[Palaeontology, Vol. 60, Part 6, 2017, pp. 837–852]

EOCENE PACHYNOLOPHINAE (PERISSODACTYLA, PALAEOTHERIIDAE) FROM CHINA, AND THEIR PALAEOBIOGEOGRAPHICAL IMPLICATIONS by BIN BAI1,2 1Key Laboratory of Vertebrate Evolution & Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology & Paleoanthropology, Chinese Academy of Sciences, Beijing, China 2State Key Laboratory of Palaeobiology & Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China; [email protected]

Typescript received 29 March 2017; accepted in revised form 27 June 2017

Abstract: The perissodactyl family Palaeotheriidae China, in which the complete dentition is known. Qianohip- has traditionally been considered to be a nearly endemic pus is characterized by a molariform P2 and non-molariform European group within Equoidea, but a few palaeotheres P3–4; a relatively high degree of lophodonty; the absence of have been reported from Asia. Here, I reanalyse a maxilla mesostyles; an angular bending in the protoloph on P3-M3 containing M1–3 from the Lunan Basin, Yunnan Province, and the metaloph on M1–3 at the paraconule and meta- China. This element was initially assigned to a new tapiro- conule, respectively; and weakly developed ‘metastylid’ on morph species, Lophialetes yunnanensis, but is here placed in the lower cheek teeth. A cladistic analysis supports a close a new genus Lophiohippus within Pachynolophinae based relationship between Lophiohippus yunnanensis and Paran- mainly on the absence of mesostyles, the strongly oblique chilophus, and suggests that Qianohippus is closely related to metalophs, the strong development of lophodonty, parastyles some derived pachynolophs. The appearance of the pachyno- overlapping metastyles of preceding teeth and situated mesial lophins Lophiohippus and Qianohippus in China supports the to the paracone, and the fact that M3 is longer than wide existence of a biogeographical connection between and has a large and buccally deflected metastyle. Lophiohip- and Asia in the Middle-Late Eocene, and the dispersal route pus differs from European Anchilophus and Paranchilophus in was probably along the Tethyan microcontinents in the that the parastyles are situated mesial or even slightly lingual, south. rather than mesiobuccal, to the paracones, and M3 is mark- edly relatively larger than M1. I further reanalyse Qianohip- Key words: Palaeotheriidae, Pachynolophinae, Lophiohip- pus magicus from the Shinao Basin of Guizhou Province, pus, Qianohippus, phylogeny, palaeobiogeography.

P ALAEOTHERIIDAE was historically regarded as a group of Eocene Lingcha Formation, whereas the others are from equoids that flourished in Palaeogene Europe but also Middle–Upper Eocene strata. The Chinese palaeotheriid had a scattered distribution in China. Traditionally, material, in contrast with the numerous complete skulls Palaeotheriidae was thought to be the sister group to and skeletons from Messel in Germany and other locali- , the two clades collectively forming the super- ties in Europe (Franzen 2010), is mainly limited to tooth- family Equoidea (Franzen 1989; Froehlich 1999; Rose bearing maxillae and mandibles. 2006). Recent phylogenetic work, however, has suggested The holotype of ‘Lophialetes’ yunnanensis Huang & Qi, that equids are more closely related to tapiromorphs than 1982, a species of the well established genus Lophialetes to palaeotheriids, although palaeotheriids have been rep- (Matthew & Granger 1925; Radinsky 1965), is a maxilla resented in the recent analysis only by Pachynolophus with three molars (IVPP V 6508) that was only briefly eulaliensis (Bai et al. 2014). Known palaeotheriids from described when the species was first erected. The speci- China include sinense from Xintai Basin, men was collected from the Lumeiyi Basin, Yunnan Pro- Shandong Province (Zdansky 1930), Propachynolophus vince by an IVPP field crew in 1970. I am skeptical of the hengyangensis from the Hengyang Basin, Hunan Province referral of this maxilla to Lophialetes, and suggest that it (Young 1944; Li et al. 1979) and Qianohippus magicus represents a palaeotheriid rather than a tapiromorph, from the Shinao Basin, Guizhou Province (Miao 1982; based on reexamination of the type specimen. Accord- Fig. 1). Propachynolophus hengyangensis is from the Lower ingly, the present paper describes IVPP V 6508 in more

© The Palaeontological Association doi: 10.1111/pala.12319 837 838 PALAEONTOLOGY, VOLUME 60

FIG. 1. E 90° 100° 110° 120° Distribution of Palaeotheriidae at Palaeogene locali- ties in China. 1, ‘Propachynolophus’ hengyangensis, Lower Eocene, Heng- yang Basin, Hunan Province; 2, Lophiohippus yunnanensis, Middle 40° Eocene, Lunan Basin, Yunnan Pro- Beijing vince; 3, ‘Propalaeotherium’ sinense, Middle Eocene, Xintai Basin, Shan- dong Province; 4, Qianohippus mag- 3 icus, Upper Eocene, Shinao Basin, Guizhou Province. 30°

4 1 N 20° 2

detail, and reanalyses its phylogenetic relationships. Here, The phylogenetic analyses presented in this paper were I also take the opportunity to redescribe and reanalyse conducted with a parsimony criteria in PAUP 4.0 (Swof- Qianohippus magicus, a palaeotheriid that has rarely been ford 2002) and TNT (Goloboff et al. 2008). The matrix mentioned by researchers since its original description by constructed for analysis was based on data from Danilo Miao (1982) even though the dentition is completely et al. (2013), with ‘Lophialetes’ yunnanensis and Qianohip- known in this species. Finally, the palaeobiogeography pus magicus added, and contained a total of 28 taxa and of palaeotheriids is discussed based on a reanalysis of 72 characters (Appendix 1; Bai 2017). All characters were Middle–Late Eocene palaeotheriids from China. unordered and equally weighted. The heuristic search algorithm was used with 1000 replications of random stepwise addition and tree-bisection-reconnection (TBR) MATERIAL AND METHOD branch swapping.

The specimens of ‘Lophialetes’ yunnanensis (IVPP V 6508) Institutional abbreviations. AMNH FM, American Museum of and Qianohippus magicus (IVPP V 6519–6520) are housed Natural History, Fossil , New York; IVPP, Institute of in the Institute of Vertebrate Paleontology and Paleoan- Vertebrate Paleontology and Paleoanthropology, Beijing, China. thropology (IVPP), Chinese Academy of Sciences, Beijing, China. The upper dentition of the holotype (IVPP V 6519) of Qianohippus magicus is currently unavailable; the SYSTEMATIC PALAEONTOLOGY figure presented in this work is based on a cast (AMNH FM 144356) that was made from IVPP V 6519. Order PERISSODACTYLA Owen, 1848 Remy (2012) used the terms ‘crochet’ and ‘anticrochet’ Superfamily EQUOIDEA Hay, 1902 for the mesiobuccal end of the metaloph and a crista on Family PALAEOTHERIIDAE Bonaparte, 1850 the lingual side of the paracone, respectively. However, Subfamily PACHYNOLOPHINAE Pavlow, 1888 ‘crochet’ and ‘anticrochet’ have also been used for struc- Tribe ANCHILOPHINI Remy, 2012 tures on the metaloph and protoloph in rhinocerotoids. Genus LOPHIOHIPPUS nov. To avoid confusion and uncertainty regarding homolo- gies, I use the terms ‘postcrista’ and ‘crista’ as respective Type and only species. Lophiohippus yunnanensis (Huang replacements for ‘crochet’ and ‘anticrochet’ as used by & Qi, 1982). Remy (2012). Our usage is appropriate partly because the term ‘crista’ has previously been used for the structure on Derivation of name. Greek ‘lophia’ meaning crest, with the lingual side of the paracone in tapiroids and reference to the protolophs and metalophs of the upper rhinocerotoids (Radinsky 1965). molars lacking the paraconules and metaconules; and BAI: EOCENE PACHYNOLOPHINAE FROM CHINA 839

Greek ‘hippos’ meaning horse, a common used root in equid names.

Type locality and horizon. As for the type and only spe- cies.

Diagnosis. As for the type and only species.

Lophiohippus yunnanensis (Huang & Qi, 1982) Figure 2

1982 Lophialetes yunnanensis Huang & Qi, p. 315, fig. 1, pl. 1, figs 4–5.

LSID. urn:lsid:zoobank.org:act:83E11014-F0C4-474B-A779- A872888DDCB0

Holotype. IVPP V 6508, a left maxilla with M1–3.

Type locality and horizon. Lumeiyi Formation (field local- ity number: 70002), Lunan Basin, Yunnan Province, China. Middle Eocene.

Emended diagnosis (modified from Huang & Qi 1982). Upper molars highly lophodont, and gradually increasing in size from M1 to M3. Parastyles overlapping metastyles of preceding teeth, and situated mesial to the paracone. Paracone rib relatively narrow and hemicylin- drical. Metacone long and flat. Metaloph strongly oblique and joining paracone on moderately worn tooth. Metas- tyle of M3 large and deflected buccally.

Differential diagnosis. Differs from Anchilophus and Paranchilophus in having the parastyles situated mesial or even slightly lingual, rather than mesiobuccal, to the para- cones, the parastyles overlapping the metastyles of the preceding teeth, the metastyle of M3 more buccally deflected, and M3 relatively pronouncedly larger than M1. FIG. 2. Left maxilla of Lophiohippus yunnanensis (IVPP V 6508) with M1–3. A, occlusal view. B, buccal view. C, Description lingual view. Scale bar represents 1 cm.

M1–2. These teeth are generally similar in morphology (Fig. 2). However, M1 is roughly quadrate in outline and heavily worn, metacone is more lingually situated than the paracone and while M2 is larger, relatively mesiodistally longer on the buccal slightly lingually depressed, bearing a very weak rib on the buc- side and only moderately worn. The lingual side of the proto- cal side. The postmetacrista is considerably elongated and direc- cone of M1 is damaged, as are those of the protocone and hypo- ted slightly buccally, and bears a large wear facet on the lingual cone of M2. The parastyle is rib-like, high, and situated mesial side. The metastyle is relatively high, and overlapped by the to the paracone. The buccal side of the paracone bears a half- parastyle of the posteriorly adjacent tooth. The parastyle of M2 cylindrical rib, which is separated from the parastyle by a rela- lies further from the paracone than that of M1. No mesostyle is tively deep groove and extends to the root. The centrocrista has present on the ectoloph. The protoloph extends from the proto- a flat buccal surface and is slightly buccally bowed. The cone toward the paracone without bearing any trace of a 840 PALAEONTOLOGY, VOLUME 60 paraconule. The metaloph is straight and strongly oblique, (Remy 2015), although the definition and phylogenetic extends towards the paracone rather than the metacone, and position of the latter are controversial (Froehlich 1999). lacks a metaconule. The metaloph widens towards the mesiobuc- Some genera commonly assigned to Pachynolophinae, cal end. The buccal cingulum is narrow, weak, and interrupted such as Propachynolophus, Pachynolophus, Anchilophus at the base of the paracone. The mesial and distal cingula are and Propalaeotherium, have been considered to be equids slightly wider than the buccal cingulum, and a narrow cingulum by some authors (Savage et al. 1965; Franzen 1989, 2007; is present low on the lingual slope of the central valley. Rose 2006). Recently, Danilo et al. (2013) proposed that Palaeotheriidae is composed of ‘Pachynolophs’ and M3. This tooth is the largest of the three molars, and the hypo- Palaeotheriinae, and excluded Propachynolophus and cone is partially broken. M3 is roughly trapezoidal in outline, ‘Pachynolophus’ hookeri from Palaeotheriidae. Generally, the buccal side being considerably longer than the lingual side Palaeotheriinae is characterized by the presence of at least (Fig. 2). M3 is generally similar to M2 in morphology, but dif- incipiently distinct mesostyles on the upper molars, fers from the latter in that the metacone is more lingually placed, the postmetacrista is longer than the centrocrista, and whereas ‘Pachynolophinae’ is characterized by reduction the metastyle is more prominent and buccally deflected. A large or absence of the mesostyles. Remy (2012) proposed the wear facet, whose apparent size is increased even further by existence within ‘Pachynolophinae’ of a new tribe, Anchi- breakage, occurs on the lingual side of the postmetacrista and lophini, which is diagnosed by its small to medium size, indicates the presence of a prominent hypoconulid on m3. The lophodont and brachyodont teeth, and the absence of buccal cingulum is rather weak. mesostyles. These anchilophin characters are also present For measurements of IVPP V 6508, see the relevant table in in IVPP V 6508, suggesting that the Yunnan specimen Huang & Qi (1982). should be referred to Anchilophini rather than any other group of palaeotheres. It is necessary to mention that some authors have argued that ‘Pachynolophinae’ should Comparisons be included in Tapiromorpha (Hooker 1994; McKenna & Bell 1997; Hooker & Weidmann 2000) or even in Bron- Huang & Qi (1982) assigned IVPP V 6508 to the tapiro- totherioidea (McKenna & Bell 1997). morph genus Lophialetes, probably based mainly on its According to Remy (2012), Anchilophini consists of the small size and gross morphological features (presumably, two genera, Anchilophus and Metanchilophus, with the for- in particular, the elongated postmetacristae of the mer including the two subgenera Anchilophus and Paran- molars). However, they correctly noted that IVPP V 6508 chilophus. However, Paranchilophus has sometimes been was distinguishable from Lophialetes expeditus in that the regarded as an entirely distinct genus from Anchilophus molars of the former increase in size from M1 to M3, the (Casanovas-Cladellas & Santafe-Llopis 1989; Checa & parastyle overlaps the metastyle of the preceding tooth, Colombo 2004) and this usage is followed here. With the metaloph is straight but rather oblique, and the regard to the upper molars, Paranchilophus mainly differs metastyle of M3 is buccally deflected. In Lophialetes,by from Anchilophus in that the parastyles are more mesially contrast, the upper molars are roughly uniform in size, projected, the pseudomesostyles (sensu Badiola et al. 2005) the parastyles are fan-shaped and do not overlap the pre- are more frequently present, the metastyles are better ceding metastyles, the curved metalophs join the ecto- developed, and the crista and postcrista are more promi- lophs mesial to the metacones, and the metastyle of M3 is nent. The holotype of Paranchilophus, Par. remyi, further highly reduced (Radinsky 1965). The upper molars of differs from Anchilophus desmaresti in having a less molar- Lophialetes further differ from those of ‘Lophialetes’ yun- iform P4 with a small, retracted hypocone. These apparent nanensis in that the paracone ribs are broadly convex, the differences support recognition of Anchilophus and Paran- metacone has a flat buccal surface, the metacone is more chilophus as separate genera, and provide a basis for lingually placed relative to the paracone, and the meta- regarding the Yunnan specimen as closer to Paranchilo- cone of M3 is fairly short. Regarding ‘Lophialetes’ yunna- phus than to Anchilophus. IVPP V 6508 further resembles nensis, the considerably elongated postmetacrista on M3, Paranchilophus in size (Fig. 3; Appendix 2), and in having the prominent ribs on the buccal sides of the parastyles upper molars that gradually increase in size from M1 to and paracones, the rather weak ribs present on the buccal M3. In IVPP V 6508 the metaloph is rather oblique, and sides of the metacones, and the high metastyles indicate the mesiobuccal end of this structure, which meets the that IVPP V 6058 lacks tapiromorph affinities, but are ectoloph, is wider than its distolingual end. The wide reminiscent of some palaeothere characters. mesiobuccal end of the metaloph was attributed to the Palaeotheriidae is an equoid group that is nearly end- presence of a well-developed but badly worn crista and emic to Europe, but is also known from a small amount postcrista, a character shared with Paranchilophus (Remy of Chinese material. Palaeotheriidae is generally consid- 2012). However, the Yunnan specimen differs from both ered to consist of Palaeotheriinae and ‘Pachynolophinae’ Anchilophus and Paranchilophus in that the parastyles are BAI: EOCENE PACHYNOLOPHINAE FROM CHINA 841

FIG. 3. Scatter plot of M2 and M3 proportions in Anchilophus, Paranchilophus, Lophiohippus, Metanchilophus, Pachynolophus (= Pa.) and Qianohippus, and regression lines for width as a function of length (measurements in mm). (See Appendix 2.) situated mesial or even slightly lingual, rather than Diagnosis. As for the type and only species. mesiobuccal, to the paracones, the parastyles are more flat- tened and overlap the metastyles of the preceding teeth, the metastyle of M3 is more buccally deflected, and in that Qianohippus magicus Miao, 1982 M3 is relatively pronouncedly larger than M1 (the surface ratio between M3 and M1 is approximately 1.40). Even Holotype. IVPP V 6519, a left maxilla with P2-M3, but though the parastyle is mesially situated to the paracone, with the mesiolingual part of M1 broken off. mainly due to the well-developed paracone rib, the prepar- acrista extends mesiobuccally as in Paranchilophus and Paratype. IVPP V 6520, a mandible with left p2–m3, and other palaeotheres. By contrast, the preparacrista extends right p2–3, m2–3. mesially or mesiolingually from the paracone to the para- style in ceratomorphs. Therefore, I erect a new genus Type locality and horizon. Shinao Formation, Shinao Lophiohippus for the Yunnan specimen. Basin, Guizhou Province, China. Upper Eocene. Checa & Colombo (2004) erected Bepitherium jordi- fusalbae based on some material from the Lower Eocene Diagnosis. Upper cheek teeth with relatively high degree of Spain, and speculated that this species might be closely of lophodonty, and lacking mesostyles. P2 molariform related to Paranchilophus based on the shared presence of but P3–4 unmolarized. Protoloph on P3–M3 and met- a transverse protoloph and an oblique metaloph on the aloph on M1–3 with an angular bending at paraconule upper molars. However, Bepitherium is peculiar among and metaconule, respectively. Upper molars with distinct perissodactyls in apparently possessing postprotocristae ribs on buccal sides of paracones and metacones, and on the upper molars, as can be inferred from correspond- cristae on lingual sides of paracones. The p2–4 sub- ing wear facets visible in published illustrations (Checa & molariform with posthypocristids extending distolingually Colombo 2004, figs 2, 4) and its phylogenetic position to reach distal margins of crowns. The p2–3 lacking ento- remains uncertain. conids, but p4 having an incipient entoconid. Trigonids of lower molars nearly Π-shaped. Hypoconulid of m1–2 relatively large and high. ‘Metastylids’ of lower cheek Subfamily PACHYNOLOPHINAE Pavlow, 1888 teeth weak and indistinct. Genus QIANOHIPPUS Miao, 1982 Differential diagnosis. Differs from Propachynolophus, Type and only species. Qianohippus magicus Miao, 1982. Pachynolophus, Anchilophus, Paranchilophus and Metan- chilophus in having the following characteristics: P2 Type locality and horizon. As for the type and only species. molariform but P3–4 unmolarized; protoloph on P3–M3 842 PALAEONTOLOGY, VOLUME 60 and metaloph on M1–3 with an angular bending at para- Description conule and metaconule, respectively; lower molars with The known material of Qianohippus consists of a left maxilla small mesoconids; and hypoconulid of m1–2 large and with P2–M3 (IVPP V 6519) (Fig. 4) and a mandible with left high. Further differs from Propachynolophus in having the p2–m3 and right p2, m2–3 (IVPP V 6520) (Fig. 5). following additional characteristics: upper molars lack P2 is quadrilateral in outline with a convex distal border. The mesostyles and lingual cingula; upper cheek teeth more paracone and metacone are large, roughly equal in size, and widely lophodont; parastyles relatively large and rib-like; para- separated, each bearing prominent ribs on the buccal surface. The cones on upper molars with distinct cristae; metalophs of parastyle is situated mesiobuccal to the paracone. The mesostyle is upper molars contact midpoints of centrocristae; ‘metas- absent, whereas the metastyle is relatively prominent. The pro- tylid’ of lower molars less prominent; and horizontal toloph and metaloph are completely separated on the lingual side ramus of mandible becoming less deep posteriorly. Fur- of the tooth. The protoloph extends from the protocone to the lin- ther differs from Pachynolophus (except Pa. zambranensis gual side of the parastyle, whereas the metaloph extends from the and Pa. lavocati) and Metanchilophus (except M. dumasi, hypocone to the mesiolingual side of the base of the metacone. A M. depereti and M. castrensis) in having more lophodont relatively wide basin is present distal to the metaloph. upper cheek teeth, upper molars with cristae on their lin- P3 and P4 are roughly triangular in outline. In these teeth, the ectoloph is similar to that of P2 except that the paracone gual surfaces, and Π-shaped trigonids of the lower and the metacone are more separated, and the parastyle is in a molars. Further differs from Anchilophus and Paranchilo- more buccal position relative to the paracone. The paraconule phus in being larger and in having less lophodont upper and metaconule are prominent, and the protocone is very large cheek teeth with distinct metacone ribs, non-molariform and conical. The preprotocrista extends from the protocone to P3–4, double-rooted p1, and Π-shaped trigonids of the the distolingual side of the paraconule, and the preparaconule lower molars. crista extends from the mesiobuccal side of the paraconule to

FIG. 4. Left maxilla of Qianohip- pus magicus (AMNH FM 144356, cast of IVPP V 6519) with P2–M3. A, occlusal view (stereograph). B, buccal view. C, lingual view. Scale bar represents 1 cm. BAI: EOCENE PACHYNOLOPHINAE FROM CHINA 843

FIG. 5. Lower jaw of Qianohippus magicus (IVPP V 6520). A, occlusal view. B, buccal view. C, occlusolin- gual view. Scale bar represents 1 cm.

the parastyle. Thus, the protoloph has an angular bend at the lingual ones. A distinct crista is present on the lingual surface of paraconule rather than being a curved ridge. The metaloph, the paracone, but a postcrista is absent. The distal cingula of the passing through the metaconule, contacts the mesiolingual side upper molars are more distinct than the mesial ones, and the of the base of the metacone on P3 and the midpoint of the cen- buccal cingula are continuous and prominent. trocrista on P4. The basin distal to the metaloph is fairly large, The symphyseal region of the mandible is narrow and long, approaching the size of the trigon basin, and bears a low ridge and its posterior border is situated slightly anterior to p1. The distobuccal to the protocone. The buccal and distal cingula are postcanine diastema is 16.0 mm in length, and bears a sharp relatively prominent. ridge. The ventral border of the horizontal ramus is straight, M1 and M2 are roughly square, but are slightly wider than whereas the alveolar border rises slightly towards the posterior long. M3 is trapezoidal in outline, with relatively short distal end of the mandible. and lingual borders. The crown height is moderate, and the On the left side of the mandible, the form of the alveolus degree of lophodonty is high. On M1–3 the ectoloph is similar mesial to p2 indicates that p1 had two roots. The p2 is oblong, to that of P4 in lacking a mesostyle, but has a relatively larger and the talonid is wider than the trigonid. The paralophid parastyle, which is nearly as high as the paracone. The metastyle extends nearly mesially from the protoconid to the high para- of M3 is large, keel-like, and deflected buccally, whereas those of conid, and descends lingually to the base of the trigonid. The M1 and M2 are low and small. The preprotocrista extends nearly distinct metaconid lies a short distance distolingual to the proto- transversely from the protocone to the distolingual side of the conid. The incipient ‘metastylid’ is distinguished by a metaconid paraconule, and the preparaconule crista extends from the buttress, which is situated distobuccal to the metaconid (Hooker mesiobuccal side of the paraconule to the junction of the pre- 1994, fig. 2E, F; Hooker & Dashzeveg 2004). The hypoconid is paracrista and the parastyle. Similarly, the prehypocrista extends large and situated at the distobuccal corner of the crown, and from the hypocone nearly transversely to the distolingual side of cristid obliqua extends from the hypocone to the midpoint of the metaconule, and the premetaconule crista extends from the the protolophid. A short ridge (posthypocristid) extends dis- mesiobuccal side of the metaconule to the middle line of the tolingually from the hypocone to a point lingual to the middle centrocrista. Thus, the protoloph and the metaloph have an of the distal margin of the tooth. The lingual border of the talo- angular bend at the paraconule and metaconule, respectively, nid is rimmed by a low ridge lacking an entoconid. No cingu- instead of forming curved ridges. The buccal halves of the pro- lum is present on the lingual side of the tooth, but a weak toloph and metaloph are consequently not aligned with their cingulum is evident at the base of the ectoflexid. 844 PALAEONTOLOGY, VOLUME 60

The morphology of p3–4 is generally similar to that of p2, However, Qianohippus is more similar to Palaeotheriidae but in p3–4 the metaconid is more widely separated from the than to any other groups of perissodactyls in having the protoconid, the protolophid is less oblique, the paralophid is following combined characters: prominent paracone and nearly perpendicular to the protolophid, the posthypocristid is metacone ribs on the upper cheek teeth; relatively distinct more prominent, and the cingulum at the base of the ectoflexid paraconules and metaconules on the upper molars; the is better developed. Further, p4 is more molariform than p3 in cristids obliquae of the lower molars lingually extended; having a more distinct ‘metastylid’, a small mesoconid on the and m3 with a large hypoconulid lobe. Qianohippus fur- cristid obliqua, and an incipient entoconid in a low position. ther differs from post-Early Eocene North American On m1–2 the trigonid is similar to that of p4, but the mesial branch of the paralophid is more prominent and lies perpendic- equids in the lack of mesostyles. Partly because the origi- ular to the buccal branch of the paralophid, which in turn forms nal description of this taxon was written in Chinese with- a right angle with the protolophid. Thus, the trigonid is Π- out an English summary, Qianohippus has rarely been shaped. The metaconid buttress indicates the presence of the mentioned or cited subsequently in relevant studies, incipient ‘metastylid’, but the separation between the two apices except for McKenna & Bell (1997). is hardly discernable. The cristid obliqua extends mesiolingually According to a recent revision of Pachynolophus from the hypoconid to a small mesoconid as in p4, and on (Danilo et al. 2013), ten valid species have been named – unworn m2 3 continues nearly mesially to reach the middle of within this genus, ranging in age from Early to Late the protolophid in a high position. On worn m1, however, the Eocene (MP 8–20 (Mammal Palaeogene levels)). cristid obliqua contacts the protolophid buccal to the ‘metasty- Qianohippus resembles most species of Pachynolophus in lid’. The entoconid of m1–2 is conical and placed at the level that the upper cheek teeth lack mesostyles, and in the distal to the hypoconid. The hypolophid extends from the hypo- – conid and joins the entoconid slightly below the apex. The talo- non-molariform morphology of P3 4 and the presence of nid is as wide as the trigonid on m1, but narrower than the weak ‘metastylids’. However, some species of Pachynolo- trigonid on m2. The hypoconulid is large, rising from the distal phus, including Pa. eulaliensis, Pa. garimondi, Pa. lavocati, border of the tooth nearly to the height of the hypoconid. The Pa. bretovensis and Pa. zambranensis, have pseudome- middle of the hypoconulid bears a cuspule from which extend sostyles (Badiola et al. 2005; Danilo et al. 2013). The two short ridges: a buccal ridge extends toward the middle of degree of lophodonty exhibited by Qianohippus is greater the hypolophid, whereas a lingual ridge extends to the distal side than that seen in most species of Pachynolophus, but simi- of the base of the entoconid. No cingulum is present on the lin- lar to that seen in Pa. zambranensis and Pa. lavocati gual side of m1. A weak cingulum is present on the buccal side (Remy 1972; Badiola et al. 2005). The protocones of P3 of the hypoconid. A weak cingulum rises considerably from the and P4 in Qianohippus are large and conical as in base of the mesiobuccal corner of the crown on m2. Pa. livinierensis, whereas those of other species of The m3 is generally similar to m2, but on m3 the ‘metastylid’ Pachynolophus are more crescentic and more confluent is a little more distinct, the talonid is considerably narrower than the trigonid, and the hypoconulid is enlarged to form a third with the protolophs (Savage et al. 1965). Further, lobe. A distobuccally placed cuspule on the hypoconulid lobe is Qianohippus is larger than Pachynolophus,M2of interpreted as the hypoconulid. From this cuspule, a ridge Qianohippus being about 17% longer than that of the lar- extends mesially to the middle of the hypolophid in a high posi- gest known species of Pachynolophus, Pa. zambranensis tion, and a short ridge extends distolingually. The lingual ridge (Badiola et al. 2005; Fig. 3; Appendix 2). of the hypoconulid lobe is lower, and this ridge joins the dis- Remy (2012) named a new tribe, Anchilophini, within tolingual side of the base of the entoconid but is separated from Pachynolophinae, including Anchilophus (comprising the the hypoconulid by a notch. A weak cingulum rises considerably two subgenera Anchilophus and Paranchilophus) and from the base of the mesiobuccal corner of the crown as on m2. Metanchilophus as discussed above. Anchilophini is char- For measurements of Q. magicus, see Miao (1982, table 1). acterized by lophodont cheek teeth, and the lack of the mesostyles and lingual cingula on the upper cheek teeth; these characters are also present in Qianohippus. In mor- Comparisons phology and size, Qianohippus is obviously more similar to Metanchilophus than to Anchilophus and Paranchilo- Miao (1982) described the palaeothere Qianohippus from phus, since the latter two genera are very small and also the Shinao Basin, Panxian County, Guizhou Province, characterized by highly reduced paraconules and meta- China. Miao (1982) realized that Qianohippus was distinc- conules on the upper cheek teeth. Six species of Metan- tive in lacking mesostyles on the upper cheek teeth, and chilophus were reviewed or erected by Remy (2012). in the highly lophodont character of the cheek teeth; he Qianohippus is larger than most specimens of Metan- also suggested that Qianohippus was more derived than, chilophus, but similar in size to M. dumasi (Fig. 3; but not actually descended from Pachynolophus. The Appendix 2). The degree of lophodonty present in specific phylogenetic position of Qianohippus remains Qianohippus is similar to that in M. dumasi, M. depereti obscure as suggested by its species name magicus. and M. castrensis, but greater than that in M. radegondensis, BAI: EOCENE PACHYNOLOPHINAE FROM CHINA 845

M. gaudini and M. chaubeti. Qianohippus is clearly more simple in form (Kitts 1957). However, some cerato- primitive than the European genus Metanchilophus in morphs resemble Qianohippus in that P2 is more molari- that the premolars are not molariform. Specifically, P3– form than P3–4. This is true, for example, of the 4 are sub-triangular in outline and lack hypocones, p2– paraceratheres Forstercooperia, Juxia and Paraceratherium 3 lack entoconids, and p4 has only a weak entoconid. (Granger et al. 1936; Wood 1963; Qiu & Wang 2007; The upper molars of Qianohippus further differ from Wang et al. 2016), as well as the rhinocerotoid those of Metanchilophus in having a crista on the lin- douglassi (Wood 1934). Thus, the combination of a gual surface of the paracone, but resemble them in molariform P2 and a non-molariform P3–4 is known in lacking the corresponding postcrista seen in Anchilophus different groups of perissodactyls as a result of a parallel and Paranchilophus.ThelowermolarsofQianohippus evolution. In contrast to the angularly bent protolophs differ from those of Metanchilophus in having Π-shaped and metalophs of the upper molars seen in Qianohippus, trigonids, a less distinct ‘metastylids’, a more enlarged the equivalent structures in other ‘pachynolophs’ are gen- hypoconulid on m2, and small mesoconids on the cris- erally curved with the preprotocrista and prehypocrista tids obliquae, accounting for the somewhat bifurcated oriented mesiobuccally instead of nearly transversely. mesial ends of the cristids obliquae on slightly worn teeth. With regard to the low level of molarization of the DISCUSSION premolars, Qianohippus is more similar to M. depereti, the earliest and most primitive Metanchilophus, than to Cladistic analysis any other species of Metanchilophus.InM. depereti, however, P2 is less molarized than in Qianohippus, with A phylogenetic analysis of Palaeotheriidae based on the the protocone extending in a curve onto the distal cin- data matrix of Danilo et al. (2013) with the addition of gulum; the hypocone in P3–4 is more or less separated Lophiohippus yunnanensis and Qianohippus magicus from the protocone, and usually contacts the distal cin- resulted in three equally most parsimonious trees (MPTs), gulum; P4 is the most molarized of the premolars; and each having a tree length (TL) of 306, a consistency index p4 is more molarized than that of Qianohippus, having (CI) of 0.327, and a retention index (RI) of 0.474. The a large entoconid (Remy 2012). Qianohippus further dif- strict consensus tree (Fig. 6) is generally consistent with fers from M. depereti in that the upper molars are more that of Danilo et al. (2013), but some relationships are square, the buccal cingula are weaker, the metaconules more clearly resolved. Danilo et al. (2013) proposed the are more distinct, and M3 is generally less trapezoidal in existence of three evolutionary grades within Pachynolo- outline. phus, essentially forming successive sister taxa to a clade Qianohippus differs from Propalaeotherium and Euro- comprising the more derived ‘pachynolophs’ and the hippus mainly in that the upper cheek teeth lack mesos- Palaeotheriinae. The present analysis posits Pachynolophus tyles, the upper molars are more lophodont, the trigonids eulaliensis and Pa. cesserasicus as basal taxa within of the lower molars are Π-shaped instead of crescentic, Palaeotheriidae (Node A), representing successive sister and the ‘metastylids’ are less distinct (Remy et al. 2016). taxa to a group containing two main subclades (Node B). However, Qianohippus is similar to Propalaeotherium has- One subclade (Node C) consists exclusively of species siacum in that a relatively large basin occurs distal to the of Pachynolophus, with Pa. livinierensis–Pa. boixedatensis protocone on P3–4, the talonid of m2 is obviously nar- forming the sister group of Pa. duvali–Pa. garimondi– rower than the trigonid, m3 tapers distally to a consider- Pa. bretovensis. Node C is supported by two unequivocal able degree, and the horizontal ramus of the mandible synapomorphies: M3 larger than M2 (54:2), and low has a straight ventral border (Haupt 1925; Savage et al. height of the lower molar cingulum (61:1). In the second 1965). subclade (Node D) within the group defined by Node B, Although Qianohippus shows some similarities with Qianohippus is the basal most taxon and stands as sister Pachynolophus, Metanchilophus or Propalaeotherium, it has to a clade comprising derived Pachynolophus species (i.e. two autapomorphies. First, P2 is molariform, whereas Pa. lavocati and Pa. zambranensis), more derived ‘pachy- P3–4 are non-molariform. Second, the protoloph on P3– nolophs’, and Palaeotheriinae. Node D is supported by M3 and the metaloph on M1–3 has an angular bend at six unequivocal synapomorphies: P4 metaconule weak the paraconule and metaconule, respectively. In Anchilo- (27:0); upper molars moderately hypsodont (28:1); upper phini, Lophiotherium and most other perissodactyls with molars lack a groove on the protoloph (29:1); metaloph molariform premolars, by contrast, P4 and/or P3 are on upper molars contacts the centrocrista (38:1); parastyle more molariform than P2 (Savage et al. 1965; Remy situated buccal to line connecting paracone and metacone 2012). In the North American taxon Orohippus,P3–4 on upper molars (42:1); and distal cingulum extension have four cusps of roughly equal size, whereas P2 is present on all upper molars (50:1). These results imply 846 PALAEONTOLOGY, VOLUME 60

FIG. 6. Strict consensus of three equally most parsimonious trees showing phylogenetic positions of Lophiohippus yunnanensis and Qianohippus magicus within Palaeotheriidae. The numbers on the tree represent Bremer support values. For convenience, capital letters (A–G) below the branches are used to denote monophyletic groups discussed in the text. Abbreviations: Ca, Cardiolophus; Cy, Cym- balophus; Eu, Eurohippus; Ha, Hallensia; Hy, ; Lo, Lophiotherium; Me, Metanchilophus; Pa, Pachynolophus; Pal, Palaeother- ium; Par, Paranchilophus; Pl, Pliolophus; Pla, Plagiolophus; Pr, Propachynolophus; Xe, Xenicohippus. that derived ‘pachynolophs’ (including Pa. lavocati and (including Paranchilophus) and Metanchilophus, was not Pa. zambranensis) are more closely related to the Asian supported by this analysis. Qianohippus than to the indigenous European Pachynolo- Basal relationships among the Equoidea were not well phus. Further, Lophiohippus yunnanensis is sister to Paran- resolved in the cladogram obtained by Danilo et al. (2013) chilophus remyi, confirming that the Yunnan species is but the results presented here favour some hypotheses pro- closely related to Paranchilophus as suggested by the mor- posed by those authors. The analysis shows that Equidae phological comparisons presented above. The Paranchilo- sensu stricto, represented by Pliolophus vulpiceps and Xeni- phus–Lophiohippus clade (Node F) is supported by two cohippus osborni, is the sister group to ‘Hyracotherium’ aff. unequivocal synapomorphies: absence of mesostyles on cuniculus and ‘Pachynolophus’ hookeri – Cymbalophus the upper molars (43:0), and extreme reduction of buccal cuniculus. Thus, the latter three forms are more reasonably cingula on the upper molars (45:2). The Paranchilophus– included in an expanded Equidae (node G), which the Lophiohippus clade forms an unresolved trichotomy analysis positions as the sister group to Palaeotheriidae (Node E) with Metanchilophus dumasi and a clade con- (node A). Propachynolophus, Hyracotherium leporinum and sisting of Eurohippus–Lophiotherium and Palaeotheriinae. Hallensia form a basal group within Equoidea, although Thus, the monophyly of the putative tribe ‘Anchilophini’, the genus Propachynolophus is recovered as paraphyletic as proposed by Remy (2012) and comprising Anchilophus suggested by Danilo et al. (2013). BAI: EOCENE PACHYNOLOPHINAE FROM CHINA 847

Comments on other Eocene ‘Palaeotheriidae’ from China Krause & Maas 1990). Because of this connection, the Faunal Resemblance Index for mammalian genera is Zdansky (1930) described miscellaneous cheek teeth of about 50% between Europe and North America at the ‘Propalaeotherium’ sinense from the Guanzhuang Forma- beginning of the Eocene (Krause & Maas 1990; Franzen tion of Shandong Province, China. Savage et al. (1965) 2010). Further, there is a coexistence of two different suggested a close relationship between ‘P.’ sinense and mammalian faunas corresponding to the provinces in Eurohippus parvulus (= Propalaeotherium parvulum) based northern and southern Europe during the early Eocene on Zdansky’s figures. However, ‘P.’ sinense was suggested (Marandat et al. 2012). Near the Paleocene–Eocene to be closely related to Danjiangia by Tong & Wang boundary, mammal dispersals also seem to have occurred (2006), and to Lambdotherium by Hooker et al. (2007). between Europe plus western Asia and eastern Asia via Parallel suggestions of affinity with Danjiangia and Lamb- the Turgai Strait (Beard 1998; Hooker & Dashzeveg 2003; dotherium are not surprising, because Danjiangia is con- Ni et al. 2005; Smith et al. 2006; Beard et al. 2010; Ting sidered to be closer to Lambdotherium than to et al. 2011) and between Europe and the Indian subconti- as initially suggested (Wang 1995; Hooker & nent via the Kohistan–Ladakh island arc along the Tethys Dashzeveg 2003, 2004). Unlike Propalaeotherium and shore (Smith et al. 2016). After the Early Eocene, Europe Eurohippus,‘P.’ sinense resembles both Danjiangia and is thought to have been isolated until the Eocene–Oligo- Lambdotherium in lacking metaconules on the upper cene boundary, and during this period the mammalian molars; in having transversely wide upper molars with fauna of Europe was mostly endemic. short, relatively transverse metalophs, large parastyles, and The appearance of Lophiohippus yunnanensis and relatively short postmetacristae; and in having strongly Qianohippus in southwest China indicates that pachyno- crested lower molars, of which m1–2 bear relatively lin- lophs, at least, must have dispersed between Europe and gually situated hypoconulids and m3 has an oblique Asia during the Middle–Late Eocene. The precise timing hypolophid and short hypoconulid lobe (Bonillas 1936; of such an event cannot be confidently nailed down Tong & Wang 2006; Hooker et al. 2007). The large and because the ages of the strata bearing Lophiohippus and buccally projecting parastyle of ‘P.’ sinense is more similar Qianohippus are controversial. Lophiohippus yunnanensis to that of Danjiangia than to Lambdotherium. However, was unearthed from the Lumeiyi Formation of the Lunan the buccal ridge of the hypoconulid of m3 in ‘P.’ sinense Basin, Yunnan Province. The mammalian fauna of this contacts the hypolophid lingual to its midpoint as in formation is a mixture of characteristic Irdinmanhan and Lambdotherium, instead of contacting the entoconid as in Sharamurunian taxa, and age estimates for the formation Danjiangia. As a result, ‘P.’ sinense should be assigned to range from 46.5 to 37.8 Ma, corresponding to MP 12–16 Lambdotheriidae as proposed by Hooker et al. (2007), in Europe (Russell & Zhai 1987). Considering that L. yun- but a reliable generic referral for the species sinense will nanensis shows derived characters and is known from field not be possible until more complete material representing locality 70002, in the upper part of the Lumeiyi Formation the species has been discovered. It is necessary to mention (Huang & Qi 1982; Russell & Zhai 1987) I presume the that the phylogenetic position of Lambdotherium still age of this species to be Middle Eocene Sharamurunian. It remains controversial, as this taxon may be either a basal is worth noting that the hyracodontid Prohyracodon from brontothere or a palaeothere (Wallace 1980; Lucas & Hol- Middle Eocene deposits of Romania was also present in the brook 2004; Mihlbachler 2008). Lumeiyi Formation in Yunnan, China (Wood 1929; Chow Propachynolophus hengyangensis from the Hengyang & Xu 1961). The Shinao Formation, bearing Qianohippus Basin, Hunan Province, was initially assigned to Propa- magicus and situated in the Shinao Basin of Guizhou Pro- laeotherium based on a left m3 (Young 1944; Li et al. vince, has traditionally been considered to be Late Eocene 1979). Li et al. (1979) and Ting (1995) described addi- in age (Miao 1982). tional material from the same basin, comprising a mand- The hypothesis of intermittent faunal exchanges ible with p2–m2 and a left m3. Propachynolophus between Europe and Asia in the Middle and Late Eocene hengyangensis has been variously suggested to be a is becoming supported by more and more evidence. In palaeothere, a ceratomorph, or a (Li et al. terms of palaeotheres, Metais & Sen (2017) recently 1979; Ting 1995) and this issue will be discussed exten- reported a pes of sp. cf. Pal. magnum from sively in a separate paper. Middle–Late Eocene of eastern Thrace, Greece, extending the geographical range of Palaeotherium out of western Europe. The appearance of Palaeotherium in the Thrace Palaeobiogeography Basin is not unexpected, considering that dental remains of Plagiolophus cf. minor have been previously reported At the beginning of the Eocene, Europe was connected to from the Late Eocene of Tscherno More, Bulgaria (Niko- North America via Greenland (McKenna 1975, 1983; lov & Heissig 1985). Further, footprints of palaeothere- 848 PALAEONTOLOGY, VOLUME 60 like have been reported from pre- Middle–Late Eocene, the Tethyan microcontinents and deposits of Iran (Abbassi & Lockley 2004; Ataabadi & islands, such as Balcano–Rhodopia, Anatolia and central Khazaee 2004). Beside palaeotheres, Middle–Late Eocene Iran, may likewise have facilitated dispersals between Eur- rhinocerotid Epiaceratherium naduongense and anthra- ope and Asia, either bypassing or traversing India (Bohme€ cotheriid Bakalovia orientalis from Na Duong of northern et al. 2013; Metais & Sen 2017). It is noteworthy that the Vietnam are more similar to the taxa from Monteviale of maximal number of dispersal events (MDE) from main- northern Italy and Tscherno More of Bulgaria, respec- land Asia to India rose after 44 Ma (Klaus et al. 2016) tively, than to their relatives in Southeast Asia (Bohme€ favouring the hypothesis of traversing India. However, et al. 2013). the main mammalian exchanges between Europe and Asia Similarly, some Middle Eocene (MP14) rodents of the occurred at the beginning of the Oligocene, when the clade Remyidae from the Iberian Peninsula, especially Turgai Strait became a corridor between the two land- Zamoramys and Frontanyamys, show similarities with cha- masses (Stehlin 1909; Meng & McKenna 1998; Bai & pattimyids and yuomyids from the Indian subcontinent Wang 2012). (Pelaez-Campomanes & Lopez-Mart ınez 1996; Quer & Agusti 2010; Gupta & Kumar 2015) although some authors have attributed these similarities to morphologi- CONCLUSION cal convergence (Hartenberger 1993). Furthermore, an isolated left M2 from Middle Eocene (MP 14) deposits in Although palaeotheriids flourished in the Eocene of Eur- the Duero Basin of Iberia shows affinities with Asian ana- ope, a small number of palaeotheriids has been also galids (Pelaez-Campomanes et al. 1989), and especially reported from China. Considering that ‘Propalaeotherium’ with some Asian species that are particularly similar in sinense is probably close to Lambdotheriidae and that the size and morphology (for example Zhujigale lirenensis possible palaeothere affinities of ‘Propachynolophus’ Zhang & Tong, 1981). However, most Asian anagalids hengyangensis are controversial, Lophiohippus yunnanensis occur in Paleocene deposits. Tong (1997) also recognized and Qianohipphus magicus represent the only known that the late Middle Eocene chiropteran Lapichiropteryx unequivocal representatives of Palaeotheriidae in Asia. and insectivore Yuanqulestes from Zhaili, Yuanqu Basin, Although the phylogenetic relationships of L. yunnanensis Shanxi Province showed similarities with their European and Q. magicus with other European palaeotheres are relatives. These commonalities corroborate the occurrence partially resolved in this cladistic analysis, the results are of limited mammalian exchanges between Europe and supported by relatively low Bremer values and thus open Asia before the Oligocene (Tong 1997). to debate. A more comprehensive cladistic analysis Based on the above-mentioned occurrences of closely including more palaeothere groups (especially Metanchilo- related taxa in both Europe and Asia, I consider there to phus and Propalaeotherium) and more characters will be have been a geographical connection between Europe and needed in the future, as will attempts to recover new – Asia in the Middle Late Eocene. The dispersal route palaeothere material from Asia. Furthermore, based on – between Europe and Asia in the Middle Late Eocene was the evidence from palaeotheres and some other mam- either across the Turgai Strait in the north or along the malian fossils, I consider there to have been intermittent Tethyan shore in the south (Maas et al. 2001; Missiaen & faunal exchanges via the Tethyan microcontinents Gingerich 2014). However, the Turgai Strait is widely between Europe and Asia in the Middle–Late Eocene. considered to have been a barrier between Europe plus western Asia and eastern Asia during the Middle and Late Acknowledgements. I thank Zhaoqun Zhang, Xijun Ni, Qian Li, Eocene (Krause & Maas 1990; Qiu & Wang 2007) reduc- Yingqi Zhang (all IVPP), and K. C. Beard (University of Kansas) ing the plausibility of the northern route. By contrast, a for discussion; Wei Gao (IVPP) for the photographs used in Fig- corridor was present between Asia and Europe during the ures 2 and 5, and L. Meeker (AMNH) for those used in Figure 4. initial collision between India and Asia in the Early I am grateful to C. Sullivan for improving the English text and Eocene (Chatterjee et al. 2013). Interestingly, a number of commenting on the manuscript. I am indebted to Jin Meng Early Eocene mammalian taxa from Vastan, India show (AMNH) and Yuanqing Wang (IVPP) for comments on the ear- close affinities with those from Euroamerica (Smith et al. lier draft of the manuscript. I appreciate J. A. Remy, J. L. Fran- zen, P. Li, O. Maridet, M. Mihlbachler, L. Checa-Soler, and H. B. 2007; Rana et al. 2008; Rose et al. 2009a, b, 2013; Kumar Wang for providing the references. The review comments of F. et al. 2010) although some of the Vastan mammals have Lihoreau, J. Remy, editor L. Hautier (all CNRS, Universite Mont- Asian affinities (Rose et al. 2008). Faunal dispersals pellier 2) and J. L. Franzen (Senckenberg Forschungsinstitut) between India and Europe in the Early Eocene could have greatly improved the final manuscript. Funding was provided by taken place via some hypothetical microcontinents and grants from the China Scholarship Council, the National Natural islands north of India (or the Kohistan–Ladakh island Science Foundation of China (41672014, 41572021, 41002009), arc) (Gingerich et al. 1997; Smith et al. 2016). In the the State Key Laboratory of Palaeobiology and Stratigraphy BAI: EOCENE PACHYNOLOPHINAE FROM CHINA 849

(Nanjing Institute of Geology and Palaeontology, CAS) BONILLAS, Y. 1936. The dentition of Lambdotherium. Journal (No.163103), and Youth Innovation Promotion Association CAS. of Mammalogy, 17, 139–142. CASANOVAS-CLADELLAS, M. L. and SANTAFE-LLO- PIS, J. V. 1989. Dos nuevos Paleoteridos (Mammalia, Peris- DATA ARCHIVING STATEMENT sodactyla) del yacimiento Eocenico de Llamaquique (Oviedo). Trabajos de Geologıa, 8,37–52. The data matrix for this study is available in the Dryad Digital CHATTERJEE, S., GOSWAMI, A. and SCOTESE, C. R. Repository: https://doi.org/10.5061/dryad.cv87j 2013. The longest voyage: tectonic, magmatic, and This published work and the nomenclatural act it contains, paleoclimatic evolution of the Indian plate during its north- have been registered in Zoobank: http://zoobank.org/References/ ward flight from Gondwana to Asia. Gondwana Research, 23, 6A01F3AA-5D57-4D10-95F1-044614D89A8C 238–267. CHECA, L. and COLOMBO, F. 2004. A new early Eocene Editor. Lionel Hautier palaeothere (Mammalia, Perissodactyla) from northeastern Spain. Journal of Vertebrate Paleontology, 24, 507–512. CHOW, M. C. and XU, Y. X. 1961. New primitive true rhino- REFERENCES ceroses from the Eocene of Iliang, Yunnan. Vertebrata PalAsi- atica, 5, 291–304. ABBASSI, N. and LOCKLEY, M. G. 2004. Eocene bird and CRUSAFONT PAIRO, M. and REMY, J. A. 1970. Les mammal tracks from the Karaj Formation, Tarom Mountains, Equoidea (Perissodactyla) de l’Eoc ene preaxial pyreneen Northwestern Iran. Ichnos, 11, 349–356. espagnol. Bulletin du Museum national d’Histoire naturelle, ATAABADI, M. and KHAZAEE, A. 2004. New Eocene 2eme serie, 42, 428–434. mammal and bird footprints from Birjand Area, eastern Iran. DANILO, L., REMY, J. A., VIANEY-LIAUD, M., Ichnos, 11, 363–370. MARANDAT, B., SUDRE, J. and LIHOREAU, F. 2013. BADIOLA, A., PEREDA-SUBERBIOLA, X. and A new Eocene locality in southern France sheds light on the CUESTA, M. A. 2005. A new species of Pachynolophus basal radiation of Palaeotheriidae (Mammalia, Perissodactyla, (Mammalia, Perissodactyla) from Zambrana (Alava, Basque- Equoidea). Journal of Vertebrate Paleontology, 33, 195–215. Cantabrian Region). Phylogenetic analysis of Pachynolophus FRANZEN, J. L. 1989. Origin and systematic position of the and first mention in the Late Eocene of the Iberian Peninsula. Palaeotheriidae. 102–108. In PROTHERO, D. R. and Geobios, 38,1–16. SCHOCH, R. M. (eds). The evolution of Perissodactyls. BAI, B. 2017. Data from: Eocene Pachynolophinae (Perisso- Oxford University Press, 537 pp. dactyla, Palaeotheriidae) from China and their palaeobiogeo- FRANZEN, J. E. 2007. Eoz€ane Equoidea (Mammalia, Perisso- graphical implications. Dryad Digital Repository. https://doi. dactyla) aus der Grube Messel bei Darmstadt (Deutschland) org/10.5061/dryad.cv87j Funde der Jahre 1969–2000. Schweizerische Palaeontologische -and WANG, Y.-Q. 2012. Proeggysodon gen. nov., a primi- Abhandlungen, 127,1–245. tive Eocene eggysodontine (Mammalia, Perissodactyla) from FRANZEN, J. L. 2010. The rise of horses. The Johns Hopkins Erden Obo, Siziwangqi, Nei Mongol, China. Vertebrata PalAsi- Univeristy Press, 211 pp. atica, 50, 204–218. FROEHLICH, D. J. 1999. Phylogenetic systematics of basal -WANG, Y., MENG, J., LI, Q. and JIN, X. 2014. New perissodactyls. Journal of Vertebrate Paleontology, 19, 140–159. Early Eocene basal tapiromorph from Southern China and Its GINGERICH, P. D., ABBAS, S. G. and ARIF, M. 1997. phylogenetic implications. PLoS One, 9,1–9. Early Eocene Quettacyon parachai (Condylarthra) from the BEARD, K. C. 1998. East of Eden: Asia as an important center Ghazij Formation of Baluchistan (Pakistan): oldest Cenozoic of taxonomic origination in mammalian evolution. 5–39. In land mammal from south Asia. Journal of Vertebrate Paleontol- BEARD, K. C. and DAWSON, M. R. (eds). Dawn of the ogy, 17, 629–637. age of mammals in Asia. Bulletin of Carnegie Museum of Nat- GOLOBOFF, P. A., FARRIS, J. S. and NIXON, K. C. 2008. ural History, 34, 348 pp. TNT, a free program for phylogenetic analysis. Cladistics, 24, -WANG, Y. Q., MENG, J., NI, X. J., GEBO, D. L. and 774–786. LI, C. K. 2010. Paleocene Hapalodectes (Mammalia: Mesony- GRANGER, W., GREGORY, W. K. and OSBORN, H. F. chia) from Subeng, Nei Mongol: further evidence of “East of 1936. Further notes on the gigantic extinct rhinoceros, Eden” dispersal at the Paleocene–Eocene boundary. Vertebrata Baluchitherium, from the Oligocene of Mongolia. Bulletin of PalAsiatica, 48, 375–389. the American Museum of Natural History, 72,1–73. € BOHME, M., AIGSTORFER, M., ANTOINE, P. O., GUPTA, S. and KUMAR, K. 2015. Early Eocene rodents APPEL, E., HAVLIK, P., METAIS, G., PHUC, L. T., (Mammalia) from the Subathu Formation of type area SCHNEIDER, S., SETZER, F., TAPPERT, R., TRAN, (Himachal Pradesh), NW sub-Himalaya, India: palaeobiogeo- D. N., UHL, D. and PRIETO, J. 2013. Na Duong (North- graphic implications. Journal of Earth System Science, 124, ern Vietnam) – an exceptional window into Eocene ecosys- 1201–1221. tems from South-East Asia. Zitteliana, A53, 120–167. HARTENBERGER, J. L. 1993. New rodents from the middle BONAPARTE, C. L. 1850. Conspectus systematis Mastozoolo- Eocene of Europe and remarks about the early history of the giae. Editio altera reformata. E. J. Brill, 2 pp. group. Kaupia, 3, 165–171. 850 PALAEONTOLOGY, VOLUME 60

HAUPT, O. 1925. Die Palaeohippiden der eoz€anen Su€bwasser- MARANDAT, B., ADNET, S., MARIVAUX, L., MARTI- ablagerungen von Messel bei Darmstadt. Abhandlungen der NEZ, A., VIANEY-LIAUD, M. and TABUCE, R. 2012. Hessischen Geologishen Landesanstalt, 6,1–159. A new mammalian fauna from the earliest Eocene (Ilerdian) HAY, O. P. 1902. Bibliography and catalogue of the fossil ver- of the Corbieres (Southern France): palaeobiogeographical tebrata of North America. Bulletin of the United States Geologi- implications. Swiss Journal of Geosciences, 105, 417–434. cal Survey, 179,1–868. MATTHEW, W. D. and GRANGER, W. 1925. The smaller HOOKER, J. J. 1994. The beginning of the equoid radiation. perissodactyls of the Irdin Manha Formation, Eocene of Mon- Zoological Journal of the Linnean Society, 112,29–63. golia. American Museum Novitates, 199,1–9. -and DASHZEVEG, D. 2003. Evidence for direct mam- M C KENNA, M. C. 1975. Fossil mammals and early Eocene malian faunal interchange between Europe and Asia near the North Atlantic land continuity. Annals of the Missouri Botani- Paleocene–Eocene boundary. 479–500. In WING, S. L., cal Garden, 62, 335–353. GINGERICH, P. D., SCHMITZ, B. and THOMAS, E. - 1983. Holarctic landmass rearrangement, cosmic events, (eds). Causes and consequences of globally warm climates in the and Cenozoic terrestrial organisms. Annals of the Missouri Early Paleogene. Geological Society of America Special Paper, Botanical Garden, 70, 459–489. 369, 614 pp. -and BELL, S. K. 1997. Classification of mammals above the -- 2004. The origin of chalicotheres (Perissodactyla, species level. Columbia University Press, 631 pp. Mammalia). Palaeontology, 47, 1363–1386. MENG, J. and M C KENNA, M. C. 1998. Faunal turnovers of -and WEIDMANN, M. 2000. The Eocene mammal faunas Palaeogene mammals from the Mongolian plateau. Nature, of Mormont, : systematic revision and resolution 394, 364–367. of dating problems. Schweizerische Palaeontologische Abhand- METAIS, G. and SEN, S. 2017. First occurrence of Palaeotheri- lungen, 120,1–143. idae (Perissodactyla) from the late–middle Eocene of eastern HOOKER, J., DASHZEVEG, D. and POLLY, P. D. 2007. Thrace (Greece). Comptes Rendus Palevol, 16, 382–396. Lambdotheriid perissodactyls: evidence of an origin and mod- MIAO, D. S. 1982. Early Tertiary fossil mammals from the Shi- est radiation in Asia. Journal of Vertebrate Paleontology, 27, nao Basin, Panxian County, Guizhou Province. Acta Palaeon- 91A. tologica Sinica, 21, 526–536. HUANG, X. S. and QI, T. 1982. Notes on late Eocene - MIHLBACHLER, M. C. 2008. Species taxonomy, phylogeny, oids from the Lunan Basin eastern Yunnan. Vertebrata PalAsi- and biogeography of the Brontotheriidae (Mammalia: Perisso- atica, 20, 315–326. dactyla). Bulletin of the American Museum of Natural History, KITTS, D. B. 1957. A revision of the genus Orohippus (Perisso- 311,1–475. dactyla, Equidae). American Museum Novitates, 1864,1–40. MISSIAEN, P. and GINGERICH, P. D. 2014. New basal KLAUS, S., MORLEY, R. J., PLATH, M., ZHANG, Y.-P. Perissodactyla (Mammalia) from the lower Eocene Ghazij for- and LI, J.-T. 2016. Biotic interchange between the Indian sub- mation of Pakistan. Contributions from the Museum of Paleon- continent and mainland Asia through time. Nature Communi- tology, University of Michigan, 32, 139–160. cations, 7, 12132. NI, X. J., HU, Y. M., WANG, Y. Q. and LI, C. K. 2005. A KRAUSE, D. W. and MAAS, M. C. 1990. The biogeographic clue to the Asian origin of euprimates. Anthropological Science, origins of late Paleocene-early Eocene mammalian immigrants 113,3–9. to the Western Interior of North America. 71–105. In NIKOLOV, I. and HEISSIG, K. 1985. Fossile S€augetiere aus BOWN, T. M. and ROSE, K. D. (eds). Dawn of the age of dem Obereoz€an und Unteroligoz€an Bulgariens und ihre mammals in the northern part of the Rocky Mountain Inte- Bedeutung fur€ die Pal€aogeographie. Mitteilungen der Bay- rior, North America. Geological Society of America Special erischen Staatssammlung fur€ Pal€aontologie und Historische Paper, 243, 241 pp. Geologie, 25,61–79. KUMAR, K., ROSE, K. D., RANA, R. S., SINGH, L., OWEN, R. 1848. Description of teeth and portions of jaws of SMITH, T. and SAHNI, A. 2010. Early Eocene artiodactyls two extinct Anthracotherioid quadrupeds (Hyopotamus vec- (Mammalia) from western India. Journal of Vertebrate Paleon- tianus and Hyop. bovinus) discovered by the Marchioness of tology, 30, 1245–1274. Hastings in the Eocene deposits on the NW coast of the Isle LI, C. K., QIU, Z. X., YAN, D. F. and XIE, S. H. 1979. of Wight: with an attempt to develope Cuvier’s idea of the Notes on some early Eocene mammalian fossils of Hengtung, Classification of Pachyderms by the number of their toes. Hunan. Vertebrata PalAsiatica, 17,71–80. Quarterly Journal of the Geological Society of London, 4, 103– LUCAS, S. G. and HOLBROOK, L. T. 2004. The skull of the 141. Eocene perrisodactyl Lambdotherium and its phylogenetic sig- PAVLOW, M. 1888. Etudes sur l’Histoire paleontologique des nificance. 81–87. In LUCAS, S. G., ZEIGLER, K. E. and ongules en Amerique et en Europe. II. Le developpement des KONDRASHOV, P. E. (eds). Paleogene mammals. New Equidae. Rhinoceridae et Tapiridae. Bulletin de la Societe Mexico Museum of Natural History and Science Bulletin, 26, Imperiale des Naturalistes de Moscou, 2, 135–182. 230 pp. PELAEZ-CAMPOMANES, P. and LOPEZ-MART INEZ, MAAS, M. C., THEWISSEN, J. G. M., SEN, S., N. 1996. Strange Eocene rodents from Spain. Palaeovertebrata, KAZANCI, N. and KAPPELMAN, J. 2001. Enigmatic new 25, 323–338. ~ ungulates from the early middle Eocene of central Anatolia, -DE LA PENA, A. and LOPEZ MARTINEZ, N. 1989. Turkey. Journal of Vertebrate Paleontology, 21, 578–590. Primeras faunas de micromamıferos del Paleogeno de la BAI: EOCENE PACHYNOLOPHINAE FROM CHINA 851

Cuenca del Duero. Stvdia Geologica Salmanticensia, 5, 135– Eocene Thermal Maximum. Proceedings of the National Acad- 157. emy of Sciences, 103, 11223–11227. QIU, Z. X. and WANG, B. Y. 2007. Paracerathere fossils of -RANA, R. S., MISSIAEN, P., ROSE, K. D., SAHNI, China. Palaeontologia Sinica, New Series C, 29,1–396. A., SINGH, H. and SINGH, L. 2007. High bat (Chiroptera) QUER, R. and AGUSTI, J. 2010. A new genus of rodents diversity in the Early Eocene of India. Naturwissenschaften, 94, (Remyidae, Mammalia) from the Iberian Eocene. Palaeontol- 1003–1009. ogy, 53,53–58. -KUMAR, K., RANA, R. S., FOLIE, A., SOLE, F., RADINSKY, L. B. 1965. Early Tertiary of Asia. Bul- NOIRET, C., STEEMAN, T., SAHNI, A. and ROSE, K. letin of the American Museum of Natural History, 129, 181–264. D. 2016. New early Eocene vertebrate assemblage from west- RANA, R. S., KUMAR, K., ESCARGUEL, G., SAHNI, A., ern India reveals a mixed fauna of European and Gondwana ROSE, K. D., SMITH, T., SINGH, H. and SINGH, L. affinities. Geoscience Frontiers, 7, 969–1001. 2008. An ailuravine rodent from the lower Eocene Cambay STEHLIN, H. G. 1909. Remarques sur les faunules de mam- Formation at Vastan, western India, and its palaeobiogeo- miferes des couches eocenes et Oligocenes du Bassin de Paris. graphic implications. Acta Palaeontologica Polonica, 53,1–14. Bulletin SocieteeGeologique de France, 9, 488–520. REMY, J. A. 1967. Les Palaeotheridae (Perissodactyla) de la SWOFFORD, D. L. 2002. PAUP*. Phylogenetic analysis using faune de mammiferes de Fons 1 (Eocene superieur). Parsimony (*and other methods). Version 4. Sinauer Associates, Palaeovertebrata, 1,1–46. Sunderland, MA, 142 pp. - 1972. Etude du cr^ane de Pachynolophus lavocati n. sp. TING, S. Y. 1995. An Early Eocene mammalian fauna from (Perissodactyla, Palaeotheriidae) des Phosphorites du Quercy. Hengdong, Hunan Province, China. PhD thesis, Louisiana Palaeovertebrata, 5,45–78. State University, Baton Rouge, 201 pp. -2012. Revision systematique des Anchilophini (Palaeotheri- TING, S., TONG, Y. S., LYDE, W. C., KOCH, P. L., MENG, idae, Perissodactyla, Mammalia). Palaeovertebrata, 37,1–165. J., WANG, Y. Q., BOWEN, G. J., LI, Q. and SNELL, K. E. -2015. Les Perissodactyles (Mammalia) du gisement Bar- 2011. Asian early Paleogene chronology and mammalian faunal tonien superieur de Robiac (Eoc ene moyen du Gard, Sud de turnover events. Vertebrata PalAsiatica, 49,1–28. la France). Palaeovertebrata, 39,1–98. TONG, Y. S. 1997. Middle Eocene small mammals from REMY, J.-A., KRASOVEC, G. and MARANDAT, B. 2016. Liguanqiao Basin of Hennan Province and Yuanqu Basin of A new species of Propalaeotherium (Palaeotheriidae, Perisso- Shanxi Province, Central China. Palaeontologia Sinica, New dactyla, Mammalia) from the Middle Eocene locality of Series C, 26,1–256. Aumelas (Herault, France). Palaeovertebrata, 40,1–8. -and WANG, J. W. 2006. Fossil mammals from the Early ROSE, K. D. 2006. The beginning of the age of mammals. John Eocene Wutu Formation of Shandong Province. Palaeontologia Hopkins University Press, 428 pp. Sinica, New Series C, 28,1–195. - DELEON, V. B., MISSIAEN, P., RANA, R. S., WALLACE, S. M. 1980. A revision of North American early SAHNI, A., SINGH, L. and SMITH, T. 2008. Early Eocene Brontotheriidae (Mammalia, Perissodactyla). Master’s Eocene lagomorph (Mammalia) from Western India and the thesis, University of Colorado, Boulder, 157 pp. early diversification of Lagomorpha. Proceedings of the Royal WANG, Y. 1995. A new primitive chalicothere (Perissodactyla, Society B, 275, 1203–1208. Mammalia) from the early Eocene of Hubei, China. Vertebrata -RANA, R. S., SAHNI, A., KUMAR, K., MISSIAEN, PalAsiatica, 33, 138–159. P., SINGH, L. and SMITH, T. 2009a. Early Eocene pri- WANG, H. B., BAI, B., MENG, J. and WANG, Y. Q. 2016. mates from Gujarat, India. Journal of Human Evolution, 56, Earliest known unequivocal rhinocerotoid sheds new light on 366–404. the origin of Giant Rhinos and phylogeny of early rhinocero- ---- SINGH, L. and SMITH, T. 2009b. First toids. Scientific Reports, 6,1–9. tillodont from India: additional evidence for an early Eocene WOOD, H. E. 1929. Prohyracodon orientale Koch, the old- faunal connection between Europe and India? Acta Palaeonto- est known true rhinoceros. American Museum Novitates, 395, logica Polonica, 54, 351–355. 1–7. -KUMAR, K., RANA, R. S., SAHNI, A. and SMITH, T. -1934. Revision of the Hyrachyidae. Bulletin of the American 2013. New hypsodont tillodont (Mammalia, Tillodontia) from Museum of Natural History, 67, 181–295. the early Eocene of India. Journal of Paleontology, 87, 842–853. -1963. A primitive rhinoceros from the late Eocene of Mon- RUSSELL, D. E. and ZHAI, R. J. 1987. The Palaeogene of golia. American Museum Novitates, 2146,1–11. Asia: mammals and stratigraphy. Sciences de la Terre Series C, YOUNG, C.-C. 1944. Note on the first Eocene mammal from 52,1–488. South China. American Museum Novitates, 1268,1–3. SAVAGE, D., RUSSELL, D. and LOUIS, P. 1965. European ZDANSKY, O. 1930. Die altterti€aren S€augetiere Chinas nebst Eocene Equidae (Perissodactyla). University of California stratigraphischen Bemerkungen. Palaeontologia Sinica (C), 6, Publications on Geological Science, 56,1–94. 5–87. SMITH, T., ROSE, K. D. and GINGERICH, P. D. 2006. ZHANG, Y. P. and TONG, Y. S. 1981. New anagaloid mam- Rapid Asia–Europe–North America geographic dispersal of mals from Paleocene of South China. Vertebrata PalAsiatica, earliest Eocene primate Teilhardina during the Paleocene– 19, 133–144. 852 PALAEONTOLOGY, VOLUME 60

APPENDIX 1

Character states for Lophiohippus yunnanensis and Qianohippus magicus based on the matrix of Danilo et al. (2013).

Lophiohippus yunnanensis: ????? ????? ????? ????? ????? ??11- 1-1-0 00102 000-2 1--?? 0?12? 0???? ????? ????? ?? Qianohippus magicus: ????? ????? 21201 11011 11001 1011- 1-020 00100 010-0 01111 00101 00011 01010 00101 00

APPENDIX 2

Measurements of M2 and M3 in various palaeothere species. Measurements of Anchilophus, Paranchilophus and Metanchilophus are mean values from different localities provided by Remy (2012). Measurements of Lophiohippus yunnanensis and Qianohippus magicus are from Huang & Qi (1982) and Miao (1982), respectively. Measurements of Pachynolophus species are from Savage et al. (1965), Remy (1967, 1972), Crusafont Pairo & Remy (1970), Badiola et al. (2005), and Danilo et al. (2013).

Species M2L M2W M3L M3W

Anchilophus desmaresti 8.7 9.6 9.0 9.7 8.3 8.9 8.3 9.0 Paranchilophus jeanteti 11.2 11.4 11.9 11.9 Paranchilophus remyi 12.5 12.9 13.2 13.5 Lophiohippus yunnanensis 12.2 11.9 13.7 12.5 Metanchilophus dumasi 11.3 13.8 12.1 13.9 12.3 15 12.6 14.4 12.5 14.6 11.9 13.9 13.1 15.8 12.9 15.5 Metanchilophus radegondensis 9.6 11.8 9.4 11.2 Metanchilophus gaudini gaudini 10.0 12.4 10.0 12.1 9.8 12.3 10.0 12.1 9.3 11.9 9.6 11.6 Metanchilophus gaudini fontensis 9.8 12.7 10.1 12.3 Metanchilophus depereti 11.7 13.8 11.3 13.5 11.8 14.2 11.5 13.9 Metanchilophus castrensis 11.2 13.3 11.0 12.8 11.1 14.1 11.4 13.4 Metanchilophus chaubeti 9.0 10.1 8.5 10.0 Qianohippus magicus 14.3 15.6 13.4 14.9 Pachynolophus eulaliensis 8.3 10.1 8 9.5 Pachynolophus duvali 9 11 8.9 11.5 Pachynolophus cesserasicus 11.7 13.8 12 14.2 Pachynolophus livinierensis 8.2 10.7 9.4 11.3 Pachynolophus garimondi 10.5 11.63 11.33 11.95 Pachynolophus boixedatensis 9.7 12.2 10.5 12.8 Pachynolophus lavocati 10 12.1 10.9 11.3 Pachynolophus bretovensis 10.2 11.9 9.4 11.5 Pachynolophus zambranensis 12.2 12.55 NONE NONE

L, length; W, width.