Protadelomys cf. alsaticus, Hartenberger, 1969

Vianey-Liaud, Monique & Hautier, Lionel, 2022, Revision of the genus PRotadelomYS, a middle Eocene theridomyoid rodent: evolutionary and biochronological implications, Swiss Journal of Palaeontology (8) 141 (1), pp. 1-98 : 65-67

? Protadelomys cf. alsaticus from Cuzal (Lot, Quercy)

Remarks

Tese rodents have been referred to as Protadelomys (cf.) alsaticus ( Marandat et al. 1993) based on the presence of frequent enamel wrinkles and size similarities, which are smaller than that of the teeth of P. lugdunensis .

Material and measurements (Additional file 5: S5, Fig. 41 Table 5).

Most of the teeth, except the two lower dp4, are slightly larger than the teeth of P. alsaticus from Bouxwiller ( Table 4). Te difference is only statistically significant for the m1 ( Table 8).

Morphological comparison

Upper teeth. ( Fig. 42a to m). Te two DP4 from Cuzal display some differences with P. alsaticus from Bouxwiller. On the DP4 from both localities, the protoloph is oriented forward and connects to the junction anteroloph–preprotocrista. Te paraconule is absent in the species from Cuzal whereas it is is always present in P. alsaticus from Bouxwiller. Two mesostyles and mesolophs are present on the two DP4 like in Bouxwiller. Contrary to P. alsaticus from Bouxwiller, the hypocone is as strong as the protocone, which is more lingual. Te metalophule I is not distinct, while it is on a few DP4 from Bouxwiller. Te metaconule is not bulged and reduced to extraridges, which join the hypocone and the posteroloph ( CUZ 176). In P. alsaticus , the metaconule is strong with no lingual connection or junction with the postprotocrista. Te P4 from Cuzal are triangular with a reduced hypocone, whereas the hypocone is less reduced in Bouxwiller. Te floor of the mesoflexus of the P4 is flatter and more wrinkled than in P. alsaticus . On CUZ 188, the anteroloph is very short and weakly swollen at the level of the anterostyle, which joins the preprotocrista, not on CUZ 177 and CUZ 189 Te paracone is slightly smaller than the metacone. A thin postparacrista plunges to the mesostyle area. On CUZ 188 ( Fig. 42d ), the buccal protoloph is forked, one part oriented forwards to the anterostyle, the other backwards, directed to the lingual metaloph. Tey are less distinct on the other P4 and correspond to low extraridges. Te P4 lack a paraconule. Te mesostyle prolongs in a mesoloph on CUZ 188 and 189, it is duplicated mesially on the former, and interrupted on CUZ 177. A short metalophule I joins the distal mesoloph on CUZ 188. Te metaloph II is thicker and directed towards ( CUZ 177) or connected ( CUZ 189) to the robust metaconule. Te latter is more ( CUZ 188) or less ( CUZ 177, 189) fused with the postprotocrista. A small ridge connects the metaconule to the hypocone, which is weak and stretched on CUZ 188.

Te upper molars of cf.? P. alsaticus from Cuzal display some variable features. On all of them, as well on the M1 as on the M2, the hypocone is only slightly less robust than the protocone. Te smallest M1 ( CUZ 154: Fig. 42 k , and 155: Fig. 42j ) have shorter protocone + pre- and post-protocristae, but the other features vary like in the other M1 from Cuzal ( CUZ 178, 181, 182, 186) and like in? P. alsaticus from the type locality, Bouxwiller, with numerous extraridges. Elsewhere, we noted a few differences with? P. alsaticus from Bouxwiller. Te size difference between the two main lingual cusps, the protocone and hypocone, is more important in typical alsaticus . Te paraconule and metaconule are present but less bulged than in the type population. In the upper molars from Cuzal, the protoloph connects the preprotocrista or the protocone; the buccal metaloph II is nearly always present and connects the hypocone and often both the posteroloph through mesiodistal extraridges ( CUZ 156, 178, 182); the extraridges are more numerous in the flexi; a metalophule I is present or sketched (6/8). A mediobuccal crest of the metaconule is generally present, merging with various extraridges. A narrow pinched sinus is more frequently present, below the endoloph. Te morphology of upper M3 (at least CUZ 180) is close to that of the large M3 from Bouxwiller.

Lower teeth. ( Fig. 42n to x). Te lower dp4 have a narrower pre-lobe, due to the absence of the protoconid and metalophulid I. Te protocristid is low, and an ectostylid limits the base of the sinusid on CUZ 187 ( Fig. 42n ). Te entolophid is low and weak. Te posterolophid is absent on CUZ 161 and replaced by a linguodistal notch. Like the dp4, the p4 differs from typical? P. alsaticus in the absence of protoconid and in the ratio of the length of the anterior lobe, markedly longer than the posterior lobe. Te anterior is delimited lingually by the metaconid + the postmetacristid and buccally by the mesiodistal protocristid + the postprotocristid + the ectolophid and mesoconid, the posterior lobe extends from the hypoconid, through the post-hypocristid + the hypoconulid + the posterolophid to the entoconid.

Unlike typical?without? P. alsaticus , the anterolophid is more often present as a lingual prolongation of the relatively bulbous anteroconid on m1 and m2. It is generally distinct from the premetacristid, which is generally absent. It connects to the metaconid flank only on a few worn teeth (m1, m2: CUZ 164). Like in typical alsaticus , the anteroflexid is closed distally by a complete (buccolingual) metalophulid I on lower molars. A low anterolophulid can divide the anteroflexid (m1–2: CUZ 168, 169, 170, 175; m3: CUZ 164).

Te path of the metalophulid I is more constant than in typical?without? P. alsaticus . It is complete in all cases, rectilinear from the anterior part of the metaconid to the protoconid, and slightly oblique mesiolingual to distobuccal. Its lingual part is never completely mesial, as it is typically in? without? P. alsaticus . Additional thin ridges (one to three) descend from the lingual metaconid flank to the talonid basin.

Te postprotocristid is strong, thick distally and oblique buccomesio-distolingually; it is always longer than the prehypocristid, like in typical? P. alsaticus . Tere is less variation in the ectolophid area, from the distal end of the postprotocristid to the mesial end of the prehypocristid. Te mesoconid occupies most of the ectolophid, which is short. Te direction of the ectolophid mesial part generally makes an angle with that of the postprotocristid. Similarly, its short distal part makes an angle with the prehypocristid; it is slightly lingual than the mesial one. Te mesial and distal parts are similar in height but low, seeming interrupted on unworn teeth. Te premesoconid, mesolophid, and postmesoconid ridges are always distinct, more or less long. At least one ectomesolophid is present (13/ 15 m 1–2), but it can be duplicated ( CUZ 170). Te entolophid is more or less continuous, connecting the entoconid to the prehypocristid or to the postmesoconid ridge. Two m3 only are present; their morphology is similar to that of m1–2, but with a reduced posterior lobe.

Comparison. Overall, we found more similarities between the species of Cuzal and? P. alsaticus than with the other species of Protadelomys ( P. cartieri , P. lugdunensis ) and? Protadelomys (? P. maximini and? P. nievesae ), notably in its size, the organization of the postprotocristid–ectolophid, the connections between the lophs and the lingual cusps, the alignment of the pre- and post-cristae, and the numerous extra-ridges. Among the differences, some could indicate a more progressive grade than typical? P. alsaticus , like the more robust hypocone, the less bulged conules, and the transverse lophs and metalophulid I that are better defined than in typical alsaticus . However, the evolutionary significance of the absence of the protoconid on p4 and dp4 remains unclear, as it is present on p4 and dp4 of? P. nievesae ,? P. alsaticus , and P. cartieri . In contrast, it is poorly developed or absent on p4 and dp4 of? P. maximini and P.lugdunensis . Te weak morphological variation of the lower molars is also noticeable.

Figures

Fig. 41 Bivariate graph (width/length) of the size of the upper (A) and lower (B) teeth of?Protadelomys alsaticus Hartenberger, 1969 from Cuzal (Quercy) (red marks) compared to the size of the teeth of?Protadelomys alsaticus Hartenberger, 1969 from Bouxwiller (Bas-Rhin) (black marks)

Fig. 42 (See legend on previous page.)