SOME EARLY TERTIARY PERRISODACTYLA FROM LUNAN BASIN,E.YUNNAN

This paper describes a small collection of Perrisodactyla from the Upper Eoceneand Lower Oligocene“Lunan Formation”of Lunan Basin in eastern Yunnan.Itcontains:a)a note on the generic affiliation of“Parabrontops lunanensis”;b)des-cription of three new species;a lophialetid,Breviodon sahoensis;a deperetellid,Deperetella dienensis,and a hyracodontid,Forstercooperia shiwapuenis;c)new dataon lower dentition of Prohyracodon and Deperetella similis and on premolars ofEomorops quadridentatus;and d)discussions on some related taxonomic problems.1)A note on the generic affiliation of“Parabrontops lunanensis”. A skulldescribed by Chow and Hu(1959)as“Parabraontops lunanensis”is reexamined andfound that it differs markedly from the genotypic species P.gobiensis(Osborn)(Granger and Gregory,1943)that a generic separation from the latter will bejustified.It is named here as“Dianotitan”(gen.nov.)(“Dian”is a abbreviatedname for Yunnan). The skull of the genus is much more brachyocephalic and the indices of the skull,as well as those of the cheek teeth,differ greatly as compared with those given byGranger and Gregory for Parabrontops and other Mongolian forms;yet,on the otherhand,in many respects,it is more similar to those in Metatitan or Protitan.ButDianotitan is similar to Parabrontops in the specialization of anterior teeth and inthe development of the naso-frontal horns.It represents very likely an early offsetfrom the line leading from the early Late Eocene Protitan to the Oligocene Parabron-tops.And a recent investigation on the stratigraphical section of the Lunan District(for some years around 1960 annexed to the Ilian county)shows that the white marlyfreshwater limestone bed yielding the skull is more probably of late(or latest)Eocene rather than Oligocene.2)Notes on Eomorops quadridentatus Zdansky,1930.An upper jaw with P~3-M~1 is referable to this species,but differs from the type in that the teeth are morenearly quadratic,and the premolars with more backward slanting protoloph andrelatively longer ectoloph.This is the best represented one of the Asiatic speciesgrouped under the genus.The Asiatic forms as a whole differ from E.amarorum inthat the upper premolars are slightly more molariformed,with more quadratic outlineand larger parastyles and without inner cingulum,and lower molars with more lingualconnection between hyolophid and metalophid.They may be generically differentfrom the North American one.An isolated M~3(V 2404.2)from the Hoti fauna of Yuanchu Basin(Hu,1959)described as that of E.major has very weak mesostyles(or entirely suppressed), should be grouped with the genus Litolophus,as was defined by Radinsky(1964). 3)Breviodon sahoensis(sp.nov.)A left mandible with C-M_3 and part of aright one of the same individual with M_2 and M_3(type,V 801,of Geol.Mus.Cat.No.,for all the specimens described in this paper),from Village“Little Saho”(“Hsiaosaho”)in Lunan Basin,and another jaw with P_4-M_3(V 801.1). Diagnosis:A species of Breviodon,essentially identical with B.acares(Ra-dinsky,1965),in the structure of lower jaw and lower teeth,but about 30% largerin size,cross-section of C more rounded,relatived length of diastema and symphysesslightly shorter,third lobe of M_3 with sharply crested straight hyld at posterior end.This species is closely related to B.acares,but evidently slightly more advancedtham the latter as diagnosed.4)Deperetella similis(Zdansky)Two upper jaw fragments with P~3-P~4(V 29),a right mandible fragment with P_3-M_3(V 713)and two left ones(V 31),one withP_3-P_4 and the other with DP_3 and P_4;from Upper Eocene of Kaofenpei(V 713)and Hsiaosaho(V 31,V 29)in Lunan.The lower cheek teeth is in the main similar to those in D.birmanicum as wasinfered by Radinsky(1965),but it differs from the Burmese species in lacking theposterior spur on P_4,and the lophid of M_1-M_3 broadly connex posteriorly.5)Deperetella dienensis sp.nov.An upper jaw fragment with P~4 and M~1(V 31.1,type)close to those of D.cristata,but differs in being smaller by about 20%,P~4 relatively smaller,with transverse lophs less seperated lingually and posterior lobeof ectoloph more developed;parastyle high and with strong posterior crest behind themetaloph;external cingula scarecely present.It shows characteristics intermediatebetween this genus and Teleolophus.6)Teleolophus cf.magnus Radinsky,1965.An upper third molar(V 793),from Upper Eocene of Lunan,similar to T.magnus,but differs in being slightlylarger in size and with more lingually extended lophs.7)Prohyracodon progressa Chow et Xu.Two upper and four lower jaw frag-ments from various localities in Upper Eocene of Lunan.The lower cheek-teeth aretypically rhinocerotoid and“hyracodontid”,M_1 to M_3 progressively larger,and essen-tially similar in construction,hypolophid joining to metalophid nearly at its base,paraconid hardly developed,paralophid very low,and ext.and int.cingula absent.Radinsky(1967)considered this species as a synonym of P.meridionale. Theevidences from the new material of lower,as well as of upper,teeth,seem to indicatethat this species is more progressive in premolar structure,constantly of smaller sizeand with more reduced posterior lobe in M~3.We incline to have the two separated atleast for the present.8)Prohyracodon meridionale Chow et Xu.Two upper and one lower jaw fromUpper Eocene of Hsiaosaho(“Saho”),Lunan Basin.The lower cheek teeth aresimilar to those of the preceding species,but of larger size and with less molariformpremolars.In V 771,the roots of C and P~1 are preserved,the former being com-paratively large,with a short diastema(about 5 mm.)behind it,and the latter single-rooted.The upper teeth of this species appear to be nearer to those of P.orientale,which may be also of late Eocene age,than to P.progressa. 9)Forstercooperia shiwopuensis sp.nov.Posterior of a left maxilla with DP~4,M~1 and M~2(V 714),from Upper Eocene of Shiwopu in Lunan. Diagnosis:A hyrocodontid rhinoceros comparatively larger in size(about that ofF.totadontata Wood);molars showing appearance of that of a lophiodontid;para-one of M~2 columnar and near the middle of ectoloph,which is broadly underlatingand with long pasterior lobe bending exterowards;and molar protoloph and meta-oph curved backward lingually.This species differs from the related forms in having“lophiodon-like”molars.Possibly it may represent the upper molars of F.totadentata,which is still unknown.We agree with Radinsky in considering Papaceras(P.confluens)as a synonym ofForstercooper,but incline to retain the genus Juxia as distinct for it has larger I~1(a specialization towards later indricotheres),markedly retracted nasal incision andnore molariformed premolars,etc.10)Forstercooperia sp.Two mandible fragments,both with M_1 and M_2(V 806,W 807);Upper Eocene of Dahimapan,Lunan.Teeth resemble those of“F.confluens(Wood),but differ in that the lower molars are wider,with more developed cingula,M_1 somewhat longer,and the mandibular ramus shallower.11)“Indricotherium”cf.parvum Chow.An isolated second upper P(V 792)from the lower Oligocene of Lunan,may be assigned to I.parvum,of which the 2ndp is unknown.