Hartenbergeromys pailladensis, Vianey-Liaud & Lihoreau & Solé & Gernelle & Vautrin & Bronnert & Bourget & Vidalenc & Tabuce, 2024

Vianey-Liaud, Monique, Lihoreau, Fabrice, Solé, Floréal, Gernelle, Killian, Vautrin, Quentin, Bronnert, Constance, Bourget, Hélène, Vidalenc, Dominique & Tabuce, Rodolphe, 2024, A revision of the late early Eocene mammal faunas from Mas de Gimel and Naples (Montpellier, Southern France) and the description of a new theridomorph rodent, Geodiversitas 46 (10), pp. 387-422 : 405-410

Hartenbergeromys pailladensis n. sp.

( Figs 9 ; 10 ; Table 1 )

urn:lsid:zoobank.org:act:11CEEC60-37D4-4DF7-8092-A1B3923A8E32

Hartenbergeromys aff. hautefeuillei – Escarguel 1999: 209-210.

HOLOTYPE. — UM-MGL-601 : left M1.

TYPE LOCALITY. — Mas de Gimel (Hérault, France, late early Eocene, MP10).

OTHER LOCALITY. — Naples (Hérault).

DIAGNOSIS. — Hartenbergeromys with numerous thin high extra ridges on upper and lower molars. Crested cusps and complete pericingulum on upper molars. Metacone smaller than protocone and hypocone smaller than protocone on upper molars, anteroloph and posteroloph as high as the other lophs. Metaconid only slightly protruding in dp4 and p4. Protoconid stronger in molars than in dp4 and p4. Four main cuspids (proto-, meta-, ento- and hypoconid) crested, delimiting an incomplete pericingulid, due to the presence of the sinusid and of the narrow mesoflexid opening. Labial metalophulid I strong and generally short, never connected to a complete transverse lingual metalophulid I. Entolophid rarely complete, often connecting the mesoconid.

Differs from H. hautefeuillei and H. marandati by more crested cusps and cuspids, the development of the pericingulum, and the smaller metacone and hypocone on molars.

MATERIAL. — 24 specimens from Mas de Gimel and 27 from Naples (measurements in Table 1 ) are available in the collection.

REMARKS

Escarguel (1999: 200-210) described the type specimens of Hartenbergeromys hautefeuillei from the locality of Prémontré. In the same paper, he referred the specimens from Mas de Gimel and Naples as to Hartenbergeromys aff. hautefeuillei . Discussing the phylogeny of Theridomorpha, Vianey-Liaud & Marivaux (2017) followed the conclusions of Escarguel (1999) using the diagnosis of H. hautefeuillei including the features of the specimens from Mas de Gimel and Naples in their phylogenetic analysis ( Hartenbergeromys aff. hautefeuillei in Vianey-Liaud & Marivaux 2017: fig. 7). More recently, following a more detailed phylogenetic analysis including numerous early Eocene rodents ( Vianey-Liaud & Marivaux 2021), we reconsidered the material of Hartenbergeromys hautefeuillei from Prémontré, and we can highlight differences in morphological characters between the Mas de Gimel/Naples populations and that of Prémontré.

DESCRIPTION

Upper teeth

The crown is not very high, the lingual flank is slightly higher than the labial one and sometimes weakly wrinkled.

DP4. There are two available specimens, a worn right DP4 from Mas de Gimel (UM-MGL-647) and an almost unworn left DP4 from Naples (UM-NAP-57) ( Fig. 9A, B ). The first has a long anteroflexus and anteroloph ending lingually with a worn stretched anterostyle. This style is weakly attached to the preprotocrista. The protocone is worn following a plane inclined posteromesially from the indistinct endoloph, towards the anterostyle. The hypocone is worn symmetrically, sloping backwards to its junction with the lingual end of the posteroloph. It is only slightly smaller than the protocone. The paracone is slightly stronger than the metacone, but of same height. The labial protoloph bears a swollen worn paraconule, which is aligned labiolingually with it. The paraconule connects the preprotocrista close to the protocone summit with a short lingual protoloph. The labial metaloph, transverse, is short and separates from the metaconule. The latter is strong and obliquely stretched distomesially, towards its attachment with the postprotocrista, close to the protocone summit. The posteroloph ends at the level of the base of the labial metaloph, making the posteroflexus open labially.

P4. There are two available P4s, both from Naples (UM-NAP-58 and 59). Although they show the same characteristic globular morphology ( Escarguel 1999: 209), they differ by the morphology and nature of the mesial lophs. On UM-NAP-58 (pl. 22, fig. n in Escarguel 1999; here: Fig. 9D ) the anteroloph is absent; therefore, the anteriormost loph is made by the labial protoloph joining the preprotocrista. In UM-NAP-59 ( Fig. 9C ) instead the anteroloph is present and well distinct from the protoloph, which joins the preprotocrista closer to the protocone summit than on UM-NAP-58. A short mesoloph fills the labial part of the mesoflexus; it is separated from the mesostyle on UM-NAP-59, and linked to it on UM-NAP-58. On UM-NAP-59, it ends between the extremities of the extra ridges developed labially from the metaconule and distally from the labial part of the protoloph. A paraconule is present on UM-NAP-59 as developed as the metaconule. On both P4s, extra ridges descend from the conules and the protoloph to the mesoflexus. On UM-NAP-59, an anterolophule connects the paraconule to the anteroloph, and a posterolophule connects the metaconule to the posteroloph.

There is a pericingulum-like structure from the paraconepreparacrista, through the anteroloph, continuing to the preprotocrista, then the protocone-postprotocrista, turning distally at the level of a weak swelling, which resembles more a posterostyle than a hypocone, ending in the posteroloph up to the metacone flank. On UM-NAP-59, the postprotocrista and premetacrista are linked to the mesiodistally stretched mesostyle continuing labially the pericingulum. This is less continuous on UM-NAP-58, on which there are furrows between the mesostyle and the two main cusps.

M1-2. There are eight complete M1-2s available (six from Naples, two from Mas de Gimel; Fig. 9 A-E), among which it is difficult to separate M1 from M2, whereas it is relatively easy for H. hautefeuillei from Prémontré ( Vianey-Liaud & Marivaux 2021: 81). In the latter «the paracone is more labial than the metacone, but this metacone is even more lingual on M2 than on M1. The parastyle is thicker and more elongated or curved labially on M1; the hypocone (and not the protocone as it was incorrectly indicated in the 2021 paper, p. 81) is more reduced and labial on M2, and the posteroloph is shorter ». However, all the M1-2s from Naples and Mas de Gimel have a relatively short posteroloph, ending at the level of the labial part of the metaloph. Among them, the two upper molars from Mas de Gimel have a thicken and curved parastyle (M2: UM-MGL-606; M2: UM-MGL-790) and two of the molars from Naples (M1: UM-NAP-55; and M2: UM-NAP-47), whereas it is not distinct on the M1 UM-NAP-50 and the M1 or M2 UM-NAP-48. Protocone and hypocone are nearly at the same lingual level in all the M1-2s.

Apart from this weak difference between M1 and M2, what is striking in the upper teeth of H. pailladensis n. sp. is the development of the pericingulum including the anteroloph and the “internal cingulum” (terminology used in Escarguel 1999, fig. 5) encompassing the preprotocrista, the protocone, the posprotocrista, the endoloph and the hypocone, all aligned in continuity and with a nearly indistinct lingual sinus. The hypocone, quite smaller than the protocone, connects the posteroloph through a marked angle; this posteroloph is relatively shorter and slightly higher than the anteroloph. A narrow furrow marks the junction of the posteroloph with the distal flank of the metacone. The metacone is quite smaller than the paracone. The mesostyle can be stretched mesiodistally into two elements connected to the postprotocrista and the robust premetacrista, the whole forming the outer part of the pericingulum. Most often, at least one short mesoloph arises lingually from the mesostyle towards the metaconule without fusing with it. The paraconule is most often crescentshaped and directed mesiodistally towards the mesoflexus or/and the anteroflexus. Two to three low short ridges also descend from the protoloph towards the anteroflexus and mesoflexus, as well as from the protocone (protocrista). The ridge underlining the premetacrista-metacone-metaloph arch drops down to join the flank of the metaconule. The latter is crested with short ridges that are clearly visible on little worn teeth, one descending into the posteroflexus and attaching to the posterocingulum, the other, mediolabial, directed towards the mesoloph without joining it. On unworn teeth, like the holotype UM-MGL-601 ( Fig. 9E ), the pericingulum is overlying the flexi floor, and the four main cusps (paracone, metacone, protocone and hypocone), as well as the paraconule and metaconule are slightly protruding above the pericingulum level, all being of same height. The paracone, metacone, protocone and hypocone, as well as the paraconule and metaconule, protrude. Then the wear affects primarily the lingual half of the tooth, and highlights its labial half, the wear surface of the latter descending labiolingually from the labial cusps (UM-MGL-639, Fig. 9F ).

M3. There are three M3s from Naples (UM-NAP-52, NAP-56, NAP-64), one from Mas de Gimel (UM-MGL-626) ( Fig. 9 J-L). On all these teeth, the tiny hypocone is more lingual than the protocone. The M3s differ from the M1-2s in their triangular shape due to the quite more reduced and more labial hypocone. They display a complete pericingulum without discontinuities either at the junction posterolophmetacone-metaloph, or at the junction anteroloph-protocone. The mesostylar area is longer than on M1-2, bearing one (UM-NAP-52 Fig. 9K , UM-NAP-64, Fig. 9L ) to three (UM-NAP-56) short labial mesolophs.

Lower teeth

The crown has its lingual flank nearly as high as the labial one and rarely thinly wrinkled. The ectoflexid (sinusid) is always marked and on the lingual profile, the mesoflexid opening is narrow.

dp4. There are two available dp4s from Mas de Gimel, a damaged left one (UM-MGL-649) and a well-preserved right one (UM-MGL-664). On the latter ( Fig. 10A ), the trigonid is shorter labiolingually than the talonid; it is closed with a low premetacristid-anterolophid and the metaconid is only slightly protruding. The protoconid is slightly more distal. Protoconid and metaconid connect with the metalophid I, which limits the anteroflexid distally. From there, a bifurcate mesiodistal ridge descends labially to the mesoflexid. The postprotocristid, whose distal part is indistinct from the mesial ectolophid, joins the ectolophid bearing the mesoconid. Then at the level of the junction between the distal ectolophid and the prehypocristid, the entolophid develops up to the base of the entoconid. There the entoconid appears isolated, separated also from the posterolophid. The hypoconid is followed with a strong posthypocristid, and then a strong distinct hypoconulid precedes the short posterolophid. An additional extra ridge lies in the posteroflexid, parallel to the entolophid.

p4. There are five available p4s, three, damaged, from Mas de Gimel (UM-MGL-616, MGL-644, and MGL-786), two better preserved from Naples (UM-NAP-44 and NAP-53). The two well-preserved long roots of UM-NAP-44 fuse below the crown along the 1/3 to 1/2 of their height ( Fig. 10C ). As on dp4, the metaconid is slightly protruding, but more than the protoconid. The latter is crested similarly as other cuspids of the crown. As formerly stated ( Escarguel 1999: 210), the wrinkles are numerous along the distal slope of the trigonid and in the talonid, and one can recognize the metalophid I linking the protoconid and the metaconid, as well as the mesoconid and the ectolophid (UM-NAP-44; Fig. 10C ), and elements of the entolophid connected to the prehypocristid and the posterior cingulum on both. On UM-NAP-53, the postmetacristid ends distally in a metastylid swelling, separated from the mesostylid, which closes the mesoflexid lingually ( Fig. 10B ).

m1 or m2. There are ten m1-2s from Mas de Gimel (m1s: UM-MGL-620, MGL-637, MGL-648, MGL-652; m2s:

UM-MGL-618, MGL-625, MGL-635, MGL-653, MGL-750, MGL-751) and eight from Naples (m1s: UM-NAP-32, NAP-39, NAP-43; m2s: UM-NAP-33, NAP-34, NAP-35, NAP-40, NAP-41) ( Fig. 10 D-K). The only difference between m1 and m2 is the narrower labiolingual width of the anterolophid-trigonid of m1 compare to m2.

As for dp4 and p4, the metaconid is only slightly protruding, but the protoconid is stronger than on these teeth. The four main cuspids (proto-, meta-, ento- and hypoconid) are crested, and their shape appears clearly on unworn teeth, delimiting an incomplete pericingulid, due to the presence of the sinusid and of the narrow mesoflexid opening.

The preprotocristid, attached to the mesial flank of the protoconid is either separated from the (labiolingual) premetacristid or joins it to make a complete transverse anterolophid. Distal to it, the protoconid bears a strong labial metalophulid I, which is generally short, never connected to a complete transverse lingual metalophulid I. The only case of a connection is the m1 UM-NAP-43 ( Fig. 10E ). Descending along the labiodistal flank of the metaconid, there is rather one short oblique ridge, sometimes joining the mesiodistal ridges developed distally from the anterolophid. There can be several (one to three) of these ridges, and another developed from the labial metalophid to the basin ( Fig. 10 G-K). The postmetacristid can show a metastylid-mesostylid thickening, and can be prolonged in a short lingual mesolophid (UM-MGL-618, MGL-648; UM-NAP-41; Fig. 10G, D, J ). The protoconid is crested and stretched mesiodistally. It attaches to the mesial ectolophid through the postprotocristid. The mesoconid is aligned obliquely with the mesolophid. Distally, the mesoconid forms an angle with the distal ectolophid. The mesoconid makes another angle with the prehypocristid. The hypoconid is obliquely stretched to the posthypocristid.

The ridges are numerous in the basin, one of which derived from the mesoconid is a labial mesolophid. Another joins the distal ectolophid directly to the entoconid. This entolophid is either complete (UM-NAP-39, NAP-40 [ Fig. 10F ]) or broken in several elements (UM-NAP-35, NAP-41 [ Fig. 10H, J ]; UM-MGL-618 [ Fig. 10G ]). It connects to the posterolophid (UM-MGL-648 ( Fig. 5A ); UM-NAP-34) or to the distal ectolophid and the posterolophid (UM-MGL-618).

m3. There are four m3s from Naples (UM-NAP-36, NAP-37, NAP-38, NAP-46) and three from Mas de Gimel (UM-MGL-617, MGL-787, MGL-749) ( Fig. 10 L-O). The main difference between m3s and m1-2s is their narrower labiolingual width of the talonid.

The labial metalophulid I (named anterior arm of the protoconid in Escarguel 1999: 210) is rarely present, short and oblique mesiodistally (UM-MGL-617 and UM-NAP-38, Fig. 10L ). On the two same specimens, the lingual metalophulid I is like on m1-2 as oblique ridges descending on the metaconid lingual flank, and directed to the basin. On the other m3s, the metalophulid I is absent and therefore, the anteroflexid is not individualized. The anterolophid and the premetacristid do not join on UM-NAP-38, NAP-46 ( Fig.10 L-M) and UM-MGL-617, thus a mesiodistal furrow, bordered with mesiodistal ridges, opens the trigonid mesially. Instead, they join on UM-NAP-36 and NAP-37 ( Fig. 10O, N ). The postmetacristid shows a metastylid-mesostylid thickening, and is prolonged in a short lingual mesolophid (UM-NAP-36, NAP-37, NAP-46). A distolabial spur of the protoconid is present on UM-NAP-37, NAP-38, NAP-46 and UM-MGL-617. The postprotocristid,ectolophid, mesoconid, distal ectolophid and prehypocristid are like in m1-2. Numerous ridges converge into the talonid basin. Likewise, numerous ridges converge from the posterolophid to the posteroflexid.The entolophid is either discontinuous or continuous (UM-NAP-36, NAP-38; UM-MGL-617) and the most often connects the entoconid to the mesoconid. On UM-NAP-37, it connects the base of the entoconid and twice the posterior cingulum. The external walls of the unworn UM-NAP-46 are very finely wrinkled.

COMPARISONS AND DISCUSSION

DP4 of Hartenbergeromys pailladensis n. sp. differs from that of H. hautefeuillei by less salient cusps above the grinding surface, less well-defined lophs on unworn tooth, and less lingual hypocone relative to the protocone. P4 differs mainly in its pericingulum and the less salient main cusps and more horizontal wear pattern. Moreover, the endoloph and hypocone are indistinct on UM-NAP-58, NAP-59 whereas they are well marked on some P4s of H. hautefeuillei . The main differences with upper molars of H. hautefeuillei and H. marandati are the more crestiform than bulging cusps, the metacone and hypocone respectively smaller relative to the paracone and protocone; the complete development of a relatively high pericingulum, as well as the different mode of wear and the size of teeth clearly lower for H. pailladensis n. sp. The three species of Hartenbergeromys are quite similar in size. Nevertheless, molars of H. pailladensis n. sp. appear intermediate in size between those of the larger H. marandati and the smaller H. hautefeuillei . Regarding lower molars only, the main differences with H. hautefeuillei and H. marandati are the more crestiform than pointed bulging cusps. In H. pailladensis n. sp., the entoconid is crested and displays pre- and postentocristids, the crested hypoconid is prolonged to the posthypocristid; the crested protoconid and metaconid have pre- and postcristids.

Escarguel (1999) proposed that the specimens from Mas de Gimel and Naples he named Hartenbergeromys aff. hautefeuillei display a set of derived characters relative to H. hautefeuillei from Prémontré. He mentioned several characters, “making the population from Mas de Gimel and Naples even more derived than that of Prémontré” (very wrinkled enamel surface, anteroloph absent on P4, strongly developed lingual cingulum on upper molars, complete or almost complete hypolophid on m1-m3)”. These characters require some comments.

The absence of anteroloph on P4 is actually variable in Hartenbergeromys pailladensis n. sp., as well as in H. marandati and H. hautefeuillei ( Escarguel 1999: 202; Vianey-Liaud & Marivaux: 80-82). The entolophid (= hypolophid) in H. pailladensis n. sp. is neither more nor less complete than in the two other Hartenbergeromys species. Teeth enamel surfaces of H. pailladensis n. sp. are not much more wrinkled than H. hautefeuillei (see Vianey-Liaud & Marivaux 2021: 82-93). Finally, we agree with Escarguel (1999) regarding the strong development of crested cusps giving a pericingulum on upper teeth. This trait could be however related to a difference in eating habits with H. hautefeuillei , together with a chronological difference.

To conclude, Hartenbergeromys pailladensis n. sp. only occurs in Mas de Gimel and Naples whereas H. hautefeuillei occurs in Prémontré, Grauves, Saint-Agnan, and possibly Azillanet (pending new discoveries, the only two teeth from that locality are here attributed to H. aff. hautefeuillei ).

Figures

FIG. 9. — Upper deciduous (DP4), premolar (P4) and molars (M1-2-3) of Hartenbergeromys pailladensis n. sp. from the two closely related localities: MGL, Mas de Gimel (Hérault), and NAP, Naples (Hérault): A, UM-MGL-647, right DP4; A1, occlusal view; A2, lingual view; B, UM-NAP-57, enamel cover of a left DP4, unworn: B1, lingual view; B2, occlusal view; C, UM-NAP-59, left P4: C1, occlusal view; C2, labial view; D, UM-NAP-58, left P4, occlusal view; E, MicroCTScan of UM-MGL-601, holotype, unworn left M1: E1, occlusal view; E2, lingual view; E3, labial view; E’, same as E (UM-MGL-601), but drawings, to compare both figurations; F, UM-MGL-639, worn right M1: F1, occlusal view; F2, lingual view; G, UM-NAP-47, unworn left M1: G1, occlusal view; G2, lingual view; H, UM- NAP-55, right M1-2, moderately worn, roots partially preserved, occlusal view; I, UM-NAP-48, left M2, moderately worn, roots partially preserved: I1, occlusal view; I2, lingual view; I3, labial view; J, UM-NAP-56, left M3, weakly worn, roots broken; J1, occlusal view; J2, lingual view; J3, labial view; K, UM-NAP-52, right M3, nearly unworn: K1, occlusal view; K2, lingual view; K3, labial view; L, UM-NAP-64, right M3, nearly unworn, roots absent, occlusal view. Scale bar: 1 mm. The background of the profiles is greyed out. On Fig. F open cracks are filled with horizontal stripes.

FIG. 10. — Lower deciduous (dp4), premolars (p4) and molars (m1-2-3) of Hartenbergeromys pailladensis n. sp.from the two closely related localities: MGL,Mas de Gimel (Hérault), and NAP, Naples (Hérault): A, UM-MGL-664, right dp4, showing the diverging roots: A1, occlusal view; A2, labial view; A3, lingual view; B, UM-NAP-53,right p4, nearly unworn: B1, occlusal view; B2, labial view, enamel cover partially erased, dentine blackened; B3, lingual view; C, UM-NAP-44, left p4: C1, occlusal view; C2, labial view; C3, lingual view, enamel cover partially erased, dentine blackened; two strong vertical roots, fused at their upper part; D, UM-MGL-648, right m1, nearly unworn, MicroCTscan, occlusal view; D’, same as D, drawings; E, UM-NAP-43, left m1, nearly unworn, incomplete roots: E1, occlusal view; E2, labial view; F, UM-NAP-39, left m1, weakly worn, incomplete roots: F1, occlusal view; F2, lingual view; G, UM-MGL-618, worn left m2, occlusal view; H, UM-NAP-35, unworn left m2: H1, occlusal view; H2, lingual view; I, UM-NAP-33, moderately worn right m2: I1, occlusal view; I2, lingual view; J, UM-NAP-41, worn m2 with labial side damaged, occlusal view; K, UM-NAP-34, unworn right m2: K1, occlusal view; K2, lingual view; L, UM-NAP-38, right m3, occlusal view; M, UM-NAP-46, left m3, unworn: M1, occlusal view; M2, lingual view; M3, labial view; N, UM-NAP-37, left m3, weakly worn, incomplete roots: N1, occlusal view; N2, lingual view; O, UM-NAP-36, right m3: O1, occlusal view; O2, labial view. Scale bar: 1 mm. The background of the profiles is greyed out on E2, F2, H2, M2.

FIG. 5. — Hyaenodontidae and Carnivoraformes from Mas de Gimel:A, trigonid of right lower m1? of Matthodon peignei Solé,Marandat & Lihoreau,2020 UM- MGL-70 in occlusal (A1) lingual (A2) and labial (A3) views; B, left m3 of Leonhardtina meridianum Solé,Marandat & Lihoreau, 2020 UM-MGL-707 in lingual (B1) and occlusal (B2) views; C, talonid of a left m1 of Lesmesodon gunnelli Solé,Morlo,Schaal & Lehmann,2021 UM-MGL-36 in occlusal (C1) and lingual (C2) views; D, left M3 of Uintacyon cf. hookeri Solé, 2014 UM-MGL-108 in occlusal (D1) and labial (D2) views. Scale bars: A, 2 mm; B, C, 1 mm; D, 0.5 mm.