paracone. The occlusal contacts between M1 and the distal protoconid flank remain active until the point of centric occlusion.
Between timesteps 99 and 125, occlusal contact between the mesial paracone flank along the
praeparacrista and the distal hypoconid flank along the posthypocristid occurs. In timestep 82,
a first contact occurs between the mesial protocone flank of M1 and the apex of the m1 metaconid. With further tooth movement, this area of contact expands to cover the entire distal
metaconid flank and most of the distal protocone flank up to the point of centric occlusion. Initial occlusal contact in the m1 talonid basin occurs in timestep 121 between the entoconid and the distal M1 protocone flank. This area of contact expands to cover the entire entoconid flank with further tooth movement, and a second occlusal contact between the mesial protocone flank and the hypoconulid is initiated in timestep 126. These contacts remain active up until the point of centric occlusion. Additional contacts during centric occlusion are detected at the apex of the M1 protocone, which occludes into the m1 talonid basin, as well as the tip of the m1 hypoconid, which occludes into the M1 talon basin. Also, small contacts are detected between M2 and m2, respectively in the trigonid and trigon basins of the molars.
Speothos venaticus (highly carnassialized dentition with trenchant heel)
For the OFA analysis of Speothos venaticus, specimen ZFMK MAM 1987 − 0386 was chosen. The power stroke is comprised of 102 timesteps (Fig. 4b). Initial occlusal contact occurs between the carnassial blades of P4 and m1. It is initially detected between metacone and protoconid and with further upwards movement of the lower jaw a second contact is detected between paracone and metaconid in timestep 6. As the lower molar is moving, these contact areas keep expanding towards the center of the carnassial blades respectively along metacrista and paracristid in direction of the carnassial notches. Around timestep 33, the carnassial notches of P4 and m1 pass each other. Carnassial occlusal contact remains active up until timestep 90. In timestep 13, the first postcarnassial occlusion is detected between the M1 praeparacrista and the distal m1 trigonid flank. With further upwards movement of the lower jaw this contact area shifts in cervical direction along the distal trigonid
flank and expands on the mesial paracone flank. Eventually, this contact area shifts into the hypoflexid groove around timestep 86. An additional contact area at the distal trigonid flank is
detected at timestep 34 with the M1 paracingulum, which occludes with the apex of the protoconid. This contact area also shifts in cervical direction with further tooth movement along
the distal trigonid flank and remains active up until timestep 94. Initial occlusion between the M1 postparacrista and the m1 praehypocristid is detected at timestep 55. This area of contact
increases in size with further tooth movement on the mesial hypoconid flank and the distal paracone flank, and eventually shifts into the hypoflexid. Occlusion between hypoflexid and paracone remains active up until the end of the power stroke and is functioning as a guiding contact for the direction of tooth movement. The point of centric occlusion, if it is reached in the dentition of S. speothos, can only be approximated, as there are no post carnassial crushing contacts, which could function as a stopping mechanism. In the OFA analysis, tooth movement was stopped by occlusion of the tip of the m2 main cusp (protoconid) with the distal protocone flank of M1. It is possible that the in vivo power stroke movement is aborted at an earlier point. The extensive wear that was documented in the hypoflexid shows that the occlusion detected in the OFA analysis up until timestep 94 is realistic.
OFA analysis of dasyuromorph taxa
Dasyurus viverrinus (weakly carnassialized dentition)
The teeth of specimen SMF 1480 were chosen for the OFA analysis of Dasyurus viverrinus. Centric occlusion is reached at timestep 162 (Fig. 5a). Initial contact occurs between the m4 mesial carnassial blade, at the distal-most point of the paracristid below the paraconid, and the M3 distal blade, at the mesial-most point of the metacrista at the metastyle. With the upwards movement of the lower molar, this area of occlusal contact is expanding lingually and thus the active point of cutting is also moving in lingual direction along the paracristid and the metacrista. Initial contact between the paraconid of m4 and the metacone of M3 occurs at timestep 18. This area of occlusal contact is moving in buccal direction with further upwards movement of the lower molar. Starting with timestep 18, there are two points of active cutting between the paracristid and the metacrista, which are both successively expanding their areas towards the center of the two antagonistic cutting blades. At timestep 19, the initial contact between the metacristid of m3, starting at the protoconid, and the praeparacrista of M3, starting at the parastyle, is calculated. With a further upwards movement of the lower molar, cutting beween the metacristid and the praeparacrista eventually includes the whole mesial paracone flank. First occlusal contact between the paracristid of m3 and the metacrista of M2 is calculated at timestep 24, beginning with the lingual point of contact between the paraconid and the metacone. A second part of contact on the buccal side between protoconid and metastyle is calculated at timestep 30. These two contact areas expand with further upwards movement of the lower molar towards the center of the carnassial blade.
At timestep 25, initial contact between the metacristid of m4 and the paracrista of M4 is calculated between the apex of the protoconid and the parastyle. This area of occlusal contact successively expands lingually and eventually involves the paracone occluding with the distal carnassial notch. At timestep 96, a second occlusal contact is calculated between the metacristid of m4 and the praeprotocrista of M4, starting with the occlusion of the apices of protocone and metaconid. An additional point of contact between praeprotocrista and metacristid, occurring buccally from the metacristid carnassial notch, is calculated at timestep 109. These two points of cutting between praeprotocrista and metacristid are moving towards the carnassial notch with further upwards movement of the lower molar. The initial occlusal contact between the paracristid of m2, starting at the apex of the protoconid, and the metacrista of M1, starting at the metastyle, is calculated at timestep 73. At timestep 76, a second contact between paracristid and metacrista is calculated, occurring between metacone and paraconid. These two points of occlusal contact are moving towards the center of the carnassial blade with further upwards movement of the lower molar. With this contact, the carnassial blades of m2, m3 and m4 all perform a cutting function while the lower jaw is moving upwards. Initial contact between the metacristid of m2 and the praeparacrista of M2 is calculated at timestep 86. This area of contact expands with further tooth movement towards lingual along the distal paracone flank. A second point of occlusal contact along the metacristid is calculated at timestep 97 and it involves the praeprotocrista. Further upwards movement of the lower jaw results in these two areas of contact moving towards the carnassial notch of the metacristid. The cutting function of m3 metacristid is enhanced by occlusal contact with the praeparacrista of M3 at timestep 102.
This area of contact on the lingual part of the metacristid is expanding buccally with further tooth movement, while the occlusal contact with the mesial paracone flank expands lingually onto the mesial protocone flank, with both areas expanding towards the carnassial notch of the lower molar. With this contact, the distal trigonid blades of all lower carnassials perform a cutting function during further tooth movement. In addition to the cutting contacts that are calculated at the mesial and distal trigonid flanks, occlusion also occurs on the talonid. At timestep 91, the first contact between the praemetacrista of M3 and the posthypocristid of m3 occurs. Further upwards movement of m2 results in contact between the praemetacrista of M2 and the posthypocristid of m2 at timestep 100. Initial contact between the postparacrista of M3 and the praehypocristid of m3 occurs at timestep 103. A similar contact at timestep 110 occurs between the postparacrista of M2 and the praehypocristid of m2. With further upwards movement of the lower jaw, the protocones of M2, M3 and M4 move into the talonid basins of the antagonistic lower molars. Occlusal contact in the respective talonid basins successively occurs with the occlusion of the buccal entoconid flank and the postprotocrista. This contact occurs between M3 and m3 in timestep 110, between M2 and m2 in timestep 117 and between M4 and m4 in timestep 131. The calculated contact area shifts into the talonid basins of all lower molars and onto the buccal protocone flank of the upper molars with further upwards movement of the lower jaw. This upwards movement is stopped at timestep 162, when the point of centric occlusion is reached.
Thylacinus cynocephalus (highly carnassialized dentition with trenchant heel)
For the OFA analysis of Thylacinus cynocephalus, specimen ZMB_Mam_036877 was chosen. The complete chewing path is comprised of 168 steps and consists of one single phase until the point of centric occlusion is reached (Fig. 5b). Initial occlusal contact occurs between the metacrista of M3, starting on the buccal side in proximity to the metastyle, and the distalmost point of the m4 paracristid, in proximity to the apex of the paraconid. With further upwards movement of the lower molars, this contact area expands in mesial direction towards the carnassial notch of m4 and in direction of the metacone of M3. In timestep 18 the first contact between the M3 metacone and the m4 protoconid occurs, marking a second point of occlusion between the M3 and m4 carnassial blades. Both contact areas keep expanding on the occluding flanks and approach each other with further tooth movement, eventually wrapping around the carnassial notch of the lower molar and fusing in timestep 58. In timestep 31, occlusal contact occurs between the mesial paracone flank of M3 and the distal trigonid flank of m3. With further tooth movement, this contact area expands along the praeparacrista and postparacrista of M3 and along the distal trigonid flank of m3 in cervical direction. This occlusal contact remains up until timestep 120. In timestep 61, two points of contact between the carnassial blades of M2 and m3 are detected. The first occurs on the buccal side, in proximity to the metastyle and the protoconid. The second contact occurs on the lingual side, in proximity to the metacone and the paraconid. Both contacts expand with further tooth movement, approximating each other along the metacrista and the paracristid. Eventually, they wrap around the carnassial notch of m3 and fuse in timestep 99. First contact between the mesial paracone flank of M2 and the distal trigonid blade of m2 occurs in timestep 62. With further tooth movement, the area of occlusal contact expands along the postparacrista and the praepacacrista of M2 and expands in cervical direction of both antagonistic flanks and remains up until timestep 127. In timestep 86, the first occlusal contact between the carnassial blades of M1 and m2 is detected. It occurs on the buccal side of the blades between the metastyle of M1 and the protoconid of m2. With further upwards movement of the lower molars, this contact area expands in lingual direction along the metacrista and the paracristid. A second point of contact on the lingual side is detected in timestep 97. It occurs between the metacone of M1 and the paraconid of m2. With further tooth movement, this contact expands in lingual direction. Both areas of contact approximate each other in the following timesteps and merge in timestep 118, wrapping around the carnassial notch of the lower molar. The first contact between the mesial paracone flank of M4 and the distal trigonid flank of m4 occurs in timestep 53. This contact remains during most of the rest of the chewing path, with the distal trigonid flank of m4 occluding along the paracone of M4 up until 15 timesteps before centric occlusion. Eventually, the contact wraps around the paracone and covers the hypoflexid. In addition to the trigonids occluding with the paracones and metacones, there are occlusal contacts between the talonids and the paracones and metacones. The first contact occurs in timestep 63 between the distal talonid flank of m3 and the mesial metacone flank of M3. It starts on the lingual side, along the praemetacrista in proximity to me metacone and along the posthypocristid in proximity to the hypoconulid. With further tooth movement, this occlusal contact expands in buccal direction along the praemetacrista and along the posthypocristid towards the hypocone. This occlusion remains until timestep 112. In timestep 100, the first occlusal contact between the distal paracone flank of M3 and the mesial talonid flank of m3 is detected. This contact area remains small and is only active for a shorter duration, up until timestep 136. The first occlusal contact between the distal talonid flank of m2 and the mesial metacone flank of M2 occurs in timestep 107 on the lingual side. The area of contact expands with further tooth movement along the praemetacrista in lingual direction from the metacone and from the hypoconulid towards the hypoconid. It remains active until timestep 131.The mesial talonid flank of m2 occludes with the distal paracone flank of M2 first in timestep 133. The area of contact remains small and is active until timestep 155.