Protadelomys cartieri (Stehlin & Schaub, 1951)

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 : 8-18

publication ID	https://doi.org/10.1186/s13358-022-00245-3
persistent identifier	https://treatment.plazi.org/id/497F1B1D-FFB5-DF2F-C483-46A0FC79F957
treatment provided by	Felipe
scientific name	Protadelomys cartieri (Stehlin & Schaub, 1951)
status

Treatment

Holotype. Ef 1002: right P4–M3.

Type locality. Egerkingen (Swiss Jura), Huppersand?; middle Eocene, MP 14.

Original diagnosis. Stehlin & Schaub, 1951 (translation from German).

Upper teeth subtriangular to quadrangular; pseudypoconus (= hypocone) still directly connected to the protocone; sinus absent; conules well present; transverse crests of lower molars low or incomplete; no indication of a mesoconid.

Remarks about the diagnosis of Protadelomys cartieri .

Hartenberger defined the genus Protadelomys for the species cartieri from Egerkingen previously referred to the genus Adelomys (type: right P4–M3; Fig. 25 View Fig , in Stehlin & Schaub, 1951), then to Masillamys (Taler, 1966) . Stehlin and Schaub (1951) provided some dental features in their diagnosis, (e.g., the lack of the mesoconid on lower teeth), which were not taken into account in the definition of the species P. cartieri by the following authors ( Escarguel, 1998; Hartenberger, 1969; Peláez-Campomanes, 1995).

Emended diagnosis. Species of Protadelomys with slender lower jaw. Upper teeth with buccal protoloph and metaloph slightly lower than the paracone and metacone; buccal metalophule I variably present; buccal metalophule II free or fused to the metaconule; lingual protoloph connecting protocone and lingual metaloph absent or very low and connecting hypocone; short high endoloph; sinus shallow and short linguobuccally; paraconule smaller than the metaconule. On lower p4, protoconid weak and stretched in the protoconid ridge; on lower molars, metalophulid I and entolophid are low, complete or interrupted buccally; no indication of a mesoconid.

Differential diagnosis. Protadelomys cartieri differs from P. lugdunensis :— in its relatively slender dentary; on lower teeth, in the presence of a thicker protoconid on p4, in the absence of mesoconid and anterolophulid, and in its weak antesinusid and anterocingulid; on upper teeth, it differs in its narrower P4 and smaller M2.

Material from Egerkingen and Measurements

S1; Tables 1, 8; Fig. 3 View Fig

A few lower molars are too worn (Ek 68, 44, 75, 76) or damaged (Ek 73) to be identified with certainty. Te length and width of upper teeth, except that of P4 ( Fig. 3 View Fig , Table 1) are poorly correlated, whereas these dimensions are better correlated on the lower teeth, except p4. Tese p4 are far smaller than m1, which are smaller than m2. Te m3 are longer but not wider than m1–m2. Te M1 are generally longer than M2 (not on the type, on which both have same length. Te M3 are narrower and as long as M1–2.

Description. Figures 4 View Fig , 5 View Fig , 6 View Fig , 7 View Fig , 8 View Fig , 9 View Fig and 10 View Fig

Skull. Te specimen Ek 245, described and figured in Hartenberger (1969: 38–41) is now badly damaged. Te remaining parts include a fragment with left P4 and M1. Te casts of the two dental rows with P4 to M3 are still available. A fragment of the left maxillary He 14, bearing M1–M2, shows the base of the hystricomorphous infra-orbitary foramen.

Upper teeth

Description of the type Ef 1002 ( Fig.4a View Fig ). Te P4 is smaller than the M1–2 ( Fig. 3A View Fig ; Additional file 1: S1). It is triangular since the hypocone is nearly absent. A weak parastyle connects to the preparacrista, which swells at the level of an anterostyle. Te parastyle is lingually connected to a distinct anteroloph. Tere is no distinct paraconule. Te paracone is bulged, prolonged in a short protoloph oriented anteriorly to the anteroloph. Te enamel of the mesoflexus is smooth. A low ridge and mesostyle a little higher than this ridge terminates the mesoflexus buccally. Te metacone and the paracone are at the same level. A short buccal part of the metalophule II ends at the base of the metaconule, which is rounded and strong. Tis metaconule connects to the postprotocrista through a well-distinct lingual metalophule. Te buccal metalophule I is absent. Te posteroloph is long and ends against the postprotocrista. Te hypocone is indistinct.

Te curved parastyle is longer and stronger on M1 than on M2. Te anteroloph ends at the anterostyle. A short antesinus marks the anterostyle at its junction with the preprotocrista, which is more distinct on M1 than on M2. Te paracone and metacone are swollen, little prominent, and prolonged lingually in complete transverse buccal protoloph and metalophule II. Paraconule and metaconule are slightly protruding, the paraconule being smaller than the metaconule. Protocone and hypocone are equal on M1, the hypocone being a little smaller than the protocone on M2. Te protoloph connects to the protocone. Te metalophule joins the hypocone slightly mesially to its center. On the three molars, a distinct mesostyle extends lingually in a short mesoloph. A short premetacrista is present on M1–2. Te posteroloph is long; it extends from the post-hypocrista to the base of the metacone, without merging with the latter.

Te M3 is badly preserved, with the cusps and lophs less visible than on the M1–2. It is triangular and lacks a distinct hypocone.

Other teeth

P4. Te teeth are triangular on the type Ef 1002 and on Ek H 006 ( Fig. 6c View Fig ), due to the absence of hypocone. Te hypocone can, however, be small [Ek 48, Ek 123, ( Fig. 5a, d View Fig ) Ek 601 ( Fig. 6b View Fig )], more developed [Ek 245 ( Fig. 5 View Fig , b, c), Ek H 005 ( Fig. 6a View Fig )], or as robust as the protocone (Ek 35). Te size of the P4 is independent of the presence/absence of the hypocone. Te anteroloph is long (holotype Ef 1002, and EK H005, EK H006, Ek 35, Ek 245), short (Ek 123, EK 601 ), or absent ( EK 48 ). Paracone and metacone are swollen and similar in size. Te paraconule is generally absent, and can be absent, or indistinguishable from the anterostyle on Ek 245, at the level of the connection with the protoloph. Te paracone is isolated, without buccal protoloph, the protoloph being reduced to its low lingual ridge on Ek H 006 ( Fig. 6c View Fig ); it is more generally short and directed or connected to the anteroloph at the anterostyle level; it is transverse and joins the anterior arm of the protocone on Ek H 005 ( Fig. 6a View Fig ). Te mesoflexus is narrow, buccally edged by a more or less swollen mesostyle; the latter being lengthened mesiodistally (Ek 245), or swollen (3/8). In Ek 48, Ek H 006, and Ek 123, the mesostyle is connected to a mesoloph, which is short or nearly reaching the metaconule level. On Ek 123, a short postparacrista connects the paracone with the mesostyle. On four teeth (Ek 35, Ek 245 (left and right), Ef 1002), the mesostyle is twofold; it is unique on the others. Te paraconule is absent (Ek 48, Ek 35) or pulled forward, merging with the anterostyle. Te buccal metalophule I is reduced or absent. Te metaconule, swollen, is in line with the metacone through the metalophule II. Te lingual metalophule is oriented towards the posterior part of the protocone, joining it only on two specimens (Holotype and Ek 245). Te P 4 Ek 245 shows a short sinus, a metaconule connected to the hypocone and to the postprotocrista. Furthermore, there is a weak ridge marking the buccal metalophule I, several wrinkles around the metaconule, in the mesoflexus and the posteroflexus. On Ek 35, there is a sinus separating protocone and hypocone; a short thin remnant of the lingual protoloph connected with the protocone is visible, separated from the thick buccal protoloph, which turns forwards .

M1 and M2. Te molars display close dimensions, M2 being a little shorter than M1, and M3 much narrower ( Table 1). Te M2 differs from the M 1 in their narrower and shorter distal area: the hypocone is more buccal and a little smaller than the protocone, whereas the protocone and hypocone are equal in size on M1. Te lingual flank of the crowns is higher than the buccal one. Te cusps are bulbous and their apex is acute on juveniles. In adults, the buccal cusps merge within the thick buccal parts of the protoloph and metaloph. Tese lophs are slightly less high than these cusps. Te lingual parts of these lophs are very low or absent. Lingually, the protocone merges within its pre- and post- cristae, which are aligned mesiodistally; it is the same for the hypocone that displays shorter and weaker anterior and posterior arms. Te postprotocrista prolongs through the endoloph. Te endoloph is short and high. Te sinus is barely marked; its height is less than one-third of the crown height, so that it is often indistinguishable on worn teeth.

M1 are easily distinguished from M2 due to their strong parastyle, which lengthens the buccal edge of the tooth as opposed to the lingual edge and gives it a trapezoidal outline. Te protocone and hypocone are closer on M1 than on M2. On M2, the parastyle elongates as an extension of the anteroloph; it is sometimes swollen [Eg 596 ( Fig. 7a View Fig ), Ek 123 ( Fig. 5a View Fig ), holotype ( Fig. 4a View Fig ), and Ek H006 ( Fig. 6c View Fig )]. Moreover, M2 mostly show a metacone lingual to the paracone and the hypocone more buccal than the protocone, both making the posterior lobe of the tooth narrower buccolingually than the anterior lobe, and the posteroloph shorter.

Te anteroloph is lower and thinner than the anterostyle and the preprotocrista. Te paraconule, merged in the protoloph, can be variably stretched distomesially, more or less swollen. Te protoloph ensures the connection from the paracone to the middle of the protocone, this connection being weak on unworn or weakly worn teeth.

Te mesostyle is always present and can be constituted by one or two (mesial and/or distal) small low cusps (e.g., Fig. 5c View Fig ) (9/29). It is nearly in line with the paracone and metacone, e.g., on the holotype and EK H005 ( Fig. 3a View Fig , 6a View Fig ), but it is more buccal on Ek 45 ( Fig. 7d View Fig ). A short premetacrista can be present (9/29) and exceptionally, a postparacrista. A mesoloph is often observed (20/29), reaching the level of the metaconule only in three specimens. On Ek 124, the top of the arched metacone is doubled ( Fig. 7f View Fig 1 View Fig , f 3 View Fig ). Te metaconule is strong and bulged, a little lower than the metacone; its position is slightly mesial to that of the metacone and hypocone. Te buccal metalophule I is variably present (19/29), sometimes highly reduced; it is lower and thinner than the buccal metalophule II and rarely connects the metaconule (4/29). Te buccal metalophule II can be free or join the metaconule (12/29). Te ridge connecting the metaconule and the hypocone is very low, therefore these two cusps appear separated on unworn teeth. Te enamel surface is generally smooth. Some rare low wrinkles are present at the bottom of the flexi (10/29) ( Fig. 5c View Fig , 6a View Fig , 7g,h View Fig ). Te unworn specimen Ek 87 ( Fig. 7h View Fig ) displays unusual features, which might be related to wear differences. Te protocone and hypocone are a little closer than on the other molars, both being acute. Te mesostyle is slender, without mesoloph. Te lingual parts of the protoloph and metaloph are absent; therefore, the paraconule and the twinned metaconule are isolated. Te buccal metalophule II is short and transverse. Te paraconule and metaconule are isolated.

M3. Te strongly reduced hypocone sometimes separates from the protocone (4/7) with a shallow sinus. On weakly worn teeth, this sinus communicates with the opposite flexus (2/4) ( Fig. 7j, k View Fig ). Te paracone represents the only salient cusp, on unworn teeth. Te metacone is weakly prominent from the buccal ridge it forms with the mesostylar area. Te paraconule and metaconule are present, but low. Te hypocone is isolated on one weakly worn tooth (Eg 597) and appears connected to the postprotocrista on more worn teeth. Te posteroloph usually connects to the metacone and the hypocone.

Dentary. Te body of the mandible Eg 587 ( Fig. 8a View Fig ) is slender than that of Em 21 [? P. cf. lugdunensis ( Fig. 8b View Fig )]. Te diastema of Eg 587 is longer and the radius of curvature of the incisor larger than that of Em 21. Te mental foramen opens anteriorly to the p4, at the level of the posterior part of the diastema. Te masseteric crest is strong and starts ventral to the mesial root of m1.

Lower teeth ( Figs. 9 View Fig , 10 View Fig ). Among the observed materials from Egerkingen, a few specimens (Ek 67, 69, 70, 76, 81, Ek 248, Ek H002, and Ek H002-4) display the dental morphological features of the lower jaw of Protadelomys cartieri figured by Stehlin and Schaub (1951, Eg 587) such as the absent mesoconid and the broken distal ectolophid. Te mandible Ek 248 is slightly larger than Eg 587, but the size ratio between the different dental loci is similar (see lines connecting p4, m1, m2, and m 3 in both specimens, in Fig. 3B View Fig ).

dp4. Only three teeth can be identified as dp4 based on the low crown and of the morphology of cusps and ridges, and we can condidently refer Ek 81 to Protadelomys cartieri . It differs from the dp4 Ek 80 in its wider and shorter crown. Te metaconid is mesiomedian. Te low protoconid is more arcuate than in Ek 80 ( Fig. 10c View Fig ). Te low ectocingulid is present and long. Te strong bulbous hypoconulid is more buccal, connected to the entolophid, making it oblique posteriorly. Te posterolophid is long. Te dp4 Ek 80 is slender and less bulbous than Ek 81 ( Fig. 9d View Fig ). We cautiously refer this dp4 to P. cartieri . Two mesiodistal extra-ridges develop from the distolingual side of its metaconid to the talonid basin. Its entolophid, similarly poswardly oriented and linked to the hypoconulid, is shorter. Its posterolophid is very short lingually to the hypoconulid.

p4. Te p4 are smaller than the m1 and m2 ( Table1, Fig.3B View Fig , Additional file 1: S1). A weak and low anteroconid is present only on Ek H002 ( Fig. 9a View Fig ). Te metaconid, the highest cusp, shows two symmetrical cristids, the postmetacristid lingually and the premetacristid buccally, the latter being curved towards the protoconid area. Present on EK H002 and Ek 127, the protoconid is almost absent on Eg 587 ( Fig. 4b View Fig ), Ek 248, H002-4, and Ek 67 ( Fig. 9 View Fig ). A low ectocingulid is visible on Ek 67only ( Fig. 9e View Fig ). Te postprotocristid angles at its end, bearing a short spur or a swelling, considered here as a kind of “premesoconid”, as there is neither a distinct mesoconid nor a mesolophid or an ectomesolophid. It connects to the short mesiodistal ridge descending from the metaconid on Ek H002-4; it is free on the others and reduces to a low wrinkle on Ek 67. Te ectolophid interrupts distal to the premesoconid and before its connection with the entolophid and the prehypocristid. Te entolophid is not continuous showing breaks at is center, close to the mesial end of the prehypocristid. On Ek 67, the entolophid connects also with the hypoconulid. Te hypoconulid is usually bulbous. Te posterolophid is short and reduced; it is absent on Ek 67.

Te two p4 (Ek 67, 127) are variants of P. cartieri . Tey differ from the one described above in their more lengthened mesiodistally postprotocristid, and Ek 127 ( Fig. 9f View Fig ) shows a swelling at the protoconid level, when its sinusid is less deep buccolingually than on Ek 67. Te ectolophid is very short and interrupted shallowly at the hypoconid level. Tere is no prehypocristid on Ek 127, but the hypoconid area appears worn here. Te lingual part of the entolophid is present on Ek 127 only, the entolophid being reduced to a short low ridge on Ek 67. Te post-hypocristid is long and the hypoconulid is moderately swollen. Te posterolophid is thin and join the entoconid on Ek 127, closing the posterosynclinid lingually.

m1–m2. Tese teeth display a bulbous and low anteroconid, which individualizes from the protoconid flank on unworn and weakly worn molars. A short anterocingulid can be present, and the anteroflexid is narrower on m2.

A very short anterolophid directs lingually from the apex of the anteroconid. It is separated from the metalophulid I by a shallow anteroflexid, which is open buccally and lingually ( Fig. 9 a, b View Fig ). An anterolophulid is distinct on the worn m1 of Eg 587, or on the unworn Ek 70 ( Fig. 9g View Fig ). On Ek 248, the anteroflexid closes buccally, whereas it remains open on Eg 587. Te lingual and buccal parts of the metalophulid I does not connect on m2 and m3; therefore, the anteroflexid communicates with the basin. On the other teeth, a low and postwardly angled metalophulid I extends from the metaconid to the apex of the protoconid. Te thick postprotocristid slightly swells at its distal end, and rarely bears a premesoconid spur on m2 (Ek H002 and H002-4, Ek 70). Te mesial ectolophid and the mesoconid cannot be distinguished from the oblique postprotocristid, except on the weakly worn m1 of EK 250 ( Fig. 10a View Fig 1 View Fig ). Te distal ectolophid, very short and low, appears interrupted on the occlusal surface. Very low and rare extra-ridges are present on the posterior slope of the metalophulid I to the basin ( Figs. 9a, b View Fig ; 10a View Fig 2 View Fig ). Te distal part of the ectolophid is much lower than the occlusal surface, and only a short crest joins the very low prehypocristid.

Te entolophid is almost straight and only slightly angled. It is interrupted at its buccal part, before joining the prehypocristid. Te entoconulid is variably present and slightly swollen. Te salient hypoconulid separates shallow notches from the post-hypocristid and from the posterolophid on the less worn specimen (m1 of Ek H002). Te short posterolophid does not reach the summit of the entoconid leaving the posteroflexid opened lingually. Te weakly worn m2 Ek 70 differs from Ek H002, H002-4, and Eg 587 in having a longer buccal anterocingulid, a strong anterolophulid, and a weak ectomesostylid. Ek H002 is not the specimen figured pl.I, Fig.2 View Fig under this number in Hartenberger, 1969. We noticed that the latter actually corresponds to Ek 250 (NHMB collections).

m3. One weakly worn m3 of the tooth row Eg 587

( Fig. 4b View Fig ), one on Ek 248 ( Fig. 10a View Fig ) and two isolated much worn m3 (Ek 68, 76) are available. Te anteroconid is small, not connected to the premetacristid, bearing a short buccal cingulid. A few low and short extra-ridges are visible in the basin. Te thick postprotocristid ends in a short lingual spur. Te very short ectolophid shows the break observed on m1–m2.

Material from Lissieu (Rhône) referred here to Protadelomys cartieri (Stehlin & Schaub, 1951) Description. Among the smallest m1 and m3 of the Lissieu assemblage, five lower teeth stand out from the material assigned to P. lugdunensis : one right m1 ( LIS 54, Fig. 11b View Fig ), one weakly worn right m2 ( LIS 60, Fig. 11c View Fig ), and three strongly worn m3 ( LIS 30, 33, ( Fig. 11d View Fig ) and 45–3). Tese teeth present some similarities with the typical lower teeth of P. cartieri from Egerkingen, based on the characteristics of the ectolophid, the mesial area, and of the relative proportions of the synclinids.

p4. One p4, LIS 41 ( Fig. 11a View Fig ), has a size compatible with the p4 of P. lugdunensis LIS 42, 37 and 40, but its crown is higher. Te anteroconid, which is buccally displaced, is stretched mesiodistally, connects to a short metalophulid, and joins buccally the protoconid ridge. Te mesiodistally stretched protoconid is more distinct on LIS 41 than on the other p4 from Lissieu, and the postprotocristid is higher than the ectolophid and makes an obtuse angle with the stretched protoconid. Te postprotocristid is stretched along a mesiolingual to distobuccal axis, and bears distobuccally a bulged postmesoconid spur. Te lingual entolophid is distally oriented from the entoconid, and not connected to its buccal part, reduced to a spur. As the protoconid is present and the ectolophid angles at the level of the mesoconid, which is indistinct, this p4 is referred to as P. cartieri .

m1. On LIS 54 ( Fig. 11b View Fig ), the low anteroconid separates from the protoconid, and nearly connects the plunging premetacristid. Te metalophulid I is complete, low, and curved distally. Te postprotocristid is almost as high as the protoconid, and its distal end is swollen; no distinct mesial ectolophid is observed. Te ectolophid is very low, interrupted, and reaches the base of the postprotocristid swelling and of the prehypocristid. Te entolophid, swollen at the level at the base of an entoconulid, attaches directly to the hypoconid. Te hypoconulid is present and small. Te posterolophid joins the base of the entoconid.

m2. On LIS 60 ( Fig. 11d View Fig ), the anteroconid, low, is closer to the metalophulid I (anteroflexid narrower) than on the m1, the anterolophid is hardly distinct and the premetacristid is absent. Te ectolophid is interrupted and very short and the entolophid distally attaches to a short prehypocristid.

m3. Among the three m3 (L = 1. 8 to 1. 95 mm) that are smaller than those of P. lugdunensis (L = 2. 2 to 2. 4 mm), only one ( LIS 33) is unworn enough to permit the identification of possible relationships between the cusps and crests ( Fig. 11c View Fig ). However, on the m3, the mesosynclinid is not elongated relative to the posterosyclinid, as is the case in P. lugdunensis . LIS 33 shows a small anteroconid connected to the mesial metalophulid (premetacristid). Te distal metalophulid I is not visible due to wear; only its thick buccal part is distinguishable and distally bent like on the m3 of P. lugdunensis . Apart from this case, the postprotocristid is short, located just in front of the mesoconid. Te quite short ectolophid shows the break observed on m1–m2, like in typical specimens of P. cartieri .

Material referred to Protadelom y s cartieri (Stehlin & Schaub, 1952) from Laprade

Upper teeth

M1–2. One M1 ( LAP 259: Fig.12a View Fig ) and two M2 ( LAP 193: Fig.12c View Fig , 260: Fig.12b View Fig ) are referred to Protadelomys cartieri . Tey differ from P. lugdunensis from the same locality in their smaller size (but this is not statistically significant, owing to the limited sample, Table 8), in their higher crowns, as well as in the following features: the paraconule does not protrude forwards and swells within the protoloph on the M1, less on the M2; the metalophule II is short and can be posteriorly directed ( LAP 193, 259); the metalophule I is very reduced; the metaconule is closer to the hypocone than to the metaloph and connects at mid-hypocone by a short low ridge; only a small mesostyle on LAP 259 is present, which is a little stronger and prolonged in a short mesoloph on LAP 260 and LAP 193.