Protadelomys cf. maximini, Escarguel, 1998

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 : 83-86

? Protadelomys cf. maximini morphotype 2

Upper teeth

DP4. ( Fig. 50a ). Te smallest DP4 from Saint-Maximin (SMX3-44), trapezoidal, differs from the small DP4 attributed to? P. cf. maximini morphotype 1, in its narrower size, and relatively longer anteroloph. Its hypocone occupied a very lingual position when compared to the protocone, whereas the two cusps are roughly located at the same lingual level on typical? P. maximini , and slightly less lingual in? P. cf. maximin i morphotype 1.

M1–M2. ( Fig. 50b, c ). Tree M1–2 (SMX3-46, 47, and 48) are smaller than the molars of typical? P. maximini . Te enamel surface is slightly ornamented, with only a few granules. Te hypocone is conical. Te arms of the protocone are mesiodistal, the posterior one being short and ending at the level of the short endoloph. Te postparacrista is weak while the premetacrista is slightly stronger and frames a small mesostyle, which prolonged in a short and slender buccal mesoloph. Paraconule and metaconule are protruding and nearly equal in size. Te metaconule is linked to the apex of the hypocone. Tere is a mid-protocone ridge (protocrista) directed towards the paraconule on SMX3-47 ( Fig. 50c ). On the latter, unworn, the metalophule II is straight, and does not connect to the metaconule. Short ridges represent vestigial metalophule I, which is directed towards, on the unworn M1 or joining the mesoloph on SMX3-48.

LoWer teeth

dp4 .. ( Fig. 50d to f). Te specimen SMX1-207 previously considered as a p4 ( Escarguel, 1998: 372), is here considered as a dp4 due to the distal direction of its posterior root and to a distinct low protoconid close to the metaconid. Tis specimen is one of the shortest dp4 (1. 13 × 1. 37 mm), with SMX3-40: Fig. 50d , SMX3-41: Fig. 50f , SMX3-42: Fig. 50e , and SMX2-202 (the latter being figured as P. maximini : Fig. 4–3 , in Escarguel, 1998). Te metaconid and protoconid are almost unworn on SMX1- 207, the second being much lower and slender than the metaconid, and placed a little more distally, which indicates that this tooth likely corresponds to a dp4 rather than a p4; a mesial notch separates the protoconid from the metaconid. Te long posprotocristid ends with a weak premesoconid swelling, before joining the mesiodistal ectolophid, which is small. Te mesoconid is tiny. Te center of the basin is not well distinct on SMX1-207, but a long mesiodistal ridge, a short mesolophid, and an entolophid nearly complete are perceivable. Te posterolophid does not reach the entoconid and the hypoconulid. SMX3-42 display similar features as SMX1-207. SMX2-202 and SMX3-41 have neither a long mesiodistal ridge, nor a long entolophid, but show small low granules and ridges in the basin. On SMX3-40, the entolophid is better individualized.

m1–m2. ( Fig. 50g, h ). Te m1 SMX1-222 and 226 have the anterolophid reduced to the anteroconid, whereas it is longer on SMX-225. Tis anteroconid–anterolophid does not connects the short premetacristid (= mesial metalophulid I) on SMX1-222 and 226; but it does on SMX1- 225. A more distal lingual metalophulid I descends from the metaconid and joins the transverse buccal metalophulid I on the three m1. Te thick oblique postprotocristid develops from the protoconid apex; it bears a low premesoconid swelling or a spur, in front of the mesoconid, which is slightly stretched and in line with the postprotocristid. A postmesoconid spur is present at the junction with the distal ectolophid, which is lower than the postprotocristid. Te prehypocristid is low and short. Some elements of the entolophid join this spur. Tere are low and thin extra-ridges in the basins. Te posterolophid is long, connecting the distal flank of the entoconid, through a postentocristid. Te hypoconulid is small. Te entolophid is low, variably long and incomplete and does not reach the hypoconid or ectolophid. SMX1-225 also presents a short ectomesolophid.

Te unique m2 SMX1-400 displays a similar morphology to that of the m1, but the anterolophid is longer, slender, and connected to the premetacristid. Its lingual metalophulid I does not fuses the buccal metalophulid I. Te weak entolophid is reduced to its lingual part.

? Protadelomys nievesae ( Peláez-Campomanes, 1995) .

Type locality. Casa Ramòn (Huesca, Spain); middle Eocene ( MP 12 ?) .

Remarks. P. Peláez-Campomanes described the new species Protadelomys nievesae (1995) from Casa Ramòn (Huesca, Spain). Here we provide a specimen list with their measurements as Additional file 7: Data S7 and compare them with? P. maximini ( Escarguel, 1998) ,? P. alsaticus , Protadelomys cartieri , and P. lugdunensis (Hartenberger, 1969) .

Original diagnosis. Peláez-Campomanes, 1995: 301. “ Te cheek teeth are small. Te permanent and the deciduous premolars are smaller than the molars. Te metalophule is directed towards the protocone instead of towards the hypocone in DP4 and P4. Te anterior lobe of P4 is slightly larger than the posterior one. Te lower molars do not have a mesoconid ”.

“ P. nievesae differs from P. cartieri by its smaller premolars and its P4 which has a poorly developed anterior part.

P. nievesae differs from P. alsaticus by the following features: DP4 with well-developed mesostyle and the metaconule and the paraconule connected to the adjacent cusps; P4 and DP4 with the metalophule directed towards the protocone; P4 with the anterior lobe poorly developed and lower molars without mesoconid.

P. nievesae differs from P. lugdunensis by its smaller size, its lower molars without ectomesolophid and its P4 with the anterior lobe poorly developed”.

Material and measurements. (Additional file 7: S7; Fig. 51 ; Table 7). Te holotype RP022 is probably an m2, because the mesial (trigonid) and distal (talonid) sides show similar widths.

Te teeth are significantly smaller than those of the other species of? Protadelomys as well as from Protadelomys cartieri and P. lugdunensis . (Bivariate graphs in Figs. 3 , 14 , 28 , 44 , 51 ; Tables 6, 7, 8.)

Remarks about differential diagnosis, and comparisons? Protadelomys nievesae differs from? P. maximini and? P. alsaticus in its DP4 showing a less stretched protocone and hypocone, shorter pre- and post-protocristae and hypocristae. DP4 of? P. nievesae and? P. maximini share well-developed buccolingually transverse protoloph and metaloph. Te DP4 and molars of? P. nievesae and of? P. alsaticus differ from? P. maximini in showing a less reduced hypocone. Te reduced anterior part of the P4 (anteroloph short to absent and reduced anteroflexus) is present in 7/9 teeth of? P nievesae ; the anteroloph is otherwise long and presents a narrow anteroflexus on 2/9. Te reduced anterior part is not a unique feature of? P nievesae , but mainly characterizes? P. maximini (5/5 P4). Te number of P4 with reduced anterior part varies also in P. cartieri (5/9) and P. lugdunensis (3/5). Owing to the weak number of P4, we consider that these differences are not significant.

On the upper molars of? P. nievesae and? P. alsaticus , the cusps and conules are more bulged and distinct from the lophs than in? P. maximini , and the endoloph is lower. The sinus is variably present in? P. nievesae and less individualized in? P. alsaticus , whereas it is nearly absent in? P. maximini . The hypocone is generally distinct on unworn P4 of? P. nievesae . On upper molars, a lingual metaloph is not always distinct. When present, it joins the hypocone or the endoloph in? P. maximini , although more rarely. In the latter, it is very low as on molars of? P. nievesae . In? P. nievesae , the metaloph is sometimes oriented towards the protocone on DP4 (2/5) and on P4 (1/8), towards the hypocone on DP4 (2/5) and more frequently on P4 (5/8) and towards the posteroloph on P4 (2/8). This lingual metaloph is more often distinct on molars of P. cartieri and P. lugdunensis even if these teeth are only moderately worn; on these molars it connects the hypocone, or the endoloph. In Protadelomys and? Protadelomys species, the size of the mesostyle is variable, and the mesoloph is variably long, although it never bypasses the metaconule level.

Te dp4 basin floor of? P. maximini is flatter than that of the dp4 of? P. alsaticus or? P. nievesae . Te p4 protoconid is often absent, exceptionally present and well distinct in? P nievesae (2/7) whereas it is present only on one p4 of? P. maximini , on which it is low. On lower molars, the entolophid is generally relatively high and complete (11/15) or shortly interrupted (4/15) in? P. nievesae , whereas it is more often discontinuous and low in? P. maximini . It is generally complete in P. cartieri , P. lugdunensis , and? P. alsaticus .

Figures

Fig. 50 Teeth of?Protadelomys cf. maximini morphotype 2, from Saint-Maximin (Gard).a SMX3-44, right DP4; occlusal view. b SMX3-45; right M1; b1, occlusal view; b2, lingual aspect; b3, buccal aspect. c: SMX3-47, left M1; occlusal view. d SMX3-40, right dp4; d1, occlusal view; d2, buccal aspect; d3, lingual aspect. e SMX3-42,right dp4; e1, occlusal view; e2, buccal aspect; e3, lingual aspect. f SMX3-41, right dp4; f1, occlusal view; f2, buccal aspect; f3, lingual aspect. g SMX1-222, left m1; g1, occlusal view; g2, buccal aspect; g3, lingual aspect. h SMX1-225, left m1; h1, occlusal view; h2, buccal aspect; h3, lingual aspect. Scale bar=1 mm

Fig. 4 Protadelomys cartieri (Stehlin & Schaub,1951), from Egerkingen (Swiss Jura). a. Ef 1002, Holotype, right upper tooth row, P4–M1–3; a1, occlusal view, a2, lingual aspect; a3, buccal aspect. b. Eg 587,right lower tooth row, p4–m1-3; b1, occlusal view; b2, buccal aspect. Scale bar: 1 mm

Fig. 51 Bivariate graph (width/length) of the size of the upper (A) and lower (B) teeth of?Protadelomys nievesae Pelǻez Campomanes, 1995 from Casa Ramòn (Huesca, Spain) (black marks) compared to the size of teeth of?Protadelomys maximini Escarguel,1998 from Saint-Maximin (Gard) (red marks)

Fig. 3 Bivariate graph of the size (width/length) of the upper (A) and lower (B) teeth of the rodent’s species from Egerkingen (Swiss Jura).The colored lines joins the different loci on a same jaw. A upper teeth. Protadelomys cartieri (Stehlin & Schaub,1951): Ef 1002, Holotype,P4 to M3, red line; Ek 245, M1 to M3, orange line; EK H006, P4 to M2, purple line; EK H005, M1 to M3, blue line; He 14, M1–M2, geen line; Eg 596, M1–M2, turquoise line. Homoetreposciurus egerkingensis nov. gen, nov. sp.: Ek 85, M1, black circle. B lower teeth. Protadelomys cartieri (Stehlin & Schaub, 1951): Ek H002, p4–m1, blue line;: Ek 250,p4–m2, yellow line; Ek 587, p4–m3, orange line; Ek 248, p4–m3, green line. Protadelomys lugdunensis Hartenberger, 1969: Em 21, p4 to m3. Homoetreposciurus egerkingensis nov. gen, nov. sp.: Ek H004,p4 to m3, purple line; Ek 79, dp4, purple circle. Eoelfomys nov. gen. nov. sp: Ek H003, p4 to m3, red line

Fig. 14 Bivariate graph of the size (width/length) of the upper (A) and lower (B) teeth of Protadelomys lugdunensis Hartenberger,1969 from Lissieu (Rhône) (red marks) compare to the size of the teeth of Protadelomys cartieri (Stehlin & Schaub, 1951), from Egerkingen (Swiss Jura) (black marks)

Fig. 28 Bivariate graph of the size (width/length) of the upper (A) and lower (B) teeth of?Protadelomys alsaticus Hartenberger, 1969 from Bouxwiller (Bas-Rhin) (black marks,PaB) compared to the size of the teeth of Protadelomys cartieri (Stehlin & Schaub, 1951), from Egerkingen (Swiss Jura) (red marks, PcE)

Fig. 44 Bivariate graph (width/length) of the size of the upper (A) and lower (B) teeth of?Protadelomys maximini Escarguel, 1998 from Saint-Maximin (Gard) (red marks), compared to the size of teeth of?Protadelomys alsaticus Hartenberger,1969 from Bouxwiller (Bas-Rhin) (black marks)