Orolophus maldani ( Lemoine, 1878 )

Bronnert, Constance & Métais, Grégoire, 2023, Early Eocene hippomorph perissodactyls (Mammalia) from the Paris Basin, Geodiversitas 45 (9), pp. 277-326 : 296-303

Orolophus maldani ( Lemoine, 1878)

( Figs 11-13 )

Pachynolophus maldani Lemoine, 1878: 24 , pls I-V; 56, pls I-IV.

Pachynolophus paracuspidens Lemoine, 1878: 19 .

Orotherium remense Lemoine, 1891: 286 .

Propachynolophus maldani – Teilhard de Chardin 1921: 61, figs 33-34.

Propachynolophus levei Hooker, 1994: 57-59 , fig. 24.

Pliolophus aff. vulpiceps – Hooker 1994: 54, fig. 16.

Orolophus maldani – Remy 2017: 14, figs 1-2.

LECTOTYPE ( Savage et al. 1965). — MNHN-AL5199 , right fragmentary mandible with p4 and m2-m3 .

MATERIAL. — Ageian: symphysis ( MNHN-AL 5200); mandible dp3-m1 (R: MNHN-AL 5201); mandible m1-m2 (R: MNHN-AL 5203); mandible m2-m3 (R: MNHN-AL5194; L: MNHN-AL 5204); dP4 (R: MNHN-AL6555; L: MNHN-AL 6556); M1 (L: MNHN-AL 6561); M2 (L: MNHN-AL 6564); M1/2 (L: MNHN-AL5207, AL6550, AL6552, AL6562, AL6554); dp3 (R: MNHN-AL 5206); dp4 (L: MNHN-AL 5206); m1/2 (L: MNHN-AL 6543); m3 (R: MNHN-AL6546; L: MNHN-AL 5205), metatarsal II (R: MNHN.F.AL18001) .

Condé-en-Brie: maxillary dP3-dP4 (L: MNHN-CB 1530); maxillary P3-M3 (L: MNHN-CB16165 [cast]); dP3 (R: MNHN-CB4252, MNHN-CB4705; L: MNHN-CB1595, M.CB1C, M.CB306, CB4251, CB786, CB213, CB 664, CB 4915); dP4 (R: MNHN-CB1556, CB1558, CB1561, CB1564, CB1575, M.CB19, M.CB298, CB77; L: MNHN-CB 4667); P2 (R: MNHN-CB1586; L: MNHN-CB 1591); P3 (R: MNHN-CB1569, CB1181; L: MNHN-CB 1583); P4 (R: MNHN-CB1563, M.CB72, CB5-CA; L: MNHN-CB 1581, CB 215); M1 (R: MNHN-CB 4689, CB 4689); M1/2 (R: MNHN-CB1559, CB1566, CB1567, CB1532, M.CB1B, M.CB299, M.CB114, CB4935, CB4736, CB1A; L: MNHN-CB1565, CB1573, CB1531, M.CB297, M. CB 225); dp3 (R: MNHN-M.CB194, M.CB199, CB572, CB4730; L: MNHN-M.CB305, M.CB197, M. CB 196, CB 312); dp4 (R: MNHN-CB1576, CB1589, CB1593, M.CB301, CB221, CB4709; L: MNHN-CB 223); p2 (R: MNHN-CB219; L: MNHN-CB1594, CB 4702, CB 669); p3 (R: MNHN-CB1580, CB1592, M.CB193; L: MNHN-CB 1600, CB 4700); p4 (R: MNHN-CB 1599); m1 (R: MNHN-M.CB38, CB4688; L: MNHN-CB 4701); m2 (R: MNHN-M.CB198, M.CB295, MNHN-CB4686, CB4757; L: MNHN-CB 918); m1/2 (R: MNHN-CB1579, CB1584, CB1598, CB4703; L: MNHN-CB1578, CB1587, CB1590, M. CB 296, CB 4687); m3 (R: MNHN-M.CB195, CB8-CA; L: MNHN-CB1571, CB1585, CB 4704, CB 222); incisor (MNHN-M. CB 303) .

Cuis: dP4 (R: MNHN-CUI7-L; L: MNHN-CUI6-L); M1/2 (R: MNHN-2003-2 unnumbered; L: MNHN-CUI8-L, CUI10-L, MNHN-CUI11-L, MNHN-2003 unnumbered); dp4 (L: MNHN-CUI15550); p3 (R: MNHN-CUI15549); m1/2 (L: MNHN-2003-2 unnumbered); m3 (L: MNHN-2003-2-80), tibia (R: MNHN.F.CUI18000) .

Gland: M1/2 (L: MNHN-GLD41-L [broken]); M3 (L: MNHN-GLD335-L) .

Grauves: dP3 (R: MNHN-GR7825, GR242, GR175-L); dP4 (R: MNHN-GR10254, GR1-L); P2 (R: MNHN-GR7803); P4 (R: MNHN-GR7402); M1/2 (R: MNHN-GR7570, GR7568, GR7575, GR7379; L: MNHN-GR7378, GR10779, GR277-L, GR273-L, GR9-L, GR41-L, GR19-L, GR25-L, GR227); mandible p4-m3 (L: MNHN-GR10773); dp3 (R: MNHN-GR7808; L: MNHN-GR7807); dp4 (R: MNHN-GR7809, GR7830; L: MNHN-GR7889); lower premolar (MNHN-GR37-L); p2 (R: MNHN-GR6-L, GR51-L); p3 (R: MNHN-GR3-L); p4 (R: MNHN-GR5-L, GR274-L; L: MNHN-GR7829, GR7829); m1 (L: MNHN-GR178); m1/2 (R: MNHN-GR7383, GR10235, GR10229, GR49-L, GR44-L; L: MNHN-GR7382, GR16-L); m3 (R: MNHN-GR22-L; L: MNHN-GR7569, GR?8-L, GR63-L); astragalus (R: MNHN.F.GR18005); calcaneus (L:MNHN.F.GR18007); metatarsal III (L: MNHN.F.GR18008); distal phalanx (MNHN.F.GR18006) .

Mancy: mandible p4-m1 (R: MNHN-MA2-L); mandible p4-m3 (R: MNHN-MA14792); dP4 (L: MNHN-MA24-L); M1/2 (R: MNHN-MA48-L, MA53-L; L: MNHN-MA44) .

Mont Bernon: P4 (R: MNHN-BER1); dp4 (L: MNHN-B6-L), humerus (R: MNHN.F.MTB18001) .

Monthelon: dP4 (R: MNHN-MTH13-L; L: MNHN-MTH7-L). Oosterzele: M1/2 (R: IRSNB M 1867; L: IRSNB.M 1868); m1 (L: IRSNB.M 1863); m3 (R: IRSNB.M 1864, [broken], IRSNB.M 1865); M1 (R: IRSNB.M 1866) .

Prémontré: maxillary with canine (R: MNHN-SLP-29-PE1378); maxillary dP2 (L: MNHN-SLP-29-PE1070); maxillary dP3-dP4 (L: MNHN-SLP-29-PE1863); maxillary P1 (R: MNHN-SLP-29- PE1559); maxillary P1-P2 (R: MNHN-SLP-29-PE1296); maxillary P2-P4 (R: MNHN-SLP-29-PE2388); maxillary P3 (L: MNHN-SLP-29-PR1953); maxillary M1-M2 (L: MNHN-SLP-29-PE1864, SLP-29-PE706, SLP-29-PE761 [composite?]); maxillary M1-M3 (R: MNHN-SLP-29-PE681); mandible dp2-m2 (L: MNHN-SLP-29-PE1467); mandible p3-p4 (R: MNHN-SLP-29-PE1362); mandible p3-m1 (R: MNHN-SLP-29-PE584); mandible p4-m3 (R: MNHN-SLP-29-PE1553, SLP-29-PE480); mandible m1 (R: MNHN-SLP-29-PE1069); mandible m3 (L: MNHN-SLP-29- PE1317); dP2 (R: MNHN-SLP-29-PE1436, SLP-29-PE631, SLP-29-PE1475; L: MNHN-SLP-29-PE950, SLP-29-PE717, SLP-29-PE44); dP3 (R: MNHN-SLP-29-PE803, SLP-29-PE742, SLP-29-PE1728, SLP-29-PE45, SLP-29-PR1973, SLP-29-PR1560, PRE448; L: MNHN-SLP-29-PE1243, SLP-29-PE1004, SLP-29-PE100, SLP-29-PE67, SLP-29-PR2049, PRE996); dP4 (R: MNHN-SLP-29-PE1703, SLP-29-PE1430, SLP-29-PE1275, SLP-29-PE807, SLP-29-PE150, SLP-29-PR1928, SLP-29-PR2054, SLP-29-PR3289, SLP-29-PR3077, SLP-29-PR1913, SLP-29- PE1998, PRE241, PRE1070; L: MNHN-SLP-29-PE1358, SLP-29-PE1201, SLP-29-PE1323, SLP-29-PR1988, SLP-29-PR3283, SLP-29-PR3000); P2 (R: MNHN-SLP-29-PE1421, SLP-29-PE599; L: MNHN-SLP-29-PE10); P3 (R: MNHN-SLP-29-PE644, SLP-29-PE1548, SLP-29-PE12, SLP-29-PE252, SLP-29-PE1914, SLP-29-PR1896; L: MNHN-SLP-29-PE731, SLP-29-PE590, SLP-29-PE254, SLP-29-PR1971); P4 (R: MNHN-SLP-29-PE678, SLP-29-PE622; L: MNHN-SLP-29-PE741, PRE246, PRE236, PRE995); M1 (R: MNHN-SLP-29-PE1383, SLP-29-PE896, SLP-29-PR1912, SLP-29-PR3287, SLP-29-PR3001, SLP-29- PR3107, PRE1065; L: MNHN-SLP-29-PE701, PRE1064); M2 (L: MNHN-SLP-29-PE508); M1/2 (R: MNHN-SLP-29-PE1695, SLP-29-PE1479, SLP-29-PE1527, SLP-29-PE987, SLP-29-PE707, SLP-29-PE151, SLP-29-PE1367, SLP-29-PE147, SLP-29-PE149, SLP-29-PE1699, SLP-29-PE479, SLP-29-PE448, SLP-29-PE982, SLP-29-PE865, PRE1069, PRE1067, PRE1068; L: MNHN-SLP-29-PE1544, SLP-29-PE394, SLP-29-PE1707, SLP-29-PE501, SLP-29-PE388, SLP-29-PE148, SLP-29-PE223, SLP-29-PE503, SLP-29-PR1925, SLP-29-PR1969, SLP-29-PR2009, SLP-29- PR3290, SLP-29-PR3288, SLP-29-PR3003, PRE238, PRE863, PRE1080); M3 (R: MNHN-SLP-29-PE1721, SLP-29-PE688, SLP-29-PE152, SLP-29-PE1009, SLP-29-PR1909, PRE235; L: MNHN-SLP-29-PE834, SLP-29-PE224, SLP-29-PE997, SLP-29-PE806, SLP-29-PR1903, SLP-29-PR1968, SLP-29-PR1891, PRE1066); dp3 (R: MNHN-SLP-29-PR1983, SLP-29-PE1355, SLP-29-PE1143, SLP-29-PE1057, SLP-29-PE1384, SLP-29- PE993, SLP-29-PE966, SLP-29-PE1012, SLP-29-PE878, SLP-29-PE303, SLP-29-PE1818, SLP-29-PE113, SLP-29-PE103, PRE997; L: MNHN-SLP-29-PR3022, SLP-29-PR1919, SLP-29- PR58, SLP-29-PE1562, SLP-29-PE868, SLP-29-PE263, PRE239, PRE244); dp4 (R: MNHN-SLP-29-PE1434, SLP-29-PE1024, SLP-29-PE1552, SLP-29-PE1438, SLP-29-PE488, SLP-29-PE185, SLP-29-PE653, SLP-29-PE1026, SLP-29-PE751, SLP-29-PE624, SLP-29-PE392, SLP-29-PE88, PRE247, PRE243; L: MNHN-SLP-29-PR2477, SLP-29-PR3026, SLP-29-PR2424, SLP-29- PR2044, SLP-29-PR2008, SLP-29-PE879, SLP-29-PE1713, SLP-29-PE1473, SLP-29-PE95, SLP-29-PE1048, SLP-29-PE1382, SLP-29-PE856, PRE242); p2 (L: MNHN-SLP-29-PE772, SLP-29-PE1499, SLP-29-PE1180, SLP-29-PE165); p3 (R: MNHN-SLP-29-PE180, SLP-29-PE1214, SLP-29-PE17, SLP-29-PE759; L: MNHN-SLP-29-PE1472, SLP-29-PE1474, SLP-29-PE1459); p4 (R: MNHN-SLP-29-PR1949, SLP-29-PE1325, SLP-29-PE977, SLP-29-PE745; L: MNHN-SLP-29-PE770, SLP-29-PE763, SLP-29-PE596, SLP-29-PE719); m1/2 (R: MNHN-SLP-29-PE667, SLP-29-PE1177, SLP-29-PE1848, SLP-29-PE1320, SLP-29- PE827, SLP-29-PE694, SLP-29-PE669, PRE240; L: MNHN-SLP-29-PR3106, SLP-29-PR2026, SLP-29-PE1375, SLP-29-PE951, SLP-29-PE1340, SLP-29-PE730, PRE245); m2 (R: MNHN-SLP-29-PE22; L: MNHN-SLP-29-PE1406, SLP-29-PE768, SLP-29-PE757); m3 (R: MNHN-SLP-29-PR3211, SLP-29-PE1306, SLP-29-PE682, SLP-29-PE48, PRE861; L: MNHN-SLP-29- PR1990, SLP-29-PR1954, SLP-29-PE1410, SLP-29-PE693); tibia (L:MNHN.F.PMT112); humerus (R: MNHN.F.PMT114; L: MNHN.F.PMT115); scapula (R: MNHN.F.PMT116); ulna (R: MNHN.F.PMT117, MNHN.F.PMT118); metatarsal II (L: MNHN.F.PMT119); calcaneus (R: MNHN.F.PMT123, MNHN.F.PMT124, MNHN.F.PMT125; L:MNHN.F.PMT126, MNHN.F.PMT127); astragalus (R: MNHN.F.PMT132, MNHN.F.PMT133, MNHN.F.PMT134, MNHN.F.PMT135; L: MNHN.F.PMT128, MNHN.F.PMT129, MNHN.F.PMT130, MNHN.F.PMT131); distal phalanx (MNHN.F.PMT137, MNHN.F.PMT138, MNHN.F.PMT139, MNHN.F.PMT140, MNHN.F.PMT141, MNHN.F.PMT142, MNHN.F.PMT143, MNHN.F.PMT144); navicular (R: MNHN.F.PMT145, MNHN.F.PMT146; L: MNHN.F.PMT147) .

St Agnan: dP2 (R: MNHN-STA658; L: MNHN-STA633); dP4 (L: MNHN-STA24); P2 (R: MNHN-STA634, STA644, STA649; L: MNHN-STA648); P3 (L: MNHN-STA639, STA643, STA645); P4 (R: MNHN-STA635, STA656); P3-4 (R: MNHN-STA638); M1 (R:, MNHN-STA894); M1/2 (R: MNHN-STA869, STA637, STA652, STA653, STA654; L: MNHN-STA651, STA641, STA897); dp2 (L: MNHN-STA893); dp3 (R: MNHN-STA883; L: MNHN-STA881); dp4 (R: MNHN-STA627); p3 (L: MNHN-STA642); m1/2 (R: MNHN-STA624, STA628, STA629, STA630, STA632, STA876; L: MNHN-STA878, STA998, STA631, STA640, STA647, STA657); m3 (R: MNHN-STA1000-L; L: MNHN-STA626); incisor (MNHN-STA896) .

Sézanne-Broyes: maxillary M1-M2 (L: MNHN-SEZ325); maxillary M1-M3 (L: MNHN-SZ7306); dP4 (R: MNHN-SEZ342, SEZ344; L: MNHN-SEZ337, SEZ343); P2 (L: MNHN-SEZ359); P3 (R: MNHN-SEZ347; L: MNHN-SEZ268); P4 (R: MNHN-SEZ355, SEZ357, SEZ358; L: MNHN-SEZ356); M1/2 (R: MNHN-SEZ332, SEZ333, SEZ338, SEZ339, SEZ341, SEZ360, SEZ7337; L: MNHN-SEZ331, SEZ340, SEZ345, SEZ7335); M3 (L: MNHN-SEZ7334); dp3 (L: MNHN-SEZ349); dp4 (R: MNHN-SEZ7340); p3 (R: MNHN-SEZ312; L: MNHN-SEZ7272); p4 (R: MNHN-SEZ313, SEZ351, SEZ353; L: MNHN-SEZ346, SEZ352); m1 (R: MNHN-SEZ314); m2 (R: MNHN-SEZ315); m1/2 (L: MNHN-SEZ326, SEZ7336); m3 (R: MNHN-SEZ316, SEZ329) .

TYPE LOCALITY. — Environs d’Epernay, Cuisien (Ageian), MP10.

DISTRIBUTION. — Condé-en-Brie, St Agnan (Aisne, France), Sézanne-Broyes (Marne, France), MP8-9; Cuis, Grauves, Mancy, Mont Bernon, Monthelon (Marne, France), Prémontré (Aisne, France); Oosterzele ( Belgique), MP10.

EMENDED DIAGNOSIS (modified from Remy 2017). — Small palaeotheriid Equoidea , with an estimated P2-M3 length of about 40 mm, a bunolophodont and brachyodont dentition, an occasional mesostyle and a parastyle not very protruding on upper molars, a protocone mesially shifted on P4, a distal expansion of the postero-lingual cingulum on P3-P4, narrow lower molars with thick and continuous labial cingulids, a cristid obliqua joining the middle of the protolophid and a hypoconulid linked to the hypolophid.

DIFFERENTIAL DIAGNOSIS (modified from Remy 2017). — Differs from species of Pachynolophus in having a wider P2 and an occasional mesostyle on upper molars. Further differs from more advanced Palaeotheriidae (Lophiotherium, “propalaeotheres”, and Palaeotheriinae) in possessing an inconstant mesostyle on upper molars, a parastyle less protruding and a shallower protoloph groove on upper molars, a lingual cingulum on these teeth stronger than in most of them, a P4 triangular (instead of being subquadrangular), and a hypoconulid more developed en m1-m2. Smaller than Propalaeotherium gaudryi , larger than Pliolophus and Cymbalophus . Possesses a hypoconulid linked to hypolophid, whereas there is a hypoconulid-hypoconid junction in Pliolophus , Cymbalophus and Hyracotherium .

DESCRIPTION

Teeth

The maxillary has a short post-P1 diastema. The post-canine diastema can be long ( Fig. 11 D’) or very short (MNHN-SLP-29-PE1559). The P1 is more or less elongated, and displays a single cusp in the middle of the tooth ( Fig. 11R ). The P2 is two-rooted, narrower anteriorly than posteriorly ( Fig. 11M, R, T ). The metacone is very small, closely appressed to the paracone and indistinguishable if the tooth shows wear. The cusps appear further apart and the metacone is larger on MNHN.STA-648 and MNHN-STA649. A bulge is present at the level of the protocone. The parastyle is absent. The parastyle of P3 is small but well formed ( Fig. 11 E-H, N-P, S). The paracone and metacone are closely appressed. The paraconule and the metaconule can be large ( Fig. 11G ), but the metaconule is often absent ( Fig. 11F ) or reduced ( Fig. 11N ). The sizes of the two conules do not vary together. The cingulum can be large and continuous or interrupted. The protoloph is interrupted before joining the preparacrista. MNHN-SLP-29-PR1953 is a P3 that has grown at 90° to the normal angle; its lingual side is found in anterior position ( Fig. 11 E’). The parastyle of P4 is smaller than the paracone ( Fig. 11Q , S-T). The paraconule is almost as large as the paracone. Two lingual bulges are present at the level of the metaconule ( Fig. 11R ). The cingulum is continuous. The centrocrista of upper molars is slightly flexed ( Fig. 11S , U-Z). The mesostyle is absent, but on some specimens a thin ridge is present ( Fig. 11R, V , X-Y, C’). The paraconule is located in the center of the protoloph. The metaconule is a little less developed than the paraconule, and it is sometimes difficult to discern ( Fig. 11 A’). The protoloph is interrupted before joining the preparacrista. The metaloph is interrupted at the base of the metacone ( Fig. 11U , X-Y) or connected by a metacone fold which joins the centrocrista in its center ( Fig. 11V ). This last morphology is found on a very reduced number of teeth. The parastyle is smaller than the other cusps. The cingulum is sometimes interrupted at the level of the hypocone.

There is no diastema between p1 and p2 ( Fig. 12Z ). The posterior border of the symphysis extends back to the level of p1. The p1 is two-rooted but on some specimens the roots are fused. The p2 protoconid is high and the metaconid is absent or small ( Fig. 12A, G ). The hypoconid is poorly developed, and a small paraconid is present. A ridge extends between the hypoconid and the protoconid. Two other crests extend posteriorly to the protoconid, joining the labial and the lingual border of the tooth respectively. The metaconid of p3 is smaller than the protoconid ( Fig. 12B, C , H-I). It is very close to the latter and slightly posteriorly placed. The hypoconid is lower than the other cusps but well-developed. A small bulge (possibly an incipient entoconid) is sometimes present lingually to the hypoconid ( Fig. 12C ). The paralophid is very short. The cristid obliqua joins the lingual edge of the protoconid. A ridge extends posteriorly from the metaconid. The p4 entoconid is absent ( Fig. 12D ), but a small bulge is sometimes present on the cingulum ( Fig. 12I ). The protoconid and the metaconid are quite close and transversely aligned. The metaconid is either twinned or simple. The paralophid is short and joins the lingual edge of the tooth. The cristid obliqua runs from the hypoconid to a point situated at half height of the protolophid between the midpoint of protoconid and the metaconid. The paralophid of lower molars is variable, it can join the lingual edge of the tooth ( Fig. 12Y ) or be very short ( Fig. 12Z ). The cusps are aligned transversely. The metaconid is twinned. The cristid obliqua joins the midpoint of the protolophid at a half height. The protolophid is high, the hypolophid is lower. The cingulum is labially continuous. The hypoconulid is displaced lingually and it is attached medially to the hypolophid. The post-hypocristid is very small or absent. On some teeth, the hypoconulid is linked very close to the hypoconid by a postcristid ( Fig. 12S ). The cingulum of m3 is continuous labially ( Fig. 12V, X, Y ). The cristid obliqua joins the protolophid medially and at mid-height. The lophids are deeply notched. The paralophid is longer than on the other molars. The lobe of the hypoconulid is developed, it has the same size as the anterior part of the talonid. The postcristid links the hypoconulid to the center of the hypolophid. Two teeth of Condé-en-Brie (MNHN-CB1585, CB1571) show the hypoconulid linked to the hypoconid by a postcristid ( Fig. 12T, U ). The hypoconulid lobe forms a horseshoe in occlusal view.

Ontogeny

MNHN-SLP-29-PE1553 ( Fig. 12W ) shows that m3 is completely erupted while p4 only begins to erupt. On MNHN-SLP-29-PE1467 ( Fig. 12Z ), the m3 is absent but the alveoli seem to indicate that it was erupting while the dp2 to dp4 were still present.

Deciduous teeth

The DP2 is narrower anteriorly ( Fig. 11I, J ). The paracone is developed, the metacone is extremely reduced and closely appressed to the paracone. A crest is sometimes present at the lingual side of the metacone ( Fig. 11J ). The parastyle is small and projected anterolabially. Sometimes a small metacone is present posteriorly to the paracone ( Fig. 11J ). The parastyle of DP3 is projected anteriorly ( Fig. 11 A-C). The paraconule is less developed than the metaconule. The centrocrista is high and very slightly flexed. A mesostyle can be present ( Fig. 11B ). The metaloph is interrupted at the base of the metacone, sometimes oriented towards the paracone ( Fig. 11B ), sometimes ended by a metacone fold ( Fig. 11C ). The protoloph joins the preparacrista in its center or slightly posteriorly. The cingulum is developed. A small crest can be present between the protocone and the hypocone ( Fig. 11C ). The DP4 is molarized and very similar to molars ( Fig. 11K, L ). The centrocrista is slightly flexed labially. The conules are developed. The cingulum usually forms a ridge connecting the hypocone anteriorly. Sometimes, a mesostyle can be present ( Fig. 11L ).

The dp2 is narrow ( Fig. 12Z ). Two crests, one labial and one lingual, extend posteriorly from the protoconid. A small hypoconid appears to be present, a crest extends anteriorly from the hypoconid in the center of the tooth. The paraconid of dp3 is developed ( Fig. 12E, J, Z ). The cristid obliqua is oriented toward the center of the protolophid ( Fig. 12Z ). The metaconid is larger than the protoconid and the paralophid is developed. A postcristid links the hypolophid to the hypoconulid ( Fig. 12J ). The hypolophid can be absent and the hypoconulid can be linked to the hypoconid (MNHN. MCB-0196). Sometimes a crest extends posteriorly from the protoconid on its labial side. The lingual wall is developed between the metaconid and the entoconid. The dp4 is slightly narrower at the anterior part of the trigonid than at the posterior part of the talonid ( Fig. 12F, K, Z ). The metaconid is twinned. The cristid obliqua joins the metaconid on its labial side. The hypoconulid is salient and displaced lingually. The anterior, labial and posterior cingulums are continuous.

Postcranial elements

Humerus. The proximal part is missing. The distal trochlea is poorly marked ( Fig. 13 E-G). The epicondyles are poorly developed but the medial epicondyle is projected further than the lateral epicondyle. A distinct capitular keel is present ( Fig. 13G ). The supracondylar foramen is present in the radial fossa.

Ulna. The bone is elongated, arched anteriorly and compressed mediolaterally. A slight depression is present along the dorsolateral side of the bone ( Fig. 13D ). The olecranon process is extended posteriorly and relatively long. The trochlear notch is concave proximodistally. The medial and lateral coronoid processes bear oval facets for the humerus. A lateral radial facet is present below the lateral coronoid process. The medial radial facet, situated below the medial coronoid process is smaller than the lateral radial facet. A prominent ridge extends from the lateral coronoid process and runs along the anterior border of the shaft. A second ridge extends along the shaft from the medial coronoid process.

Tibia. The proximal articular surface is triangular in dorsal view. The lateral condyle is slightly convexe and the medial condyle is more flat. The lateral intercondyloid eminence is slightly higher than the medial intercondyloid eminence. The diaphysis is slightly S-shaped in anterior view. The anterior tibial crest extends for about a third of the diaphysis. The distal end of the tibia has a medially extended medial malleolus and fovea on the mid-ventral surface ( Fig. 13A, B ).

Calcaneus. This bone is elongated and medio-laterally flattened ( Fig. 13 J-L). The distal part has a small, slightly concave astragalar facet. The sustentacular facet is rounded, slightly triangular. The proximal part of the ectal facet faces anteromedially below the tuber. The distal part of the ectal facet is distally facing. The cuboid facet is concave transversely and slightly convexe anteroposteriorly.

Astragalus. The trochlea is well marked, slightly oblique proximo-distally ( Fig. 13H, I ). The trochlea does not reach the navicular facet. The articular facets are well defined. In posterior view, a small facet of articulation with the calcaneus is present distolaterally. The navicular facet is saddle-shaped. The sustentacular facet is slightly concave. The astragalus MNHN.F.PMT134 ( Fig. 13O, P ) is much larger and has worn facets, however it seems to display the same morphology. It could be a large individual, or possibly a different species of larger size so far only represented by postcranial material, the locality of Prémontré not having yielded fossils of large size. This astragalus is much smaller than that of Propalaeotherium gaudryi , the only contemporary larger hippomorph species.

Navicular. The articular facet with the astragalus is concave ( Fig. 13S ). The articular facets with the mesocuneiform and the ectocuneiform are connected ( Fig. 13T ). Two small facets of articulation with the cuboid are present on the lateral face. A small facet of articulation with the entocuneiform is present posteriorly.

Metatarsals. The metatarsal II is curved medio-distally ( Fig. 13Q, R ). Proximally, a mediolateral compression is present. The proximal facet is slightly concave. Postero-medially on the proximal part, a small elliptical facet of articulation with the entocuneiform is present. The distal trochlea is asymmetrical. The metatarsal III is long and straight. The distal articulation is keeled and symmetric in shape.

Distal phalanges. Median ungual phalanges: They are bifid, constricted latero-medially in the center ( Fig. 13 V-Y, D’, E’). The distal part bears two foramina in dorsal view, and a single foramen where the phalanx is constricted. In ventral view, the proximal part has two large foramina. The narrowest and longest phalanges might be attributed to fore limbs ( Fig. 13V, W ), and the widest and shortest to hind limbs ( Fig. 13X, Y , D’-E’). On the hind limb phalanges, sometimes two foramina can be present on the distal part.

Lateral and medial ungual phalanges. They are bifid, constricted obliquely latero-medially.The distal part bears several foramina in dorsal view, and one in ventral view on the shortest side of the phalanx. In dorsal view, a foramen is present in the middle of the phalanx. The phalanx MNHN.F.PMT139 ( Fig. 13Z , A’) is slightly shorter and wider than MNHN.F.PMT137 ( Fig. 13 B’-C’). The former could belong to a hind limb, and the latter to a fore limb.

COMPARISONS

There is no noticeable difference between the mandibles and lower dentition of Orolophus maldani and Pachynolophus eulaliensis . On the other hand, the P2 displays closely appressed paracone and metacone, the metacone being sometimes indistinguishable due to wear, while these two cusps are more distant in P. eulaliensis . The postprotocrista is generally more developed on P3-4 of P. eulaliensis , although it varies in O. maldani . An entoconid is usually present on p4 of P. eulaliensis , but sometimes it is absent. This entoconid is generally absent in O. maldani , although a cingular bulge is observable on some specimens. The lophodonty is less marqued than in Pachynolophus lavocati Remy, 1972 and in Pachynolophus livinierensis Savage, Russell & Louis, 1965 . The metaconule of upper molars is more developed than in Pachynolophus duvali Pomel, 1847 and in P. livinierensis . The conules of upper molars and premolars are more developed than those of P. lavocati . Orolophus is much smaller than Pachynolophus cayluxi Filhol, 1888 . The labial cusps of upper premolars of P. cayluxi are oriented slightly more lingually than those of Orolophus . The metaconule of upper molars is more developed in Orolophus than in “ Hyracotherium ” remyi Checa-Soler, 1997 . The lophodonty of O. maldani is more developped than in Hallensia . The centrocrista of the upper molars are more flexed than in Pliolophus and Cymbalophus . The hypoconulid of the lower molars is linked to the hypolophid, whereas it is linked to the hypoconid in Cymbalophus and in most specimens of Pliolophus . The teeth are smaller than in Propalaeotherium gaudryi .

COMMENTS ON “ PROPACHYNOLOPHUS LEVEI ”

P. levei has been described by Hooker (1994) on the basis of a maxilla with P3-M3 from Condé-en-Brie and three isolated teeth from Avenay and Sézannes-Broyes. The study of a large number of O. maldani specimens reveals that there is no difference between O. maldani and P. levei . The maxillary, holotype of the species, comes from the Levé collection, now lost, but two casts have been deposited at MNHN (MNHN.CB16165, Fig. 11S ) and NHM (BMNH. M49399). This poorly known species was hardly comparable with O. maldani , which was poorly represented and described. The affinities of the two species have been discussed by Remy (2017), with the support of a phylogenetic analysis in which he coded several characters which differ between the two taxa. However, these differences appear to fall in the range of intraspecific variability, observable with a larger sample: Character 8, lophodonty. P. gaudryi and O. maldani are coded with a higher degree of lophodonty than P. levei and P. remyi . But the observations do not indicate such a difference for P. levei , which present the same degree of lophodonty than O. maldani . Character 17, metaconule of P3. Absent in P. levei and weak in O. maldani . Observations on a large sample indicate that this trait varies from absent to present in O. maldani . Character 22, lingual cingulum of the P4. Continuous in P. levei and reduced to the level of protocone in O. maldani . This is a very variable character. Character 23, postero-lingual cingulum of P4. Distal expansion in O. maldani , absent in P. levei . This is also a very variable character. Character 26, position of the protocone on P4. Placed mesially in O. maldani , central in P. levei . This character can vary. Character 40, mesostyle. Absent in P. levei , sometimes present in O. maldani . This character from present to absent in Orolophus . Character 41, morphology of the mesostyle. Linked to the previous character. Character 44, morphology of the lingual cingulum of the upper molars. Continuous in P. levei , interrupted in O. maldani . This character varies, as on premolars. Character 54, relative area M3 / M2. M3 <M2 for P. levei , and small difference in O. maldani . This requires to be testing on a large sample. Only a small sample of O. maldani were available to Remy (2017), which did not allow him to observe all the intraspecific variations of this species. The characters that differentiate O. maldani from P. levei (known from a few specimens; Hooker 1994) in the phylogenetic analysis of Remy (2017), are mainly related to the cingula which are variable structures, but also to characters coded according to states that would require the knowledge of the intraspecific variability, thus requiring a wide sampling (for example, characters 40 and 54).

Therefore, our observation of a larger population of Orolophus has demonstrated that the type of P. levei is included within the variability of O. maldani , and it is thus considered as a junior synonym of Orolophus maldani .

Figures

FIG. 11. — Upper teeth of Orolophus maldani (Lemoine, 1878) from the Paris Basin in occlusal (A-L, N-D’), lingual (M) and lateral (E’) views: A, left DP3 (MNHN- SLP-29-PE100); B, right DP3 (MNHN-SLP-29-PR1973 [reversed]); C, right DP3 (MNHN-GR7825 [reversed]); D, M, left P2 (MNHN-SLP-29-PE10); E, left P3 (MNHN-SLP-29-PE731);F, right P3 (MNHN-SLP-29-PE252 [reversed]);G, right P3 (MNHN-SLP-29-PE12 [reversed]);H, left P3 (MNHN-SLP-29-PE254);I, left DP2 (MNHN-SLP-29-PE950); J, left DP2 (MNHN-SLP-29-PE717);K, left dP4 (MNHN-MTH7);L: right DP4 (MNHN-SLP-29-PR1913 [reversed]);N, left P3 (MNHN-SLP- 29-PE590); O, right P3 (MNHN-SLP-29-PR1896 [reversed]); P, right P3 (MNHN-SLP-29-PR1914 [reversed]); Q, left P4 (MNHN-SLP-29-PE741); R, right maxillary with P1-P2 (MNHN-SLP-29-PE1296 [reversed]); S, left maxillary with P3-M3 (holotype of “Propachynolophus levei”, MNHN.CB16165 [cast]); T, right maxillary with P2-P4 (MNHN-SLP-29-PE2388 [reversed]); U, left M1/2 (MNHN-SLP-29-PE147); V, left M3 (MNHN-SLP-29-PE224); W, left M1/2 (MNHN-CB1531); X, left M1/2 (MNHN-SLP-29-PE148); Y, left M3 (MNHN-SLP-29-PR1968); Z, right M1/2 (MNHN-SLP-29-PE149 [reversed]); A’, right M1/2 (MNHN-SLP-29-PE987 [reversed]); B’, right M1 (MNHN-CB4689 [reversed]); C’, right M2 (MNHN-SLP-29-PE508 [reversed]); D’, left maxillary with P3 (MNHN-SLP-29-PE1953); E’, right upper canine (MNHN-SLP-29-PE1378); A-R, T-D’, coated with magnesium. Scale bar: 5 mm.

FIG. 12. — Lower teeth of Orolophus maldani (Lemoine, 1878) from the Paris Basin in occlusal (A-Z) and lateral (A’) views: A, right p2 (MNHN-SLP-29-PE1499); B, right p3 (MNHN-SLP-29-PE180); C, left p3 (MNHN-SLP-29-PE1472 [reversed]); D, right p4 (MNHN-SLP-29-PE1325); E, right dp3 (MNHN-SLP-29-PE1355); F, left dp4 (MNHN-SLP-29-PE856 [reversed]); G, left p2 (MNHN-SLP-29-PE165 [reversed]); H, right p3 (MNHN-SLP-29-PE1214); I, right mandible with p3-p4 (MNHN-SLP-29-PE1362); J, right dp3 (MNHN-SLP-29-PE303); K, right dp4 (MNHN-SLP-29-PE392); L, left p4 (MNHN-SLP-29-PE763 [reversed]); M, left m1/2 (MNHN-SLP-29-PE1340 [reversed]); N, right m3 (MNHN-PRE861); O, right m3 (MNHN-SLP-29-PE1306); P, right m1/2 (MNHN-CB4687); Q, right m1/2 (MNHN- CB1584);R, right m2 (MNHN-CB4686);S, right m2 (MNHN-CB198);T, left m3 (MNHN-CB1571 [reversed]);U, left m3 (MNHN-CB1585 [reversed]);V, right mandible with p4, m2-m3 (holotype,MNHN-AL5199);W, right mandible with p4-m3 (MNHN-SLP-29-PE1553);X, right mandible with p4-m3 (MNHN-SLP-29-PE480);Y, right mandible with p4-m3 (MNHN-MA14792); Z, A’, right mandible with dp2-m2 (MNHN-SLP-29-PE1467); A-U, W-Z, coated with magnesium. Scale bars: 5 mm.

FIG. 13. — Postcranial elements of Orolophus maldani (Lemoine, 1878) from the Paris Basin: A, B, left tibia (MNHN.PMT-112) in anterior (A) and posterior (B) views; C, D, right ulna (MNHN.F.PMT117) in lateral (C) and anterior (D) views;E, F, right humerus (MNHN.F.PMT115) in posterior (E) and anterior (F) views;G, right humerus (MNHN.F.PMT114) in anterior view; H, right astragalus (MNHN.F.PMT133) in anterior view; I, left astragalus (MNHN.F.PMT136 [reversed]) in anterior view; J, right calcaneus (MNHN.F.PMT123) in anterior view; K, L, left calcaneus (MNHN.F.PMT126 [reversed]) in anterior (K) and medial (L) views; M, N, right astragalus (MNHN.F.GR18005) in anterior (M) and posterior (N) views; O, P, right astragalus (MNHN.F.PMT134) in anterior (O) and posterior (P) views; Q, R, left metatarsal II (MNHN.F.PMT119) in anterior (Q) and posterior (R) views; S-U, right navicular (MNHN.F.PMT146) in dorsal (S), ventral (T) and medial (U) views; V, W, distal phalanx (MNHN.F.PMT142) in dorsal (V) and ventral (W) views; X, Y, distal phalanx (MNHN.F.PMT140) in dorsal (X) and ventral (Y) views; Z, A’, distal phalanx (MNHN.F.PMT139) in dorsal (Z) and ventral (A’) views; B’, C’, distal phalanx (MNHN.F.PMT137) in dorsal (B’) and ventral (C’) views;D’, E’, distal phalanx (MNHN.F.PMT141) in dorsal (D’) and ventral (E’) views. Scale bars: 1 cm.