Masillamys, TOBIEN, 1954

Vianey-Liaud, Monique, Marivaux, Laurent & Lehmann, Thomas, 2019, A Reevaluation Of The Taxonomic Status Of The Rodent Masillamys Tobien, 1954 From Messel (Germany, Late Early To Early Middle Eocene, 48 - 47 M. Y.), Fossil Imprint 75 (3 - 4), pp. 454-483 : 471-477

Masillamys mattaueri ( HARTENBERGER, 1975)

Text-figs 10 , 11

R e m a r k s. We revise and redescribe the type population of M. mattaueri, from Mas de Gimel, and Naples (same stratigraphical level) in order to apply an accurate terminology and avoid subjectivity. Owing to Escarguel (1999), the species M. mattaueri is present in the ‘ageian’ fauna (early Eocene, MP?; Paris Basin), the localities of Saint-Agnan, Grauves, Prémontré (early Eocene, MP 8–9, MP 10; Paris Basin), Mas de Gimel (type population), Naples, Azillanet, Mailhac and Bellevue (early Eocene, MP 10; Languedoc, Southern France) and Vielase (earlymiddle Eocene, MP 10/11; Quercy, France). The M2 referred to this species from Prémontré ( Escarguel 1999: pl. 24g) shows a crown relatively flat and the main cusps not as bulged as for M. mattaueri. Moreover, the preprotocrista, protocone, postprotocrista, endoloph and hypocone are aligned on the lingual border of the tooth, and the sinus is absent, features not found in typical M. mattaueri. The upper teeth from Mailhac (Aude, France) are too small to be representative of M. mattaueri. The material from Southern France will be revised later.

Masillamys cf. mattaueri from Vielase (Quercy). The features used to justify the inclusion of this species within the genus Masillamys are not unique apomorphies, like the bulged cusps and the relatively low crown, the break of the mesial ectolophid or the posterolophid break between the hypoconulid and the entoconid ( Escarguel 1999: 224), or the development of a short mesoloph, or of a stretched and protruding paraconule. Most are seen in all the basal Theridomorpha. The absence of connection between the metaconule and the protocone, postprotocrista or hypocone is not general neither in the type population of M. mattaueri (3/7 M1) and of M. beegeri and M. krugi (see description above and below), nor in the population from Vielase.

The well-developed hypocone is at same height than the protocone, with high lingual and buccal margins; on m1–3, the postprotocristid is frequently strong towards the talonid basin together with a strong entolophid. The increase of size from m1 to m3 is not seen in the type population ( Escarguel 1999: 225).

For us, if the species from Viélase belongs undoubtly to Masillamys , there are some differences with M. mattaueri, like the more numerous strong and higher extra-ridges, the size slightly smaller and the increase of size from m1 to m3. It is the reason why we consider it as M. cf. mattaueri.

The jaw of Decticadapis sciuroides from Basin de Paris (‘ageian’ fauna). This jaw was referred to M. mattaueri ( Escarguel 1999: 109, 146, 154, 214, 216, 225, pl. 24i, j). The strong entoconid, the well-defined hypoconulid, the absence of any entolophid, the short oblique postprotocristid and the strong mesoconid are rather features characterizing Euromys thaleri (Vianey-Liaud and Marivaux, in prep) than Masillamys .

R e f e r r e d m a t e r i a l. Montpellier University, Institut des Sciences de l’Evolution (ISE-M). From Mas de Gimel locality (MGL).

H o l o t y p e. MGL 225 ( Hartenberger 1975: pl. 1, fig. 17).

Ty p e l o c a l i t y. Mas de Gimel (Montpellier, Languedoc, France; early middle Eocene, MP 10).

O t h e r l o c a l i t i e s.?Saint Agnan (Paris Basin,

MP 8–9), Grauves (Paris Basin, MP 10).

O r i g i n a l d i a g n o s i s. Species slighly larger than Microparamys russelli and more evolved. Ectolophid and transverse ridges well-developed on lower teeth. On upper teeth, strong hypocone and weakly marked sinus. ( Hartenberger 1975: 784, translation from French).

P r e v i o u s e m e n d e d d i a g n o s i s. Small sized species of the genus Masillamys larger than Hartenbergeromys hautefeuillei and Pantrogna marandati. P4 and p4 of large size relative to molars. DP4 strongly molarized; hypocone very lingual; anterior part of P4 reduced; hypocone weak or not distinct from the posterior cingulum. M1–2 with strong hypocone, conules and mesostyle; lingual sinus [= anteroflexus = anterosyncline] transverse weakly marked; posterior cingulum much reduced; metacone clearly more lingual than paracone. M3 with conules developed; lingual sinus and mesostyle marked. Trigonid of dp4 bicuspidate; ectolophid and posterior cingulid developed and continuous. Trigonid of p4 unicuspidate; complete ectolophid, lined by a low central ridge descending from the metaconid to the talonid. On m1–2, anterolophid and metalophid complete and high, closing the talonid basin; posterior arm of the protoconid not reaching the mesoconid; posterior cingulid deeply separated from the hypoconulid and entoconid. Trigonid of m3 open; posterior arm of the protoconid directed to the entoconid; entoconid isolated, sharp and massive. ( Escarguel 1999, translation from French).

N e w e m e n d e d d i a g n o s i s. Species of Masillamys smaller than M. beegeri and M. krugi, and larger than M. parvus, with M1 slightly longer than M2. DP4 without ectocingulum. P4 with very low anteroloph; differs from P4 of M. krugi and M. beegeri in the paracone slightly stronger than the metacone, the paraconule present and strong; the preprotocrista and postprotocrista aligned obliquely, whereas they are mesiodistally aligned for M. krugi, and making an obtuse ‘V’ for M. beegeri. Buccal metaloph weakly connected to or separated from the metaconule. On M1, protocone slighly lingual with respect to the hypocone, whereas it is at the same level as the hypocone on the other species of Masillamys . On lower teeth, ectolophid longer than in M. beegeri; lingual and buccal parts of the entolophid rarely joined and lingual part often double; postentocristid absent.

M a t e r i a l a n d m e a s u r e m e n t s. See Tab. 1 and

Text-figs 8 , 9 .

Type. L = 2.20 mm; Wtri = 1.90 mm; Wtal = 1.92 mm;

Ltri = 1.07 mm ( Escarguel 1999: pl. 23, figs a, b).

D e s c r i p t i o n. Upper teeth. See Text-fig. 10 .

DP4. Only three DP4 are available. The parastyle is swollen and curved on MGL 624 and 634, less on the bud MGL 630. The three teeth display a swollen anterostyle at the lingual end of the anteroloph. The anteroflexus is relatively wide mesiodistally. The postparacrista and premetacrista are present. There are one or two mesostyles prolonged by two short buccal mesolophs. The protoloph is tranverse buccolingually on the two first and oblique postwardly on MGL 630. This protoloph is weakly connected to the rounded protruding paraconule. This paraconule is stronger on MGL 630 than on the others. It is connected to ( MGL 624), directed to ( MGL 634) the extremity of the anterior arm of the protocone. On MGL 630, it is weakly attached to the protocone by a low lingual protoloph. The buccal metaloph is transverse buccolingual on MGL 624; it shows two branches on MGL 634: the distal one (metalophule II) is curved to the posteroloph; the mesial one (metalophule I) is weaker and linked to the metaconule. Metalophule I and II are present on MGL 630, but the metalophule II does not reach the posteroloph. The low and weak lingual

1.75 1.8 1.85 1.9 1.95 2 2.05 2.1 2.15 2.2 2.25 2.3 2.35 2.4 2.45

metaloph is directed from the base of the metaconule to the beginning of the endoloph or ends at the level of the postprotocrista, thereby leaving the metaconule separated from the protocone along the main part of its elevation. A median arm of the prococone (protocrista) is distinct on MGL 630. The metaconule is stronger than the paraconule; the former is doubled buccally on MGL 630. The hypocone is more lingual than the protocone, and the sinus below the endoloph is narrow and very shallow. The posteroloph is slighly swollen lingually (posteroconule) and relatively short, ending slighly buccally at the level of the metalophule II. The posteroflexus is open buccally. There are a few low and slender extra-ridges within the mesoflexus (one to two from the buccal protoloph, one to two from the mesial metaconule flank).

P4. Only five P4 are available, among them one is damaged. The four others show shape variation associated with morphological differences. MGL 609 (figured in Escarguel 1999) and MGL 629 are trapezoidal, but much narrower mesiodistally than MGL 608; MGL 610 is narrow and oval. It is not possible to decide if these differences reflect distinct species, because there are too less material. Two molars, one M1 ( MGL 651) and one M2 ( MGL 615) showing a similar pattern of wear of MGL 629, could belong to the same individual.

The anteroloph is always very low; it is adorned to the mesial flank of the teeth on three specimens, and more distinct from this flank on MGL 609 . It appears longer on MGL 609 and 629, reaching the mesiobuccal corner of the paracone; it is shorter buccally and weaker on the two others, their lingual end being reduced. On MGL 629 , the anteroloph is discontinuous, with a break lingual to the parastylar area, and another lingual to a worn flat enlarged area overflowing (projecting) at the level of the paraconule. The paracone is thicker than the metacone on MGL 605 and 610, less thick to equal on MGL 609 and 629. The postparacrista, connected to the mesostyle, is more ( MGL 609 ) or less ( MGL 629 and 610) displaced lingually, curving then buccally towards the mesostyle; it is rather convex on MGL 608 . This postparacrista is lined by a low and short ectocingulum, relatively strong on MGL 629 , weak on MGL 609 , reduced to a trace on MGL 610 , and absent on MGL 608 . The mesostyle is prolonged by a short and thin buccal mesoloph. The buccal protoloph is short and the paraconule distinct, facing or attached to the mesial extremity of the preprotocrista on MGL 610 and 608; it is longer on MGL 609 and 629, on which the paraconule is indistinct, its flat area being worn. On MGL 609 , there are four low ridges converging to the basin, two from the postparacrista, being parallel to the mesoloph, one from the distal flank of the paracone, and another from the protoloph. On MGL 629 , there is one extra-ridge only from the postparacrista, and it is blunted. Extra-ridges are also present on MGL 610 , but shorter; only one thick and bifid is present along the paracone of MGL 608 . The premetacrista is short and thick on all specimens. The buccal metaloph is short, thinning at the metaconules area, and its connections vary. On MGL 608 , it connects to the buccal extremity of the short posteroloph (metalophule II) and more mesially (metalophule I) to the metaconule. On MGL 610 , there is a very short ridge towards the posteroloph, and another ridge, which is longer and slighly stronger towards the large metaconule. On MGL 609 and 629, there is no connection with the long posteroloph, and the thick metalophule II is directed to the metaconule (609), or attached to it ( MGL 629 ). For all specimens, the metaconule is bulged and strong, but it shows singularities on MGL 609 and 629. On MGL 609 , the metaconule area is elongated obliquely, its distal extremity reaching the posteroloph, and its mesial one connecting the apex of the protocone. On this specimen, one low extraridge occupies the same position as the ‘metalophule I’. There are also one to two extra-ridges extending from the metaconule towards the basin, as found on the other P4; finally, a small extrametaconule is present lingual, and it is weakly linked to the extremity of the postprotocrista. On MGL 629 , the metaconule is duplicated, the more buccal is aligned with the metacone-buccal metaloph, and then the larger second is placed in between the first and the protocone: it is much worn, and separated by a notch from the apex of the protocone. Both show thin ridges connected to the lingual part of the posteroloph. The endoloph is not distinct, the hypocone being close to the distal end of the postprotocrista. The hypocone is small, but more ( MGL 608 and 629) or less ( MGL 609 and 610) distinct. The buccal roots are visible and separated on their upper parts, below the crown for MGL 608 , and fused on MGL 609 and 629. They are not preserved on MGL 610 .

M1. Seven molars were referred to M1; among them, two are missing in the collection. Our description is therefore based on five M1. All have the protocone and hypocone along the same mesiodistal axis, and buccally, the metacone is placed only slightly lingual to the paracone.

Three ( MGL 604, 605 and 650) are similar in shape: they are trapezoidal, with the anteroloph + parastyle projecting mesially, whereas the posteroloph is straight transversely. The parastyle area is elongated and only slighly swollen; it ends lingually by an anterostyle, which connects the extremity of the preprotocrista. The latter is nearly aligned with the postprotocrista, both making a wide angle with the protocone. A very shallow antesinus is well marked on the unworn MGL 604. The shallow and narrow sinus underlines a short endoloph, which is only slightly lower than the main cusps ( Text-fig. 10h, i, j ). As seen on the unworn tooth, the hypocone is isolated, i.e. it has no well-developed pre- and e2 – buccal aspect, e3 – occlusal view. f) MGL 629, right P4; f1 – occlusal view, f2 – lingual aspect, f3 – buccal aspect. g) MGL 651, left M1; g1 – occlusal view, g2 – lingual aspect, g3 – buccal aspect. h) MGL 604, left M1; h1 – occlusal view, h2 – lingual aspect, h3 – buccal aspect. i) MGL 628, left M1; i1 – occlusal view, i2 – lingual aspect, i3 – buccal aspect. j) MGL 605, left M1; j1 – occlusal view, j2 – lingual aspect, j3 – buccal aspect. k) MGL 606, left M2; k1 – occlusal view, k2 – lingual aspect, k3 – buccal aspect. l) MGL 602, left M2; l1 – occlusal view, l2 – lingual aspect, l3 – buccal aspect. m) MGL 622, left M2; m1 – occlusal view, m2 – buccal aspect, m3 – lingual aspect. n) MGL 614, left M3; n1 – occlusal view, n2 – lingual aspect, n3– buccal aspect. o) MGL 611, left M3; o1 – occlusal view, o2 – lingual aspect. Scale bar 1 mm.

post-hypocristae. The short posteroloph is swollen lingually in a small posteroconule. On the other teeth, which are worn, these structures are connected. The anteroflexus is wide, compared to the narrower posteroflexus. The paracone is prolonged lingually by a transverse protoloph, which becomes thin and curves to the protruding paraconule. It bears a plunging postprotocrista, the buccal end of which is concave and separated from the mesostyle by a slot. There is a weak extra-ridge descending from the buccal protoloph to the anteroflexus, parallel to the paraconule; it is better visible on the two worn teeth. Distally, there are one ( MGL 650) to two extra-ridges descending to the centre of the mesoflexus. The lingual protoloph is linked to the summit of the protocone ( MGL 604) or to the preprotocrista (the two others). The mesostyle is unique; it is isolated or underlined by a small ectocingulum ( MGL 605 and 650); it is slighly buccal to the paracone-metacone. It prolonges lingually in a single or double ( MGL 650) mesoloph. The short premetacrista + metacone + buccal metaloph make an arch. At its lingual end, there is, distally, a thin and low connection with the metaconule; mesially, a thicker and longer distomesial extraridge descends in the basin. The metaconule is bulged, much stronger than the paraconule. It can bear one more centripetal extra-ridge. A very weak ridge (lingual metaloph) connects the metaconule to the postprotocrista. The surrounding crown enamel is rough. There are rare short extra-ridges in the mesoflexus, or undulations along the inner borders of the anteroloph and posteroloph on MGL 650.

MGL 628 is less trapezoidal, but as the parastyle is long and swollen, and the paracone and metacone on the same mesiodistal line, it is clearly a M1. It is not worn, and the extra-ridges appear clear and more numerous – as well in the mesoflexus as on the mesial flank of the protoloph or the distal flank of the metaloph and metaconule –, than on the three other M1 ( MGL 604, 605 and 650). Therefore, there is a well-defined metalophule I, and a junction of the metalophule II with the posteroloph. There are two successive metaconules; the buccalmost is the weaker, stretched in a distal ridge, the stronger is the lingualmost, which bears two distal and two mesial extra-ridges. One can see a short posthypocrista. The mesostyle is double, and the mesoloph relatively long, as it is fused to low granules aligned into the mesoflexus. The other features of this tooth are similar to those described above for the other teeth.

MGL 651 has the same pattern of wear as that of the MGL 629 P4, and could belong to the same individual (as the MGL 615 M2). It is trapezoidal but narrower than the other teeth. As it is worn, the connections between the different structures and the extra-ridges are hardly visible. However, it appears that the parastyle turns to fuse with the buccomesial border of the paracone, and the anteroloph is thickened at its junction with the preprotocrista. The postparacrista is scarved by a short buccal notch; it is separated from the parastyle by a slot and the unique mesostyle is prolonged in a short mesoloph as for the other teeth. The paraconule is protruding and the protoloph is connected to the preprotocrista. Pre- and post-protocristae are less diverging than on the other teeth. One can distinguish a metaconule similar in size to the paraconule. The metaconule is included within the metaloph, which is connected both to the posprotocrista and to a not well-defined endoloph-hypocone.

M2. Six molars were previously identified as M2, one being strongly digested. Our description is therefore based on five M2. All bear a protocone that is situated more lingual than the hypocone. Similarly, the metacone is placed slighly lingual to the paracone, but always more than on M1. Therefore, the mesial width is larger than the distal one.

Five ( MGL 602, 606, 615, 618 and 622) have a similar shape, bearing a straight anteroloph leaving the anteroflexus open buccally. On MGL 623, the anteroloph is somewhat digested mesiobuccally and buccally, it turns to fuse with the buccomesial corner of the paracone. The preprotocrista is long and thick, and the postprotocrista and endoloph are shorter than on M1. The hypocone is only slighly larger than the anterostyle, and swollen at the end of the preprotocrista, as seen on the unworn MGL 602. The protoloph is straight until the paraconule, then oblique to the middle of the protocone ( MGL 602, 606, 622 and 623), or more mesial on the preprotocrista. The paraconule is often smaller than the main metaconule, sometimes only slighly protruding ( MGL 618 and 622). On the heavily worn MGL 615, its most worn area (dentine released by wear at the level of the paraconule) appears larger than the metaconule area. The postparacrista joins the mesostyle (except on MGL 615). The latter can bear one ( MGL 602, 622, 623 and 633) or two ( MGL 606 and 618) short mesolophs. The premetacrista can be absent (? MGL 615), short ( MGL 618, 622 and 623), moderate ( MGL 602) or long ( MGL 606). MGL 606 displays the most lingual metacone and then the shorter posteroloph. On MGL 622, the metacone is displaced lingually and surrounded buccodistally by the posteroloph. The metaloph is lingually isolated from the lingual cusps on the main part of its height. However, there are very low connections from the postprotocrista, the endoloph or/and the hypocone to the base of the metaconule ( MGL 602, 615 and 623). The bulged metaconule is single ( MGL 606, 615 and 618) or doubled buccally ( MGL 602, 622 and 623). There are four distomesial extra-ridges (two descending from the mesial flank of the metaloph, one from each metaconule to the mesoflexus ( MGL 602 and 623); there are three mesiodistal extra-ridges from the protoloph distal flank and one from the paraconule ( MGL 602 and 622). On MGL 606, two extra-ridges descend from the distal flank of the protoloph, one from the paraconule and one from the metacone-buccal metaloph, and two from the unique metaconule. The mesial flank of the paraconule displays weak undulations on MGL 623 to weak extra-ridges on MGL 606.

M3. Nine molars were identified as M3; two are badly damaged and their structures hidden ( MGL 631 and 638), the mesial border of MGL 621 is broken, and MGL 234 is strongly worn. The anterostyle is present at the preprotocrista/anteroloph junction. The parastyle is faintly swollen; it is separated buccally from the paracone. The latter is the highest cusp, prolonged by a strong postparacrista, which joins a unique ( MGL 613), double ( MGL 621 and 627) to tripled ( MGL 611 and 614) mesostyle. One to three short mesolophs are present, the most distal reaching the metaconule on two teeth ( MGL 611 and 613). Mesial and distal extra-ridges descend from the buccal protoloph. The paraconule displays also such ridges; the mesial one allows its connection with the anteroloph on MGL 611 and 627. There is a slot or a weak connection between the paraconule and the thick lingual protoloph, attached to the middle of the protocone or to its anterior arm. There is a long curved low cingulum from the most distal mesostyle to the hypocone; this cingulum being expanded posteriorly on all the M3 except on MGL 627 where it it less expanded posteriorly. The metacone can be double ( MGL 614 and 621). The hypocone is particularly reduced, and the endoloph can be distinct. The sinus is weak or absent. The metaconule is slighly bulged ( MGL 613, 621 and 627), or stretched and indistinct from the centripetal extra-ridges ( MGL 611 and 614).

Lower teeth. See Text-fig. 11.

p 4 . Only two p4 are available. The posterior root is flattened posteriorly, and the two roots are fused at least at their upper part, below the crown. The metaconid area (metaconid + it arms + protocristid, until the gutter of the mesoflexid) relative to the posterior part of the tooth (from the bottom of the mesoflexid slot to the distal border, appears shorter than on Pantrogna . As a result, the postmetacristid is shorter. The metaconid is more median (entirely for MGL 641; less for MGL 220). One mesiodistal extra-ridge descends from the metaconid apex to the bottom of the mesoflexid. Lingually, the postmetacristid is higher, and stops at a narrow slot, which represents the lingual opening of the mesoflexid. Buccally, the protoconid is present but reduced, lower than the metaconid, and attached to it by a short metalophid; following the protoconid, the postprotocristid goes mesiodistally to the mesoconid. A very narrow slot marks the contact postprotocristid-mesoconid. There is no distinct mesolophid and only a short ectomesolophid. There is no strong cingulid on the buccal slope of the protocristid and sinusid: only two short sloping ridges on MGL 641, and wrinkles on MGL 220. The entolophid is made of two parts, aligned obliquely from the entoconid to the postmesoconid or to the prehypocristid. The lingual half is fused to a short extra-ridge, making a connection with the mesiodistal extra-ridge of the metaconid on MGL 641. It is free on the other teeth. As seen on MGL 220 (the less worn), the prehypocristid is thin, short and distinct from the low and interrupted distal ectolophid. The hypoconulid is subsumed within the posterolophid, marked only by a thickening. The posterolophid is well separated from the entoconid on MGL 220; it weakly connects to a short postentocristid on MGL 641. The buccal surface of enamel is wrinkled, mainly on the sinusid flanks.

m1–m2. Six teeth from Mas de Gimel are m1 of M. mattaueri, and seven are m2. MGL 219 previously considered as a m2 is identified here as a m1 of another species, probably belonging to the genus Pseudoparamys ( Tab. 1). The shape and size differences between m1 and m2 are rather minimal. The m1 are only slighly narrower than the m2 ( Text-fig. 9 ), and even two couples of m1–m2 are of same size ( MGL 612 m 1 and MGL 228 m 2; MGL 226 m 1 and MGL 225 m 2). On m1, the metaconid is slighly higher than the entoconid, and occupies a slighly more buccal position; but this is not quite evident, due to various states of wear and preservation. The hypoconid is also slighly more buccal than the protoconid on m1, and at the same level on m2.

Lower molars have generally a mesial arm (premetacristid) plunging to the straight linguobuccal anterolophid, which ends at the mesial flank of the protoconid, thereby closing the anteroflexid buccally. There is neither an antesinusid nor a swollen anteroconid. The anterolophid is as high as the metalophulid I and posterior arm of the hypoconid, as seen on the type and on weakly worn teeth. When the teeth are not too much heavily worn, it is possible to see that the transverse buccal metalophulid I joins the lingual metalophulid I, as on the type. On MGL 226 , another linguobuccal ridge can be observed between the mesial premetacristid and the lingual metalophulid I. One to four mesiodistal low to very low extraridges descend from the lingual metalophulid I and from the buccal metalophulid I to the bottom of the talonid basin. The postmetacristid ridge descends moderately steeply to the mesoflexid lingual opening, which can be marked by a narrow and shallow slot. There is a swelling at the end of the postmetacristid (a kind of mesostylid), which can make a short flat on the lingual aspect; this flat being much less developed than in M. krugi. It is followed by a short lingual mesolophid on some teeth ( MGL 226 , 227 , 231 and 233). The long oblique postprotocristid is strong, ending in a premesoconid swelling, weakly connected to the short mesial ectolophid. The weakly bulged mesoconid bears a more or less long ectomesolophid. Postprotocristid, mesial ectolophid and mesoconid are nearly aligned obliquely, whereas the distal ectolophid is offset lingually and joins the short prehypocristid. Buccally, the sinusid is wide and asymmetrical; its flanks bear extra-ridges and sometimes a sloping postprotoconid spur or prehypoconid spur. The mesoconid rarely bears a short mesolophid ( MGL 222 ). Its distal extremity bears a short ridge linked to a strong postmesoconid swelling or ridge, which is separated ( MGL 222 , 227 , 233 and 665) or faintly connected to the lingual entolophid (all the other teeth), making a nearly continuous entolophid. The latter is however lower than the other transverse lophids. The short distal ectolophid is weaker than the mesial one, more often broken on weakly worn teeth. The prehypocristid is short and weak. The posteroflexid is wide, due to the lack of connection of the entolophid with the hypoconid or with its prehypocristid. The posthypocristid is thick and high with respect to the hypoconulid. The latter is bulged and slighly higher than the posthypocristid. In the continuity, the short posterolophid is much lower, ending at the base of the entoconid, thereby living the posteroflexid open lingually. The enamel borders of the crown are rough and sometimes wrinkled. There are also some low granules and wrinkles in the flexids, more or less related to the main extra-ridges .

m3. Among the five teeth measured as m3 of M. mattaueri from Mas de Gimel ( Escarguel 1999: 330), only three are available, two are lacking ( MGL 224 and 645). There are also one much worn ( MGL 232) and one damaged ( MGL 639) m3. Two relatively well-preserved ( MGL 619 and 632) show few differences from the m2, out of the lower metaconid and the posterolophid shorter to absent. The buccal metalophulid is well developed and transverse as on m1–m2. The lingual metalophulid is less developed, reduced and never joining the buccal metalophulid, or replaced by mesiodistal extra-ridges. The postprotocristid + mesoconid + ectolophid are oblique. The extra-ridges are as on the other molars. The m3 MGL 646 is larger than the others, with a flatter crown, the entoconid more isolated and the hypoconulid doubled.

Figures

Text-fig. 10. Upper teeth of Masillamys mattaueri (HARTENBERGER) from Mas de Gimel (Hérault, France; MP 10, late early Eocene). a) MGL 624, right DP4; a1 – occlusal view, a2 – buccal aspect, a3 – lingual aspect. b) MGL 634, right DP4; b1 – occlusal view, b2 – buccal aspect, b3 – lingual aspect. c) MGL 608, right P4; c1 – occlusal view, c2 – lingual aspect, c3 – buccal aspect. d) MGL 610, right P4; d1 – occlusal view, d2 – lingual aspect, d3 – buccal aspect. e) MGL 609, left P4; e1 – lingual aspect,

Text-fig. 11. Lower teeth of Masillamys mattaueri (HARTENBERGER) from Mas de Gimel (Hérault, France; MP 10, late early Eocene). a) MGL 641, left p4; a1 – occlusal view, a2 – buccal aspect, a3 – lingual aspect. b) MGL 220, right p4; b1 – occlusal view, b2 – buccal aspect, b3 – lingual aspect. c) MGL 233, right m1; c1 – occlusal view, c2 – buccal aspect, c3 – lingual aspect. d) MGL 665, right m1; d1 – occlusal view, d2 – buccal aspect, d3 – lingual aspect. e) MGL 225, holotype, right m2; e1 – occlusal view, e2 – buccal aspect, e3 – lingual aspect. f) MGL 222, left m1; f1 – lingual aspect, f2 – occlusal view, f3 – buccal aspect. g) MGL 231, right m2; g1 – occlusal view, g2 – buccal aspect, g3 – lingual aspect. h) MGL 646, left m3; h1 – buccal aspect, h2 – lingual aspect, h3 – occlusal view. i) MGL 619, right m3; i1 – buccal aspect, i2 – lingual aspect, i3 – occlusal view. Scale bar 1 mm.

Text-fig. 8. Bivariate graph (length/width) of upper teeth of Masillamys mattaueri (HARTENBERGER) from Mas de Gimel (Hérault, France; MP 10, late early Eocene).

Text-fig. 9. Bivariate graph (length/width) of lower teeth of Masillamys mattaueri (HARTENBERGER) from Mas de Gimel (Hérault, France; MP 10, late early Eocene).

Text-fig. 4. Bivariate graph (length/width) of the teeth of the three species of Masillamys from Messel.