中国晚新生代猫科剑齿虎的分类述评及古生态探讨

Chinese Machairodontinae(Carnivora,Felidae)and their ecological significance

猫科剑齿虎类是晚新生代哺乳动物群中最常见且重要的化石组分之一,它的研究对分析和对比动物群具有极其重要的生物地层学意义和古生态意义.中国晚新生代陆相地层中出产了非常丰富的剑齿虎类化石,然而在前人的报道中,受限于有限的化石材料,一些属种的有效性有待讨论.基于对经典材料的实地观测,以及对部分近年来未受关注类群的探讨,结合最新的研究进展,中国的剑齿虎类得到了一次全面的梳理.最终确认有效属种共6属13种,分别是:恐剑齿虎Machairodus horribilis、巴氏剑齿虎Ma.palanderi、钝齿锯齿虎Homotherium crenatidens、最后锯齿虎H.ultimum、欧亚副剑齿虎Paramachaerodus transasiaticus、马氏副剑齿虎Par.maximiliani、巨颏巨颏虎Megantereon megantereon、泥河湾巨颏虎Meg.nihowanensis、意外巨颏虎Meg.inexpectatus、大后猫Metailurus major、最晚后猫Met.ultimus、横断山后猫Met.hengduanshanensis和冠恐猫Dinofelis cristata.分析了剑齿虎类尤其是那些中间形态类型的系统关系及存在的问题.结合不同地点的动物群组合特征,对中国相关剑齿虎类的古生态进行了探讨.恐剑齿虎的生态位很可能与现生虎近似,主要捕食中大型有蹄类.副剑齿虎类和巨颏虎类与现生美洲豹相似,两者分别以中小型及大型食草动物为主要取食对象,上述类群主要生活在林地环境.巴氏剑齿虎和锯齿虎类则与现生狮近似,以捕食中大型猎物为主,后猫类与现生豹近似,偏好于捕食与自身体型相当或稍大的猎物,这些类群主要生活在相对更加开阔的地带.恐猫类的生境尚不十分明了,其捕猎习性可能近似于现生的狮或虎.

Being a common element in late Cenozoic mammalian faunas,saber-toothed felids(or machairodonts)are of important significance for biostratigraphic inferences and paleoecological reconstructions.Late Cenozoic strata in China have produced abundant fossils of saber-toothed felids,including typical forms with extremely elongated and compressed upper canine and very specialized jaw joint structure,such as Machairodus,Megantereon,Homotherium,as well as some intermediate forms which morphology lies between Felinae and Machairodontinae,such as Paramachaerodus,Metailurus,Dinofelis.Our review suggest that there were at least 13 species of 6 genera of Machairodontinae existed in China,including:Machairodus horribilis,Ma.palanderi,Homotherium crenatidens,H.ultimum,Paramachaerodus transasiaticus,Par.maximiliani,Megantereon megantereon,Meg.nihowanensis,Meg.inexpectatus,Metailurus major,Met.ultimus,Met.hengduanshanensis and Dinofelis cristata.Ma.horribilis and Ma.palanderi are two advanced forms of this genus that stand the same broad evolutionary stage with European species Ma.giganteus.Compared with Ma.giganteus,Ma.horribilis is larger in size with broader end of mastoid process and less reduced paraoccipital process,it has a two-rooted P2,its p3 and p4 develop additional cuspids.While,Ma.palanderi is smaller in size,also preserves P2,its p3 is more retracted with more reduced mesial cuspid,the metaconid-talonid complex is also more reduced.For the two pleistocene species of Homotherium,the younger age H.ultimum is more advanced than H.crenatidens,it has extremely reduced p3,elongated and more blade-like p4 with high and posteriorly tilted cuspids and P4 without any trace of protocone.Par.maximiliani is the most advanced forms of this genus,compared with other earlier aged forms,it has a more elongated and blade-like P4 with well-developed ectostyle and smaller protocone,the talonid of m1 is extremely reduced.Compared to Meg.megantereon,Meg.nihowanensis shows relatively more derived traits,as the p3 and the protocone of P4 is more reduced,the mastoid process and postglenoid process protruding more ventrally,covering the auditory bulla in lateral view.The specialized P4 with extremely reduced protocone shows that Meg.inexpextatus is a more advanced form than the other two,which also found in younger deposits.A well-preserved skull from Nihowan Basin confirms that the species D.abeli establied based on specimens from Mianchi,Henan Province should be treated as a synonym of Siwalik species D.cristata,this species shows the most Panthera-like features in the genus.Furthermore,we examined phylogenetic studies focused on Machairodontinae,especially those including highly controversial intermediate forms,and made some comments on them.Combining the mammal fauna of different sites in China,we briefly discussed the paleoecology of relevant groups,and inferred their preferred habitat and prey groups.The niche of Ma.horribilis was probably similar to that of the extant tiger,which mainly preys on medium to large ungulates.The niches of Paramachaerodus and Megantereon are found to be similar to that of the extant jaguar.The former fossil form mainly feeds on small to medium-sized herbivores,while the latter is more likely to handle larger ones.The three fossil groups mentioned above mainly lived in woodland environment.The niches of Ma.palanderi and Homotherium were probably similar to that of the lion,which mainly preys on medium to large ungulates.In contrast,the niche of Metailurus was close to that of the leopard,which prefers to hunt preys of similar or slightly larger size than itself.These three taxa mainly live in more open areas than woodlands.The preferred habitat of Dinofelis cristata is still unknown,but its hunting habits may be similar to that of extant lions or tigers.